Search

The Reionization Era Bright Emission Line Survey (REBELS) is a cycle-7 ALMA Large Program (LP) that is identifying and performing a first characterization of many of the most luminous star-forming galaxies known in the z>6.5 universe. REBELS is providing this probe by systematically scanning 40 of the brightest UV-selected galaxies identified over a 7-deg**2 area for bright 158-micron [CII] and 88-micron [OIII] lines and dust-continuum emission. Selection of the 40 REBELS targets was done by combining our own and other photometric selections, each of which is subject to extensive vetting using three completely independent sets of photometry and template-fitting codes. Building on the observational strategy deployed in two pilot programs, we are increasing the number of massive interstellar medium (ISM) reservoirs known at z>6.5 by ~4-5x to >30. In this manuscript, we motivate the observational strategy deployed in the REBELS program and present initial results. Based on the 60.6 hours of ALMA observations taken in the first year of the program (November 2019 to January 2020), 18 highly significant >~7sigma [CII] lines have already been discovered, the bulk of which (13/18) also show >~3.3 sigma dust-continuum emission. These newly discovered lines more than triple the number of bright ISM-cooling lines known in the z>6.5 universe, such that the number of ALMA-derived redshifts at z>6.5 already rival Lya redshift discoveries. An analysis of the completeness of our search results vs. star formation rate (SFR) suggests an ~79% efficiency in scanning for [CII] when the SFR(UV+IR) is in excess of 28 M_sol/yr. These new LP results further demonstrate ALMA's efficiency as a "redshift machine", particularly in the epoch of reionization., Comment: 30 pages, 4 tables, 18 figures, accepted for publication in ApJ

Attempts to trace star formation with rest-frame UV/optical observations at redshifts z > 2 are affected by the presence of potentially substantial, yet uncertain, dust attenuation. Recent studies have demonstrated the existence of a population of galaxies that are virtually invisible in the observed optical/near-infrared (NIR) due to dust obscuration, but which could contribute substantially to the star formation history at 2 < z < 6. Here, we make use of ultradeep 3 GHz Karl G. Jansky Very Large Array observations from the COSMOS-XS survey to investigate the contribution 20of radio-selected "optically dark" galaxies (undetected to a depth of KS ∼ 25.9 mag) to the cosmic star formation rate density (SFRD). We identify 19 such "optically dark" sources and utilize recent deblended far-infrared photometry to determine photometric redshifts based on IR and radio information for 11 of them. Through stacking, we infer that the remaining eight sources reside predominantly at high redshift (z > 4). Therefore, we conservatively assume these sources lie between z = 2 and z = 5. We derive the radio luminosity function (LF) for the sample with and without "optically dark" sources by fixing the faint and bright end shape of the radio LF to the local values and allowing for luminosity evolution.

Star-forming galaxies are composed of various types of galaxies. However, the luminosity functions at z ≳ 4–5 suggest that most galaxies have a relatively low stellar mass (log Mstar ∼ 10) and a low dust attenuation (AFUV ∼ 1.0). The physical properties of these objects are quite homogeneous. We used an approach where we combined their rest-frame far-infrared and submillimeter emissions and utilized the universe and the redshift as a spectrograph to increase the amount of information in a collective way. From a subsample of 27 ALMA-detected galaxies at z > 4.5, we built an infrared spectral energy distribution composite template. It was used to fit, with CIGALE, the 105 galaxies (detections and upper limits) in the sample from the far-ultraviolet to the far-infrared. The derived physical parameters provide information to decipher the nature of the dust cycle and of the stellar populations in these galaxies. The derived IR composite template is consistent with the galaxies in the studied sample. A delayed star formation history with τmain = 500 Myr is slightly favored by the statistical analysis as compared to a delayed with a final burst or a continuous star formation history. The position of the sample in the star formation rate (SFR) versus Mstar diagram is consistent with previous papers. The redshift evolution of the log Mstar versus AFUV relation is in agreement with an evolution in redshift of this relation. This evolution is necessary to explain the cosmic evolution of the average dust attenuation of galaxies. Evolution is also observed in the Ldust/LFUV (IRX) versus UV slope βFUV diagram: younger galaxies have bluer βFUV. We modeled the shift of galaxies in the IRX versus the βFUV diagram with the mass-weighted age as a free parameter, and we provide an equation to make predictions. The large sample studied in this paper is generally consistent with models that assume rapid dust formation from supernovae and removal of dust by outflows and supernovae blasts. However, we find that high mass dusty star-forming galaxies cannot be explained by the models.

