Publishing type：Research paper (scientific journal)  

We report the physical characterization of four CO emitters detected near the bright submillimeter galaxy (SMG) SSA22-AzTEC26. We analyze the data from Atacama Large Millimeter/submillimeter Array band 3, 4, and 7 observations of the SSA22-AzTEC26 field. In addition to the targeted SMG, we detect four line emitters with signal-to-noise ratio >5.2 in the cube smoothed with a 300 km s−1 FWHM Gaussian filter. All four sources have NIR counterparts within 1″. We perform UV-to-FIR spectral energy distribution modeling to derive the photometric redshifts and physical properties. Based on the photometric redshifts, we reveal that two of them are CO(2-1) at redshifts of 1.113 and 1.146 and one is CO(3-2) at z = 2.124. The three sources are massive galaxies with a stellar mass ≳1010.5 M ⊙, but have different levels of star formation. Two lie within the scatter of the main sequence (MS) of star-forming galaxies at z ∼ 1-2, and the most massive galaxy lies significantly below the MS. However, all three sources have a gas fraction within the scatter of the MS scaling relation. This shows that a blind CO line search can detect massive galaxies with low specific star formation rates that still host large gas reservoirs and that it also complements targeted surveys, suggesting later gas acquisition and the need for other mechanisms in addition to gas consumption to suppress star formation.

DOI： 10.3847/1538-4357/ace0c0

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arXiv

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Other Link： http://arxiv.org/pdf/2301.09296v3

Publishing type：Research paper (scientific journal)  

DOI： 10.3847/1538-4357/acd449

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IOP Publishing Ltd  

We present the results of 300 pc resolution Atacama Large Millimeter/submillimeter Array imaging of the [O iii] 88 & mu;m line and dust continuum emission from a z = 8.312 Lyman-break galaxy MACS0416_Y1. The velocity-integrated [O iii] emission has three peaks that are likely associated with three young stellar clumps of MACS0416_Y1, while the channel map shows a complicated velocity structure with little indication of a global velocity gradient unlike what was found in [C ii] 158 & mu;m at a larger scale, suggesting random bulk motion of ionized gas clouds inside the galaxy. In contrast, dust emission appears as two individual clumps apparently separating or bridging the [O iii]/stellar clumps. The cross-correlation coefficient between dust and ultraviolet-related emission (i.e., [O iii] and ultraviolet continuum) is unity on a galactic scale, while it drops at <1 kpc, suggesting well-mixed geometry of multiphase interstellar media on subkiloparsec scales. If the cutoff scale characterizes different stages of star formation, the cutoff scale can be explained by gravitational instability of turbulent gas. We also report on a kiloparsec-scale off-center cavity embedded in the dust continuum image. This could be a superbubble producing galactic-scale outflows, since the energy injection from the 4 Myr starburst suggested by a spectral energy distribution analysis is large enough to push the surrounding media creating a kiloparsec-scale cavity.

DOI： 10.3847/1538-4357/acd637

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DOI： 10.1093/mnras/stad1321

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DOI： 10.3847/1538-3881/acb707

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DOI： 10.1093/mnras/stad784

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DOI： 10.3847/1538-4357/acb8ab

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We report the multi-wavelength properties of millimeter galaxies hosting
X-ray detected active galactic nuclei (AGNs) from the ALMA Lensing Cluster
Survey (ALCS). ALCS is an extensive survey of well-studied lensing clusters
with ALMA, covering an area of 133 arcmin$^2$ over 33 clusters with a 1.2 mm
flux-density limit of ${\sim}$60 $\mathrm{\mu Jy}$ ($1\sigma$). Utilizing the
archival data of Chandra, we identify three AGNs at $z=$1.06, 2.09, and 2.84
among the 180 millimeter sources securely detected in the ALCS (of which 155
are inside the coverage of Chandra). The X-ray spectral analysis shows that two
AGNs are not significantly absorbed ($\log N_{\mathrm{H } }/\mathrm{cm}^{-2} <
23$), while the other shows signs of moderate absorption ($\log
N_{\mathrm{H } }/\mathrm{cm}^{-2}\sim 23.5$). We also perform spectral energy
distribution (SED) modelling of X-ray to millimeter photometry. We find that
our X-ray AGN sample shows both high mass accretion rates (intrinsic 0.5--8 keV
X-ray luminosities of ${\sim}10^{\text{44--45 } }\,\mathrm{erg\ s^{-1 } }$) and
star-formation rates (${\gtrsim}100\,M_{\odot}\,\mathrm{yr}^{-1}$). This
demonstrates that a wide-area survey with ALMA and Chandra can selectively
detect intense growth of both galaxies and supermassive black holes (SMBHs) in
the high-redshift universe.

DOI： 10.3847/1538-4357/acb4e9

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arXiv

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Other Link： http://arxiv.org/pdf/2301.09275v1

Language：English   Publishing type：Research paper (scientific journal)   Publisher：IOP Publishing Ltd  

We present Karl G. Jansky Very Large Array K-band (19 GHz) observations of the redshifted CO(1-0) line emission toward the radio galaxy TN J0924-2201 at z = 5.2, which is one of the most distant radio galaxies with CO detected. With an angular resolution of similar to 2 '', the CO(1-0) line emission is resolved into three clumps, within +/- 500 km s(-1) relative to its redshift, which is determined by Ly alpha. We find that the clumps are located off-center and 12-33 kpc away from the center of the host galaxy, which has counterparts in the Hubble Space Telescope i band, Spitzer/IRAC, and the Atacama Large Millimeter/submillimeter Array (ALMA) band 6 (230 GHz; 1.3 mm). With the ALMA detection, we estimate the infrared luminosity LIR and the star formation rate (SFR) of the host galaxy to be (9.3 +/- 1.7) x 10(11)L(circle dot) and 110 +/- 20 M-circle dot yr(-1), respectively. We also derive the 3 sigma upper limit of M-H2 < 1.3 x 10(10) M-circle dot at the host galaxy. The 2 detected CO(1-0) line luminosities of the three clumps, L '(CO (1-0)) = (3.2-4.7) x 10(10) K km s(-1) pc(2), indicate the presence of three massive molecular gas reservoirs, with M-H2 = (2.5-3.7) x 10(10) M-circle dot, assuming a CO-to-H-2 conversion factor of alpha(CO) = 0.8 M-circle dot (K km s(-1) pc(2))(-1), although the SFR is not elevated due to the nondetection of the ALMA -1.3 mm continuum (SFR < 40 M-circle dot yr(-1)). From the host galaxy, the nearest molecular gas clump, labeled "clump A," is apparently in alignment with the radio jet axis, showing radio-CO alignment. The origins of these three clumps around TN J0924-2201 can possibly be interpreted as outflows, mergers, or jet-induced metal enrichment.

