掲載種別：研究論文（学術雑誌）   出版者・発行元：Astrophysical Journal  

We report the detection of an ionized gas outflow from an X-ray active galactic nucleus hosted in a massive quiescent galaxy in a protocluster at z = 3.09 (J221737.29+001823.4). It is a type-2 QSO with broad (W 80 > 1000 km s-1) and strong ( log(L[OIII] /erg s-1) ≈ 43.4) [O iii]λ λ 4959,5007 emission lines detected by slit spectroscopy in three-position angles using Multi-Object Infra-Red Camera and Spectrograph (MOIRCS) on the Subaru telescope and the Multi-Object Spectrometer For Infra-Red Exploration (MOSFIRE) on the Keck-I telescope. In the all slit directions, [O iii] emission is extended to ∼15 physical kpc and indicates a powerful outflow spreading over the host galaxy. The inferred ionized gas mass outflow rate is 22 ± 3 M ⊙ yr-1. Although it is a radio source, according to the line diagnostics using Hβ, [O ii], and [O iii], photoionization by the central QSO is likely the dominant ionization mechanism rather than shocks caused by radio jets. On the other hand, the spectral energy distribution of the host galaxy is well characterized as a quiescent galaxy that has shut down star formation several hundred Myr ago. Our results suggest a scenario that QSOs are powered after the shutdown of the star formation and help complete the quenching of massive quiescent galaxies at high redshift.

DOI： 10.3847/1538-4357/ac7f2d

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その他リンク： https://iopscience.iop.org/article/10.3847/1538-4357/ac7f2d/pdf

掲載種別：研究論文（学術雑誌）   出版者・発行元：Publications of the Astronomical Society of Japan  

We present observations of [N II] 205 μm, [O III] 88 μm, and dust emission in a strongly-lensed, submillimeter galaxy (SMG) at z = 6.0, G09.83808, with the Atacama Large Millimeter/submillimeter Array (ALMA). Both [N II] and [O III] line emissions are detected at >12σ in the 0.″8-resolution maps. Lens modeling indicates that the spatial distribution of the dust continuum emission is well characterized by a compact disk with an effective radius of 0.64 ± 0.02 kpc and a high infrared surface brightness of ΣIR = (1.8 ± 0.3) × 1012 L⊙ kpc-2. This result supports that G09.83808 is the progenitor of compact quiescent galaxies at z ∼4, where the majority of its stars are expected to be formed through a strong and short burst of star formation. G09.83808 and other lensed SMGs show a decreasing trend in the [N II] line to infrared luminosity ratio with increasing continuum flux density ratio between 63 and 158 μm, as seen in local luminous infrared galaxies (LIRGs). The decreasing trend can be reproduced by photoionization models with increasing ionization parameters. Furthermore, by combining the [N II]/[O III] luminosity ratio with far-infrared continuum flux density ratio in G09.83808, we infer that the gas phase metallicity is already Z ≈ 0.5-0.7 Z⊙. G09.83808 is likely one of the earliest galaxies that has been chemically enriched at the end of reionization.

DOI： 10.1093/pasj/psac018

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出版者・発行元：Astrophysical Journal  

We introduce an ALMA band 3 spectroscopic survey targeting the brightest submillimeter galaxies (SMGs) in the COSMOS field. Here we present the first results based on the 18 primary SMGs that have 870 μm flux densities of S 870 = 12.4-19.3 mJy and are drawn from a parent sample of 260 ALMA-detected SMGs from the AS2COSMOS survey. We detect emission lines in 17 and determine their redshifts to be in the range of z = 2-5 with a median of 3.3 ± 0.3. We confirm that SMGs with brighter S 870 are located at higher redshifts. The data additionally cover five fainter companion SMGs, and we obtain line detection in one. Together with previous studies, our results indicate that for SMGs that satisfy our selection, their brightest companion SMGs are physically associated with their corresponding primary SMGs ≥40% of the time, suggesting that mergers play a role in the triggering of star formation. By modeling the foreground gravitational fields, <10% of the primary SMGs can be strongly lensed with a magnification μ > 2. We determine that about 90% of the primary SMGs have lines that are better described by double Gaussian profiles, and the median separation of the two Gaussian peaks is 430 ± 40 km s-1. This allows estimates of an average baryon mass, which, together with the line dispersion measurements, puts our primary SMGs on the similar mass-σ correlation found on local early-type galaxies. Finally, the number density of our z > 4 primary SMGs is found to be 1-0.6+0.9×10-6 cMpc-3, suggesting that they can be the progenitors of z ∼3-4 massive quiescent galaxies.

DOI： 10.3847/1538-4357/ac61df

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掲載種別：研究論文（学術雑誌）   出版者・発行元：Monthly Notices of the Royal Astronomical Society  

We present results from a new cosmological hydrodynamics simulation campaign of protocluster (PC) regions, FOREVER22: FORmation and EVolution of galaxies in Extremely overdense Regions motivated by SSA22. The simulations cover a wide range of cosmological scales using three different zoom set-ups in a parent volume of $(714.2rm cMpc){3}$: PCR (Proto-Cluster Region; V = (28.6 cMpc)3, SPH particle mass, mSPH = 4.1 × 106 M, and final redshift, zend = 2.0), BCG (Brightest proto-Cluster Galaxy; V ∼(10 cMpc)3, mSPH = 5.0 × 105 M and zend = 4.0), and First (V ∼(3 cMpc)3, mSPH = 7.9 × 103 M and zend = 9.5) runs, that allow us to focus on different aspects of galaxy formation. In the PCR runs, we follow 10 PCs, each harbouring 1-4 SMBHs with ${rm M_{rm BH}}ge 10{9}{rm M_{odot }}$. One of the PC cores shows a spatially close arrangement of seven starburst galaxies with ${rm SFR} gtrsim 100{rm {rm M_{odot }}{rm yr{-1}}}$ each, that are dust-obscured and would appear as submillimetre galaxies with flux 1 mJy at $1.1 rm mm$ in observations. The BCG runs show that the total SFRs of haloes hosting BCGs are affected by AGN feedback, but exceed $1000{rm {rm M_{odot }{rm yr{-1}}}$ at z 6. The First runs resolve mini-haloes hosting population (Pop) III stars and we show that, in PC regions, the dominant stellar population changes from Pop III to Pop II at z 20, and the first galaxies with ${rm SFR} gtrsim 18{rm {rm M_{odot }}{rm yr{-1}}}$ form at z ∼10. These can be prime targets for future observations with the James Webb Space Telescope. Our simulations successfully reproduce the global star formation activities in observed PCs and suggest that PCs can kickstart cosmic reionization.

DOI： 10.1093/mnras/stab3092

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その他リンク： https://academic.oup.com/mnras/article-pdf/509/3/4037/41475398/stab3092.pdf

出版者・発行元：Astrophysical Journal  

We examine possible environmental sources of the enhanced star formation and active galactic nucleus (AGN) activity in the z = 3.09 SSA22 protocluster using Hubble WFC3 F160W (~1.6 µm) observations of the SSA22 field, including new observations centered on eight X-ray selected protocluster AGN. To investigate the role of mergers in the observed AGN and star formation enhancement, we apply both quantitative (Sérsic-fit and Gini-M20) and visual morphological classifications to F160W images of protocluster Lyman-break galaxies (LBGs) in the fields of the X-ray AGN and z ~ 3 field LBGs in SSA22 and GOODS-N. We find no statistically significant differences between the morphologies and merger fractions of protocluster and field LBGs, though we are limited by small number statistics in the protocluster. We also fit the UV-to-near-IR spectral energy distributions of F160W-detected protocluster and field LBGs to characterize their stellar masses and star formation histories. We find that the mean protocluster LBG is a factor of ~2 times more massive and more attenuated than the mean z ~ 3 field LBG. We take our results to suggest that ongoing mergers are not more common among protocluster LBGs than field LBGs, though protocluster LBGs appear to be more massive. We speculate that the larger mass of the protocluster LBGs contributes to the enhancement of SMBH mass and accretion rate in the protocluster, which in turn drives the observed protocluster AGN enhancement.

DOI： 10.3847/1538-4357/ac0f84

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掲載種別：研究論文（学術雑誌）   出版者・発行元：Astrophysical Journal  

We present observations of a giant Lyα blob (LAB) in the SSA22 protocluster at z = 3.1, SSA22-LAB1, taken with the Atacama Large Millimeter/submillimeter Array. Dust continuum, along with [C II] 158 μm and CO(4–3) line emission have been detected in LAB1, showing complex morphology and kinematics across a ∼100 kpc central region. Seven galaxies at z = 3.0987–3.1016 in the surroundings are identified in [C II] and dust continuum emission, with two of them potential companions or tidal structures associated with the most massive galaxies. Spatially resolved [C II] and infrared luminosity ratios for the widely distributed media (L[CII]/LIR ≈ 10-2-10-3) suggest that the observed extended interstellar media are likely to have originated from star formation activity and the contribution from shocked gas is probably not dominant. LAB1 is found to harbor a total molecular gas mass Mmol = (8.7 ± 2.0) × 1010 Me, concentrated in the core region of the Lyα-emitting area. While (primarily obscured) star formation activity in the LAB1 core is one of the most plausible power sources for the Lyα emission, multiple major mergers found in the core may also play a role in making LAB1 exceptionally bright and extended in Lyα as a result of cooling radiation induced by gravitational interactions.

DOI： 10.3847/1538-4357/ac1106

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掲載種別：研究論文（学術雑誌）   出版者・発行元：Astrophysical Journal  

We report a massive quiescent galaxy at zspec= -3.0922+0.008-0.004 spectroscopically confirmed at a protocluster in the SSA22 field by detecting the Balmer and Ca II absorption features with the multi-object spectrometer for infrared exploration on the Keck I telescope. This is the most distant quiescent galaxy confirmed in a protocluster to date. We fit the optical to mid-infrared photometry and spectrum simultaneously with spectral energy distribution (SED) models of parametric and nonparametric star formation histories (SFHs). Both models fit the observed SED well and confirm that this object is a massive quiescent galaxy with a stellar mass of log (M∗/M⊙=11.26+0.03-0.04 and 11.54+0.03-0.00 and a star formation rate of SFR/M⊙ yr-1 < 0.3 and = -0.01+0.03-0.01 for parametric and nonparametric models, respectively. The SFH from the former modeling is described as an instantaneous starburst whereas that of the latter modeling is longer-lived, but both models agree with a sudden quenching of the star formation at ~0.6 Gyr ago. This massive quiescent galaxy is confirmed in an extremely dense group of galaxies predicted as a progenitor of a brightest cluster galaxy formed via multiple mergers in cosmological numerical simulations. We discover three new plausible [O III]λ5007 emitters at 3.0791 ≤ zspec ≤ 3.0833 serendipitously detected around the target. Two of them just between the target and its nearest massive galaxy are possible evidence of their interactions. They suggest the future great size and stellar mass evolution of this massive quiescent galaxy via mergers.

DOI： 10.3847/1538-4357/ac0cf8

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掲載種別：研究論文（学術雑誌）   出版者・発行元：Astrophysical Journal  

We present Atacama Large Millimeter/submillimeter Array [C ii] 158 μm line and underlying far-infrared (FIR) continuum emission observations (0.″70 × 0.″56 resolution) toward HSC J124353.93+010038.5 (J1243+0100) at z = 7.07, the only low-luminosity (M 1450 > -25 mag) quasar currently known at z > 7. The FIR continuum is bright (1.52 mJy) and resolved with a total luminosity of L FIR = 3.5 × 1012 L o˙. The spatially extended component is responsible for ∼40% of the emission. The area-integrated [C ii] spectrum shows a broad wing (FWHM = 997 km s-1, L [C ii] = 1.2 × 109 L o˙), as well as a bright core (FWHM = 235 km s-1, L [C ii] = 1.9 × 109 L o˙). This wing is the first detection of a galactic-scale quasar-driven outflow (atomic outflow rate >447 M o˙ yr-1) at z > 7. The estimated large mass-loading factor of the total outflow (e.g., ⪆9 relative to the [C ii]-based star formation rate) suggests that this outflow will soon quench the star formation of the host. The core gas dynamics are governed by rotation, with a rotation curve suggestive of a compact bulge (∼3.3 × 1010 M o˙), although it is not yet spatially resolved. Finally, we found that J1243+0100 has a black hole mass-to-dynamical mass (and -to-bulge mass) ratio of ∼0.4% (∼1%), consistent with the local value within the uncertainties. Our results therefore suggest that the black hole-host coevolution relation is already in place at z ∼ 7 for this object.

DOI： 10.3847/1538-4357/abf6dc

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その他リンク： https://iopscience.iop.org/article/10.3847/1538-4357/abf6dc/pdf

掲載種別：研究論文（学術雑誌）   出版者・発行元：Astrophysical Journal  

We report the detection of [O i] 145.5 μm in the BR 1202-0725 system, a compact group at z = 4.7 consisting of a quasar (QSO), a submillimeter-bright galaxy (SMG), and three faint Lyα emitters. By taking into account the previous detections and upper limits, the [O i] /[C ii] line ratios of the now five known high-z galaxies are higher than or on the high end of the observed values in local galaxies ([O i] /[C ii] ⪆ 0.13). The high [O i] /[C ii] ratios and the joint analysis with previous detection of [N ii] lines for both of the QSO and the SMG suggest the presence of warm and dense neutral gas in these highly star-forming galaxies. This is further supported by new CO (12-11) line detections and a comparison with cosmological simulations. There is a possible positive correlation between the [N ii] 122/205 line ratio and the [O i] /[C ii] ratio when all local and high-z sources are taken into account, indicating that the denser the ionized gas, the denser and warmer the neutral gas (or vice versa). The detection of the [O i] line in the BR 1202-0725 system with a relatively short amount of integration with Atacama Large Millimeter/submillimeter Array (ALMA) demonstrates the great potential of this line as a dense gas tracer for high-z galaxies.

