Faculty Profiles - TAMURA Yoichi

Papers - TAMURA Yoichi

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ALMA detection of the [OIII] 88 μm line in a highly-magnified Lyman break galaxy at z = 6.1 International journal

Kaho Sunaga, Yoichi Tamura, Minju Lee, Ken Mawatari, Akio K. Inoue, Takuya Hashimoto, Hiroshi Matsuo, Akio Taniguchi

Proceedings of the International Astronomical Union Vol. 15 ( S341 ) page： 309 - 311 2020.6

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

<title>Abstract</title>We present a 4.7σ detection of the [OIII] 88 <italic>μ</italic>m line in a gravitationally-lensed Lyman break galaxy, RXC J2248-ID3, using the Atacama Large Millimeter/submillimeter Array (ALMA). We did not detect [CII] 158 <italic>μ</italic>m and rest-frame 90 <italic>μ</italic>m dust continuum emission, suggesting that the bulk of the interstellar medium (ISM) is ionized. Our two-component SED model combining the previous Hubble Space Telescope (HST) data and new photometry obtained from Very Large Telescope (VLT), Spitzer and ALMA suggests the presence of young (∼2 Myr) and mature (∼600 Myr) stellar components with the metallicity of <italic>Z</italic> = 0.2Z<sub>⊙</sub>. Our findings are in contrast with previous results claiming a very young, metal-poor stellar component.

DOI： 10.1017/s174392131900245x

Rapid evolution and transformation into quiescence?: ALMA view on z > 6 low-luminosity quasars International journal Open Access

Takuma Izumi, Masafusa Onoue, Yoshiki Matsuoka, Tohru Nagao, Michael A. Strauss, Masatoshi Imanishi, Nobunari Kashikawa, Seiji Fujimoto, Kotaro Kohno, Yoshiki Toba, Hideki Umehata, Tomotsugu Goto, Yoshihiro Ueda, Hikari Shirakata, John D. Silverman, Jenny E. Greene, Yuichi Harikane, Yasuhiro Hashimoto, Soh Ikarashi, Daisuke Iono, Kazushi Iwasawa, Chien-Hsiu Lee, Takeo Minezaki, Kouichiro Nakanishi, Yoichi Tamura, Ji-Jia Tang, Akio Taniguchi

Proceedings of the International Astronomical Union Vol. 15 ( S352 ) page： 139 - 143 2020.6

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

<title>Abstract</title>We present ALMA [CII] line and far-infrared (FIR) continuum observations of seven <italic>z</italic> > 6 low-luminosity quasars (<italic>M</italic><sub>1450</sub> > −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) × 10<sup>8</sup> L<sub>⊙</sub>, 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><sub>FIR</sub> < 10<sup>11</sup><italic>L</italic><sub>⊙</sub> to ∼2 × 10<sup>12</sup><italic>L</italic><sub>⊙</sub>. 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

Panchromatic Analysis for Nature of HIgh-z galaxies Tool (PANHIT) International journal

Ken Mawatari, Akio K. Inoue, Satoshi Yamanaka, Takuya Hashimoto, Yoichi Tamura

Proceedings of the International Astronomical Union Vol. 15 ( S341 ) page： 285 - 286 2020.6

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

<title>Abstract</title>We have developed a new SED fitting tool specialized for frontier redshift galaxies. It is a common case for high-<italic>z</italic> galaxies that the available data are restricted to rich optical to near-infrared photometry and few far-infrared (FIR) data deep enough to detect the faint object (e.g., <italic>HST</italic>/WFC3 + <italic>Spitzer</italic>/IRAC + ALMA). In such situation, one cannot perform a complicated modeling of dust emission in FIR regime. We then adopt simple treatment for the dust emission using empirical LIRG templates. Instead, we adopt a sophisticated and physically motivated modeling for stellar and nebular emission parts in rest-frame UV-to-optical regime. Our new code fits not only broad band photometry but also spectral emission line flux. There is an option to fit observed SED with two templates with different physical properties. Our new code, PANHIT, is now in public, and was already applied to some high-<italic>z</italic> frontier galaxies.