DOI： 10.3847/1538-4357/acaf58

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DOI： 10.1093/pasj/psac082

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Publishing type：Research paper (scientific journal)  

We present a set of multiwavelength mosaics and photometric catalogs in the Atacama Large Millimeter/ submillimeter Array (ALMA) lensing cluster survey fields. The catalogs were built by the reprocessing of archival data from the Complete Hubble Archive for Galaxy Evolution compilation, taken by the Hubble Space Telescope (HST) in the Reionization Lensing Cluster Survey, Cluster Lensing And Supernova survey with Hubble, and Hubble Frontier Fields. Additionally, we have reconstructed the Spitzer Infrared Array Camera 3.6 and 4.5 μm mosaics, by utilizing all the available archival IPAC Infrared Science Archive/Spitzer Heritage Archive exposures. To alleviate the effect of blending in such a crowded region, we have modeled the Spitzer photometry by convolving the HST detection image with the Spitzer point-spread function using the novel GOLFIR software. The final catalogs contain 218,000 sources, covering a combined area of 690 arcmin2, a factor of ∼2 improvement over the currently existing photometry. A large number of detected sources is a result of reprocessing of all available and sometimes deeper exposures, in conjunction with a combined optical–near-IR detection strategy. These data will serve as an important tool in aiding the search of the submillimeter galaxies in future ALMA surveys, as well as follow-ups of the HST dark and high-z sources with JWST. Coupled with the available HST photometry, the addition of the 3.6 and 4.5 μm bands will allow us to place a better constraint on the photometric redshifts and stellar masses of these objects, thus giving us an opportunity to identify high-redshift candidates for spectroscopic follow-ups and to answer the important questions regarding the Epoch of Reionization and formation of the first galaxies. The mosaics, photometric catalogs, and the best-fit physical properties are publicly available at https:// github.com/dawn-cph/alcs-clusters.

DOI： 10.3847/1538-4365/ac9909

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Publishing type：Research paper (scientific journal)   Publisher：American Astronomical Society  

Abstract

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 (W₈₀ &gt; 1000 km s⁻¹) and strong ($\mathrm{log}({L}_{[\mathrm{OIII}]}$/erg s⁻¹) ≈ 43.4) [O iii]λλ 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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Other Link： https://iopscience.iop.org/article/10.3847/1538-4357/ac7f2d/pdf

Publishing type：Research paper (scientific journal)   Publisher：Oxford University Press (OUP)  

Abstract

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 &amp;gt;12σ in the ${0{^{\prime \prime}_{. } }8}$-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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Publisher：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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Publishing type：Research paper (scientific journal)   Publisher：Oxford University Press (OUP)  

<title>ABSTRACT</title>
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 $(714.2~\rm cMpc)^{3}$: 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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Other Link： https://academic.oup.com/mnras/article-pdf/509/3/4037/41475398/stab3092.pdf

Publisher：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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Publishing type：Research paper (scientific 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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arXiv

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Other Link： http://arxiv.org/pdf/2107.01162v1

Publishing type：Research paper (scientific 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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Publishing type：Research paper (scientific journal)   Publisher：American Astronomical Society  

DOI： 10.3847/1538-4357/abf6dc

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Other Link： https://iopscience.iop.org/article/10.3847/1538-4357/abf6dc/pdf

Publishing type：Research paper (scientific journal)   Publisher：American Astronomical Society  

DOI： 10.3847/1538-4357/abe7ea

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Other Link： https://iopscience.iop.org/article/10.3847/1538-4357/abe7ea/pdf

Language：English   Publishing type：Research paper (scientific journal)   Publisher：IOP PUBLISHING LTD  

We present bright [C ii] 158 mu m line detections from a strongly magnified and multiply imaged (mu similar to 20-160) sub-L* (MUV=-19.75-0.44+0.55) 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 >= 8 sigma 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 (similar to 6 '') arc with a local magnification of mu similar to 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 similar to 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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Publishing type：Research paper (scientific journal)   Publisher：EDP Sciences  

<italic>Context.</italic> 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.


<italic>Aims.</italic> In order to shed light on the properties of galaxies in the high-redshift Universe and their interstellar media, we observe the Lyman-<italic>α</italic> emitting galaxy <ext-link ext-link-type="aoi">z7_GSD_3811</ext-link> at <italic>z</italic> = 7.664 with bands 6 and 8 at the Atacama Large Millimeter/submillimeter Array (ALMA).


<italic>Methods.</italic> We target the far-infrared [O <sc>III</sc>] 88 <italic>μ</italic>m and [C <sc>II</sc>] 158 <italic>μ</italic>m 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 <sc>III</sc>] and [C <sc>II</sc>] emission in high-redshift galaxies.


<italic>Results.</italic> The [O <sc>III</sc>] 88 <italic>μ</italic>m and [C <sc>II</sc>] 158 <italic>μ</italic>m emission lines are undetected at the position of z7_GSD_3811, with 3<italic>σ</italic> upper limits of 1.6  ×  10⁸ <italic>L</italic>_⊙ and 4.0  ×  10⁷ <italic>L</italic>_⊙, 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 <italic>μ</italic>Jy beam⁻¹, respectively. Similar to several other high-redshift galaxies, z7_GSD_3811 exhibits low [C <sc>II</sc>] emission for its star formation rate compared to local galaxies. Furthermore, our upper limit on the [O <sc>III</sc>] line luminosity is lower than the previously observed [O <sc>III</sc>] 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 <sc>III</sc>] and [C <sc>II</sc>] lines could indicate that z7_GSD_3811 has a low metallicity (<italic>Z</italic> ≲ 0.1 <italic>Z</italic>_⊙).