DOI： 10.3847/1538-4357/abe7ea

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その他リンク： https://iopscience.iop.org/article/10.3847/1538-4357/abe7ea/pdf

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Astrophysical Journal  

We present bright [C II] 158 μm line detections from a strongly magnified and multiply imaged (μ ∼ 20–160) sub–L* (MUV = -19.75-+0.440.55) Lyman-break galaxy (LBG) at z = 6.0719 ± 0.0004, drawn from the ALMA Lensing Cluster Survey (ALCS). Emission lines are identified at 268.7 GHz at 8σ exactly at the positions of two multiple images of the LBG, behind the massive galaxy cluster RXCJ0600−2007. Our lens models, updated with the latest spectroscopy from VLT/MUSE, indicate that a sub region of the LBG crosses the caustic, and is lensed into a long (∼6″) arc with a local magnification of μ ∼ 160, for which the [C II] line is also significantly detected. The source plane reconstruction resolves the interstellar medium (ISM) structure, showing that the [C II] line is co-spatial with the rest-frame UV continuum at a scale of ∼300 pc. The [C II] line properties suggest that the LBG is a rotation-dominated system, whose velocity gradient explains a slight difference in redshifts between the whole LBG and its sub-region. The star formation rate (SFR)–L[CII] relations, for whole and sub-regions of the LBG, are consistent with those of local galaxies. We evaluate the lower limit of the faint-end of the [C II] luminosity function at z = 6, finding it to be consistent with predictions from semi-analytical models and from the local SFR–L[CII] relation with a SFR function at z = 6. These results imply that the local SFR–L[CII] relation is universal for a wide range of scales, including the spatially resolved ISM, the whole region of the galaxy, and the cosmic scale, even in the epoch of reionization.

DOI： 10.3847/1538-4357/abd7ec

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掲載種別：研究論文（学術雑誌）   出版者・発行元：Astronomy and Astrophysics  

Context. Characterizing the galaxy population in the early Universe holds the key to understanding the evolution of these objects and the role they played in cosmic reionization. However, there have been very few observations at the very highest redshifts to date. Aims. In order to shed light on the properties of galaxies in the high-redshift Universe and their interstellar media, we observe the Lyman-α emitting galaxy z7_GSD_3811 at z = 7.664 with bands 6 and 8 at the Atacama Large Millimeter/submillimeter Array (ALMA). Methods. We target the far-infrared [O iii] 88 µm and [C ii] 158 µm emission lines and dust continuum in the star-forming galaxy z7_GSD_3811 with ALMA. We combine these measurements with earlier observations in the rest-frame ultraviolet (UV) in order to characterize the object and compare the results to those of earlier studies that observed [O iii] and [C ii] emission in high-redshift galaxies. Results. The [O iii] 88 µm and [C ii] 158 µm emission lines are undetected at the position of z7_GSD_3811, with 3σ upper limits of 1.6 × 108 L and 4.0 × 107 L, respectively. We do not detect any dust continuum in band 6 nor band 8. The measured rms in the band 8 and band 6 continua are 26 and 9.9 µJy beam−1, respectively. Similar to several other high-redshift galaxies, z7_GSD_3811 exhibits low [C ii] emission for its star formation rate compared to local galaxies. Furthermore, our upper limit on the [O iii] line luminosity is lower than the previously observed [O iii] lines in high-redshift galaxies with similar UV luminosities. Our ALMA band 6 and 8 dust continuum observations imply that z7_GSD_3811 likely has a low dust content, and our non-detections of the [O iii] and [C ii] lines could indicate that z7_GSD_3811 has a low metallicity (Z. 0.1 Z).

DOI： 10.1051/0004-6361/202038180

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掲載種別：研究論文（学術雑誌）   出版者・発行元：Astrophysical Journal  

We present Atacama Large Millimeter/submillimeter Array [C ii] 158 μm line and far-infrared (FIR) continuum emission observations toward HSC J120505.09-000027.9 (J1205-0000) at z = 6.72 with a beam size of ∼0.″8 × 0.″5 (or 4.1 kpc × 2.6 kpc), the most distant red quasar known to date. Red quasars are modestly reddened by dust and are thought to be in rapid transition from an obscured starburst to an unobscured normal quasar, driven by powerful active galactic nucleus (AGN) feedback that blows out a cocoon of interstellar medium. The FIR continuum of J1205-0000 is bright, with an estimated luminosity of L FIR ∼ 3 × 1012 L o˙. The [C ii] line emission is extended on scales of r ∼ 5 kpc, greater than that of the FIR continuum. The line profiles at the extended regions are complex and broad (FWHM ∼ 630-780 km s-1). Although it is not practical to identify the nature of this extended structure, possible explanations include (i) companion/merging galaxies and (ii) massive AGN-driven outflows. For the case of (i), the companions are modestly star-forming (∼10 M o˙ yr-1) but are not detected by our Subaru optical observations (y AB,5σ = 24.4 mag). For the case of (ii), our lower limit to the cold neutral outflow rate is ∼100 M o˙ yr-1. The outflow kinetic energy and momentum are both much lower than predicted in energy-conserving wind models, suggesting that the AGN feedback in this quasar is not capable of completely suppressing its star formation.

DOI： 10.3847/1538-4357/abd7ef

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その他リンク： https://iopscience.iop.org/article/10.3847/1538-4357/abd7ef/pdf

掲載種別：研究論文（学術雑誌）   出版者・発行元：Astrophysical Journal  

We report the discovery of a 10 comoving megaparsec (cMpc)-scale structure traced by massive submillimeter galaxies (SMGs) at z ∼ 4.6. These galaxies are selected from an emission line search of ALMA Band 7 observations targeting 184 luminous submillimeter sources (S 850μm ≥ 6.2 mJy) across 1.6 degrees2 in the COSMOS field. We identify four [C ii] emitting SMGs and two probable [C ii] emitting SMG candidates at z = 4.60-4.64 with velocity-integrated signal-to-noise ratio of S/N > 8. Four of the six emitters are near-infrared blank SMGs. After excluding one SMG whose emission line is falling at the edge of the spectral window, all galaxies show clear velocity gradients along the major axes that are consistent with rotating gas disks. The estimated rotation velocities of the disks are 330-550 km s-1 and the inferred host dark-matter halo masses are ∼2-8 1012 M o˙. From their estimated halo masses and [C ii] luminosity function, we suggest that these galaxies have a high (50%-100%) duty cycle and high (∼0.1) baryon conversion efficiency (SFR relative to baryon accretion rate), and that they contribute ≃2% to the total star formation rate density at z = 4.6. These SMGs are concentrated within just 0.3% of the full survey volume, suggesting they are strongly clustered. The extent of this structure and the individual halo masses suggest that these SMGs will likely evolve into members of a ∼1015 M o˙ cluster at z = 0. This survey reveals a synchronized dusty starburst in massive halos at z > 4, which could be driven by mergers or fed by smooth gas accretion.

DOI： 10.3847/1538-4357/abcc72

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その他リンク： https://iopscience.iop.org/article/10.3847/1538-4357/abcc72

掲載種別：研究論文（学術雑誌）   出版者・発行元：Astrophysical Journal  

We report the discovery of a Multi Unit Spectroscopic Explorer (MUSE) galaxy group at z = 4.32 lensed by the massive galaxy cluster ACT-CL J0102-4915 (aka El Gordo) at z = 0.87, associated with a 1.2 mm source that is at a 2.07 0.88 kpc projected distance from one of the group galaxies. Three images of the whole system appear in the image plane. The 1.2 mm source has been detected within the Atacama Large Millimetre/submillimetre Array (ALMA) Lensing Cluster Survey (ALCS). As this ALMA source is undetected at wavelengths λ < 2 μm, its redshift cannot be independently determined, however, the three lensing components indicate that it belongs to the same galaxy group at z = 4.32. The four members of the MUSE galaxy group have low to intermediate stellar masses (∼107-1010 M o˙) and star formation rates (SFRs) of 0.4-24 M o˙ yr-1, resulting in high specific SFRs (sSFRs) for two of them, which suggest that these galaxies are growing fast (with stellar mass doubling times of only ∼2 107 yr). This high incidence of starburst galaxies is likely a consequence of interactions within the galaxy group, which is compact and has high velocity dispersion. Based on the magnification-corrected sub-/millimeter continuum flux density and estimated stellar mass, we infer that the ALMA source is classified as an ordinary ultra-luminous infrared galaxy (with associated dust-obscured SFR ∼ 200-300 M o˙ yr-1) and lies on the star formation main sequence. This reported case of an ALMA/MUSE group association suggests that some presumably isolated ALMA sources are in fact signposts of richer star-forming environments at high redshifts.

DOI： 10.3847/1538-4357/abd4d0

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その他リンク： https://iopscience.iop.org/article/10.3847/1538-4357/abd4d0

記述言語：英語  

CiNii Research

掲載種別：研究論文（学術雑誌）   出版者・発行元：Astronomy and Astrophysics  

Deep surveys with the Atacama Large Millimeter Array (ALMA) have uncovered a population of dusty star-forming galaxies which are faint or even undetected at optical to near-infrared wavelengths. Their faintness at short wavelengths makes the detailed characterization of the population challenging. Here we present a spectroscopic redshift identification and a characterization of one of these near-infrared-dark galaxies discovered by an ALMA deep survey. The detection of [Ca I](1-0) and CO(4-3) emission lines determines the precise redshift of the galaxy, ADF22.A2, to be za =a 3.9913a ±a 0.0008. On the basis of a multi-wavelength analysis, ADF22.A2 is found to be a massive, star-forming galaxy with a stellar mass of Ma - = 1.1-0.6+1.3 × 1011 MaS and SFR = 430-150+230a MaS yr-1. The molecular gas mass was derived to be M(H2)[CI]a =a (5.9a ±a 1.5)×1010a MaS , indicating a gas fraction of ≈35%, and the ratios of L[CI](1-0)/LIR and L[CI](1-0)/LCO(4-3) suggest that the nature of the interstellar medium in ADF22.A2 is in accordance with those of other bright submillimeter galaxies. The properties of ADF22.A2, including the redshift, star-formation rate, stellar mass, and depletion time scale (τdepa ≈a 0.1-0.2 Gyr), also suggest that ADF22.A2 has the characteristics expected for the progenitors of quiescent galaxies at zaaa 3. Our results demonstrate the power of ALMA contiguous mapping and line scan, which help us to obtain an unbiased view of galaxy formation in the early Universe.

DOI： 10.1051/0004-6361/202038146

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掲載種別：研究論文（学術雑誌）   出版者・発行元：Publications of the Astronomical Society of Japan  

We make use of the ALMA twenty-Six Arcmin2 survey of GOODS-S At One-millimeter (ASAGAO), deep 1.2 mm continuum observations of a 26-arcmin2 region in the Great Observatories Origins Deep Survey-South (GOODS-S) obtained with Atacama Large Millimeter/sub-millimeter Array (ALMA), to probe dust-enshrouded star formation in K-band selected (i.e., stellar mass selected) galaxies, which are drawn from the FourStar Galaxy Evolution Survey (ZFOURGE) catalog. Based on the ASAGAO combined map, which was created by combining ASAGAO and ALMA archival data in the GOODS-South field, we find that 24 ZFOURGE sources have 1.2 mm counterparts with a signal-to-noise ratio >4.5 (1σ ≃ 30-70 μJy beam−1 at 1.2 mm). Their median redshift is estimated to be zmedian = 2.38 ± 0.14. They generally follow the tight relationship of the stellar mass versus star formation rate (i.e., the main sequence of star-forming galaxies). ALMA-detected ZFOURGE sources exhibit systematically larger infrared (IR) excess (IRX ≡ LIR/LUV) compared to ZFOURGE galaxies without ALMA detections even though they have similar redshifts, stellar masses, and star formation rates. This implies the consensus stellar-mass versus IRX relation, which is known to be tight among rest-frame-ultraviolet-selected galaxies, cannot fully predict the ALMA detectability of stellar-mass-selected galaxies. We find that ALMA-detected ZFOURGE sources are the main contributors to the cosmic IR star formation rate density at z = 2-3.

DOI： 10.1093/pasj/psaa057

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その他リンク： http://academic.oup.com/pasj/article-pdf/72/4/69/33562710/psaa057.pdf

出版者・発行元：Monthly Notices of the Royal Astronomical Society  

We present an ALMA study of the ∼180 brightest sources in the SCUBA-2 850-μm map of the COSMOS field from the S2COSMOS survey, as a pilot study for AS2COSMOS-A full survey of the ∼1000 sources in this field. In this pilot study, we have obtained 870-μm continuum maps of an essentially complete sample of the brightest 182 sub-millimetre sources ($S_{850\, \mu \rm m}\gt $ 6.2 mJy) in COSMOS. Our ALMA maps detect 260 sub-millimetre galaxies (SMGs) spanning a range in flux density of $S_{870\, \mu \rm m}$ = 0.7-19.2 mJy. We detect more than one SMG counterpart in 34 ± 2 per cent of sub-millimetre sources, increasing to 53 ± 8 per cent for SCUBA-2 sources brighter than $S_{850\, \mu \rm m}\gt $ 12 mJy. We estimate that approximately one-Third of these SMG-SMG pairs are physically associated (with a higher rate for the brighter secondary SMGs, $S_{870\, \mu \rm m}\gtrsim$ 3 mJy), and illustrate this with the serendipitous detection of bright [C ii] 157.74-μm line emission in two SMGs, AS2COS 0001.1 and 0001.2 at z = 4.63, associated with the highest significance single-dish source. Using our source catalogue, we construct the interferometric 870-μm number counts at $S_{870\, \mu \rm m}\gt $ 6.2 mJy. We use the extensive archival data of this field to construct the multiwavelength spectral energy distribution of each AS2COSMOS SMG, and subsequently model this emission with magphys to estimate their photometric redshifts. We find a median photometric redshift for the $S_{870\, \mu \rm m}\gt $ 6.2 mJy AS2COSMOS sample of z = 2.87 ± 0.08, and clear evidence for an increase in the median redshift with 870-μm flux density suggesting strong evolution in the bright end of the 870-μm luminosity function.

DOI： 10.1093/mnras/staa1345

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Oxford University Press  

We report on the detection of the [C II] 157.7 μm emission from the Lyman break galaxy (LBG) MACS0416 Y1 at z = 8.3113, by using the Atacama Large Millimeter/submillimeter Array (ALMA). The luminosity ratio of [O III] 88 μm (from previous campaigns) to [CII] is 9.3 ± 2.6, indicative of hard interstellar radiation fields and/or a low covering fraction of photodissociation regions. The emission of [C II] is cospatial to the 850 μm dust emission (90 μm rest frame, from previous campaigns), however the peak [C II] emission does not agree with the peak [O III] emission, suggesting that the lines originate from different conditions in the interstellar medium. We fail to detect continuum emission at 1.5 mm (160 μm rest frame) down to 18 μJy (3s). This non-detection places a strong limits on the dust spectrum, considering the 137 ± 26 μJy continuum emission at 850 μm. This suggests an unusually warm dust component (T > 80 K, 90 per cent confidence limit), and/or a steep dust-emissivity index (βdust > 2), compared to galaxy-wide dust emission found at lower redshifts (typically T ~30-50 K, βdust ~1-2). If such temperatures are common, thiswould reduce the required dust mass and relax the dust production problem at the highest redshifts.We therefore warn against the use of only single-wavelength information to derive physical properties, recommend a more thorough examination of dust temperatures in the early Universe, and stress the need for instrumentation that probes the peak of warm dust in the Epoch of Reionization.