Star-forming galaxies are composed of various types of galaxies. However, the luminosity functions at z ≳ 4–5 suggest that most galaxies have a relatively low stellar mass (log M_(star) ∼ 10) and a low dust attenuation (A_(FUV) ∼ 1.0). The physical properties of these objects are quite homogeneous. We used an approach where we combined their rest-frame far-infrared and submillimeter emissions and utilized the universe and the redshift as a spectrograph to increase the amount of information in a collective way. From a subsample of 27 ALMA-detected galaxies at z > 4.5, we built an infrared spectral energy distribution composite template. It was used to fit, with CIGALE, the 105 galaxies (detections and upper limits) in the sample from the far-ultraviolet to the far-infrared. The derived physical parameters provide information to decipher the nature of the dust cycle and of the stellar populations in these galaxies. The derived IR composite template is consistent with the galaxies in the studied sample. A delayed star formation history with τ_(main) = 500 Myr is slightly favored by the statistical analysis as compared to a delayed with a final burst or a continuous star formation history. The position of the sample in the star formation rate (SFR) versus M_(star) diagram is consistent with previous papers. The redshift evolution of the log M_(star) versus A_(FUV) relation is in agreement with an evolution in redshift of this relation. This evolution is necessary to explain the cosmic evolution of the average dust attenuation of galaxies. Evolution is also observed in the L_(dust)/L_(FUV) (IRX) versus UV slope β_(FUV) diagram: younger galaxies have bluer β_(FUV). We modeled the shift of galaxies in the IRX versus the β_(FUV) diagram with the mass-weighted age as a free parameter, and we provide an equation to make predictions. The large sample studied in this paper is generally consistent with models that assume rapid dust formation from supernovae and removal of dust by outflows and supernovae blasts. However, we find that high mass dusty star-forming galaxies cannot be explained by the models.

We make use of ultra-deep 3 GHz Karl G. Jansky Very Large Array observations of the COSMOS field from the multi-band COSMOS-XS survey to infer radio luminosity functions (LFs) of star-forming galaxies (SFGs). Using $\sim$1300 SFGs with redshifts out to $z\sim4.6$, and fixing the faint and bright end shape of the radio LF to the local values, we find a strong redshift trend that can be fitted by pure luminosity evolution with the luminosity parameter given by $α_L \propto (3.40 \pm 0.11) - (0.48 \pm 0.06)z$. We then combine the ultra-deep COSMOS-XS data-set with the shallower VLA-COSMOS $\mathrm{3\,GHz}$ large project data-set over the wider COSMOS field in order to fit for joint density+luminosity evolution, finding evidence for significant density evolution. By comparing the radio LFs to the observed far-infrared (FIR) and ultraviolet (UV) LFs, we find evidence of a significant underestimation of the UV LF by $21.6\%\, \pm \, 14.3 \, \%$ at high redshift ($3.3\,3$, even assuming the latest dust corrections and without accounting for optically dark sources., Submitted to ApJ; 27 pages, 13 figures, 4 tables

We present spectroscopic measurements for 71 galaxies associated with 62 of the brightest high-redshift submillimetre sources from the Southern fields of the Herschel Astrophysical Terahertz Large Area Survey (H-ATLAS), while targeting 85 sources which resolved into 142. We have obtained robust redshift measurements for all sources using the 12-m Array and an efficient tuning of ALMA to optimize its use as a redshift hunter, with 73 per cent of the sources having a robust redshift identification. Nine of these redshift identifications also rely on observations from the Atacama Compact Array. The spectroscopic redshifts span a range 1.41 < z < 4.53 with a mean value of 2.75, and the CO emission line full-width at half-maxima range between 110kms−1