DOI： 10.1051/0004-6361/202038180

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Publishing type：Research paper (scientific journal)   Publisher：American Astronomical Society  

Abstract

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 × 10¹²L_⊙. 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_⊙ 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_⊙ 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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Other Link： https://iopscience.iop.org/article/10.3847/1538-4357/abd7ef/pdf

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DOI： 10.3847/1538-4357/abcc72

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Publishing type：Research paper (scientific journal)   Publisher：American Astronomical Society  

DOI： 10.3847/1538-4357/abd4d0

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Other Link： https://iopscience.iop.org/article/10.3847/1538-4357/abd4d0

Language：English  

CiNii Research

Publishing type：Research paper (scientific journal)   Publisher：EDP Sciences  

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 [C <sc>I</sc>](1–0) and CO(4–3) emission lines determines the precise redshift of the galaxy, ADF22.A2, to be <italic>z</italic> = 3.9913 ± 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 <italic>M</italic>_∗ = 1.1_−0.6^+1.3 × 10¹¹ <italic>M</italic>_⊙ and SFR = 430₋₁₅₀⁺²³⁰ <italic>M</italic>_⊙ yr⁻¹. The molecular gas mass was derived to be <italic>M</italic>(H₂)^[CI] = (5.9 ± 1.5)×10¹⁰ <italic>M</italic>_⊙, indicating a gas fraction of ≈35%, and the ratios of <italic>L</italic>_[CI](1−0)/<italic>L</italic>_IR and <italic>L</italic>_[CI](1−0)/<italic>L</italic>_CO(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 (<italic>τ</italic>_dep ≈ 0.1−0.2 Gyr), also suggest that ADF22.A2 has the characteristics expected for the progenitors of quiescent galaxies at <italic>z</italic> ≳ 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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Publishing type：Research paper (scientific journal)   Publisher：Oxford University Press (OUP)  

<title>Abstract</title>
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 &amp;gt;4.5 (1σ ≃ 30–70 μJy beam−1 at 1.2 mm). Their median redshift is estimated to be $z$median = 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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Other Link： http://academic.oup.com/pasj/article-pdf/72/4/69/33562710/psaa057.pdf

Publishing type：Research paper (scientific journal)   Publisher：Oxford University Press (OUP)  

ABSTRACT

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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Other Link： http://academic.oup.com/mnras/article-pdf/495/3/3409/33344748/staa1345.pdf

Language：English   Publishing type：Research paper (scientific journal)  

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 [C ii] 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 (3σ). 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, 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.

DOI： 10.1093/mnras/staa509

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CiNii Research

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Language：English   Publishing type：Research paper (scientific journal)  

<jats:title>Abstract</jats:title>
<jats:p>We present our ALMA Band 8 observations of a damped Ly$\alpha$ 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 Ly$\alpha$ emission line. Since one possible origin of DLAs at high redshift is an outflowing gas from star-forming 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 [C ii] 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 ${4{^{\prime \prime }_{. } }7}$ and ${8{^{\prime \prime }_{. } }1}$ 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.</jats:p>

DOI： 10.1093/pasj/psaa004

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Publishing type：Research paper (scientific journal)   Publisher：American Astronomical Society  

We report the detection of a non-corotating gas component in a bright
unlensed submillimeter galaxy at z=4.3, COSMOS-AzTEC-1, hosting a compact
starburst. ALMA 0.17 and 0.09 arcsec resolution observations of [CII] emission
clearly demonstrate that the gas kinematics is 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 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 non-corotating 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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Other Link： https://iopscience.iop.org/article/10.3847/1538-4357/ab64f4

Publisher：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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Publishing type：Research paper (international conference proceedings)   Publisher：SPIE  

DOI： 10.1117/12.2561238

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Publisher：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

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Publishing type：Research paper (scientific journal)  

We present ALMA [C II] line and far-infrared (FIR) continuum observations of three z &gt; 6 low-luminosity quasars (M_1450 &gt; -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) × 10^8 L_{☉}, about one order of magnitude smaller than optically luminous (M_1450 ≲ -25 mag) quasars. The FIR continuum luminosities range from &lt; 9 × 10^{10} L_{☉} (3 σ limit) to {̃ } 2 × 10^{12} 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 (M_dyn) as a surrogate for bulge stellar mass (M_{ bulge}), we find that a significant fraction of low-luminosity quasars are located on or even below the local M_{ BH}-M_{ bulge} 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 M_{ BH}-M_{ bulge} 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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Publishing type：Research paper (scientific journal)   Publisher：Cambridge University Press (CUP)  

<title>Abstract</title>We present ALMA detection of the [O <sc>iii</sc>] 88 <italic>μ</italic>m line and 850 <italic>μ</italic>m dust continuum emission in a <italic>Y</italic>-dropout Lyman break galaxy, MACS0416_Y1. The [O <sc>iii</sc>] detection confirms the object with a spectroscopic redshift to be <italic>z</italic> = 8.3118±0.0003. The 850 <italic>μ</italic>m continuum intensity (0.14 mJy) implies a large dust mass on the order of 4×10⁶<italic>M</italic>_⊙. The ultraviolet-to-far infrared spectral energy distribution modeling, where the [O <sc>iii</sc>] emissivity model is incorporated, suggests the presence of a young (τ_age ≍ 4 Myr), star-forming (SFR ≍ 60<italic>M</italic>_⊙yr⁻¹), and moderately metal-polluted (<italic>Z</italic> ≍ 0.2<italic>Z</italic>_⊙) stellar component with a stellar mass of 3 × 10⁸<italic>M</italic>_⊙. 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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Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Astronomical Society  

DOI： 10.3847/1538-4357/ab2cd5

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Other Link： https://iopscience.iop.org/article/10.3847/1538-4357/ab2cd5

Publishing type：Research paper (scientific journal)  

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 {26}<SUB>-11</SUB><SUP>+12</SUP> and {134}<SUB>-39</SUB><SUP>+50</SUP> cm<SUP>-3</SUP> 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 &gt; 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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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 <SUB>cl</SUB>/M <SUB>☉</SUB>) = 13.4-13.6, suggesting that the protocluster would evolve into a Virgo-like cluster (&gt;10<SUP>14</SUP> M <SUB>☉</SUB>). We compare the CO line widths and the CO luminosities with other (proto)clusters (n <SUB>gal</SUB> = 91) and general field (n <SUB>gal</SUB> = 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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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, $M_{\rm UV}\approx-22.4$, and has been spectroscopically
identified in Ly$\alpha$ with a small rest-frame equivalent width of $\approx4$
\AA. Previous HST image has shown that the target is comprised of two spatially
separated clumps in the rest-frame UV. With ALMA, we have newly detected
spatially resolved [OIII] 88 $\mu$m, [CII] 158 $\mu$m, and their underlying
dust continuum emission. In the whole system of B14-65666, the [OIII] and [CII]
lines have consistent redshifts of $7.1520\pm0.0003$, and the [OIII]
luminosity, $(34.4\pm4.1)\times10^{8}L_{\rm \odot}$, is about three times
higher than the [CII] luminosity, $(11.0\pm1.4)\times10^{8}L_{\rm \odot}$. With
our two continuum flux densities, the dust temperature is constrained to be
$T_{\rm d}\approx50-60$ K under the assumption of the dust emissivity index of
$\beta_{\rm d}=2.0-1.5$, leading to a large total infrared luminosity of
$L_{\rm TIR}\approx1\times10^{12}L_{\rm \odot}$. Owing to our high spatial
resolution data, we show that the [OIII] and [CII] emission can be spatially
decomposed into two clumps associated with the two rest-frame UV clumps whose
spectra are kinematically separated by $\approx200$ km s$^{-1}$. We also find
these two clumps have comparable UV, infrared, [OIII], and [CII] 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 [OIII]-to-[CII] luminosity
ratio.