DOI： 10.1093/mnras/staa509

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CiNii Research

arXiv

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Publications of the Astronomical Society of Japan  

We present our ALMA Band 8 observations of a damped Lyα absorption (DLA) system at z = 3.150 observed in the spectrum of the quasar Q2233+131 at z = 3.295. The optical counterpart of this DLA has been identified and it shows a double-peaked Lyá emission line. Since one possible origin of DLAs at high redshift is an outflowing gas from starforming galaxies, DLA 2233+131 provides a good laboratory to investigate the nature of high-z DLAs. Motivated by this, we have carried out ALMA band 8 observations to study the [CII] line in this system. However, we do not detect any significant emission line in the observed pass bands. Instead, we have serendipitously found three submm continuum sources in the observed sky area. One appears to be the quasar Q2233+131 itself while the other two sources are newly identified submm galaxies (SMGs), called SMG1 and SMG2 in this paper. They are located at a separation of 4."7 and 8."1 from Q2233+131, respectively. Their 646 μm fluxes are 6.35 mJy and 6.43 mJy, respectively, being higher than that of Q2233+131, 3.62 mJy. Since these two SMGs are not detected in the optical images obtained with the Hubble Space Telescope and the Subaru Telescope, they have a very red spectral energy distribution. It is, therefore, suggested that they are high-redshift galaxies or very dusty galaxies at intermediate redshift, although we cannot rule out the possibility that they are optically very faint SMG analogs at low redshift. Follow-up observations will be necessary to explore the nature of this interesting region.

DOI： 10.1093/pasj/psaa004

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掲載種別：研究論文（学術雑誌）   出版者・発行元：Astrophysical Journal  

We report the detection of a noncorotating gas component in a bright unlensed submillimeter galaxy at z = 4.3, hosting a compact starburst. Atacama Large Millimeter/submillimeter Array 0.″17 and 0.″09 resolution observations of [C ii] emission clearly demonstrate that the gas kinematics are characterized by an ordered rotation. After subtracting the best-fit model of a rotating disk, we kinematically identify two residual components in the channel maps. Both observing simulations and analysis of dirty images confirm that these two subcomponents are not artificially created by noise fluctuations and beam deconvolution. One of the two has a velocity offset of 200 km s-1 and a physical separation of 2 kpc from the primary disk and is located along the kinematic minor axis of disk rotation. We conclude that this gas component is falling into the galaxy from a direction perpendicular to the disk rotation. The accretion of such small noncorotating gas components could stimulate violent disk instability, driving radial gas inflows into the center of galaxies and leading to formation of in situ clumps such as identified in dust continuum and CO. We require more theoretical studies on high gas fraction mergers with mass ratio of 1: > 10 to verify this process.

DOI： 10.3847/1538-4357/ab64f4

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その他リンク： https://iopscience.iop.org/article/10.3847/1538-4357/ab64f4

出版者・発行元：arXiv e-prints  

We report on the detection of the [CII] 157.7 $\mu$m emission from the Lyman break galaxy (LBG) MACS0416_Y1 at z = 8.3113, by using the Atacama Large Millimeter/submillimeter Array (ALMA). The luminosity ratio of [OIII] 88 $\mu$m (from previous campaigns) to [CII] is 9.31 $\pm$ 2.6, indicative of hard interstellar radiation fields and/or a low covering fraction of photo-dissociation regions. The emission of [CII] is cospatial to the 850 $\mu$m dust emission (90 $\mu$m rest-frame, from previous campaigns), however the peak [CII] emission does not agree with the peak [OIII] emission, suggesting that the lines originate from different conditions in the interstellar medium. We fail to detect continuum emission at 1.5 mm (160 $\mu$m rest-frame) down to 18 $\mu$Jy (3$\sigma$). This nondetection places a strong limit on the dust spectrum, considering the 137 $\pm$ 26 $\mu$Jy continuum emission at 850 $\mu$m. This suggests an unusually warm dust component (T $&gt;$ 80 K, 90% confidence limit), and/or a steep dust-emissivity index ($\beta_{\rm dust}$ $&gt;$ 2), compared to galaxy-wide dust emission found at lower redshifts (typically T $\sim$ 30 - 50 K, $\beta_{\rm dust}$ $\sim$ 1 - 2). If such temperatures are common, this would reduce the required dust mass and relax the dust production problem at the highest redshifts. We therefore warn against the use of only single-wavelength information to derive physical properties, recommend a more thorough examination of dust temperatures in the early Universe, and stress the need for instrumentation that probes the peak of warm dust in the Epoch of Reionization....

arXiv

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掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：Proceedings of SPIE - The International Society for Optical Engineering  

We present a conceptual study of a large format imaging spectrograph for next-generation large (50-m class) single-dish telescopes, i.e., the Large Submillimeter Telescope (LST) and Atacama Large Aperture Submillimeter Telescope (AtLAST). Recent discoveries of high-redshift star-forming galaxies at z=8-9 and candidate quiescent galaxies at z∼6 indicate the onset of earliest star formation just a few 100 million years after the Big Bang (i.e., z = 12-15), and LST/AtLAST will provide a unique pathway to uncover spectroscopically-identified ''first forming galaxies'' in the pre-reionization era, once it will be equipped with a large format imaging spectrograph. We describe the preliminary of 3-band, medium resolution (R=2000) imaging spectrograph with ∼1.5 M detectors in total based on the KATANA concept (Karatsu et al.∼2019), which exploits technologies of the integrated superconducting spectrometer (ISS) and a large-format imaging array like A-MKID.

DOI： 10.1117/12.2561238

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出版者・発行元：Proceedings of the International Astronomical Union  

The ALMA twenty-six arcmin2 survey of GOODS-S at one millimeter (ASAGAO) is a deep (1σ ∼61μJy/beam) and wide area (26 arcmin2) survey on a contiguous field at 1.2 mm. By combining with archival data, we obtained a deeper map in the same region (1σ ∼30μJy/beam-1, synthesized beam size 0.59″ × 0.53″), providing the largest sample of sources (25 sources at 5σ, 45 sources at 4.5σ) among ALMA blank-field surveys. The median redshift of the 4.5σ sources is 2.4. The number counts shows that 52% of the extragalactic background light at 1.2 mm is resolved into discrete sources. We create IR luminosity functions (LFs) at z = 1-3, and constrain the faintest luminosity of the LF at 2 < z < 3. The LFs are consistent with previous results based on other ALMA and SCUBA-2 observations, which suggests a positive luminosity evolution and negative density evolution.

DOI： 10.1017/S1743921319009542

Scopus

出版者・発行元：Proceedings of the International Astronomical Union  

Galaxies and nuclei in dense environment at high redshift provide a good laboratory to investigate accelerated, most extreme evolution of galaxies. The SSA22 proto-cluster at z = 3.1 is known to have a three-dimensional 50 (comoving) Mpc-scale filamentary structure, traced by Lyα emitters, which makes the field a suitable target in this regard. To identify dust-obscured star-formation, a contiguous 20 arcmin2 region at the node of the cosmic structure was observed in ALMA band 6. In total 57 ALMA sources have been identified above 5σ, which makes the field one of the richest field in ALMA-identified (sub)millimeter galaxies. The follow-up spectroscopy confirmed about 20 sources as exact proto-cluster members so far. Together with high X-ray AGN fraction, our results suggest that the vigorous star formation activity and the growth of super massive black holes occurred simultaneously in the densest regions at z ∼3.

DOI： 10.1017/S1743921319009591

Scopus

掲載種別：研究論文（学術雑誌）   出版者・発行元：Publications of the Astronomical Society of Japan  

We present ALMA [C II] line and far-infrared (FIR) continuum observations of three z > 6 low-luminosity quasars (M1450 > –25 mag) discovered by our Subaru Hyper Suprime-Cam (HSC) survey. The [C II] line was detected in all three targets with luminosities of (2.4–9.5) × 108 L⊙, about one order of magnitude smaller than optically luminous (M1450 ≲ –25 mag) quasars. The FIR continuum luminosities range from < 9 × 1010 L⊙ (3 σ limit) to ∼2 × 1012 L⊙, indicating a wide range in star formation rates in these galaxies. Most of the HSC quasars studied thus far show [C II]/FIR luminosity ratios similar to local star-forming galaxies. Using the [C II]-based dynamical mass (Mdyn) as a surrogate for bulge stellar mass (Mbulge), we find that a significant fraction of low-luminosity quasars are located on or even below the local MBH–Mbulge relation, particularly at the massive end of the galaxy mass distribution. In contrast, previous studies of optically luminous quasars have found that black holes are overmassive relative to the local relation. Given the low luminosities of our targets, we are exploring the nature of the early co-evolution of supermassive black holes and their hosts in a less biased way. Almost all of the quasars presented in this work are growing their black hole mass at a much higher pace at z ∼ 6 than the parallel growth model, in which supermassive black holes and their hosts grow simultaneously to match the local MBH–Mbulge relation at all redshifts. As the low-luminosity quasars appear to realize the local co-evolutionary relation even at z ∼ 6, they should have experienced vigorous starbursts prior to the currently observed quasar phase to catch up with the relation.

DOI： 10.1093/pasj/psz096

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arXiv

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掲載種別：研究論文（学術雑誌）   出版者・発行元：Proceedings of the International Astronomical Union  

We present ALMA detection of the [O iii] 88 μm line and 850 μm dust continuum emission in a Y-dropout Lyman break galaxy, MACS0416-Y1. The [O iii] detection confirms the object with a spectroscopic redshift to be z = 8.3118±0.0003. The 850 μm continuum intensity (0.14 mJy) implies a large dust mass on the order of 4×106M . The ultraviolet-to-far infrared spectral energy distribution modeling, where the [O iii] emissivity model is incorporated, suggests the presence of a young (τage 4 Myr), star-forming (SFR 60M yr-1), and moderately metal-polluted (Z 0.2Z ) stellar component with a stellar mass of 3 × 108M . An analytic dust mass evolution model with a single episode of star formation does not reproduce the metallicity and dust mass in 4 Myr, suggesting an underlying evolved stellar component as the origin of the dust mass.

DOI： 10.1017/s1743921319002436

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Science  

Cosmological simulations predict that the Universe contains a network of intergalactic gas filaments, within which galaxies form and evolve. However, the faintness of any emission from these filaments has limited tests of this prediction. We report the detection of rest-frame ultraviolet Lyman-a radiation from multiple filaments extending more than one megaparsec between galaxies within the SSA22 protocluster at a redshift of 3.1. Intense star formation and supermassive black-hole activity is occurring within the galaxies embedded in these structures, which are the likely sources of the elevated ionizing radiation powering the observed Lyman-a emission. Our observations map the gas in filamentary structures of the type thought to fuel the growth of galaxies and black holes in massive protoclusters.

DOI： 10.1126/science.aaw5949

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PubMed

arXiv

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Astrophysical Journal  

We have obtained three-dimensional maps of the universe in ∼200 × 200 × 80 comoving Mpc3 (cMpc3) volumes each at z = 5.7 and 6.6 based on a spectroscopic sample of 179 galaxies that achieves ⪆80% completeness down to the Lyα luminosity of, based on our Keck and Gemini observations and the literature. The maps reveal filamentary large-scale structures and two remarkable overdensities made out of at least 44 and 12 galaxies at z = 5.692 (z57OD) and z = 6.585 (z66OD), respectively, making z66OD the most distant overdensity spectroscopically confirmed to date, with >10 spectroscopically confirmed galaxies. We compare spatial distributions of submillimeter galaxies at z ≃ 4-6 with our z = 5.7 galaxies forming the large-scale structures, and detect a 99.97% signal of cross-correlation, indicative of a clear coincidence of dusty star-forming galaxy and dust-unobscured galaxy formation at this early epoch. The galaxies in z57OD and z66OD are actively forming stars with star-formation rates (SFRs) ⪆5 times higher than the main sequence, and particularly the SFR density in z57OD is 10 times higher than the cosmic average at the redshift (a.k.a. the Madau-Lilly plot). Comparisons with numerical simulations suggest that z57OD and z66OD are protoclusters that are progenitors of the present-day clusters with halo masses of ∼1014 M o&dot;

DOI： 10.3847/1538-4357/ab2cd5

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その他リンク： https://iopscience.iop.org/article/10.3847/1538-4357/ab2cd5

掲載種別：研究論文（学術雑誌）   出版者・発行元：Astrophysical Journal Letters  

We report the first detection obtained with the Atacama Large Millimeter/submillimeter Array of the [N ii] 122 μm line emission from a galaxy group BRI 1202-0725 at z = 4.69 consisting of a quasi-stellar object (QSO) and a submillimeter-bright galaxy (SMG). Combining this with a detection of [N ii] 205 μm line in both galaxies, we constrain the electron densities of the ionized gas based on the line ratio of [N ii] 122/205. The derived electron densities are and cm-3 for the SMG and the QSO, respectively. The electron density of the SMG is similar to that of the Galactic Plane and to the average of the local spirals. However, higher electron densities (by up to a factor of three) could be possible for systematic uncertainties of the line flux estimates. The electron density of the QSO is comparable to high-z star-forming galaxies at z = 1.5-2.3, obtained using rest-frame optical lines and with the lower limits suggested from stacking analysis on lensed starbursts at z = 1-3.6 using the same tracer of [N ii]. Our results suggest a large scatter of electron densities in global scale at fixed star formation rates for extreme starbursts. The success of the [N ii] 122 μm and 205 μm detections at z = 4.69 demonstrates the power of future systematic surveys of extreme starbursts at z > 4 for probing the interstellar medium conditions and the effects on surrounding environments.

DOI： 10.3847/2041-8213/ab412e

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arXiv

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掲載種別：研究論文（学術雑誌）   出版者・発行元：Astrophysical Journal  

We present a study of the gas kinematics of star-forming galaxies associated with protocluster 4C 23.56 at z = 2.49 using 0.″4 resolution CO (4-3) data taken with ALMA. Eleven Hα emitters (HAEs) are detected in CO (4-3), including six HAEs that were previously detected in CO (3-2) at a coarser angular resolution. The detections in both CO lines are broadly consistent in the line widths and the redshifts, confirming both detections. With an increase in the number of spectroscopic redshifts, we confirm that the protocluster is composed of two merging groups with a total halo mass of log (M cl/M o) = 13.4-13.6, suggesting that the protocluster would evolve into a Virgo-like cluster (>1014 M o). We compare the CO line widths and the CO luminosities with other (proto)clusters (n gal = 91) and general field (n gal = 80) galaxies from other studies. The 4C 23.56 protocluster galaxies have CO line widths and luminosities comparable to other protocluster galaxies on average. On the other hand, the CO line widths are on average broader by ≈50% compared to field galaxies, while the median CO luminosities are similar. The broader line widths can be attributed to both effects of unresolved gas-rich mergers and/or compact gas distribution, which is supported by our limited but decent angular resolution observations and the size estimate of three galaxies. Based on these results, we argue that gas-rich mergers may play a role in the retention of the specific angular momentum to a value similar to that of field populations during cluster assembly, though we need to verify this with a larger number of samples.