DOI： 10.1017/s1743921319002606

Dust evolution in galaxies at z > 7 International journal

Tsutomu T. Takeuchi, Ryosuke S. Asano, Sayaka Nagasaki, Takaya Nozawa, Yoichi Tamura, Ken Mawatari, Akio K. Inoue

Proceedings of the International Astronomical Union Vol. 15 ( S341 ) page： 312 - 313 2020.6

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

<title>Abstract</title>Recently huge amount of dust <italic>M</italic><sub>dust</sub> ≃ 10<sup>6−7</sup><italic>M</italic><sub>⊙</sub> in galaxies at <italic>z</italic> = 7–8 has been discovered by ALMA observations. The suggested timescale of the dust production was a few–several×10<sup>8</sup> yr, while the stellar mass was several × 10<sup>9</sup><italic>M</italic><sub>⊙</sub>. This amount of dust cannot be easily explained only by a supply from supernovae if we consider the dust destruction by reverse shocks. We propose that these values can be consistently explained if we take into account the grain growth in the interstellar medium (ISM). This scenario successfully reproduces the evolution of the dust mass, as well as the SFR, and stellar mass simultaneously. We conclude that even at such an early epoch of the Universe, the dust grain growth in the ISM plays a significant role in galaxies.

DOI： 10.1017/s1743921319003107

ALMA Observations of Molecular Gas in the Host Galaxies of Long-duration GRBs International journal

Hatsukade, Bunyo, Ohta, Kouji, Hashimoto, Tetsuya, Kohno, Kotaro, Nakanishi, Kouichiro, Niino, Yuu, Tamura, Yoichi

Yamada Conference LXXI: Gamma-ray Bursts in the Gravitational Wave Era 2019 page： 157 - 159 2020.5

DESHIMA on ASTE: On-Sky Responsivity Calibration of the Integrated Superconducting Spectrometer Reviewed

Tatsuya Takekoshi, Kenichi Karatsu, Junya Suzuki, Yoichi Tamura, Tai Oshima, Akio Taniguchi, Shin’ichiro Asayama, Tom J. L. C. Bakx, Jochem J. A. Baselmans, Sjoerd Bosma, Juan Bueno, Kah Wuy Chin, Yasunori Fujii, Kazuyuki Fujita, Robert Huiting, Soh Ikarashi, Tsuyoshi Ishida, Shun Ishii, Ryohei Kawabe, Teun M. Klapwijk, Kotaro Kohno, Akira Kouchi, Nuria Llombart, Jun Maekawa, Vignesh Murugesan, Shunichi Nakatsubo, Masato Naruse, Kazushige Ohtawara, Alejandro Pascual Laguna, Koyo Suzuki, David J. Thoen, Takashi Tsukagoshi, Tetsutaro Ueda, Pieter J. de Visser, Paul P. van der Werf, Stephen J. C. Yates, Yuki Yoshimura, Ozan Yurduseven, Akira Endo

Journal of Low Temperature Physics Vol. 199 ( 1-2 ) page： 231 - 239 2020.4

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Springer Science and Business Media LLC

We are developing an ultra-wideband spectroscopic instrument, DESHIMA (DEep Spectroscopic HIgh-redshift MApper), based on the technologies of an on-chip filter bank and microwave kinetic inductance detector (MKID) to investigate dusty starburst galaxies in the distant universe at millimeter and submillimeter wavelengths. An on-site experiment of DESHIMA was performed using the ASTE 10-m telescope. We established a responsivity model that converts frequency responses of the MKIDs to line-of-sight brightness temperature. We estimated two parameters of the responsivity model using a set of skydip data taken under various precipitable water vapor (PWV 0.4-3.0 mm) conditions for each MKID. The line-of-sight brightness temperature of sky is estimated using an atmospheric transmission model and the PWVs. As a result, we obtain an average temperature calibration uncertainty of 1 sigma=4, which is smaller than other photometric biases. In addition, the average forward efficiency of 0.88 in our responsivity model is consistent with the value expected from the geometrical support structure of the telescope. We also estimate line-of-sight PWVs of each skydip observation using the frequency response of MKIDs and confirm the consistency with PWVs reported by the Atacama Large Millimeter/submillimeter Array.