DOI： 10.1093/pasj/psz049

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Publishing type：Research paper (scientific journal)  

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

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Publishing type：Research paper (scientific journal)  

We report detections of two 1.2 mm continuum sources (S <SUB>1.2 mm</SUB> ̃ 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 arcmin<SUP>2</SUP>) 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<SUP>-3</SUP> M <SUB>☉</SUB> yr<SUP>-1</SUP> Mpc<SUP>-3</SUP> 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 <SUB>870 μm</SUB> &gt; 4.2 mJy) at z ̃ 3-5. We also uncover three more candidate near-infrared-dark faint ALMA sources without any counterparts (S <SUB>1.2 mm</SUB> ̃ 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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Publishing type：Research paper (scientific journal)   Publisher：Cambridge University Press (CUP)  

<title>Abstract</title>We present ALMA [CII] line and far-infrared (FIR) continuum observations of seven <italic>z</italic> &gt; 6 low-luminosity quasars (<italic>M</italic>₁₄₅₀ &gt; −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 L_⊙, about one order of magnitude smaller than optically luminous quasars. Also found was a wide scatter of FIR continuum luminosity, ranging from <italic>L</italic>_FIR &lt; 10¹¹<italic>L</italic>_⊙ to ∼2 × 10¹²<italic>L</italic>_⊙. 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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DOI： 10.1017/S1743921319009591

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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 {n}<SUB>{ { H</SUB> } }<SUP>PDR</SUP>}={10}<SUP>5.5{--</SUP>5.75} cm<SUP>-3</SUP> and G <SUB>0</SUB> = 10<SUP>3.5-3.75</SUP> in the central 1 kpc region and {n}<SUB>{ { H</SUB> } }<SUP>PDR</SUP>}={10}<SUP>5.0{--</SUP>5.25} cm<SUP>-3</SUP> and G <SUB>0</SUB> = 10<SUP>3.25-3.5</SUP> 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 <SUB>[O III]</SUB>/L <SUB>[N II]</SUB> = 6.4 ± 2.2 indicates a near solar metallicity with Z <SUB>gas</SUB> = 0.7-1.0 Z <SUB>☉</SUB>, suggesting a chemically evolved system at z = 4.3....

DOI： 10.3847/1538-4357/ab1415

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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 />...

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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 &lt; log (M<SUB>star</SUB>/M<SUB>☉</SUB>) &lt; 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 (M<SUB>star</SUB>/M<SUB>☉</SUB>) &gt; 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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Language：English  

We present the Atacama Large Millimeter/submillimeter Array (ALMA) detection
of the [O III] 88 $\mu$m line and rest-frame 90 $\mu$m 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 $z = 8.3118 \pm 0.0003$, making this object one of
the furthest galaxies ever identified spectroscopically. The observed 850
$\mu$m flux density of $137 \pm 26$ $\mu$Jy corresponds to a de-lensed total
infrared (IR) luminosity of $L_{\rm IR} = (1.7 \pm 0.3) \times 10^{11}
L_{\odot}$ if assuming a dust temperature of $T_{\rm dust} = 50$ K and an
emissivity index of $\beta = 1.5$, yielding a large dust mass of $4 \times 10^6
M_{\odot}$. The ultraviolet-to-far IR spectral energy distribution modeling
where the [O III] emissivity model is incorporated suggests the presence of a
young ($\tau_{\rm age} \approx 4$ Myr), star-forming (SFR $\approx 60
M_{\odot}$ yr$^{-1}$), moderately metal-polluted ($Z \approx 0.2 Z_{\odot}$)
stellar component with a mass of $M_{\rm star} = 3 \times 10^8 M_{\odot}$. An
analytic dust mass evolution model with a single episode of star-formation does
not reproduce the metallicity and dust mass in $\tau_{\rm age} \approx 4$ Myr,
suggesting a pre-existing evolved stellar component with $M_{\rm star} \sim 3
\times 10^9 M_{\odot}$ and $\tau_{\rm age} \sim 0.3$ 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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Publishing type：Research paper (scientific journal)  

DOI： 10.3847/1538-4357/aafa6f

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Publishing type：Research paper (scientific journal)  

We present the survey design, data reduction, construction of images, and source catalog of the Atacama Large Millimeter/submillimeter Array (ALMA) twenty-six arcmin<SUP>2</SUP> survey of GOODS-S at one millimeter (ASAGAO). ASAGAO is a deep (1 σ depth ̃ 61 μJy beam<SUP>-1</SUP> for a 250 kλ-tapered map with a synthesized beam size of 0{^''<SUB>.</SUB>}51 × 0{^''<SUB>.</SUB>}45) and wide area (26 arcmin<SUP>2</SUP>) 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<SUP>-1</SUP> for a deep region with a 250 kλ-taper, and a synthesized beam size of 0{^''<SUB>.</SUB>}59 × 0{^''<SUB>.</SUB>}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^{+11}_{-8}% of the extragalactic background light at 1.2 mm is resolved into discrete sources at S<SUB>1.2 mm</SUB> &gt; 135 μJy. We create infrared (IR) luminosity functions (LFs) in the redshift range of z = 1-3 from the ASAGAO sources with K<SUB>s</SUB>-band counterparts, and constrain the faintest luminosity of the LF at 2.0 &lt; z &lt; 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 (L<SUB>IR</SUB>/L<SUB>☉</SUB>) ≳ 11.8 account for ≈60%-90% of the z ̃ 2 cosmic star-formation rate density....

DOI： 10.1093/pasj/psy104

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arXiv

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Publisher：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

Web of Science

Scopus

Language：English  

Submillimeter bright galaxies in the early Universe are vigorously forming
stars at ~1000 times higher rate than the Milky Way. A large fraction of stars
is formed in the central 1 kiloparsec region, that is comparable in size to
massive, quiescent galaxies found at the peak of the cosmic star formation
history, and eventually the core of giant elliptical galaxies in the
present-day Universe. However, the physical and kinematic properties inside a
compact starburst core are poorly understood because dissecting it requires
angular resolution even higher than the Hubble Space Telescope can offer. Here
we report 550 parsec-resolution observations of gas and dust in the brightest
unlensed submillimeter galaxy at z=4.3. We map out for the first time the
spatial and kinematic structure of molecular gas inside the heavily
dust-obscured core. The gas distribution is clumpy while the underlying disk is
rotation-supported. Exploiting the high-quality map of molecular gas mass
surface density, we find a strong evidence that the starburst disk is
gravitationally unstable, implying that the self-gravity of gas overcomes the
differential rotation and the internal pressure by stellar radiation feedback.
The observed molecular gas would be consumed by star formation in a timescale
of 100 million years, that is comparable to those in merging starburst
galaxies. Our results suggest that the most extreme starburst in the early
Universe originates from efficient star formation due to a gravitational
instability in the central 2 kpc region.