DOI： 10.3847/1538-4357/ab3b5b

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arXiv

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出版者・発行元：Publications of the Astronomical Society of Japan  

We present new ALMA observations and physical properties of a Lyman break galaxy at z = 7.15. Our target, B14-65666, has a bright ultra-violet (UV) absolute magnitude, MUV ≈ -22.4, and has been spectroscopically identified in Lyα with a small rest-frame equivalent width of ≈4 Å. A previous Hubble Space TElescope (HST) image has shown that the target is composed of two spatially separated clumps in the rest-frame UV. With ALMA, we have newly detected spatially resolved [O iii] 88 μm, [C ii] 158 μm, and their underlying dust continuum emission. In the whole system of B14-65666, the [O iii] and [C ii] lines have consistent redshifts of 7.1520 ± 0.0003, and the [O iii] luminosity, (34.4 ± 4.1) × 108 Lo, is about three times higher than the [C ii] luminosity, (11.0 ± 1.4) × 108 Lo. With our two continuum flux densities, the dust temperature is constrained to be Td ≈ 50-60 K under the assumption of a dust emissivity index of βd = 2.0-1.5, leading to a large total infrared luminosity of LTIR ≈ 1 × 1012 Lo. Owing to our high spatial resolution data, we show that the [O iii] and [C ii] emission can be spatially decomposed into two clumps associated with the two rest-frame UV clumps whose spectra are kinematically separated by ≈200 km s-1. We also find these two clumps have comparable UV, infrared, [O iii], and [C ii] luminosities. Based on these results, we argue that B14-65666 is a starburst galaxy induced by a major merger. The merger interpretation is also supported by the large specific star formation rate (defined as the star formation rate per unit stellar mass), sSFR = 260+119-57:Gyr-1, inferred from our SED fitting. Probably, a strong UV radiation field caused by intense star formation contributes to its high dust temperature and the [O iii]-to-[C ii] luminosity ratio.

DOI： 10.1093/pasj/psz049

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arXiv

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掲載種別：研究論文（学術雑誌）  

We report Atacama Large Millimetre/submillimeter Array (ALMA) Cycle-5
follow-up observations of two candidate [CII] emitters at z ~ 6 in the ALMA
deep field in SSA22 (ADF22). The candidates were detected blindly in a Cycle-2
ALMA survey covering ~ 5 square arcmins, with a single tuning, along with two
CO lines associated with galaxies at lower redshifts. Various tests suggested
at least one of the two > 6-sigma [CII] candidates should be robust (Hayatsu et
al. 2017). Nevertheless, our new, deeper observations recover neither
candidate, demonstrating a higher contamination rate than expected. The cause
of the spurious detections is under investigation but at present it remains
unclarified.

DOI： 10.3847/2515-5172/ab3228

arXiv

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掲載種別：研究論文（学術雑誌）   出版者・発行元：Astrophysical Journal  

We report detections of two 1.2 mm continuum sources (S 1.2 mm ∼ 0.6 mJy) without any counterparts in the deep H- and/or K-band image (i.e., K-band magnitude ≳26 mag). These near-infrared-dark faint millimeter sources are uncovered by ASAGAO, a deep and wide-field (≃26 arcmin2) Atacama Large Millimeter/submillimeter Array (ALMA) 1.2 mm survey. One has a red IRAC (3.6 and 4.5 μm) counterpart, and the other has been independently detected at 850 and 870 μm using SCUBA2 and ALMA Band 7, respectively. Their optical-to-radio spectral energy distributions indicate that they can lie at z ≳ 3-5 and can be in the early phase of massive galaxy formation. Their contribution to the cosmic star formation rate density is estimated to be ∼1 ×10-3 M o yr-1 Mpc-3 if they lie somewhere in the redshift range of z ∼ 3-5. This value can be consistent with, or greater than, that of bright submillimeter galaxies (S 870 μm > 4.2 mJy) at z ∼ 3-5. We also uncover three more candidate near-infrared-dark faint ALMA sources without any counterparts (S 1.2 mm ∼ 0.45-0.86 mJy). These results show that an unbiased ALMA survey can reveal the dust-obscured star formation activities, which were missed in previous deep optical/near-infrared surveys.

DOI： 10.3847/1538-4357/ab0d22

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掲載種別：研究論文（学術雑誌）   出版者・発行元：Proceedings of the International Astronomical Union  

We present ALMA [CII] line and far-infrared (FIR) continuum observations of seven z > 6 low-luminosity quasars (M1450 > -25 mag) discovered by our on-going Subaru Hyper Suprime-Cam survey. The [CII] line was detected in all targets with luminosities of ∼(2-10) × 108 Lo, about one order of magnitude smaller than optically luminous quasars. Also found was a wide scatter of FIR continuum luminosity, ranging from LFIR < 1011Lo to 1/42 × 1012Lo. With the [CII]-based dynamical mass, we suggest that a significant fraction of low-luminosity quasars are located on or even below the local Magorrian relation, particularly at the massive end of the galaxy mass distribution. This is a clear contrast to the previous finding that luminous quasars tend to have overmassive black holes relative to the relation. Our result is expected to show a less-biased nature of the early co-evolution of black holes and their host galaxies.

DOI： 10.1017/s1743921319009487

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掲載種別：研究論文（学術雑誌）   出版者・発行元：Astrophysical Journal  

We present the results from Atacama Large Millimeter/submillimeter Array observations of [N ii] 205 μm, [C ii] 158 μm, and [O iii] 88 μm lines in an unlensed submillimeter galaxy at z = 4.3, COSMOS-AzTEC-1, hosting a compact starburst core with an effective radius of ∼1 kpc. The [C ii] and [N ii] emission are spatially resolved in 0.″3-resolution (1 kpc in radius). The kinematic properties of the [N ii] emission are consistent with those of the CO(4-3) and [C ii] emission, suggesting that the ionized gas feels the same gravitational potential as the associated molecular gas and photodissociation regions (PDRs). On the other hand, the spatial extent is different among the lines and dust continuum: the [C ii] emitting gas is the most extended and the dust is the most compact, leading to a difference of the physical conditions in the interstellar medium. We derive the incident far-ultraviolet flux and the hydrogen gas density through PDR modeling by properly subtracting the contribution of ionized gas to the total [C ii] emission. The observed [C ii] emission is likely produced by dense PDRs with cm-3 and G 0 = 103.5-3.75 in the central 1 kpc region and cm-3 and G 0 = 103.25-3.5 in the central 3 kpc region. We have also successfully measured the line ratio of [O iii]/[N ii] in the central 3 kpc region of COSMOS-AzTEC-1 at z = 4.3, which is the highest redshift where both nitrogen and oxygen lines are detected. Under the most likely physical conditions, the measured luminosity ratio of L [O iii]/L [N ii] = 6.4 ±; 2.2 indicates a near solar metallicity with Z gas = 0.7-1.0 Z o, suggesting a chemically evolved system at z = 4.3.

DOI： 10.3847/1538-4357/ab1415

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掲載種別：研究論文（学術雑誌）  

Recent ALMA detection of the bright [OIII] 88 um line at z = 9.11, indicates the onset of star formation at z 15. In order to uncover a large number of z=10-15 galaxies, we argue two possible pathways: (1) a blind spectroscopic survey of [OIII] 88 um line emitters, and (2) a high-cadence survey of transient sources to catch the pop-III GRBs. <P />...

arXiv

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掲載種別：研究論文（学術雑誌）   出版者・発行元：Publications of the Astronomical Society of Japan  

We present the results from ALMA CO(3-2) observations of 66 Hα-selected galaxies in three protoclusters around radio galaxies: PKS 1138-262 (z = 2.16), USS 1558-003 (z = 2.53), and 4C 23.56 (z = 2.49). The pointing areas have an overdensity of ∼100 compared to the mean surface number density of galaxies in field environments. We detect the CO emission line in 16 star-forming galaxies, including six previously published galaxies, to measure the molecular gas mass. In the stellar mass range of 10.5 < log (Mstar/M⊙) < 11.0, the protocluster galaxies have larger gas mass fractions and longer gas depletion timescales compared to the scaling relations established for field galaxies. On the other hand, the amounts of molecular gas in more massive galaxies with log (Mstar/M⊙) > 11.0 are comparable in mass to the scaling relation, or smaller. Our results suggest that the environmental effects on gas properties are mass dependent: in high-density environments, gas accretion through cosmic filaments is accelerated in less massive galaxies, while this is suppressed in the most massive system.

DOI： 10.1093/pasj/psz005

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記述言語：英語   出版者・発行元：IOP publishing  

We present the Atacama Large Millimeter/submillimeter Array detection of the [O iii] 88 μm line and rest-frame 90 μm dust continuum emission in a Y-dropout Lyman break galaxy (LBG), MACS0416-Y1 lying behind the Frontier Field cluster MACS J0416.1-2403. This [O iii] detection confirms the LBG with a spectroscopic redshift of z = 8.3118 ± 0.0003, making this object one of the farthest galaxies ever identified spectroscopically. The observed 850 μm flux density of 137 ± 26 μJy corresponds to a de-lensed total infrared (IR) luminosity of if assuming a dust temperature of T dust = 50 K and an emissivity index of β = 1.5, yielding a large dust mass of . The ultraviolet-to-far-IR spectral energy distribution modeling where the [O iii] emissivity model is incorporated suggests the presence of a young (τ age ≈ 4 Myr), star-forming ( yr -1 ), moderately metal-polluted (Z ≈ 0.2Z o ) stellar component with a mass of M star = 3 ×10 8 M o . An analytic dust mass evolution model with a single episode of star formation does not reproduce the metallicity and dust mass in τ age ≈ 4 Myr, suggesting a pre-existing evolved stellar component with M star ∼ 3 ×10 9 M and τ age ∼ 0.3 Gyr as the origin of the dust mass.

DOI： 10.3847/1538-4357/ab0374

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CiNii Research

arXiv

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掲載種別：研究論文（学術雑誌）   出版者・発行元：Astrophysical Journal  

We report Atacama Large Millimeter/submillimeter Array (ALMA) observations of 243-263 GHz absorption lines from Galactic diffuse molecular gas seen against three extragalactic radio-loud objects, J1717-337, J1625-254, and NRAO530. No significant absorption features were detected in our new sensitive ALMA Band 6 (λ ≃ 1.2 mm) spectra (1σ ≃ 2-4 mJy beam -1 with a velocity resolution of 1 km s -1 ), despite the fact that the obtained spectra cover the line frequencies of c-C 3 H 2 , CS, H 13 CN, HCO, H 13 CO + , SiO, and C 2 H, and that the lower transition absorption lines of these molecular species have been detected in ALMA Band 3 (λ ≃ 3 mm) observations toward these three Galactic molecular absorption systems. By combining the upper limits of the higher transitions that we obtain in this study and the archival detections of the lower transitions, we constrain the excitation temperatures of these species in the Galactic diffuse medium to be below 10 K, in spite of their PDR-like chemical states, where elevated column density ratios of HCO to H 13 CO + are previously reported. These constraints are in line with the widely accepted view of the diffuse molecular clouds, where the molecular excitation is almost in equilibrium with the cosmic microwave background, although its kinetic temperature can be a few tens of Kelvin. Molecular abundance patterns seem to be similar in the Galactic diffuse gas and nearby active galaxies observed with a kpc-scale beam, suggesting the importance of observations with a parsec-scale resolution, which can resolve individual molecular clouds.

DOI： 10.3847/1538-4357/aafa6f

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掲載種別：研究論文（学術雑誌）   出版者・発行元：Publications of the Astronomical Society of Japan  

We present the survey design, data reduction, construction of images, and source catalog of the Atacama Large Millimeter/submillimeter Array (ALMA) twenty-six arcmin2 survey of GOODS-S at one millimeter (ASAGAO). ASAGAO is a deep (1 σ depth ∼ 61 μJy beam−1 for a 250 kλ-tapered map with a synthesized beam size of 0.51 × 0.45) and wide area (26 arcmin2) survey on a contiguous field at 1.2 mm. By combining with ALMA archival data in the GOODS-South field, we obtained a deeper map in the same region (1 σ depth ∼ 30 μJy beam−1 for a deep region with a 250 kλ-taper, and a synthesized beam size of 0.59 × 0.53), providing the largest sample of sources (25 sources at ≥5.0 σ, 45 sources at ≥4.5 σ) among ALMA blank-field surveys to date. The number counts show that 52+−118 % of the extragalactic background light at 1.2 mm is resolved into discrete sources at S1.2 mm > 135 μJy. We create infrared (IR) luminosity functions (LFs) in the redshift range of z = 1–3 from the ASAGAO sources with Ks-band counterparts, and constrain the faintest luminosity of the LF at 2.0 < z < 3.0. The LFs are consistent with previous results based on other ALMA and SCUBA-2 observations, which suggest a positive luminosity evolution and negative density evolution with increasing redshift. We find that obscured star-formation of sources with IR luminosities of log (LIR/L) 11.8 account for ≈60%–90% of the z ∼ 2 cosmic star-formation rate density.

DOI： 10.1093/pasj/psy104

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出版者・発行元：Publications of the Astronomical Society of Japan  

We present CO J = 4-3 line and 3 mm dust continuum observations of a 100 kpc-scale filamentary Lyα nebula (SSA22 LAB18) at z = 3.1 using the Atacama Large Millimeter/submillimeter Array (ALMA). We detected the CO J = 4-3 line at a systemic zCO = 3.093 ± 0.001 at 11 σ from one of the ALMA continuum sources associated with the Lyα filament. We estimated the CO J = 4-3 luminosity of L'CO(4−3) = (2.3 ± 0.2) × 109 K km s−1 pc2 for this CO source, which is one order of magnitude smaller than those of typical z > 1 dusty star-forming galaxies (DSFGs) of similar far-infrared luminosity LIR ∼ 1012 L☉. We derived a molecular gas mass of Mgas = (4.4+−0096) × 109 M☉ and a star-formation rate of SFR =270 ± 160 M☉ yr−1. We also estimated a gas depletion time of τdep = 17 ± 10 Myr, which is shorter than those of typical DSFGs. It is suggested that this source is in the transition phase from DSFG to a gas-poor, early-type galaxy. From ALMA to Herschel multi-band dust continuum observations, we measured a dust emissivity index β = 2.3 ± 0.2, which is similar to those of local gas-poor, early-type galaxies. From recent laboratory experiments, the specific chemical compositions needed to reproduce such a high β for interstellar dust at the submillimeter wavelengths. ALMA CO and multi-band dust continuum observations can constrain the evolutionary stage of high-redshift galaxies through τdep and β, and thus we can investigate the chemical composition of dust even in the early Universe.

