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1. The ALPINE-ALMA [CII] survey: Survey strategy, observations, and sample properties of 118 star-forming galaxies at 4 z < 6

   https://doi.org/10.1051/0004-6361/201936965  

   Le Fèvre, O. ; Béthermin, M. ; Faisst, A. ; Jones, G. C. ; Capak, P. ; Cassata, P. ; Silverman, J. D. ; Schaerer, D. ; Yan, L. ; Amorin, R. ; et al ( November 2020 , Astronomy & Astrophysics)

   The ALMA-ALPINE [CII] survey is aimed at characterizing the properties of a sample of normal star-forming galaxies (SFGs). The ALMA Large Program to INvestigate (ALPINE) features 118 galaxies observed in the [CII]-158 μ m line and far infrared (FIR) continuum emission during the period of rapid mass assembly, right after the end of the HI reionization, at redshifts of 4 <   z  <  6. We present the survey science goals, the observational strategy, and the sample selection of the 118 galaxies observed with ALMA, with an average beam minor axis of about 0.85″, or ∼5 kpc at the median redshift of the survey. The properties of the sample are described, including spectroscopic redshifts derived from the UV-rest frame, stellar masses, and star-formation rates obtained from a spectral energy distribution (SED) fitting. The observed properties derived from the ALMA data are presented and discussed in terms of the overall detection rate in [CII] and FIR continuum, with the observed signal-to-noise distribution. The sample is representative of the SFG population in the main sequence at these redshifts. The overall detection rate in [CII] is 64% for a signal-to-noise ratio (S/N) threshold larger than 3.5 corresponding to a 95% purity (40% detection rate for S / N  >  5). Based on a visual inspection of the [CII] data cubes together with the large wealth of ancillary data, we find a surprisingly wide range of galaxy types, including 40% that are mergers, 20% extended and dispersion-dominated, 13% compact, and 11% rotating discs, with the remaining 16% too faint to be classified. This diversity indicates that a wide array of physical processes must be at work at this epoch, first and foremost, those of galaxy mergers. This paper sets a reference sample for the gas distribution in normal SFGs at 4 <   z  <  6, a key epoch in galaxy assembly, which is ideally suited for studies with future facilities, such as the James Webb Space Telescope (JWST) and the Extremely Large Telescopes (ELTs). 

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2. The Dragonfly Galaxy. III. Jet Brightening of a High-redshift Radio Source Caught in a Violent Merger of Disk Galaxies

   https://doi.org/10.3847/1538-4357/acd3ed  

   Lebowitz, Sophie ; Emonts, Bjorn ; Terndrup, Donald M. ; Burchett, Joseph N. ; Prochaska, J. Xavier ; Drouart, Guillaume ; Villar-Martín, Montserrat ; Lehnert, Matthew ; De Breuck, Carlos ; Vernet, Joël ; et al ( July 2023 , The Astrophysical Journal)

   The Dragonfly galaxy (MRC 0152-209), the most infrared-luminous radio galaxy at redshiftz∼ 2, is a merger system containing a powerful radio source and large displacements of gas. We present kiloparsec-resolution data from the Atacama Large Millimeter/submillimeter Array and the Very Large Array of carbon monoxide (6−5), dust, and synchrotron continuum, combined with Keck integral field spectroscopy. We find that the Dragonfly consists of two galaxies with rotating disks that are in the early phase of merging. The radio jet originates from the northern galaxy and brightens when it hits the disk of the southern galaxy. The Dragonfly galaxy therefore likely appears as a powerful radio galaxy because its flux is boosted into the regime of high-zradio galaxies by the jet–disk interaction. We also find a molecular outflow of (1100 ± 550)M_⊙yr⁻¹associated with the radio host galaxy, but not with the radio hot spot or southern galaxy, which is the galaxy that hosts the bulk of the star formation. Gravitational effects of the merger drive a slower and longer-lived mass displacement at a rate of (170 ± 40)M_⊙yr⁻¹, but this tidal debris contains at least as much molecular gas mass as the much faster outflow, namelyM_H2= (3 ± 1) × 10⁹(α_CO/0.8)M_⊙. This suggests that both the active-galactic-nucleus-driven outflow and mass transfer due to tidal effects are important in the evolution of the Dragonfly system. The Keck data show Lyαemission spread across 100 kpc, and Civand Heiiemission across 35 kpc, confirming the presence of a metal-rich and extended circumgalactic medium previously detected in CO(1–0).