DOI： 10.1038/s41586-018-0443-1

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PubMed

arXiv

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Publishing type：Research paper (scientific journal)  

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<SUP>-1</SUP> with a {0^{^''<SUB>.</SUB>}5} resolution. Combining the present survey with earlier, archived observations, we map an area of 20 arcmin<SUP>2</SUP> (71 comoving Mpc<SUP>2</SUP> at z = 3.09). Within the combined survey area we have detected 35 sources at a signal-to-noise ratio (S/N) &gt;5, with flux densities of S<SUB>1.1mm</SUB> = 0.43-5.6 mJy, equivalent to star-formation rates of ≳100-1000 M<SUB>☉</SUB> yr<SUP>-1</SUP> 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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arXiv

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We present morphological properties of dusty star-forming galaxies at z=1-3
determined with high-resolution (FWHM~0"19) Atacama Large
Milllimeter/submilimeter Array (ALMA) 1-mm band maps of our ASAGAO survey
covering a 26-arcmin^2 area in GOODS-S. In conjunction with the ALMA archival
data, the present sample consists of 42 ALMA sources with a wide rest-frame
far-infrared (FIR) luminosity L_FIR range of ~10^11-10^13 Lo. To obtain an
average rest-frame 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 the dusty star-forming galaxies have the average
FIR-wavelength Sersic index and effective radius of n_FIR=1.2+/-0.2 and
R_e,FIR=1.0-1.3 kpc, respectively, additionally with a point source at the
center, indicative of the existence of AGN. The average FIR profile agrees with
a morphology of an exponential-disk clearly distinguished from a spheroidal
profile (Sersic index of 4). We also examine the rest-frame optical Sersic
index n_opt and effective radius R_e,opt with the deep Hubble Space Telescope
(HST) images. Interestingly, we obtain n_opt=0.9+/-0.3 (~n_FIR) and
R_e,opt=3.2+/-0.6 kpc (>R_e,FIR), suggesting that the FIR-emitting disk is
embedded within a larger stellar disk. The rest-frame UV and FIR data of HST
and ALMA provide us a radial surface density profile of the total
star-formation rate (SFR), where the FIR SFR dominates over the UV SFR at the
center. Under the simple assumption of a constant SFR, a compact stellar
distribution found in z~1-2 compact quiescent galaxies (cQGs) is well
reproduced, while a spheroidal stellar morphology of cQGs (n_opt=4) cannot,
suggestive of other important mechanisms such as dynamical dissipation.

DOI： 10.3847/1538-4357/aac6c4

Web of Science

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arXiv

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We present our ALMA Cycle 4 measurements of the [CII] emission line and the
underlying far-infrared (FIR) continuum emission from four optically
low-luminosity ($M_{\rm 1450} > -25$) quasars at $z \gtrsim 6$ discovered by
the Subaru Hyper Suprime Cam (HSC) survey. The [CII] line and FIR continuum
luminosities lie in the ranges $L_{\rm [CII]} = (3.8-10.2) \times 10^8~L_\odot$
and $L_{\rm FIR} = (1.2-2.0) \times 10^{11}~L_\odot$, which are at least one
order of magnitude smaller than those of optically-luminous quasars at $z
\gtrsim 6$. We estimate the star formation rates (SFR) of our targets as
$\simeq 23-40~M_\odot ~{\rm yr}^{-1}$. 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 $L_{\rm [CII]}/L_{\rm FIR}$ ratios of the hosts, $\simeq
(2.2-8.7) \times 10^{-3}$, are fully consistent with local star-forming
galaxies. Using the [CII] dynamics, we derived their dynamical masses within a
radius of 1.5-2.5 kpc as $\simeq (1.4-8.2) \times 10^{10}~M_\odot$. 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 $z \sim 6$, 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 the most of 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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arXiv

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Language：English  

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. The abundance of star-forming galaxies is known to
decline 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 present spectroscopic observations
of MACS1149-JD1, 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 $9.1096\pm0.0006$, 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 the 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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PubMed

arXiv

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Publishing type：Research paper (scientific 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 arcmin<SUP>2</SUP> (12 sources at a 1.2 mm flux-density limit of ≈ 0.6 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 z=1.5{--}3 are found to be {90}<SUB>-19</SUB><SUP>+8</SUP>% and {57}<SUB>-25</SUB><SUP>+23</SUP>% for the ultra-luminous and luminous infrared galaxies with log {L}<SUB>{IR</SUB>}/{L}<SUB>☉ </SUB> = 12-12.8 and log {L}<SUB>{IR</SUB>}/{L}<SUB>☉ </SUB> = 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 {L}<SUB>{ { X</SUB> } }/ {L}<SUB>{IR</SUB>} ratios smaller than the “simultaneous evolution” value expected from the local black-hole-mass-to-stellar-mass ({M}<SUB>{BH</SUB>}-M <SUB>*</SUB>) relation. On the basis of the {L}<SUB>{ { X</SUB> } } and stellar mass relation, we infer that a large fraction of star-forming galaxies at z=1.5{--}3 have black hole masses that are smaller than those expected from the local {M}<SUB>{BH</SUB>}-M <SUB>*</SUB> 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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arXiv

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Language：English   Publishing type：Research paper (scientific journal)  

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Publishing type：Research paper (scientific journal)  

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 M <SUB>☉</SUB> yr<SUP>-1</SUP>. 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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arXiv

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We report the study of far-IR sizes of submillimeter galaxies (SMGs) in
relation to their dust-obscured star formation rate (SFR) and active galactic
nuclei (AGN) presence, determined using mid-IR photometry. We determined the
millimeter-wave ($\lambda_{\rm obs}=1100 \mu$m) sizes of 69 ALMA-identified
SMGs, selected with $\geq10$$\sigma$ confidence on ALMA images ($F_{\rm 1100
\mu m}=1.7$--7.4 mJy). We found that all the SMGs are located above an
avoidance region in the millimeter size-flux 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 $R_{\rm c,e} =
1.6^{+0.34}_{-0.21}$ and 1.5$^{+0.93}_{-0.24}$ kpc. Instead, the SMGs for which
the mid-IR emission corresponds to star-forming/AGN composites have more
compact millimeter-wave sizes, with median $R_{\rm c,e}=1.0^{+0.20}_{-0.20}$
kpc. 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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arXiv

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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 three-dimensional signal-to-noise ratio (S/N) cubes with 60 MHz 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 [CII] 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 [CII]
luminosity functions at unprecedentedly low luminosity levels, i.e., down to
$<~ 10^{-3}-10^{-1} $Mpc$^{-3}$ dex$^{-1}$ at $L'_{CO} ~ 10^8-10^{10}$ K km
$s^{-1}$ pc$^2$ and $<~ 10^{-3}-10^{-2}$ Mpc$^{-3}$ dex$^{-1}$ at $L_[CII] ~
10^8-10^{10} L_\odot$, respectively. Although the constraints to date are not
stringent yet, we find that the evolution of the CO and [CII] 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 [CII] luminosity functions.