DOI： 10.1093/pasj/psy087

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記述言語：英語   出版者・発行元：Nature  

Galaxies in the early Universe that are bright at submillimetre wavelengths (submillimetre-bright galaxies) are forming stars at a rate roughly 1,000 times higher than the Milky Way. A large fraction of the new stars form in the central kiloparsec of the galaxy1–3, a region that is comparable in size to the massive, quiescent galaxies found at the peak of cosmic star-formation history4 and the cores of present-day giant elliptical galaxies. The physical and kinematic properties inside these compact starburst cores are poorly understood because probing them at relevant spatial scales requires extremely high angular resolution. Here we report observations with a linear resolution of 550 parsecs of gas and dust in an unlensed, submillimetre-bright galaxy at a redshift of z = 4.3, when the Universe was less than two billion years old. We resolve the spatial and kinematic structure of the molecular gas inside the heavily dust-obscured core and show that the underlying gas disk is clumpy and rotationally supported (that is, its rotation velocity is larger than the velocity dispersion). Our analysis of the molecular gas mass per unit area suggests that the starburst disk is gravitationally unstable, which implies that the self-gravity of the gas is stronger than the differential rotation of the disk and the internal pressure due to stellar-radiation feedback. As a result of the gravitational instability in the disk, the molecular gas would be consumed by star formation on a timescale of 100 million years, which is comparable to gas depletion times in merging starburst galaxies5.

DOI： 10.1038/s41586-018-0443-1

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掲載種別：研究論文（学術雑誌）   出版者・発行元：Publications of the Astronomical Society of Japan  

To search for dust-obscured star-formation activity in the early Universe, it is essential to obtain a deep and wide submillimeter/millimeter map. The advent of the Atacama Large Millimeter/submillimeter Array (ALMA) has enabled us to obtain such maps with sufficiently high spatial resolution to be free from source confusion. We present a new 1.1 mm-wave map obtained by ALMA in the SSA22 field. The field contains a remarkable proto-cluster at z = 3.09; therefore, it is an ideal region to investigate the role of a large-scale cosmic web on dust-obscured star formation. The typical 1σ depth of our map is 73 μJy beam−1 with a 0.5 resolution. Combining the present survey with earlier, archived observations, we map an area of 20 arcmin2 (71 comoving Mpc2 at z = 3.09). Within the combined survey area we have detected 35 sources at a signal-to-noise ratio (S/N) >5, with flux densities of S1.1mm = 0.43-5.6 mJy, equivalent to star-formation rates of 100-1000 M yr−1 at z = 3.09, for a Chabrier initial mass function: 17 sources out of 35 are new detections. The cumulative number counts show an excess by a factor of three to five compared to blank fields. The excess suggests enhanced, dust-enshrouded star-formation activity in the proto-cluster on a 10 comoving Mpc scale, indicating accelerated galaxy evolution in this overdense region.

DOI： 10.1093/pasj/psy065

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出版者・発行元：Astrophysical Journal  

© 2018. The American Astronomical Society. All rights reserved.. We present morphological properties of dusty star-forming galaxies at z = 1-3 determined with the high-resolution (FWHM ∼ 0.″19) Atacama Large Milllimeter/submillimeter Array (ALMA) 1 mm map of our ASAGAO survey covering a 26 arcmin2area in GOODS-S. In conjunction with the ALMA archival data, our sample consists of 45 ALMA sources with infrared luminosity (LIR) range of ∼1011-1013Lo. To obtain an average rest-frame far-infrared (FIR) profile, we perform individual measurements and careful stacking of the ALMA sources using the uv-visibility method that includes positional-uncertainty and smoothing-effect evaluations through Monte Carlo simulations. We find that our sample has an average FIR-wavelength Sérsic index and effective radius of nFIR= 1.2 ± 0.2 and Re,FIR= 1.0-1.3 kpc, respectively, additionally with a point-source component at the center, indicative of the existence of active galactic nuclei. The average FIR profile agrees with a morphology of an exponential disk clearly distinguished from a de Vaucouleurs spheroidal profile (Sérsic index of 4). We also examine the rest-frame optical Sérsic index noptand effective radius Re,optwith deep Hubble Space Telescope (HST) images. Interestingly, we obtain nopt= 0.9 ± 0.3 (≃nFIR) and Re,opt= 3.2 ± 0.6 kpc (&gt;Re,FIR), suggesting that the dusty disk-like structure is embedded within a larger stellar disk. The rest-frame UV and FIR data of HST and ALMA provide us with a radial profile of the total star formation rate (SFR), where the infrared SFR dominates over the UV SFR at the center. Under the assumption of a constant SFR, a compact stellar distribution in z ∼ 1-2 compact quiescent galaxies (cQGs) is well reproduced, while a spheroidal stellar morphology of cQGs (nopt= 4) is not, suggestive of other important mechanism(s) such as dynamical dissipation.

DOI： 10.3847/1538-4357/aac6c4

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出版者・発行元：Publications of the Astronomical Society of Japan  

© 2018 The Author(s). We present our ALMA Cycle 4 measurements of the [C II] emission line and the underlying far-infrared (FIR) continuum emission from four optically low-luminosity (M1450&gt; -25) quasars at z ≳ 6 discovered by the Subaru Hyper Suprime Cam (HSC) survey. The [C II] line and FIR continuum luminosities lie in the ranges L[C II] = (3.8-10.2) × 108L· and LFIR = (1.2-2.0) × 1011L·, which are at least one order of magnitude smaller than those of optically-luminous quasars at z ≳ 6. We estimate the star formation rates (SFRs) of our targets as ≲ 23-40 M· yr-1. Their line and continuum-emitting regions are marginally resolved, and found to be comparable in size to those of optically-luminous quasars, indicating that their SFR or likely gas mass surface densities (key controlling parameter of mass accretion) are accordingly different. The L[C II]/LFIR ratios of the hosts, ≲ (2.2- 8.7) × 10-3, are fully consistent with local star-forming galaxies. Using the [C II] dynamics, we derived their dynamical masses within a radius of 1.5-2.5 kpc as ≲ (1.4-8.2) × 1010M·. By interpreting these masses as stellar ones, we suggest that these faint quasar hosts are on or even below the star-forming main sequence at z ∼ 6, i.e., they appear to be transforming into quiescent galaxies. This is in contrast to the optically-luminous quasars at those redshifts, which show starburst-like properties. Finally, we find that the ratios of black hole mass to host galaxy dynamical mass of most of the low-luminosity quasars, including the HSC ones, are consistent with the local value. The mass ratios of the HSC quasars can be reproduced by a semi-analytical model that assumes merger-induced black hole host galaxy evolution.

DOI： 10.1093/pasj/psy026

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記述言語：英語   出版者・発行元：Nature  

A fundamental quest of modern astronomy is to locate the earliest galaxies and study how they influenced the intergalactic medium a few hundred million years after the Big Bang 1-3 . The abundance of star-forming galaxies is known to decline 4,5 from redshifts of about 6 to 10, but a key question is the extent of star formation at even earlier times, corresponding to the period when the first galaxies might have emerged. Here we report spectroscopic observations of MACS1149-JD1 6, a gravitationally lensed galaxy observed when the Universe was less than four per cent of its present age. We detect an emission line of doubly ionized oxygen at a redshift of 9.1096 ± 0.0006, with an uncertainty of one standard deviation. This precisely determined redshift indicates that the red rest-frame optical colour arises from a dominant stellar component that formed about 250 million years after the Big Bang, corresponding to a redshift of about 15. Our results indicate that it may be possible to detect such early episodes of star formation in similar galaxies with future telescopes.

DOI： 10.1038/s41586-018-0117-z

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掲載種別：研究論文（学術雑誌）   出版者・発行元：Astrophysical Journal  

We investigate the X-ray active galactic nucleus (AGN) properties of millimeter galaxies in the Great Observatories Origins Deep Survey South (GOODS-S) field detected with the Atacama Large Millimeter/submillimeter Array (ALMA), by utilizing the Chandra 7-Ms data, the deepest X-ray survey to date. Our millimeter galaxy sample comes from the ASAGAO survey covering 26 arcmin2 (12 sources at a 1.2 mm flux-density limit of mJy), supplemented by the deeper but narrower 1.3 mm survey of a part of the ASAGAO field by Dunlop et al. Ofthe 25 total millimeter galaxies, 14 have Chandra counterparts. The observed AGN fractions at are found to be 90+8-19% and 57+23-25% for the ultra-luminous and luminous infrared galaxies with log LIR/L⊙ = 12-12.8 and log IR/L⊙ = 11.5-12, respectively. The majority (∼2/3) of the ALMA and/or Herschel detected X-ray AGNs at z = 1.5-3 appear to be star-formation-dominant populations, having / ratios smaller than the "simultaneous evolution" value expected from the local black-hole-mass-to-stellar-mass (-M ∗) relation. On the basis of the and stellar mass relation, we infer that a large fraction of star-forming galaxies at have black hole masses that are smaller than those expected from the local -M ∗ relation. This contrasts previous reports on luminous AGNs at the same redshifts detected in wider and shallower surveys, which are subject to selection biases against lower luminosity AGNs. Our results are consistent with an evolutionary scenario in which star formation occurs first, and an AGN-dominant phase follows later, in objects that finally evolve into galaxies with classical bulges.

DOI： 10.3847/1538-4357/aa9f10

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

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掲載種別：研究論文（学術雑誌）   出版者・発行元：Astrophysical Journal  

© 2017. The American Astronomical Society. All rights reserved. We study the heating mechanisms and Lyα escape fractions of 35 Lyα blobs (LABs) at z ≈ 3.1 in the SSA22 field. Dust continuum sources have been identified in 11 of the 35 LABs, all with star formation rates (SFRs) above 100 Moyr-1. Likely radio counterparts are detected in 9 out of 29 investigated LABs. The detection of submillimeter dust emission is more linked to the physical size of the Lyα emission than to the Lyα luminosities of the LABs. A radio excess in the submillimeter/radio-detected LABs is common, hinting at the presence of active galactic nuclei. Most radio sources without X-ray counterparts are located at the centers of the LABs. However, all X-ray counterparts avoid the central regions. This may be explained by absorption due to exceptionally large column densities along the line-of-sight or by LAB morphologies, which are highly orientation dependent. The median Lyα escape fraction is about 3% among the submillimeter-detected LABs, which is lower than a lower limit of 11% for the submillimeter-undetected LABs. We suspect that the large difference is due to the high dust attenuation supported by the large SFRs, the dense large-scale environment as well as large uncertainties in the extinction corrections required to apply when interpreting optical data.

DOI： 10.3847/1538-4357/aa960f

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出版者・発行元：Astrophysical Journal Letters  

We report the study of the far-infrared (IR) sizes of submillimeter galaxies (SMGs) in relation to their dustobscured star formation rate (SFR) and active galactic nuclei (AGN) presence, determined using mid-IR photometry. We determined the millimeter-wave (λobs = 1100 μm) sizes of 69 Atacama Large Millimeter/ submillimeter Array (ALMA)-identified SMGs, selected with ≥10 δ confidence on ALMA images (F1100 μm = 1.7-7.4 mJy). We found that all of the SMGs are located above an avoidance region in the sizeflux plane, as expected by the Eddington limit for star formation. In order to understand what drives the different millimeter-wave sizes in SMGs, we investigated the relation between millimeter-wave size and AGN fraction for 25 of our SMGs at z=1-3. We found that the SMGs for which the mid-IR emission is dominated by star formation or AGN have extended millimeter-sizes, with respective median Rc,e = 1.6-0.21+0.34 and 1.5 -0.24+0.93 kpc. Instead, the SMGs for which the mid-IR emission corresponds to star-forming/AGN composites have more compact millimeter-wave sizes, with median Rc,e1.0 -0.20+0.20kpc. The relation between millimeter-wave size and AGN fraction suggests that this size may be related to the evolutionary stage of the SMG. The very compact sizes for composite star-forming/AGN systems could be explained by supermassive black holes growing rapidly during the SMG coalescing, star-formation phase.

DOI： 10.3847/2041-8213/aa9572

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出版者・発行元：Astrophysical Journal  

We present the results of a blind millimeter line emitter search using ALMA Band 6 data with a single-frequency tuning toward four gravitational lensing clusters (RXJ1347.5-1145, Abell S0592, MACS J0416.1-2403, and Abell 2744). We construct 3D signal-to-noise ratio (S/N) cubes with 60 and 100 MHz binning, and search for millimeter line emitters. We do not detect any line emitters with a peak S/N > 5, although we do find a line emitter candidate with a peak S/N ≃ 4.5. These results provide upper limits to the CO(3-2), CO(4-3), CO(5-4), and [C ii] luminosity functions at z ≃ 0.3, 0.7, 1.2, and 6, respectively. Because of the magnification effect of gravitational lensing clusters, the new data provide the first constraints on the CO and [C ii] luminosity functions at unprecedentedly low luminosity levels, i.e., down to ≲10-3 - 10-1 Mpc-3 dex-1 at L'CO ∼ 108-1010 K km s-1 pc2 and ≲10-3-10-2 Mpc-3 dex-1 at L[CII] ∼ 108-1010 L⊙, respectively. Although the constraints to date are not yet stringent, we find that the evolution of the CO and [C ii] luminosity functions are broadly consistent with the predictions of semi-analytical models. This study demonstrates that the wide observations with a single-frequency tuning toward gravitational lensing clusters are promising for constraining the CO and [C ii] luminosity functions.

DOI： 10.3847/1538-4357/aa80e0

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Monthly Notices of the Royal Astronomical Society  

We present the near-infrared high-resolution imaging of an extremely dense group of galaxies at the core of the protocluster at z = 3.09 in the SSA22 field by using the adaptive optics AO188 and the Infrared Camera and Spectrograph on board the Subaru Telescope. The wide morphological variety of them suggests their ongoing dramatic evolutions. One of the two quiescent galaxies (QGs), the most massive one in the group, is a compact elliptical with an effective radius re = 1.37 ± 0.75 kpc. It supports the two-phase formation scenario of giant ellipticals today that a massive compact elliptical is formed at once and evolves in size and stellar mass by a series of mergers. Since this object is a plausible progenitor of a brightest cluster galaxy of one of the most massive clusters today, it requires strong size (≳10) and stellar mass (~ four times by z = 0) growths. Another QG hosts an active galactic nucleus and is fitted with a model composed from a nuclear component and Sérsic model. It shows a spatially extended [O III] λ5007 emission line compared to the continuum emission, plausible evidence of outflows. Massive star-forming galaxies (SFGs) in the group are two to three times larger than the field SFGs at similar redshift. Although we obtained the K-band image deeper than the previous one, we found no new candidate members. This implies a physical deficiency of low-mass galaxies with stellar mass M ≲ 4 × 1010M⊙ and/or poor detection completeness of them owing to their diffuse morphologies.