    

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3. SÍGAME Simulations of the [{ m{C}},{ m{II}}], [{ m{O}},{ m{I}}], and [{ m{O}},{ m{III}}] Line Emission from Star-forming Galaxies at zsimeq 6

   Olsen, Karen ; Greve, Thomas R. ; Narayanan, Desika ; Thompson, Robert ; Davé, Romeel ; Niebla Rios, Luis ; Stawinski, Stephanie ( January 2017 , Astrophysical journal)

   Of the almost 40 star-forming galaxies at z≳ 5 (not counting quasi-stellar objects) observed in [{{C}} {{II}}] to date, nearly half are either very faint in [{{C}} {{II}}] or not detected at all, and fall well below expectations based on locally derived relations between star formation rate and [{{C}} {{II}}] luminosity. This has raised questions as to how reliable [{{C}} {{II}}] is as a tracer of star formation activity at these epochs and how factors such as metallicity might affect the [{{C}} {{II}}] emission. Combining cosmological zoom simulations of galaxies with SÍGAME (SImulator of GAlaxy Millimeter/submillimeter Emission), we modeled the multiphased interstellar medium (ISM) and its emission in [{{C}} {{II}}], as well as in [O I] and [O III], from 30 main-sequence galaxies at z≃ 6 with star formation rates ˜3-23 {M}⊙ {yr}}-1, stellar masses ˜ (0.7{--}8)× {10}9 {M}⊙ , and metallicities ˜ (0.1{--}0.4)× {Z}⊙ . The simulations are able to reproduce the aforementioned [{{C}} {{II}}] faintness of some normal star-forming galaxy sources at z≥slant 5. In terms of [O I] and [O III], very few observations are available at z≳ 5, but our simulations match two of the three existing z≳ 5 detections of [O III] and are furthermore roughly consistent with the [O I] and [O III] luminosity relations with star formation rate observed for local starburst galaxies. We find that the [{{C}} {{II}}] emission is dominated by the diffuse ionized gas phase and molecular clouds, which on average contribute ˜66% and ˜27%, respectively. The molecular gas, which constitutes only ˜ 10 % of the total gas mass, is thus a more efficient emitter of [{{C}} {{II}}] than the ionized gas, which makes up ˜85% of the total gas mass. A principal component analysis shows that the [{{C}} {{II}}] luminosity correlates with the star formation activity of a galaxy as well as its average metallicity. The low metallicities of our simulations together with their low molecular gas mass fractions can account for their [{{C}} {{II}}] faintness, and we suggest that these factors may also be responsible for the [{{C}} {{II}}]-faint normal galaxies observed at these early epochs. 

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4. Rise of the Titans: Gas Excitation and Feedback in a Binary Hyperluminous Dusty Starburst Galaxy at z ∼ 6

   https://doi.org/10.3847/1538-4357/abcf2e  

   Riechers, Dominik A. ; Nayyeri, Hooshang ; Burgarella, Denis ; Emonts, Bjorn H. ; Clements, David L. ; Cooray, Asantha ; Ivison, Rob J. ; Oliver, Seb ; Pérez-Fournon, Ismael ; Rigopoulou, Dimitra ; et al ( January 2021 , The Astrophysical Journal)