DOI： 10.3847/1538-4357/aa80e0

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arXiv

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：OXFORD UNIV PRESS  

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 r(e) = 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 (greater than or similar to 10) and stellar mass (similar to 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 Sersic model. It shows a spatially extended [O III] lambda 5007 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-* less than or similar to 4 x 10(10) M-circle dot and/or poor detection completeness of them owing to their diffuse morphologies.

DOI： 10.1093/mnras/stx920

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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 H$\alpha$ emitters
(HAEs) and four out of 19 in 1.1 mm dust continuum. They have high stellar mass
($M_{\star}>4\times 10^{10}$ $M_{\odot}$) and exhibit a specific star-formation
rate typical of main-sequence star forming galaxies at $z\sim2.5$. Different
gas mass estimators from CO(3-2) and 1.1 mm yield consistent values for
simultaneous detections. The gas mass ($M_{\rm gas}$) and gas fraction ($f_{\rm
gas}$) are comparable to those of field galaxies, with $M_{\rm gas}=[0.3,
1.8]\times10^{11} \times (\alpha_{\rm CO}/(4.36\times A(Z)$)) M$_{\odot}$,
where $\alpha_{\rm CO}$ is the CO-to-H$_2$ conversion factor and $A(Z)$ the
additional correction factor for the metallicity dependence of $\alpha_{\rm
CO}$, and $\langle f_{\rm gas}\rangle = 0.53 \pm 0.07$ from CO(3-2). Our
measurements place a constraint on the cosmic gas density of high-$z$
protoclusters, indicating the protocluster is characterized by a gas density
higher than that of the general fields by an order of magnitude. We found $\rho
(H_2)\sim 5 \times 10^9 \,M_{\odot}\,{\rm Mpc^{-3 } }$ 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 imply a
potentially critical role of environment on early galaxy evolution at high-z
protoclusters, although future observations are necessary for confirmation.

DOI： 10.3847/1538-4357/aa74c2

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arXiv

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：OXFORD UNIV PRESS  

Using galaxies as background light sources to map intervening Ly a 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 alpha absorption relative to the cosmic mean, Delta NB497, estimated from photometric data of star-forming galaxies at 3.3 less than or similar to z less than or similar to 3.5, we have made two-dimensional Delta NB497 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 similar to 5 comoving Mpc. The Delta NB497 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. similar to 50 comovingMpc scale) Delta NB497 and the overdensity of Ly alpha emitters (LAEs) seem to be correlated, while there is no clear dependency of the Delta NB497 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 Delta NB497 at a projected distance &lt; 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 alpha emission, which suggests that the Ly alpha escape fraction from galaxies depends on hydrogen neutrality in the CGM.

DOI： 10.1093/mnras/stx038

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arXiv

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Publishing type：Research paper (scientific journal)  

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<SUP>2</SUP>, frequency ranges of 253.1-256.8 and 269.1-272.8 GHz, angular resolution of 0{^''<SUB>.</SUB>}7 and rms noise of 0.8 mJy beam<SUP>-1</SUP> at 36 km s<SUP>-1</SUP> 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<SUP>8</SUP> L<SUB>☉</SUB>. The star formation rates (SFRs) of these sources are estimated to be 10-20 M<SUB>☉</SUB> yr<SUP>-1</SUP> 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 &gt;10<SUP>-2</SUP> M<SUB>☉</SUB> yr<SUP>-1</SUP> Mpc<SUP>-3</SUP> 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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arXiv

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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 (VLA).
These SMGs were selected originally using AzTEC at 1100 micron, and are
observed by Herschel to be faint at 100--500 micron. 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 microJy at IRAC 4.5 micron and <0.2
microJy in the Ks filter. These SMGs are also faint in the radio waveband,
where F_6GHz=4.5 microJy for ASXDF1100.053.1 and F_1.4GHz=28 microJy for
ASXDF1100.231.1, suggestive of z=6.5^{+1.4}_{-1.1} and z=4.1^{+0.6}_{-0.7} for
ASXDF1100.053.1 and 231.1, respectively. ASXDF1100.231.1 has a flux excess in
the 3.6-micron filter, probably due to H$\alpha$ 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]x10^{12} and
[4.2-4.5]x10^{12} L_sun; their stellar masses are [0.9-2]x10^{11} and
[0.4-3]x10^{10} M_sun; their circularized half-light radii in the ALMA maps are
~1 and <~0.2 kpc (~2--3 kpc for 90% of the total flux). Lastly, their surface
infrared luminosity densities, Sigma_IR, are ~1x10^{12} and >~1.5x10^{13} L_sun
kpc^{-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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arXiv

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We present results from a deep 2'x3' (comoving scale of 3.7 Mpc x 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 micro-Jy/beam at a
spatial resolution of 0".7. We detect 18 robust ALMA sources at a
signal-to-noise ratio (SNR) > 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 ten 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 SNR > 10 have a median
intrinsic angular size of 0".32+0".13-0".06 (2.4+1.0-0.4 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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We report the result from observations conducted with the Atacama Large
Millimeter/submillimeter Array (ALMA) to detect [CII] 158 um fine structure
line emission from galaxies embedded in one of the most spectacular Lyman-alpha
blobs (LABs) at z=3.1, SSA22-LAB1. Of three dusty star-forming galaxies
previously discovered by ALMA 860 um dust continuum survey toward SSA22-LAB1,
we detected the [CII] 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 z_spec~3.1 galaxies within the field of
view. For LAB1-ALMA3, we find relatively bright [CII] emission compared to the
infrared luminosity (L_[CII]/L_[CII]) and an extremely high [CII] 158 um and
[NII] 205 um emission line ratio (L_[CII]/L_[NII]>55). The relatively strong
[CII] emission may be caused by abundant photodissociation regions and
sub-solar metallicity, or by shock heating. The origin of the unusually strong
[CII] emission could be causally related to the location within the giant LAB,
although the relationship between extended Lyman-alpha emission and ISM
conditions of associated galaxies is yet to be understand.