DOI： 10.1093/mnras/stx920

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出版者・発行元：Astrophysical Journal  

We investigate gas contents of star-forming galaxies associated with protocluster 4C23.56 at z = 2.49 by using the redshifted CO (3-2) and 1.1 mm dust continuum with the Atacama Large Millimeter/submillimeter Array. The observations unveil seven CO detections out of 22 targeted Hα emitters (HAEs) and four out of 19 in 1.1 mm dust continuum. They have high stellar mass (M∗ > 4 × 1010 Mo) and exhibit a specific star-formation rate typical of main-sequence star-forming galaxies at z ∼ 2.5. Different gas-mass estimators from CO (3-2) and 1.1 mm yield consistent values for simultaneous detections. The gas mass (Mgas) and gas fraction (fgas) are comparable to those of field galaxies, with Mgas = [0.3, 1.8] × 1011 × (αco/4.36 × A(Z))) M⊙, where αco is the CO-to-H2 conversion factor and A(Z) is the additional correction factor for the metallicity dependence of αco, and fgas = 0.53 ± 0.07 from CO (3-2). Our measurements place a constraint on the cosmic gas density of high-z protoclusters, indicating that the protocluster is characterized by a gas density higher than that of the general fields by an order of magnitude. We found p(H2) ∼ 5 × 109 M⊙ Mpc-3 with the CO(3-2) detections. The five ALMA CO detections occur in the region of highest galaxy surface density, where the density positively correlates with global star-forming efficiency (SFE) and stellar mass. Such correlations possibly indicate a critical role of the environment on early galaxy evolution at high-z protoclusters, though future observations are necessary for confirmation.

DOI： 10.3847/1538-4357/aa74c2

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Monthly Notices of the Royal Astronomical Society  

Using galaxies as background light sources to map intervening Ly α absorption is a novel approach to study the interplay among galaxies, the circumgalactic medium (CGM) and the intergalactic medium. Introducing a new measure of z = 3.1 HI Ly α absorption relative to the cosmic mean, ΔNB497, estimated from photometric data of star-forming galaxies at 3.3 ≲ z ≲ 3.5, we have made two-dimensional ΔNB497 maps in the z = 3.1 SSA22 protocluster region and two control fields (Subaru/XMM-Newton Deep Survey; Great Observatory Optical Deep Survey North) with a spatial resolution of ~5 comoving Mpc. The ΔNB497 measurements in the SSA22 field are systematically larger than those in the control fields, and this HI absorption enhancement extends more than 50 comovingMpc. The field-averaged (i.e. ~50 comovingMpc scale) ΔNB497 and the overdensity of Ly α emitters (LAEs) seem to be correlated, while there is no clear dependency of theΔNB497 on the local LAE overdensity in a few comoving Mpc scale. These results suggest that diffuse HI gas spreads out in/around the SSA22 protocluster. We have also found an enhancement of ΔNB497 at a projected distance < 100 physical kpc from the nearest z = 3.1 galaxies at least in the SSA22 field, which is probably due to HI gas associated with the CGM of individual galaxies. The HI absorption enhancement in the CGM-scale tends to be weaker around galaxies with stronger Ly α emission, which suggests that the Ly α escape fraction from galaxies depends on hydrogen neutrality in the CGM.

DOI： 10.1093/mnras/stx038

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掲載種別：研究論文（学術雑誌）   出版者・発行元：Publications of the Astronomical Society of Japan  

We report the identification of four millimeter line-emitting galaxies with the Atacama Large Milli/submillimeter Array (ALMA) in SSA22 Field (ADF22). We analyze the ALMA 1.1-mm survey data, with an effective survey area of 5 arcmin 2, frequency ranges of 253.1-256.8 and 269.1-272.8 GHz, angular resolution of 0.″7 and rms noise of 0.8 mJy beam -1 at 36 km s -1 velocity resolution. We detect four line-emitter candidates with significance levels above 6σ. We identify one of the four sources as a CO(9-8) emitter at z = 3.1 in a member of the proto-cluster known in this field. Another line emitter with an optical counterpart is likely a CO(4-3) emitter at z = 0.7. The other two sources without any millimeter continuum or optical/near-infrared counterpart are likely to be [C ii] emitter candidates at z = 6.0 and 6.5. The equivalent widths of the [C ii] candidates are consistent with those of confirmed high-redshift [C ii] emitters and candidates, and are a factor of 10 times larger than that of the CO(9-8) emitter detected in this search. The [C ii] luminosity of the candidates are 4-7 × 10 8 L ⊙. The star formation rates (SFRs) of these sources are estimated to be 10-20 M ⊙ yr -1 if we adopt an empirical [C ii] luminosity-SFR relation. One of them has a relatively low S/N ratio, but shows features characteristic of emission lines. Assuming that at least one of the two candidates is a [C ii] emitter, we derive a lower limit of [C ii]-based star formation rate density (SFRD) at z ∼ 6. The resulting value of >10 -2 M ⊙ yr -1 Mpc -3 is consistent with the dust-uncorrected UV-based SFRD. Future millimeter/submillimeter surveys can be used to detect a number of high-redshift line emitters, with which to study the star formation history in the early universe.

DOI： 10.1093/pasj/psx018

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出版者・発行元：Astrophysical Journal  

© 2017. The American Astronomical Society. All rights reserved.. We present the detailed characterization of two extremely red submillimeter galaxies (SMGs), ASXDF1100.053.1 and 231.1, with the Atacama Large Millimeter/submillimeter Array (ALMA) and the Jansky Very Large Array. These SMGs were originally selected using AzTEC at 1100 μm, and are observed by Herschel to be faint at 100-500 μm. Their (sub)millimeter colors are as red as - or redder - than known z ≳ 5 SMGs; indeed, ASXDF1100.053.1 is redder than HFLS 3, which lies at z =6.3. They are also faint and red in the near-/mid-infrared: ∼1 μJy at IRAC 4.5 μm and &lt;0.2 μJy in the Ksfilter. These SMGs are also faint in the radio waveband, where F6GHz=4.5 μJy for ASXDF1100.053.1 and F1.4GHz=28 μJy for ASXDF1100.231.1, suggestive of z=6.5+1.4-1.1and z= 4.1+0.6-0.7and for ASXDF1100.053.1 and 231.1, respectively. ASXDF1100.231.1 has a flux excess in the 3.6 μm filter, probably due to Hα emission at z =4-5. Derived properties of ASXDF1100.053.1 for z =5.5-7.5 and 231.1 for z =3.5-5.5 are as follows: their infrared luminosities are [6.5 -7.4] ×1012and [4.2-4.5] ×1012Lo; their stellar masses are [0.9-2] ×1011and [0.4-3] ×1010Mo; their circularized half-light radii in the ALMA maps are ∼1 and ≲0.2 kpc (∼2-3 kpc for 90% of the total flux). Last, their surface infrared luminosity densities, ΣIR, are ∼1 ×1012and ≳1.5 ×1013Lokpc-2, similar to values seen for local (U)LIRGs. These data suggest that ASXDF1100.053.1 and 231.1 are compact SMGs at z ≳ 4 and can plausibly evolve into z ≳ 3 compact quiescent galaxies.

DOI： 10.3847/1538-4357/835/2/286

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出版者・発行元：Astrophysical Journal  

We present results from a deep 2′ ×3′ (comoving scale of 3.7 Mpc ×5.5 Mpc at z = 3) survey at 1.1 mm, taken with the Atacama Large Millimeter/submillimeter Array (ALMA) in the SSA22 field. We observe the core region of a z = 3.09 protocluster, achieving a typical rms sensitivity of 60 μJy beam-1 at a spatial resolution of 0.″7. We detect 18 robust ALMA sources at a signal-to-noise ratio (S/N) > 5. Comparison between the ALMA map and a 1.1 mm map, taken with the AzTEC camera on the Atacama Submillimeter Telescope Experiment (ASTE), indicates that three submillimeter sources discovered by the AzTEC/ASTE survey are resolved into eight individual submillimeter galaxies (SMGs) by ALMA. At least 10 of our 18 ALMA SMGs have spectroscopic redshifts of z ≃ 3.09, placing them in the protocluster. This shows that a number of dusty starburst galaxies are forming simultaneously in the core of the protocluster. The nine brightest ALMA SMGs with S/N > 10 have a median intrinsic angular size of 0.32+0.13-0.06(2.4+10-0.4 physical kpc at z = 3.09), which is consistent with previous size measurements of SMGs in other fields. As expected, the source counts show a possible excess compared to the counts in the general fields at S 1.1mm ≥ 1.0 mJy, due to the protocluster. Our contiguous mm mapping highlights the importance of large-scale structures on the formation of dusty starburst galaxies.

DOI： 10.3847/1538-4357/835/1/98

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出版者・発行元：Astrophysical Journal Letters  

© 2017. The American Astronomical Society. All rights reserved. We report the result from observations conducted with the Atacama Large Millimeter/submillimeter Array (ALMA) to detect [C ii] 158 μm fine structure line emission from galaxies embedded in one of the most spectacular Lyα blobs (LABs) at z = 3.1, SSA22-LAB1. Of three dusty star-forming galaxies previously discovered by ALMA 860 μm dust continuum survey toward SSA22-LAB1, we detected the [C ii] line from one, LAB1-ALMA3 at z = 3.0993 0.0004. No line emission was detected, associated with the other ALMA continuum sources or from three rest-frame UV/optical selected zspec≃ 3.1 galaxies within the field of view. For LAB1-ALMA3, we find relatively bright [C ii] emission compared to the infrared luminosity (L[C ii]LIR≈ 0.01) and an extremely high [C ii] 158 μm and [N ii] 205 μm emission line ratio (L[C ii]L[N ii]&gt; 55). The relatively strong [C ii] emission may be caused by abundant photodissociation regions and sub-solar metallicity, or by shock heating. The origin of the unusually strong [C ii] emission could be causally related to the location within the giant LAB, although the relationship between extended Lyα emission and interstellar medium conditions of associated galaxies is yet to be understand.

DOI： 10.3847/2041-8213/834/2/L16

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掲載種別：研究論文（学術雑誌）   出版者・発行元：Astrophysical Journal  

We present stacking analyses on our ALMA deep 1.1 mm imaging in the Subaru/XMM-Newton Deep Survey Field using 1.6 and 3.6 μm selected galaxies in the CANDELS WFC3 catalog. We detect a stacked flux of ∼0.03-0.05 mJy, corresponding to LIR > 1011 L Ȯ and a star formation rate (SFR)sim; 15 M Ȯ of yr-1 at z = 2. We find that galaxies that are brighter in the rest-frame near-infrared tend to also be brighter at 1.1 mm, and galaxies fainter than m3 μm =23 do not produce detectable 1.1 mm emission. This suggests a correlation between stellar mass and SFR, but outliers to this correlation are also observed, suggesting strongly boosted star formation or extremely large extinction. We also find tendencies that redder galaxies and galaxies at higher redshifts are brighter at 1.1 mm. Our field contains z ∼2.5 Hα emitters and a bright single-dish source. However, we do not find evidence of bias in our results caused by the bright source. By combining the fluxes of sources detected by ALMA and fluxes of faint sources detected with stacking, we recover a 1.1 mm surface brightness of up to 20.3 ±1.2 Jy deg-2, comparable to the extragalactic background light measured by COBE. Based on the fractions of optically faint sources in our and previous ALMA studies and the COBE measurements, we find that approximately half of the cosmic star formation may be obscured by dust and missed by deep optical surveys. Much deeper and wider ALMA imaging is therefore needed to better constrain the obscured cosmic star formation history.

DOI： 10.3847/1538-4357/833/2/195

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出版者・発行元：Publications of the Astronomical Society of Japan  

We present a multiwavelength analysis of five submillimeter sources (S1.1mm = 0.54-2.02 mJy) that were detected during our 1.1 mm deep continuum survey in the Subaru/XMM-Newton Deep Survey Field (SXDF)-UDS-CANDELS field (2 arcmin2, 1σ = 0.055 mJy beam-1) using the Atacama Large Millimeter/submillimeter Array (ALMA). The two brightest sources correspond to a known single-dish (AzTEC) selected bright submillimeter galaxy (SMG), whereas the remaining three are faint SMGs newly uncovered by ALMA. If we exclude the two brightest sources, the contribution of the ALMA-detected faint SMGs to the infrared extragalactic background light is estimated to be ∼ 4.1+5.4-3.0Jy deg-2, which corresponds to ∼ 16+22-12 of the infrared extragalactic background light. This suggests that their contribution to the infrared extragalactic background light is as large as that of bright SMGs. We identified multiwavelength counterparts of the five ALMA sources. One of the sources (SXDF-ALMA3) is extremely faint in the optical to near-infrared region despite its infrared luminosity (LIR ≃ 1 × 1012, L⊙; or SFR ≃ 100 M⊙ yr-1). By fitting the spectral energy distributions at the optical-to-near-infrared wavelengths of the remaining four ALMA sources, we obtained the photometric redshifts (zphoto) and stellar masses (M∗): zphoto ≃ 1.3-2.5, M∗ ≃ (3.5-9.5) × 1010 M⊙. We also derived their star formation rates (SFRs) and specific SFRs as ≃30-200 M⊙ yr-1 and ≃0.8-2 Gyr-1, respectively. These values imply that they are main sequence star-forming galaxies.

DOI： 10.1093/pasj/psw073

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Monthly Notices of the Royal Astronomical Society  

© 2016 The Authors. We exploit Atacama Large Interferometer Array (ALMA) 870 μm observations to measure the star formation rates (SFRs) of eight X-ray detected active galactic nuclei (AGNs) in a z ≈ 3.1 protocluster, four of which reside in extended Lyα haloes (often termed Lymanalpha blobs: LABs). Three of the AGNs are detected by ALMA and have implied SFRs of ≈220-410 M⊙ yr-1; the non-detection of the other five AGNs places SFR upper limits of ≲210 M⊙ yr-1. The mean SFR of the protocluster AGNs (≈110-210 M⊙ yr-1) is consistent (within a factor of ≈0.7-2.3) with that found for co-eval AGNs in the field, implying that the galaxy growth is not significantly accelerated in these systems. However, when also considering ALMA data from the literature, we find evidence for elevated mean SFRs (up-to a factor of ≈5.9 over the field) for AGNs at the protocluster core, indicating that galaxy growth is significantly accelerated in the central regions of the protocluster. We also show that all of the four protocluster LABs are associated with an ALMA counterpart within the extent of their Lyα emission. The SFRs of the ALMA sources within the LABs (≈150-410 M⊙ yr-1) are consistent with those expected for co-eval massive star-forming galaxies in the field. Furthermore, the two giant LABs (with physical extents of ≳100 kpc) do not host more luminous star formation than the smaller LABs, despite being an order of magnitude brighter in Lyα emission. We use these results to discuss star formation as the power source of LABs.