DOI： 10.1007/s10909-020-02338-0

Other Link： http://link.springer.com/article/10.1007/s10909-020-02338-0/fulltext.html

ALMA uncovers the [C II] emission and warm dust continuum in a z=8.31 Lyman break galaxy Reviewed

Bakx Tom J. L. C., Tamura Yoichi, Hashimoto Takuya, Inoue Akio K., Lee Minju M., Mawatari Ken, Ota Kazuaki, Umehata Hideki, Zackrisson Erik, Hatsukade Bunyo, Kohno Kotaro, Matsuda Yuichi, Matsuo Hiroshi, Okamoto Takashi, Shibuya Takatoshi, Shimizu Ikkoh, Taniguchi Yoshiaki, Yoshida Naoki

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY Vol. 493 ( 3 ) page： 4294 - 4307 2020.4

ALMA CO Observations of the Host Galaxies of Long-duration Gamma-Ray Bursts. I. Molecular Gas Scaling Relations Reviewed

Bunyo Hatsukade, Kouji Ohta, Tetsuya Hashimoto, Kotaro Kohno, Kouichiro Nakanishi, Yuu Niino, Yoichi Tamura

The Astrophysical Journal Vol. 892 ( 1 ) page： 42 - 42 2020.3

A new off-point-less observing method for millimeter and submillimeter spectroscopy with a frequency-modulating local oscillator Reviewed

Akio Taniguchi, Yoichi Tamura, Kotaro Kohno, Shigeru Takahashi, Osamu Horigome, Jun Maekawa, Takeshi Sakai, Nario Kuno, Tetsuhiro Minamidani

Publications of the Astronomical Society of Japan Vol. 72 ( 1 ) page： 2 2020.2

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

<title>Abstract</title>
We propose a new observing method for single-dish millimeter and submillimeter spectroscopy using a heterodyne receiver equipped with a frequency-modulating local oscillator (FMLO). Unlike conventional switching methods, which extract astronomical signals by subtracting the reference spectra of off-sources from those of on-sources, the FMLO method does not need to obtain any off-source spectra; rather, it estimates them from the on-source spectra themselves. The principle uses high-dump-rate (10 Hz) spectroscopy with radio frequency modulation achieved by fast sweeping of a local oscillator of a heterodyne receiver. Because sky emission (i.e., off-source) fluctuates as $1/f$ and is spectrally correlated, it can be estimated and subtracted from time series spectra (a timestream) by principal component analysis. Meanwhile, astronomical signals remain in the timestream since they are modulated to a higher time-frequency domain. The FMLO method therefore achieves (1) a remarkably high observation efficiency, (2) reduced spectral baseline wiggles, and (3) software-based sideband separation. We developed an FMLO system for the Nobeyama $45\:$m telescope and a data reduction procedure for it. Frequency modulation was realized by a tunable and programmable first local oscillator. With observations of Galactic sources, we demonstrate that the observation efficiency of the FMLO method is dramatically improved compared to conventional switching methods. Specifically, we find that the time to achieve the same noise level is reduced by a factor of 3.0 in single-pointed observations and by a factor of 1.2 in mapping observations. The FMLO method can be applied to observations of fainter ($\sim$mK) spectral lines and larger ($\sim$deg$^{2}$) mapping. It offers much more efficient and baseline-stable observations compared to conventional switching methods.