We include a fully coupled treatment of metal and dust enrichment into the DELPHI semi-analytic model of galaxy formation to explain the dust content of 13 Lyman break galaxies (LBGs) detected by the Atacama Large millimetre Array (ALMA) REBELS Large Program at z similar or equal to 7. We find that the galaxy dust mass, M-d, is regulated by the combination of Type II supernova dust production, astration, shock destruction, and ejection in outflows; grain growth (with a standard time-scale tau(0) = 30 Myr) plays a negligible role. The model predicts a dust-to-stellar mass ratio of similar to 0.07-0.1 per cent and a UV-to-total star formation rate relation such that log(psi(UV)) = -0.05 [log(psi)](2) + 0.86 log(psi) - 0.05 (implying that 55-80 per cent of the star formation is obscured) for REBELS galaxies with stellar mass M-* = 10(9)-10(10)M(circle dot). This relation reconciles the intrinsic UV luminosity of LBGs with their observed luminosity function at z = 7. However, 2 out of the 13 systems show dust-to-stellar mass ratios (similar to 0.94-1.1 per cent) that are up to 18 times larger than expected from the fiducial relation. Due to the physical coupling between dust and metal enrichment, even decreasing to to very low values (0.3 Myr) only increases the dust-to-stellar mass ratio by a factor of similar to 2. Given that grain growth is not a viable explanation for such high observed ratios of the dust-to-stellar mass, we propose alternative solutions.

We analyse FIR dust continuum measurements for 14 galaxies (redshift z approximate to 7) in the ALMA Reionization Era Bright Emission Line Survey (REBELS) Large Program to derive their physical properties. Our model uses three input data, i.e. (a) the UV spectral slope, beta, (b) the observed UV continuum flux at 1500 angstrom, F-1500, (c) the observed continuum flux at approximate to 158 mu m, F-158, and considers Milky Way (MW) and SMC extinction curves, along with different dust geometries. We find that REBELS galaxies have 28-90.5 per cent of their star formation obscured; the total (UV+IR) star formation rates are in the range 31.5 < SFR/(M-circle dot yr(-1)) < 129.5. The sample-averaged dust mass and temperature are (1.3 +/- 1.1) x 10(7) M-circle dot and 52 +/- 11 K, respectively. However, in some galaxies dust is particularly abundant (REBELS-14, M-d' approximate to 3.4 x 10(7) M-circle dot), or hot (REBELS-18, T-d' approximate to 67 K). The dust distribution is compact ( 1 M-circle dot, which is likely inconsistent with pure SN production, and might require dust growth via accretion of heavy elements from the interstellar medium. With the SFR predicted by the model and a MW extinction curve, REBELS galaxies detected in [C II] nicely follow the local L-CII-SFR relation, and are approximately located on the Kennicutt-Schmidt relation. The sample-averaged gas depletion time is 0.11 y(p)(-2) Gyr, where y(p) is the ratio of the gas-to-stellar distribution radius. For some systems, a solution simultaneously matching the observed (beta, F-1500, F-158) values cannot be found. This occurs when the index I-m = (F-158/F-1500)/(beta - beta(int)), where beta(int) is the intrinsic UV slope, exceeds I-m* approximate to 1120 for an MW curve. For these objects, we argue that the FIR and UV emitting regions are not co-spatial, questioning the use of the IRX-beta relation.

The luminosity functions at z < 4 - 5 suggest that most galaxies have a relatively low stellar mass (logM_star = 10) and a low dust attenuation (A_FUV = 1.0). The physical properties of these objects are quite homogeneous. We used an approach where we combined their rest-frame far-infrared and submillimeter emissions and utilized the universe and the redshift as a spectrograph to increase the amount of information in a collective way. From a subsample of 27 ALMA-detected galaxies at z > 4.5, we built an infrared spectral energy distribution composite template. It was used to fit, with CIGALE, the 105 galaxies (detections and upper limits) in the sample from the FUV to the FIR. The derived physical parameters provide information to decipher the nature of the dust cycle and of the stellar populations in these galaxies. The derived IR composite template is consistent with the galaxies in the studied sample. A delayed star formation history with tau_main = 500 Myrs is slightly favored by the statistical analysis as compared to a delayed with a final burst or a continuous star formation history. The position of the sample in the star formation rate (SFR)- M_star diagram is consistent with previous papers. The redshift evolution of the log M_star versus A_FUV relation is in agreement with evolution in the redshift of this relation. This evolution is necessary to explain the cosmic evolution of the average dust attenuation of galaxies. Evolution is also observed in the L_dust/ L_FUV (IRX) versus UV slope beta_FUV diagram: younger galaxies have bluer beta_FUV. We modeled the shift of galaxies in the IRX versus the beta_FUV diagram with the mass-weighted age as a free parameter, and we provide an equation to make predictions., Comment: 40 pages, 13 figures