DOI： 10.1093/mnras/stw1509

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出版者・発行元：Astrophysical Journal Letters  

The central structure in three of the brightest unlensed z = 3-4 submillimeter galaxies is investigated through 0.″015-0.″05 (120-360 pc) 860 μm continuum images obtained using the Atacama Large Millimeter/submillimeter Array (ALMA). The distribution in the central kiloparsec in AzTEC1 and AzTEC8 is extremely complex, and they are composed of multiple ∼200 pc clumps. AzTEC4 consists of two sources that are separated by ∼1.5 kpc, indicating a mid-stage merger. The peak star formation rate densities in the central clumps are ∼300-3000 M o yr-1 kpc-2, suggesting regions with extreme star formation near the Eddington limit. By comparing the flux obtained by ALMA and Submillimeter Array, we find that 68%-90% of the emission is extended (≳1 kpc) in AzTEC4 and 8. For AzTEC1, we identify at least 11 additional compact (∼200 pc) clumps in the extended 3-4 kpc region. Overall, the data presented here suggest that the luminosity surface densities observed at ≲150 pc scales are roughly similar to that observed in local ULIRGs, as in the eastern nucleus of Arp 220. Between 10% and 30% of the 860 μm continuum is concentrated in clumpy structures in the central kiloparsec, while the remaining flux is distributed over ≳1 kpc regions, some of which could also be clumpy. These sources can be explained by a rapid inflow of gas such as a merger of gas-rich galaxies, surrounded by extended and clumpy starbursts. However, the cold mode accretion model is not ruled out.

DOI： 10.3847/2041-8205/829/1/L10

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掲載種別：研究論文（学術雑誌）   出版者・発行元：Monthly Notices of the Royal Astronomical Society  

We present a Herschel/Spectral and Photometric Imaging Receiver (SPIRE) survey of three protoclusters at z = 2-3 (2QZCluster, HS1700, SSA22). Based on the SPIRE colours (S350/S250 and S500/S350) of 250 μm sources, we selected high-redshift dusty star-forming galaxies potentially associated with the protoclusters. In the 2QZCluster field, we found a 4σ overdensity of six SPIRE sources around 4.5 arcmin (~2.2 Mpc) from a density peak of H α emitters at z = 2.2. In the HS1700 field, we found a 5σ overdensity of eight SPIRE sources around 2.1 arcmin (~1.0 Mpc) from a density peak of Lyman-break galaxies at z = 2.3. We did not find any significant overdensities in SSA22 field, but we found three 500 μm sources are concentrated 3 arcmin (~1.4 Mpc) east to the Ly α emitters overdensity. If all the SPIRE sources in these three overdensities are associated with protoclusters, the inferred star formation rate densities are 103-104 times higher than the average value at the same redshifts. This suggests that dusty star formation activity could be very strongly enhanced in z ~ 2-3 protoclusters. Further observations are needed to confirm the redshifts of the SPIRE sources and to investigate what processes enhance the dusty star formation activity in z ~ 2-3 protoclusters.

DOI： 10.1093/mnras/stw1237

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記述言語：英語   出版者・発行元：Science  

The physical properties and elemental abundances of the interstellarmedium in galaxies during cosmic reionization are important for understanding the role of galaxies in this process.We report the AtacamaLarge Millimeter/submillimeterArray detection of an oxygen emission line at awavelength of 88 micrometers froma galaxy at an epoch about 700million years after the Big Bang.The oxygen abundance of this galaxy is estimated at about one-tenth that of the Sun.The nondetection of farinfrared continuum emission indicates a deficiency of interstellar dust in the galaxy.Acarbon emission line at a wavelength of 158micrometers is also not detected, implying an unusually small amount of neutral gas.These properties might allow ionizing photons to escape into the intergalacticmedium.

DOI： 10.1126/science.aaf0714

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Publications of the Astronomical Society of Japan  

We report 1.1-mm number counts revealed with the Atacama Large Millimeter/ submillimeter Array (ALMA) in the Subaru/XMM-Newton Deep Survey Field (SXDF). The advent of ALMA enables us to reveal millimeter-wavelength number counts down to the faint end without source confusion. However, previous studies are based on the ensemble of serendipitously detected sources in fields originally targeting different sources and could be biased due to the clustering of sources around the targets. We derive number counts in the flux range of 0.2-2mJy by using 23 (4) sources detected in a continuous 2.0-arcmin2 area of the SXDF. The number counts are consistent with previous results within errors, suggesting that the counts derived from serendipitously detected sources are not significantly biased, although there could be field-to-field variation due to the small survey area. By using the best-fitting function of the number counts, we find that 40% of the extragalactic background light at 1.1mm is resolved at S1.1mm < 0.2mJy.

DOI： 10.1093/pasj/psw026

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記述言語：日本語   出版者・発行元：東京大学大学院理学系研究科・理学部  

土星の衛星エンセラダスに生命を育む海がある！？／自己抑制の仕組みでバランスを保つ植物の根／115億光年かなたの宇宙で見つかった怪物銀河の大集団

CiNii Research

出版者・発行元：Publications of the Astronomical Society of Japan  

We report on Atacama Large Millimeter/submillimeter Array (ALMA) detections of molecular absorption lines in Bands 3, 6, and 7 toward four radio-loud quasars, which were observed as the bandpass and complex gain calibrators. The absorption systems, three of which are newly detected, are found to be Galactic origin. Moreover, HCO absorption lines toward two objects are detected, which almost doubles the number of HCO absorption samples in the Galactic diffuse medium. In addition, high HCO-to-H13CO+ column density ratios are found, suggesting that the interstellar media (ISM) observed toward the two calibrators are in photodissociation regions, which observationally illustrates the chemistry of diffuse ISM driven by ultraviolet (UV) radiation. These results demonstrate that calibrators in the ALMA Archive are potential sources for the quest for new absorption systems and for detailed investigation of the nature of the ISM.

DOI： 10.1093/pasj/psv110

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Monthly Notices of the Royal Astronomical Society  

We report the discovery of an extremely dense group of massive galaxies at the centre of the protocluster at z =3.09 in the SSA22 field from near-infrared spectroscopy conducted with the multi-object infrared camera and spectrograph (MOIRCS) on the Subaru Telecope. The newly discovered group comprises seven galaxies confirmed at zspec ≈ 3.09 within 180 kpc, including fivemassive objectswith the stellarmasses larger than 1010.5 M⊙ and is associated with a bright submillimetre source SSA22-AzTEC14. The dynamical mass of the group estimated from the line-of-sight velocity dispersion of the members isMdyn ~ 1.6 ± 0.3 × 1013M⊙. Such a dense group is expected to be very rare at high redshift, as we have found only a few comparable systems in large-volume cosmological simulations. Such rare groups in simulations are hosted in collapsed haloes with Mvir = 1013.4-1014.0M⊙ and evolve into the brightest cluster galaxies (BCGs) of the most massive clusters at present. The observed AzTEC14 group at z = 3.09 is therefore very likely to be a proto-BCG in the multiple merger phase. The observed total stellar mass of the group is 5.8+5.1-2.0 × 1011M⊙, which suggests that over half the stellar mass of its descendant had been formed by z = 3. Moreover, we have identified over two members for each of the four Lyα blobs (LABs) using our new spectroscopic data. This verifies our previous argument that many of the LABs in the SSA22 protocluster associated with multiple developed stellar components.

DOI： 10.1093/mnras/stv2392

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Proceedings of the International Astronomical Union  

We have conducted 1.1 mm ALMA observations of a contiguous 105 × 50 or 1.5 arcmin2 window in the SXDF-UDS-CANDELS. We achieved a 5σ sensitivity of 0.28 mJy, giving a flat sensus of dusty star-forming galaxies with L IR ∼6×1011 L O (if T dust=40K) up to z ∼ 10 thanks to the negative K-correction at this wavelength. We detected 5 brightest sources (S/N>6) and 18 low-significant sources (5>S/N>4; they may contain spurious detections, though). One of the 5 brightest ALMA sources (S 1.1mm = 0.84 ± 0.09 mJy) is extremely faint in the WFC3 and VLT/HAWK-I images, demonstrating that a contiguous ALMA imaging survey uncovers a faint dust-obscured population invisible in the deep optical/near-infrared surveys. We find a possible [CII]-line emitter at z=5.955 or a low-z CO emitting galaxy within the field, allowing us to constrain the [CII] and/or CO luminosity functions across the history of the universe.

DOI： 10.1017/S1743921315010364

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DOI： 10.1017/S1743921315010327

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掲載種別：研究論文（学術雑誌）   出版者・発行元：Astrophysical Journal Letters  

We report the results of 1.′5 ×3′ mapping at 1.1 mm with the Atacama Large Millimeter/submillimeter Array toward the central region of the z = 3.09 SSA22 protocluster. By combining our source catalog with archival spectroscopic redshifts, we find that eight submillimeter galaxies (SMGs) with flux densities, S1.1 mm = 0.7-6.4 mJy (LIR ∼ 1012.1-1013.1 Lo) are at z = 3.08-3.10. Not only are these SMGs members of the protocluster, but they in fact reside within the node at the junction of the 50 Mpc scale filamentary three-dimensional structure traced by Lyα emitters in this field. The eight SMGs account for a star formation rate density (SFRD) ∼10 Mo yr-1 Mpc-3 in the node, which is two orders of magnitudes higher than the global SFRD at this redshift. We find that four of the eight SMGs host an X-ray-luminous active galactic nucleus. Our results suggest that the vigorous star formation activity and the growth of supermassive black holes (SMBHs) occurred simultaneously in the densest regions at z ∼ 3, which may correspond to the most active historical phase of the massive galaxy population found in the core of the clusters in the present universe. Two SMGs are associated with Lyα blobs, implying that the two populations coexist in high-density environments for a few cases.

DOI： 10.1088/2041-8205/815/1/L8

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We present results of Herschel/SPIRE observation in 2QZ cluster at z=2.23. 2QZ cluster is discovered as an overdensity of QSOs and Hα emitters (HAEs), which was originally identified as a concentration of 5 QSOs in the 2dF Quasar Redshift survey. We find an overdensity of SPIRE color selected far-infrared bright galaxies (3.9 σ compared with COSMOS field) ̃5' west of the HAEs density peak of in a radius of 6 co-Mpc. This suggests 2QZ cluster is experiencing enhanced dusty star-formation. However, SPIRE color selection with S<SUB>500</SUB>/S<SUB>350</SUB> vs S<SUB>350</SUB>/S<SUB>250</SUB> has a redshift uncertainty, we need spectroscopic observation with ALMA to confirm the precise redshifts....

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We report on the measurements of physical properties of HAEs in protocluster 4C23.56 at z = 2.49 using deep and high resolution observations with ALMA at Band 6 (270 GHz) and JVLA at S-band (3 GHz). We detect four and seven out of 24 HAEs from ALMA and JVLA, and we find that the detected samples are in massive-end (log M<SUB>★</SUB>(M<SUB>☉</SUB>)≳10.1) . We derive extinction-free SFRs and the amount of dust attenuation based on JVLA detections for those without AGN features. The detected HAEs are massive and heavily dust-obscured star forming galaxies. The majority of these HAEs are experiencing burst-like phase. We derive interstellar medium (ISM) masses from the single band ALMA observation and all but one of ALMA detections have ISM mass fractions of ̃ 25% which is a tentatively low value compared to the samples of the general field. This suggests that an accelerated galaxy evolution may have occurred in the over-dense region at this high redshift, though the uncertainty is large. <P />...

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We present the results of an ALMA survey of submillimeter galaxies (SMGs) in the SSA22 field. Totally 45 sources discovered by the AzTEC/ASTE survey were observed at 1.1mm to find 64 ALMA -identified SMGs with S/N≥4.5. This is the largest SMG survey in Band 6 in ALMA Cycle1. Previous panoramic Lyman-alpha emitter (LAE) surveys have unveiled that SSA22 is not a general field but a highly biased field at z=3.1. We find large excess in the number counts and surface number density compared to the ALESS survey in ECDFS, which suggests SMGs are preferentially formed in the dense environment at z̃3....

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出版者・発行元：Astrophysical Journal Letters  

We present the first results from the SXDF-Atacama Large Millimeter/submillimeter Array (ALMA) 1.5 arcmin2 deep survey at 1.1 mm using ALMA. The map reaches a 1σ depth of 55 μJy/beam and covers 12 Hα-selected star-forming galaxies (SFGs) at z = 2.19 or z = 2.53. We have detected continuum emission from three of our Hα-selected sample, including one compact SFG with high stellar surface density, NB2315-07. They are all red in the rest-frame optical and have stellar masses of log (M∗/Mo) > 10.9, whereas the other blue, main-sequence galaxies with = 10.0-10.8 are exceedingly faint, <290 μJy (2σ upper limit). We also find the 1.1 mm brightest galaxy, NB2315-02, to be associated with a compact (Re = 0.7 ± 0.1 kpc), dusty star-forming component. Given a high gas fraction (44+20-8% or 37+25-3%) and high star formation rate surface density (126+27-30 yr-1 kpc-2), the concentrated starburst can build up within less than 50+22-11Myr a stellar surface density matching that of massive compact galaxies at z ∼ 2, provided at least 19 ± 3% of the total gas is converted into stars in the galaxy center. On the other hand, NB2315-07, which already has such a high stellar surface density core, shows a gas fraction (23+8-8%) and is located in the lower envelope of the star formation main sequence. This compact, less SFG is likely to be in an intermediate phase between compact, dusty star-forming and quiescent galaxies.