DOI： 10.1093/pasj/psz121

Large format imaging spectrograph for the Large Submillimeter Telescope (LST)

Kotaro Kohno, Ryohei Kawabe, Yoichi Tamura, Akira Endo, Jochem J. A. Baselmans, Kenichi Karatsu, Akio Inoue, Kana Moriwaki, Natsuki H. Hayatsu, Naoki Yoshida, Yuki Yoshimura, Bunyo Hatsukade, Hideki Umehata, Tai Oshima, Tatsuya Takekoshi, Akio Taniguchi, Pamela Klaassen, Tony Mroczkowski, Claudia Cicone, Frank Bertoldi, Helmut Dannerbauer, Tomoka Tosaki

Proceedings of the SPIE Vol. 11453 page： 114530N 2020

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

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

DOI： 10.1117/12.2561238

TiEMPO: Open-source time-dependent end-to-end model for simulating ground-based submillimeter astronomical observations

Esmee Huijten, Yannick Roelvink, Stefanie A. Brackenhoff, Akio Taniguchi, Tom Bakx, Kaushal B. Marthi, Stan Zaalberg, Jochem J. A. Baselmans, Kah Wuy Chin, Robert Huiting, Kenichi Karatsu, Alejandro Pascual Laguna, Yoichi Tamura, Tatsuya Takekoshi, Stephen J. C. Yates, Maarten van Hoven, Akira Endo

Proceedings of the SPIE Vol. 11453 page： 114533C 2020

Subaru High-z Exploration of Low-Luminosity Quasars (SHELLQs). VIII. A less biased view of the early co-evolution of black holes and host galaxies Reviewed

Takuma Izumi, Masafusa Onoue, Yoshiki Matsuoka, Tohru Nagao, Michael A Strauss, Masatoshi Imanishi, Nobunari Kashikawa, Seiji Fujimoto, Kotaro Kohno, Yoshiki Toba, Hideki Umehata, Tomotsugu Goto, Yoshihiro Ueda, Hikari Shirakata, John D Silverman, Jenny E Greene, Yuichi Harikane, Yasuhiro Hashimoto, Soh Ikarashi, Daisuke Iono, Kazushi Iwasawa, Chien-Hsiu Lee, Takeo Minezaki, Kouichiro Nakanishi, Yoichi Tamura, Ji-Jia Tang, Akio Taniguchi

Publications of the Astronomical Society of Japan Vol. 71 ( 6 ) 2019.12

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

<title>Abstract</title>
We present ALMA [C ii] line and far-infrared (FIR) continuum observations of three $z \gt 6$ low-luminosity quasars ($M_{\rm 1450} \gt -25$ mag) discovered by our Subaru Hyper Suprime-Cam (HSC) survey. The [C ii] line was detected in all three targets with luminosities of $(2.4\mbox{--}9.5) \times 10^8\, L_{\odot }$, about one order of magnitude smaller than optically luminous ($M_{\rm 1450} \lesssim -25$ mag) quasars. The FIR continuum luminosities range from $\lt 9 \times 10^{10}\, L_{\odot }$ (3 $\sigma$ limit) to ${\sim } 2 \times 10^{12}\, L_{\odot }$, 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 ($M_{\rm dyn}$) as a surrogate for bulge stellar mass ($M_{\rm\, bulge}$), we find that a significant fraction of low-luminosity quasars are located on or even below the local $M_{\rm\, BH}$–$M_{\rm\, bulge}$ 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 $z \sim 6$ than the parallel growth model, in which supermassive black holes and their hosts grow simultaneously to match the local $M_{\rm\, BH}$–$M_{\rm\, bulge}$ relation at all redshifts. As the low-luminosity quasars appear to realize the local co-evolutionary relation even at $z \sim 6$, they should have experienced vigorous starbursts prior to the currently observed quasar phase to catch up with the relation.