We make use of ultra-deep 3 GHz Karl G. Jansky Very Large Array (VLA) observations of the COSMOS field from the multiband COSMOS-XS survey to infer radio luminosity functions (LFs) of star-forming galaxies (SFGs). Using ∼1300 SFGs with redshifts out to z ∼ 4.6, and fixing the faint and bright end shape of the radio LF to the local values, we find a strong redshift trend that can be fitted by pure luminosity evolution with the luminosity parameter given by α L ∝ (3.40 ± 0.11) − (0.48 ± 0.06)z. We then combine the ultra-deep COSMOS-XS data set with the shallower VLA-COSMOS 3 GHz large project data set over the wider COSMOS field in order to fit for joint density+luminosity evolution, finding evidence for significant density evolution. By comparing the radio LFs to the observed far-infrared and ultraviolet (UV) LFs, we find evidence of a significant underestimation of the UV LF by 22% ± 14% at high redshift (3.3 < z < 4.6, integrated down to 0.03 L z = 3 ⋆ ). We derive the cosmic star formation rate density (SFRD) by integrating the fitted radio LFs and find that the SFRD rises up to z ∼ 1.8 and then declines more rapidly than previous radio-based estimates. A direct comparison between the radio SFRD and a recent UV-based SFRD, where we integrate both LFs down to a consistent limit ( 0.038 L z = 3 ⋆ ), reveals that the discrepancy between the radio and UV LFs translates to a significant (∼1 dex) discrepancy in the derived SFRD at z > 3, even assuming the latest dust corrections and without accounting for optically dark sources.

We present multi-band observations of an extremely dusty star-forming lensed galaxy (HERS1) at $z=2.553$. High-resolution maps of \textit{HST}/WFC3, SMA, and ALMA show a partial Einstein-ring with a radius of $\sim$3$^{\prime\prime}$. The deeper HST observations also show the presence of a lensing arc feature associated with a second lens source, identified to be at the same redshift as the bright arc based on a detection of the [NII] 205$\mu$m emission line with ALMA. A detailed model of the lensing system is constructed using the high-resolution HST/WFC3 image, which allows us to study the source plane properties and connect rest-frame optical emission with properties of the galaxy as seen in sub-millimeter and millimeter wavelengths. Corrected for lensing magnification, the spectral energy distribution fitting results yield an intrinsic star formation rate of about $1000\pm260$ ${\rm M_{\odot}}$yr$^{-1}$, a stellar mass ${\rm M_*}=4.3^{+2.2}_{-1.0}\times10^{11} {\rm M_{\odot}}$, and a dust temperature ${\rm T}_{\rm d}=35^{+2}_{-1}$ K. The intrinsic CO emission line ($J_{\rm up}=3,4,5,6,7,9$) flux densities and CO spectral line energy distribution are derived based on the velocity-dependent magnification factors. We apply a radiative transfer model using the large velocity gradient method with two excitation components to study the gas properties. The low-excitation component has a gas density $n_{\rm H_2}=10^{3.1\pm0.6}$ cm$^{-3}$ and kinetic temperature ${\rm T}_{\rm k}=19^{+7}_{-5}$ K and a high-excitation component has $n_{\rm H_2}=10^{2.8\pm0.3}$ cm$^{-3}$ and ${\rm T}_{\rm k}=550^{+260}_{-220}$ K. Additionally, HERS1 has a gas fraction of about $0.4\pm0.2$ and is expected to last 250 Myr. These properties offer a detailed view of a typical sub-millimeter galaxy during the peak epoch of star-formation activity., Comment: 16 pages, 14 figures