DOI： 10.1088/2041-8205/811/1/L3

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出版者・発行元：Astrophysical Journal  

We present Atacama Large Millimeter/submillimeter Array (ALMA) Cycle 1 observations of the central kiloparsec region of the luminous type 1 Seyfert galaxy NGC 7469 with unprecedented high resolution (0.″5 e×0.″4 = 165 e× 132 pc) at submillimeter wavelengths. Utilizing the wide bandwidth of ALMA, we simultaneously obtained HCN(4-3), HCO+(4-3), CS(7-6), and partially CO(3-2) line maps, as well as the 860 μm continuum. The region consists of the central ∼1″ component and the surrounding starburst ring with a radius of ∼1.″5-2.″5. Several structures connect these components. Except for CO(3-2), these dense gas tracers are significantly concentrated toward the central ∼1″, suggesting their suitability to probe the nuclear regions of galaxies. Their spatial distribution resembles well those of centimeter and mid-infrared continuum emissions, but it is anticorrelated with the optical one, indicating the existence of dust-obscured star formation. The integrated intensity ratios of HCN(4-3)/HCO+(4-3) and HCN(4-3)/CS(7-6) are higher at the active galactic nucleus (AGN) position than at the starburst ring, which is consistent with our previous findings (submillimeter-HCN enhancement). However, the HCN(4-3)/HCO+(4-3) ratio at the AGN position of NGC 7469 (1.11 0.06) is almost half of the corresponding value of the low-luminosity type 1 Seyfert galaxy NGC 1097 (2.0 0.2), despite the more than two orders of magnitude higher X-ray luminosity of NGC 7469. But the ratio is comparable to that of the close vicinity of the AGN of NGC 1068 (∼1.5). Based on these results, we speculate that some heating mechanisms other than X-ray (e.g., mechanical heating due to an AGN jet) can contribute significantly for shaping the chemical composition in NGC 1097.

DOI： 10.1088/0004-637X/811/1/39

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掲載種別：研究論文（学術雑誌）   出版者・発行元：Astrophysical Journal  

We report the source size distribution, as measured by ALMA millimetric continuum imaging, of a sample of 13 AzTEC-selected submillimeter galaxies (SMGs) at zphot ∼ 3-6. Their infrared luminosities and star formation rates (SFRs) are LIR∼ 2-6 × 1012 L⊙ and ∼200-600 M⊙ yr1, respectively. The sizes of these SMGs range from 0″ 10 to 0″ 38, with a median of 0″ 20 -0″05+0″03 (FWHM), corresponding to a median circularized effective radius (Rc,e) of 0.67-0.14+0.13 kpc, comparable to the typical size of the stellar component measured in compact quiescent galaxies at z ∼ 2 (cQGs)-Re ∼ 1 kpc. The median surface SFR density of our SMGs is 100-26+42 M yr1 kpc2, comparable to that seen in local merger-driven (U)LIRGs rather than in extended disk galaxies at low and high redshifts. The discovery of compact starbursts in z ≳ 3 SMGs strongly supports a massive galaxy formation scenario wherein z ∼ 3-6 SMGs evolve into the compact stellar components of z ∼ 2 cQGs. These cQGs are then thought to evolve into the most massive ellipticals in the local universe, mostly via dry mergers. Our results thus suggest that z ≳ 3 SMGs are the likely progenitors of massive local ellipticals, via cQGs, meaning that we can now trace the evolutionary path of the most massive galaxies over a period encompassing ∼90% of the age of the universe.

DOI： 10.1088/0004-637X/810/2/133

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掲載種別：研究論文（学術雑誌）   出版者・発行元：Monthly Notices of the Royal Astronomical Society  

We present the results from a 1.1-mm imaging survey of the SSA22 field, known for having an overdensity of z =3.1 Lyman α emitting galaxies (LAEs), taken with the astronomical thermal emission camera (AzTEC) on the Atacama Submillimeter Telescope Experiment (ASTE).We imaged a 950-arcmin2 field down to a 1σ sensitivity of 0.7-1.3 mJy beam-1 to find 125 submillimetre galaxies (SMGs) with a signal-to-noise ratio ≥3.5. Counterpart identification using radio and near/mid-infrared data was performed and one or more counterpart candidates were found for 59 SMGs. Photometric redshifts based on optical to near-infrared images were evaluated for 45 of these SMGs with Spitzer/IRAC data and the median value is found to be z =2.4. By combining these estimations with estimates from the literature, we determined that 10 SMGs might lie within the large-scale structure at z = 3.1. The two-point angular crosscorrelation function between LAEs and SMGs indicates that the positions of the SMGs are correlated with the z = 3.1 protocluster. These results suggest that the SMGs were formed and evolved selectively in the high dense environment of the high-redshift Universe. This picture is consistent with the predictions of the standard model of hierarchical structure formation. © 2014 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.

DOI： 10.1093/mnras/stu447

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：Proceedings of the International Astronomical Union  

© International Astronomical Union 2015. We present recent results on Karl Jansky Very Large Array (JVLA) deep S-band (2-4 GHz) observation towards a protocluster 4C23.56 at redshift z ∼ 2.5. The protocluster 4C23.56 is known to have a significant over density (∼ 5 times) of star-burst galaxies selected to be Hα line-bright by a Subaru narrow band imaging. Now we have found 25 HAEs associated with the protocluster. These starburst HAEs are likely to become massive ellipticals at z = 0 in a cluster. Various other galaxy populations also reside in this field and the fact makes the field very unique as a tool to understand galaxy formation in a over dense region. Subsequent deep 1100-μm continuum surveys by the ASTE 10-m dish have discovered that several submillimeter bright galaxies (SMGs) coincide with HAEs, suggesting HAEs undergoing dusty starbursts. As star formation rates (SFRs) of HAEs might have been underestimated, we use radio being resistant to dust extinction. We investigate the correlation between SFR1.4GHzand SFRHαfor radio index α = 0.8 to see if the correlation holds for the sources and to check the number of dusty star forming galaxies. Our final results will allow us to evaluate quantitatively how the galaxy formation channel may be different under the condition of over-densities.

DOI： 10.1017/S1743921314009892

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We present the results from the 1.1mm continuum imaging the SSA22 field, which is known as an protocluster field which is traced by Lyα emitting galaxies (LAEs) at z = 3.1, with the AzTEC camera on ASTE telescope. We find 112 submillimeter(1.1mm)-selected galaxies (SMGs) with signal to noise ratio of ≥3.5 within 50% coverage region. Counterpart identification analysis utilizing radio(1.4GHz), MIPS ch1(24 μm) imaging data and IRAC color(3.6 μm, 4.5 μm, 5.8 μm, and 8.0 μm) diagnostics has been carried out to reveal that 48 SMGs have at least one reliable counterpart. We derived photometric redshifts of these sources and consequently seven z = 3.1 candidate SMGs are extracted. Two point angular correlation function between LAEs and these SMGs indicate that high density regions at the high redshift universe are the site of SMG/AGN formation. This picture is consistent with predictions from the standard model of hierarchical structure formation. <P />...

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We investigate the association of multiple mm-bright galaxies to the proto-cluster around 4C 23.56 at z = 2.48 by the combined observation of the AzTEC/ASTE singledish and the Plateau de Bure Interferometer. We detected 1.8 mm emissions from four HAEs associated with this proto-cluster, and detected CO line from two of them. From these observed values, we investigated their star formation rates (SFRs) and variation in mass compositions. Their SFRs are estimated as 60 to 690 M<SUB>☉</SUB> yr<SUP>-1</SUP> from their submm-mm fluxes. SFRs from mm fluxes for three HAEs are comparable to SFRs from extinction corrected Hα luminosity, but only for HAE 431, large discrepancy in two SFR estimators is seen and large star formation should be dust-obscured....

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出版者・発行元：Monthly Notices of the Royal Astronomical Society  

We present results from the AzTEC/ASTE 1.1-mm imaging survey of 35 Lyα blobs (LABs) found in the SSA22 protocluster at z = 3.1. These 1.1-mm data reach an rms noise level of 0.7-1 mJy beam-1, making this the largest millimetre-wave survey of LABs to date. While one (or possibly two) out of 35 LABs might be detected at 3σ level, no significant (≥3.5σ) emission is found in any of individual 35 LABs. From this, we estimate 3σ upper limits on the far-infrared luminosity of LFIR&lt; 2 × 1012L⊙(the dust temperature of 35K and the emissivity index of 1.5 are assumed). Stacking analysis reveals that the 1.1-mm flux density averaged over the LABs is S1.1mm&lt; 0.40 mJy (3s), which places a constraint of LFIR &lt; 4.5 × 1011L⊙. These data constrain the dust spectral energy distributions of the LABs more tightly than ever if their spectral indices at rest-frame wavelength of ≈ 240 μm are similar to those found in (ultra-)luminous infrared galaxies at 0.2 &lt; z &lt; 0.3. Our results suggest that LABs on average have little ultraluminous obscured star formation, in contrast to a long-believed picture that LABs undergo an intense episode of dusty star formation activities with star formation rates of ~103M⊙yr-1. Observations with the Atacama Large Millimeter/submillimeter Array are needed to directly study the obscured part of star formation activity in the LABs. © 2013 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.

DOI： 10.1093/mnras/stt077

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記述言語：日本語  

CiNii Research

記述言語：英語   出版者・発行元：Astronomical Society of Japan  

We present initial results from the CO survey toward high-redshift galaxies using the Nobeyama 45m telescope. Using a new wide bandwidth spectrometer equipped with a two-beam SIS receiver, we have obtained three new detections of high-redshift (z = 1.6-3.4) submillimeter galaxies (SXDF 1100.001/HXMM02, SDP9, and SDP17), one tentative detection (SDSS J160705+533558), and one non-detection (COSMOS-AzTEC1). The galaxies observed during the commissioning phase are sources with known spectroscopic redshifts from previous optical or wide-band submillimeter spectroscopy. The derived molecular gas mass and line widths from Gaussian fits are ∼ 1011M⊙and 430-530km s-1, respectively, which are consistent with previous CO observations of distant submillimeter galaxies and quasars. The spectrometer, which realizes a maximum of 32 GHz instantaneous bandwidth, will provide new science capabilities at the Nobeyama 45m telescope, allowing us to determine redshifts of bright submillimeter selected galaxies without any prior redshift information. © 2012. Astronomical Society of Japan.

DOI： 10.1093/pasj/64.4.L2

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掲載種別：研究論文（学術雑誌）   出版者・発行元：Monthly Notices of the Royal Astronomical Society  

We present 2D, integral field spectroscopy covering the rest-frame wavelengths of strong optical emission lines in nine submillimetre luminous galaxies (SMGs) at 2.0 < z < 2.7. The Gemini-North/Near-Infrared Integral Field Spectrograph (NIFS) and Very Large Telescope (VLT) Spectrograph for INtegral Field Observations in the Near Infrared (SINFONI) imaging spectroscopy allow the mapping of the gas morphologies and dynamics within the sources, and we measure an average Hα velocity dispersion of 〈σ〉 = 220 ± 80kms-1 and an average half-light radius of 〈r1/2〉 = 3.7 ± 0.8kpc. The dynamical measure, 〈Vobs/2σ〉 = 0.9 ± 0.1, for the SMGs is higher than in more quiescent star-forming galaxies at the same redshift, highlighting a difference in the dynamics of the two populations. The far-infrared star formation rates (SFRs) of the SMGs, measured using Herschel-SPIRE† far-infrared photometry, are on average 370 ± 90M⊙yr-1, which is ~2 times higher than the extinction-corrected SFRs of the more quiescent star-forming galaxies. Six of the SMGs in our sample show strong evidence for kinematically distinct multiple components with average velocity offsets of 200 ± 100kms-1 and average projected spatial offsets of 8 ± 2kpc, which we attribute to systems in the early stages of major mergers. Indeed, all SMGs are classified as mergers from a kinemetry analysis of the velocity and dispersion field asymmetry. We bring together our sample with the seven other SMGs with integral field unit observations to describe the ionized gas morphologies and kinematics in a sample of 16 SMGs. By comparing the velocity and spatial offsets of the SMG Hα components with subhalo offsets in the Millennium Simulation data base, we infer an average halo mass for SMGs in the range of 13 < log(M[h-1M⊙]) < 14. Finally, we explore the relationship between the velocity dispersion and star formation intensity within the SMGs, finding that the gas motions are consistent with the Kennicutt-Schmidt law and a range of extinction corrections, although they might also be driven by the tidal torques from merging or even the star formation itself. © 2012 The Authors. Monthly Notices of the Royal Astronomical Society © 2012 RAS.

DOI： 10.1111/j.1365-2966.2012.21386.x

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記述言語：日本語  

CiNii Research

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Astrophysical Journal  

We present the results of near- to mid-infrared slit spectroscopic observations (2.55-13.4 μm) of the diffuse emission toward nine positions in the Large Magellanic Cloud with the infrared camera on board AKARI. The target positions are selected to cover a wide range of the intensity of the incident radiation field. The unidentified infrared bands at 3.3, 6.2, 7.7, 8.6, and 11.3 μm are detected toward all the targets and ionized gas signatures; hydrogen recombination lines and ionic forbidden lines are detected toward three of them. We classify the targets into two groups: those without the ionized gas signatures (Group A) and those with the ionized signatures (Group B). Group A includes molecular clouds and photodissociation regions, whereas Group B consists of HII regions. In Group A, the band ratios of I3.3μm/ I11.3μm, I6.2μm/I11.3μm, I 7.7μm/I11.3μm, and I8.6μm/I 11.3μm show positive correlation with the IRAS and AKARI colors, but those of Group B do not follow the correlation. We discuss the results in terms of the polycyclic aromatic hydrocarbon (PAH) model and attribute the difference to the destruction of small PAHs and an increase in the recombination due to the high electron density in Group B. In the present study, the 3.3 μm band provides crucial information on the size distribution and/or the excitation conditions of PAHs and plays a key role in the distinction of Group A from B. The results suggest the possibility of the diagram of I 3.3μm/I11.3μm versus I7.7μm/I 11.3μm as an efficient diagnostic tool to infer the physical conditions of the interstellar medium.

DOI： 10.1088/0004-637X/744/1/68

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：Advances in Geosciences  

We present the results of mid-infrared (MIR) slit spectroscopic observations of the diffuse interstellar medium (ISM) in the Large Magellanic Cloud (LMC) with the Infrared Camera (IRC) onboard AKARI. We have observed seven slit points across the whole galaxy, which have the12CO (J = 1 −0) detection by NANTEN survey, and detect distinct unidentified infrared (UIR) bands (6.2 μm, 7.7 μm, 8.6 μm, 11.2 μm) for six points, while there are no signature of UIR bands in the spectra of one points. The comparison between the intensity ratios of 7.7 μm/11.2 μm and the IRAS 60μm/100 μm color are carried out. We find that the band ratios peak at positions with an intermediate IRAS 60 μm/100 μm color of I60μm/I100μm ∼0.5 and decreases at positions with lower or higher IRAS 60 μm/100 μm colors of I60μm/I100μm ∼0.4 and I60μm/I100μm ∼0.6-0.7, respectively. This result indicates the transition of the ionization state of PAHs relying on the gas phase and radiation environment.

DOI： 10.1142/9789814405744_0002

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

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J-GLOBAL

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J-GLOBAL

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記述言語：日本語   出版者・発行元：東京大学大学院理学系研究科・理学部  

土星の衛星エンセラダスに生命を育む海がある！？／自己抑制の仕組みでバランスを保つ植物の根／115億光年かなたの宇宙で見つかった怪物銀河の大集団

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