DOI： 10.1093/pasj/psz096

Detections of [O III] 88 μm in two quasars in the reionization epoch Reviewed

Hashimoto, Takuya, Inoue, Akio K., Tamura, Yoichi, Matsuo, Hiroshi, Mawatari, Ken, Yamaguchi, Yuki

Publications of the Astronomical Society of Japan Vol. 71 ( 6 ) 2019.12

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

We report on detections with the Atacama Large Millimeter/sub-millimeter Array of the far-infrared [O III] 88 μm line and the underlying dust continuum in two quasars in the reionization epoch, J205406.48-000514.8 (hereafter J2054-0005) at z = 6.0391 ± 0.0002 and J231038.88+185519.7 (hereafter J2310+1855) at z = 6.0035 ± 0.0007. The [O III] luminosities of J2054-0005 and J2310+1855 are L<SUB>[O III]</SUB> = (6.8 ± 0.6) × 10<SUP>9</SUP> and (2.4 ± 0.6) × 10<SUP>9</SUP> L<SUB>☉</SUB>, corresponding to ̃0.05% and 0.01% of the total infrared luminosity, L<SUB>TIR</SUB>, respectively. Combining these [O III] luminosities with [C II] 158 μm luminosities in the literature, we find that J2054-0005 and J2310+1855 have [O III]-to-[C II] luminosity ratios of 2.1 ± 0.4 and 0.3 ± 0.1, respectively, the latter of which is the lowest among objects so far reported at z > 6. Combining [O III] observations at z ≈ 6-9 from our study and the literature, we identify the [O III] line deficit: objects with a larger L<SUB>TIR</SUB> (total infrared luminosity) have lower L<SUB>[O III]</SUB>-to-L<SUB>TIR</SUB> ratios. Furthermore, we also find that the anti-correlation is shifted toward a higher L<SUB>TIR</SUB> value when compared with the local [O III] line deficit....

DOI： 10.1093/pasj/psz094

First [N II]122 μm Line Detection in a QSO-SMG Pair BRI 1202-0725 at z = 4.69 Reviewed

Lee, Minju M., Nagao, Tohru, De Breuck, Carlos, Carniani, Stefano, Cresci, Giovanni, Hatsukade, Bunyo, Kawabe, Ryohei, Kohno, Kotaro, Maiolino, Roberto, Mannucci, Filippo, Marconi, Alessandro, Nakanishi, Kouichiro, Saito, Toshiki, Tamura, Yoichi, Troncoso, Paulina, Umehata, Hideki, Yun, Min

The Astrophysical Journal Vol. 883 ( 2 ) page： L29 2019.10

Language：Japanese 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 > 4 for probing the interstellar medium conditions and the effects on surrounding environments....

DOI： 10.3847/2041-8213/ab412e

Large Population of ALMA Galaxies at z>6 with Very High [OIII]88um to [CII]158um Flux Ratios: Evidence of Extremely High Ionization Parameter or PDR Deficit? Reviewed

Harikane, Yuichi, Ouchi, Masami, Inoue, Akio K., Matsuoka, Yoshiki, Tamura, Yoichi, Bakx, Tom, Fujimoto, Seiji, Moriwaki, Kana, Ono, Yoshiaki, Nagao, Tohru, Tadaki, Ken-ichi, Kojima, Takashi, Shibuya, Takatoshi, Egami, Eiichi, Ferrara, Andrea, Gallerani, Simona, Hashimoto, Takuya, Kohno, Kotaro, Matsuda, Yuichi, Matsuo, Hiroshi, Pallottini, Andrea, Sugahara, Yuma, Vallini, Livia