   Abstract We report new observations toward the hyperluminous dusty starbursting major merger ADFS-27 ( z  = 5.655), using the Australia Telescope Compact Array (ATCA) and the Atacama Large Millimeter/submillimeter Array (ALMA). We detect CO ( J  = 2 → 1), CO ( J  = 8 → 7), CO ( J  = 9 → 8), CO ( J  = 10 → 9), and H 2 O (3 12  → 2 21 ) emission, and a P Cygni−shaped OH + (1 1  → 0 1 ) absorption/emission feature. We also tentatively detect H 2 O (3 21  → 3 12 ) and OH + (1 2 → 0 1 ) emission and CH + ( J  = 1 → 0) absorption. We find a total cold molecular mass of M gas  = (2.1 ± 0.2) × 10 11 ( α CO /1.0) M ⊙ . We also find that the excitation of the star-forming gas is overall moderate for a z > 5 dusty starburst, which is consistent with its moderate dust temperature. A high-density, high kinetic temperature gas component embedded in the gas reservoir is required to fully explain the CO line ladder. This component is likely associated with the “maximum starburst” nuclei in the two merging galaxies, which are separated by only 140 ± 13 km s −1 along the line of sight and 9.0 kpc in projection. The kinematic structure of both components is consistent with galaxy disks, but this interpretation remains limited by the spatial resolution of the current data. The OH + features are only detected toward the northern component, which is also the one that is more enshrouded in dust and thus remains undetected up to 1.6 μ m even in our sensitive new Hubble Space Telescope Wide Field Camera 3 imaging. The absorption component of the OH + line is blueshifted and peaks near the CO and continuum emission peak, while the emission is redshifted and peaks offset by 1.7 kpc from the CO and continuum emission peak, suggesting that the gas is associated with a massive molecular outflow from the intensely star-forming nucleus that supplies 125 M ⊙ yr −1 of enriched gas to its halo. 

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5. The ALPINE-ALMA [CII] survey: The nature, luminosity function, and star formation history of dusty galaxies up to z  ≃ 6

   https://doi.org/10.1051/0004-6361/202038487  

   Gruppioni, C. ; Béthermin, M. ; Loiacono, F. ; Le Fèvre, O. ; Capak, P. ; Cassata, P. ; Faisst, A. L. ; Schaerer, D. ; Silverman, J. ; Yan, L. ; et al ( November 2020 , Astronomy & Astrophysics)

   Aims. We present the detailed characterisation of a sample of 56 sources serendipitously detected in ALMA band 7 as part of the ALMA Large Program to INvestigate CII at Early Times (ALPINE). These sources, detected in COSMOS and ECDFS, have been used to derive the total infrared luminosity function (LF) and to estimate the cosmic star formation rate density (SFRD) up to z  ≃ 6. Methods. We looked for counterparts of the ALMA sources in all the available multi-wavelength (from HST to VLA) and photometric redshift catalogues. We also made use of deeper UltraVISTA and Spitzer source lists and maps to identify optically dark sources with no matches in the public catalogues. We used the sources with estimated redshifts to derive the 250 μ m rest-frame and total infrared (8–1000 μ m) LFs from z  ≃ 0.5 to 6. Results. Our ALMA blind survey (860 μ m flux density range: ∼0.3–12.5 mJy) allows us to further push the study of the nature and evolution of dusty galaxies at high- z , identifying luminous and massive sources to redshifts and faint luminosities never probed before by any far-infrared surveys. The ALPINE data are the first ones to sample the faint end of the infrared LF, showing little evolution from z  ≃ 2.5 to z ≃ 6, and a “flat” slope up to the highest redshifts (i.e. 4.5 <   z  <  6). The SFRD obtained by integrating the luminosity function remains almost constant between z  ≃ 2 and z  ≃ 6, and significantly higher than the optical or ultra-violet derivations, showing a significant contribution of dusty galaxies and obscured star formation at high- z . About 14% of all the ALPINE serendipitous continuum sources are found to be optically and near-infrared (near-IR) dark (to a depth K s  ∼ 24.9 mag). Six show a counterpart only in the mid-IR and no HST or near-IR identification, while two are detected as [C II] emitters at z  ≃ 5. The six HST+near-IR dark galaxies with mid-IR counterparts are found to contribute about 17% of the total SFRD at z  ≃ 5 and to dominate the high-mass end of the stellar mass function at z  >  3. 

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