DOI： 10.3847/2041-8213/834/2/L16

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arXiv

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DOI： 10.3847/1538-4357/833/2/195

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We present a multi-wavelength analysis of five submillimeter sources (S_1.1mm
= 0.54-2.02 mJy) that were detected during our 1.1-mm-deep continuum survey in
the SXDF-UDS-CANDELS field (2 arcmin^2, 1sigma = 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}_{-3.0} Jy 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 multi-wavelength 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 (L_IR ~ 1e12 L_sun or SFR ~ 100 M_sun
yr^{-1}). By fitting the spectral energy distributions (SEDs) at the
optical-to-near-infrared wavelengths of the remaining four ALMA sources, we
obtained the photometric redshifts (z_photo) and stellar masses (M_*): z_photo
~ 1.3-2.5, M_* ~ (3.5-9.5)e10 M_sun. We also derived their star formation rates
(SFRs) and specific SFRs (sSFRs) as ~ 30-200 M_sun 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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Language：English   Publishing type：Research paper (scientific journal)   Publisher：OXFORD UNIV PRESS  

We exploit Atacama Large Interferometer Array (ALMA) 870 mu m observations to measure the star formation rates (SFRs) of eight X-ray detected active galactic nuclei (AGNs) in a z approximate to 3.1 protocluster, four of which reside in extended Ly alpha haloes (often termed Lymanalpha blobs: LABs). Three of the AGNs are detected by ALMA and have implied SFRs of approximate to 220-410 M-circle dot yr(-1); the non-detection of the other five AGNs places SFR upper limits of approximate to 210 M-circle dot yr(-1). The mean SFR of the protocluster AGNs (approximate to 110-210 M-circle dot yr(-1)) is consistent (within a factor of approximate to 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 approximate to 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 Ly alpha emission. The SFRs of the ALMA sources within the LABs (approximate to 150-410 M-circle dot 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 greater than or similar to 100 kpc) do not host more luminous star formation than the smaller LABs, despite being an order of magnitude brighter in Ly alpha emission. We use these results to discuss star formation as the power source of LABs.

DOI： 10.1093/mnras/stw1509

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The central structure in three of the brightest unlensed z=3-4 submillimeter
galaxies are investigated through 0.015" - 0.05" (120 -- 360~pc) 860 micron
continuum images obtained using the Atacama Large Millimeter/submillimeter
Array (ALMA). The distribution in the central kpc in AzTEC1 and AzTEC8 are
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 Msun/yr/kpc^2, suggesting regions with extreme star formation near the
Eddington Limit. By comparing the flux obtained by ALMA and Submillimeter Array
(SMA), we find that 68-90% of the emission is extended (> 1 kpc) in AzTEC 4 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 to 30% of the 860 micron continuum is concentrated in clumpy
structures in the central kpc 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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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 (S<SUB>350</SUB>/S<SUB>250</SUB> and S<SUB>500</SUB>/S<SUB>350</SUB>) 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 10<SUP>3</SUP>-10<SUP>4</SUP> 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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Language：English  

The physical properties and elemental abundances of the interstellar medium
in galaxies during cosmic reionization are important for understanding the role
of galaxies in this process. We report the Atacama Large
Millimeter/submillimeter Array detection of an oxygen emission line at a
wavelength of 88 micrometers from a galaxy at an epoch about 700 million years
after the Big Bang. The oxygen abundance of this galaxy is estimated at about
one-tenth that of the Sun. The non-detection of far-infrared continuum emission
indicates a deficiency of interstellar dust in the galaxy. A carbon emission
line at a wavelength of 158 micrometers is also not detected, implying an
unusually small amount of neutral gas. These properties might allow ionizing
photons to escape into the intergalactic medium.

DOI： 10.1126/science.aaf0714

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PubMed

arXiv

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1093/pasj/psw026

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Language：Japanese   Publisher：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

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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Language：English   Publishing type：Research paper (scientific journal)   Publisher：OXFORD UNIV PRESS  

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 z(spec) approximate to 3.09 within 180 kpc, including fivemassive objectswith the stellarmasses larger than 10(10.5) M-circle dot 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 is M-dyn similar to 1.6 +/- 0.3 x 10(13)M(circle dot). 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 M-vir = 10(13.4)-10(14.0)M(circle dot) 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(-2.0)(+5.1) x 10(11)M(circle dot), 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 Ly alpha 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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Language：English   Publishing type：Research paper (scientific journal)  

<jats:title>Abstract</jats:title><jats:p>We have conducted 1.1 mm ALMA observations of a contiguous 105” × 50” or 1.5 arcmin<jats:sup>2</jats:sup> 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 <jats:italic>L</jats:italic><jats:sub>IR</jats:sub> ~6×10<jats:sup>11</jats:sup><jats:italic>L</jats:italic><jats:sub>⊙</jats:sub> (if <jats:italic>T</jats:italic><jats:sub>dust</jats:sub>=40K) up to <jats:italic>z</jats:italic> ~ 10 thanks to the negative K-correction at this wavelength. We detected 5 brightest sources (S/N&gt;6) and 18 low-significant sources (5&gt;S/N&gt;4; they may contain spurious detections, though). One of the 5 brightest ALMA sources (<jats:italic>S</jats:italic><jats:sub>1.1mm</jats:sub> = 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 <jats:italic>z</jats:italic>=5.955 or a low-<jats:italic>z</jats:italic> CO emitting galaxy within the field, allowing us to constrain the [CII] and/or CO luminosity functions across the history of the universe.</jats:p>

DOI： 10.1017/S1743921315010364

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DOI： 10.1017/S1743921315010327

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Publishing type：Research paper (scientific journal)   Publisher：{IOP} Publishing  