2019.10

Publishing type：Research paper (scientific journal) Publisher：arXiv e-prints

We present our new ALMA observations targeting [OIII]88um, [CII]158um, [NII]122um, and dust continuum emission for three Lyman break galaxies at z=6.0293-6.2037 identified in the Subaru/Hyper Suprime-Cam survey. We clearly detect [OIII] and [CII] lines from all of the galaxies at 4.3-11.8sigma levels, and identify multi-band dust continuum emission in two of the three galaxies, allowing us to estimate infrared luminosities and dust temperatures simultaneously. In conjunction with previous ALMA observations for six galaxies at z>6, we confirm that all the nine z=6-9 galaxies have high [OIII]/[CII] ratios of L[OIII]/L[CII]~3-20, ~10 times higher than z~0 galaxies. We also find a positive correlation between the [OIII]/[CII] ratio and the Lya equivalent width (EW) at the >91% confidence level. We carefully investigate physical origins of the high [OIII]/[CII] ratios at z=6-9 using Cloudy, and find that high density of the interstellar medium, low C/O abundance ratio, and the cosmic microwave background attenuation are responsible to only a part of the z=6-9 galaxies. Instead, the observed high [OIII]/[CII] ratios are explained by 10-100 times higher ionization parameters or low photodissociation region (PDR) covering fractions of 0-10%, both of which are consistent with our [NII] observations. The latter scenario can be reproduced with a density bounded nebula with PDR deficit, which would enhance the Lya, Lyman continuum, and C+ ionizing photons escape from galaxies, consistent with the [OIII]/[CII]-Lya EW correlation we find. <P />...

A Radio-to-millimeter Census of Star-forming Galaxies in Protocluster 4C 23.56 at z = 2.5: Global and Local Gas Kinematics Reviewed

Lee, Minju M., Tanaka, Ichi, Kawabe, Ryohei, Aretxaga, Itziar, Hatsukade, Bunyo, Izumi, Takuma, Kajisawa, Masaru, Kodama, Tadayuki, Kohno, Kotaro, Nakanishi, Kouichiro, Saito, Toshiki, Tadaki, Ken-ichi, Tamura, Yoichi, Umehata, Hideki, Zeballos, Milagros

The Astrophysical Journal Vol. 883 ( 1 ) page： 92 2019.9

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

We present a study of the gas kinematics of star-forming galaxies associated with protocluster 4C 23.56 at z = 2.49 using 0.″4 resolution CO (4-3) data taken with ALMA. Eleven Hα emitters (HAEs) are detected in CO (4-3), including six HAEs that were previously detected in CO (3-2) at a coarser angular resolution. The detections in both CO lines are broadly consistent in the line widths and the redshifts, confirming both detections. With an increase in the number of spectroscopic redshifts, we confirm that the protocluster is composed of two merging groups with a total halo mass of log (M <SUB>cl</SUB>/M <SUB>☉</SUB>) = 13.4-13.6, suggesting that the protocluster would evolve into a Virgo-like cluster (>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

ADF22: Blind Detections of [C II] Line Emitters Shown to be Spurious Reviewed International journal

Natsuki H. Hayatsu, R. J. Ivison, Paola Andreani, Hideki Umehata, Yuichi Matsuda, Naoki Yoshida, Kotaro Kohno, Bunyo Hatsukade, Akio K. Inoue, Yoichi Tamura, Tutomu T. Takeuchi, Seiji Fujimoto, Minju M. Lee, Tohru Nagao, Yiping Ao

Research Notes of the AAS Vol. 3 ( 7 ) page： 97 2019.7

Language：English 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

ALMA Observations of Molecular Gas in the Host Galaxy of AT2018cow Reviewed

Kana Morokuma-Matsui, Tomoki Morokuma, Nozomu Tominaga, Bunyo Hatsukade, Masao Hayashi, Yoichi Tamura, Yuichi Matsuda, Kazuhito Motogi, Kotaro Niinuma, Masahiro Konishi

The Astrophysical Journal Vol. 879 ( 1 ) page： L13 2019.7

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

We investigate the molecular gas in, and star-formation properties of, the
host galaxy (CGCG 137-068) of a mysterious transient, AT2018cow, at kpc and
larger scales, using archival band-3 data from the Atacama Large
Millimeter/submillimeter Array (ALMA). AT2018cow is the nearest Fast-Evolving
Luminous Transient (FELT), and this is the very first study unveiling
molecular-gas properties of FELTs. The achieved rms and beam size are 0.21 mJy
beam$^{-1}$ at a velocity resolution of $40$ km s$^{-1}$ and $3".66\times2".71$
($1.1~{\rm kpc} \times 0.8~{\rm kpc}$), respectively. CO($J$=1-0) emission is
successfully detected. The total molecular gas mass inferred from the CO data
is $(1.85\pm0.04)\times10^8$ M$_\odot$ with the Milky Way CO-to-H$_2$
conversion factor. The H$_2$ column density at the AT2018cow site is estimated
to be $8.6\times10^{20}$ cm$^{-2}$. The ALMA data reveal that (1) CGCG 137-068
is a normal star-forming (SF) dwarf galaxy in terms of its molecular gas and
star-formation properties and (2) AT2018cow is located between a CO peak and a
blue star cluster. These properties suggest on-going star formation and favor
the explosion of a massive star as the progenitor of AT2018cow. We also find
that CGCG 137-068 has a solar or super-solar metallicity. If the metallicity of
the other FELT hosts is not higher than average, then some property of SF dwarf
galaxies other than metallicity may be related to FELTs.

DOI： 10.3847/2041-8213/ab2915

The absence of [CIIi] 158 μm emission in spectroscopically confirmed galaxies at z > 8 Reviewed

N Laporte, H Katz, R S Ellis, G Lagache, F E Bauer, F Boone, A K Inoue, T Hashimoto, H Matsuo, K Mawatari, Y Tamura

Monthly Notices of the Royal Astronomical Society: Letters Vol. 487 ( 1 ) page： L81 - L85 2019.7

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

The scatter in the relationship between the strength of [C II] 158 μm emission and the star formation rate at high redshift has been the source of much recent interest. Although the relationship is well established locally, several intensely star-forming galaxies have been found whose [C II] 158 μm emission is either weak, absent, or spatially offset from the young stars. Here we present new ALMA data for the two most distant gravitationally lensed and spectroscopically confirmed galaxies, A2744_YD4 at z = 8.38 and MACS1149_JD1 at z = 9.11, both of which reveal intense [O III] 88 μm emission. In both cases we provide stringent upper limits on the presence of [C II] 158 μm with respect to [O III] 88 μm. We review possible explanations for this apparent redshift-dependent [C II] deficit in the context of our recent hydrodynamical simulations. Our results highlight the importance of using several emission line diagnostics with ALMA to investigate the nature of the interstellar medium in early galaxies....

DOI： 10.1093/mnrasl/slz094

Other Link： http://academic.oup.com/mnrasl/article-pdf/487/1/L81/28864236/slz094.pdf

ALMA 26 arcmin<SUP>2</SUP> Survey of GOODS-S at 1 mm (ASAGAO): Near-infrared-dark Faint ALMA Sources Reviewed

Yamaguchi, Yuki, Kohno, Kotaro, Hatsukade, Bunyo, Wang, Tao, Yoshimura, Yuki, Ao, Yiping, Caputi, Karina I., Dunlop, James S., Egami, Eiichi, Espada, Daniel, Fujimoto, Seiji, Hayatsu, Natsuki H., Ivison, Rob J., Kodama, Tadayuki, Kusakabe, Haruka, Nagao, Tohru, Ouchi, Masami, Rujopakarn, Wiphu, Tadaki, Ken-ichi, Tamura, Yoichi, Ueda, Yoshihiro, Umehata, Hideki, Wang, Wei-Hao, Yun, Min S.

The Astrophysical Journal Vol. 878 ( 1 ) page： 73 2019.6

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

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> > 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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