© 2015. The American Astronomical Society. All rights reserved. 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∼ 1012.1-1013.1Lo) 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 Moyr-1Mpc-3in 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 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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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 first results from the SXDF-ALMA 1.5 arcmin^2 deep survey at 1.1
mm using Atacama Large Millimeter Array (ALMA). The map reaches a 1sigma depth
of 55 uJy/beam and covers 12 Halpha-selected star-forming galaxies at z = 2.19
or z=2.53. We have detected continuum emission from three of our
Halpha-selected sample, including one compact star-forming galaxy with high
stellar surface density, NB2315-07. They are all red in the rest-frame optical
and have stellar masses of log (M*/Msun)>10.9 whereas the other blue,
main-sequence galaxies with log(M*/Msun)=10.0-10.8 are exceedingly faint, <290
uJy (2sigma upper limit). We also find the 1.1 mm-brightest galaxy, NB2315-02,
to be associated with a compact (R_e=0.7+-0.1 kpc), dusty star-forming
component. Given high gas fraction (44^{+20}_{-8}% or 37^{+25}_{-3}%) and high
star formation rate surface density (126^{+27}_{-30} Msun yr^{-1}kpc^{-2}), the
concentrated starburst can within less than 50^{+12}_{-11} Myr build up 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
centre. On the other hand, NB2315-07, which already has such a high stellar
surface density core, shows a gas fraction (23+-8%) and is located in the lower
envelope of the star formation main-sequence. This compact less star-forming
galaxy 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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We present ALMA Cycle 1 observations of the central kpc region of the
luminous type-1 Seyfert galaxy NGC 7469 with unprecedented high resolution
(0.5$"$ $\times$ 0.4$"$ = 165 pc $\times$ 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
$\mu$m continuum. The region consists of the central $\sim$ 1$"$ component and
the surrounding starburst ring with a radius of $\sim$ 1.5$"$-2.5$"$. Several
structures connect these components. Except for CO(3-2), these dense gas
tracers are significantly concentrated towards the central $\sim$ 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 anti-correlated 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 AGN position
than at the starburst ring, which is consistent to our previous findings
(submm-HCN enhancement). However, the HCN(4-3)/HCO$^+$(4-3) ratio at the AGN
position of NGC 7469 (1.11$\pm$0.06) is almost half of the corresponding value
of the low-luminosity type-1 Seyfert galaxy NGC 1097 (2.0$\pm$0.2), despite the
more than two orders of magnitude higher X-ray luminosity of NGC 7469. But the
ratio is comparable to that of the close vicinity of the AGN of NGC 1068
($\sim$ 1.5). Based on these results, we speculate that some other heating
mechanisms than X-ray (e.g., mechanical heating due to 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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arXiv

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Publishing type：Research paper (scientific journal)  

DOI： 10.1088/0004-637X/810/2/133

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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-arcmin<SUP>2</SUP> field down to a 1σ sensitivity of 0.7-1.3 mJy beam<SUP>-1</SUP> 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 cross-correlation 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....

DOI： 10.1093/mnras/stu447

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Cambridge University Press  

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 SFR1.4GHz and SFRHα for 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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We present results from the AzTEC/ASTE 1.1-mm imaging survey of 35 Ly-alpha
blobs (LABs) found in the SSA22 protocluster at z = 3.1. These 1.1-mm data
reach an r.m.s. noise level of 0.7-1 mJy/beam, making this the largest
millimetre-wave survey of LABs to date. No significant (> 3.5-sigma) emission
is found in any of individual 35 LABs, and from this, we estimate 3-sigma upper
limits on the far-infrared luminosity of L_FIR < 2e+12 Lsun. Stacking analysis
reveals that the 1.1-mm flux density averaged over the LABs is S(1.1mm) < 0.40
mJy (3-sigma), which places a constraint of L_FIR < 4.5e+11 Lsun. This
indicates that earlier 850-um measurements of the LABs may have overestimated
their flux densities. Our results suggest that LABs on average have little
ultra-luminous 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 ~ 10^3 Msun/yr. Observations with ALMA are needed to
directly study the obscured part of star-formation activity in the LABs.

DOI： 10.1093/mnras/stt077

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Language：Japanese  

CiNii Research

Language：English   Publisher：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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CiNii Books

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Publishing type：Research paper (scientific journal)  

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 &lt; z &lt; 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 &lt;σ&gt; = 220 ± 80 km s<SUP>-1</SUP> and an average half-light radius of &lt;r<SUB>1/2</SUB>&gt; = 3.7 ± 0.8 kpc. The dynamical measure, &lt;V<SUB>obs</SUB>/2σ&gt; = 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 ± 90 M<SUB>☉</SUB> yr<SUP>-1</SUP>, 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 ± 100 km s<SUP>-1</SUP> and average projected spatial offsets of 8 ± 2 kpc, 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 &lt; log (M[h<SUP>-1</SUP> M<SUB>☉</SUB>]) &lt; 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....

DOI： 10.1111/j.1365-2966.2012.21386.x

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arXiv

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Language：Japanese  

CiNii Research

Language：English   Publishing type：Research paper (scientific journal)   Publisher：IOP PUBLISHING LTD  

We present the results of near-tomid-infrared slit spectroscopic observations (2.55-13.4 mu m) 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 mu m 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 H II regions. In Group A, the band ratios of I-3.3 (mu m)/I-11.3 (mu m), I-6.2 (mu m)/I-11.3 (mu m), I-7.7 (mu m)/I-11.3 (mu m), and I-8.6 (mu m)/I-11.3 (mu m) 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 mu m 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-3.3 (mu m)/I-11.3 (mu m) versus I-7.7 (mu m)/I-11.3 (mu m) 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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arXiv

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：WORLD SCIENTIFIC PUBL CO PTE LTD  

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 the (CO)-C-12 (J = 1 -0) detection by NANTEN survey, and detect distinct unidentified infrared (UIR) bands (6.2 mu m, 7.7 mu m, 8.6 mu m, 11.2 mu m) 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 mu m/11.2 mu m and the IRAS 60 mu m/100 mu m color are carried out. We find that the band ratios peak at positions with an intermediate IRAS 60 mu m/100 mu m color of I-60 mu m/I-100 mu m similar to 0.5 and decreases at positions with lower or higher IRAS 60 mu m/100 mu m colors of I-60 mu m/I-100 mu m similar to 0.4 and I-60 mu m/I-100 mu m similar to 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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Scopus

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：ASTRONOMICAL SOC PACIFIC  

We report the results of near-infrared (NIR) to mid-infrared (MIR) slit spectroscopic observations of the diffuse emission from the Large Magellanic Cloud (LMC) with the Infrared Camera (IRC) on board AKARI. The present results suggest that the 3.3 mu m Unidentified Infrared (UIR) band provides powerful information on the size distribution and/or the excitation conditions of PAHs. A combination of the MIR bands with the 3.3 mu m band, such as the diagram of I-3.3/I-11.3 vs. I-7.7/I-11.3, is shown to be a useful diagnostic tool for the radiation conditions of the PAH emitting regions.

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J-GLOBAL

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J-GLOBAL

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J-GLOBAL

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Language：Japanese  

J-GLOBAL

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J-GLOBAL

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J-GLOBAL

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Language：Japanese  

J-GLOBAL

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Language：Japanese   Publisher：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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