International audience; Star formation rate (SFR) measurements at z > 4 have relied mostly on the rest-frame far-ultraviolet (FUV) observations. The corrections for dust attenuation based on the IRX-β relation are highly uncertain and are still debated in the literature. Hence, rest-frame far-infrared (FIR) observations are necessary to constrain the dust-obscured component of the SFR. In this paper, we exploit the rest-frame FIR continuum observations collected by the ALMA Large Program to INvestigate [CII] at Early times (ALPINE) to directly constrain the obscured SFR in galaxies at 4.4 < z < 5.9. We used stacks of continuum images to measure average infrared luminosities taking both detected and undetected sources into account. Based on these measurements, we measured the position of the main sequence of star-forming galaxies and the specific SFR (sSFR) at z ∼ 4.5 and z ∼ 5.5. We find that the main sequence and sSFR do not significantly evolve between z ∼ 4.5 and z ∼ 5.5, as opposed to lower redshifts. We developed a method to derive the obscured SFR density (SFRD) using the stellar masses or FUV-magnitudes as a proxy of FIR fluxes measured on the stacks and combining them with the galaxy stellar mass functions and FUV luminosity functions from the literature. We obtain consistent results independent of the chosen proxy. We find that the obscured fraction of SFRD is decreasing with increasing redshift, but even at z ∼ 5.5 it constitutes around 61% of the total SFRD.

We present the [C II] 158 mu m line luminosity functions (LFs) at z similar to 4-6 using the ALMA observations of 118 sources, which are selected to have UV luminosity M-1500A < -20.2 and optical spectroscopic redshifts in COSMOS and ECDF-S. Of the 118 targets, 75 have significant [C II] detections and 43 are upper limits. This is by far the largest sample of [C II] detections, which allows us to set constraints on the volume density of [C II] emitters at z similar to 4-6. But because this is a UV-selected sample, we are missing [C II]-bright but UV-faint sources, making our constraints strict lower limits. Our derived LFs are statistically consistent with the z similar to 0 [C II] LF at 10(8.25)-10(9.75)L. We compare our results with the upper limits of the [C II] LF derived from serendipitous sources in the ALPINE maps. We also infer the [C II] LFs based on published far-IR and CO LFs at z similar to 4-6. Combining our robust lower limits with these additional estimates, we set further constraints on the true number density of [C II] emitters at z similar to 4-6. These additional LF estimates are largely above our LF at L-[CII] > 10(9)L, suggesting that UV-faint but [C II]-bright sources likely make significant contributions to the [C II] emitter volume density. When we include all the LF estimates, we find that available model predictions underestimate the number densities of [C II] emitters at z similar to 4-6. Finally, we set a constraint on the molecular gas mass density at z similar to 4-6, with rho(mol) similar to (2-7) x 10(7)M Mpc(-3). This is broadly consistent with previous studies.

We present dust attenuation properties of spectroscopically confirmed star forming galaxies on the main sequence at a redshift of ∼4.4 − 5.8. Our analyses are based on the far infrared continuum observations of 118 galaxies at rest-frame 158 μm obtained with the Atacama Large Millimeter Array (ALMA) Large Program to INvestigate [C II] at Early times (ALPINE). We study the connection between the ultraviolet (UV) spectral slope (β), stellar mass (M⋆), and infrared excess (IRX = L_(IR)/L_(UV)). Twenty-three galaxies are individually detected in the continuum at > 3.5σ significance. We perform a stacking analysis using both detections and nondetections to study the average dust attenuation properties at z ∼ 4.4 − 5.8. The individual detections and stacks show that the IRX–β relation at z ∼ 5 is consistent with a steeper dust attenuation curve than typically found at lower redshifts (z < 4). The attenuation curve is similar to or even steeper than that of the extinction curve of the Small Magellanic Cloud. This systematic change of the IRX–β relation as a function of redshift suggests an evolution of dust attenuation properties at z > 4. Similarly, we find that our galaxies have lower IRX values, up to 1 dex on average, at a fixed mass compared to previously studied IRX–M⋆ relations at z ≲ 4, albeit with significant scatter. This implies a lower obscured fraction of star formation than at lower redshifts. Our results suggest that dust properties of UV-selected star forming galaxies at z ≳ 4 are characterised by (i) a steeper attenuation curve than at z ≲ 4, and (ii) a rapidly decreasing dust obscured fraction of star formation as a function of redshift. Nevertheless, even among this UV-selected sample, massive galaxies (log M⋆/M⊙ > 10) at z ∼ 5 − 6 already exhibit an obscured fraction of star formation of ∼45%, indicating a rapid build-up of dust during the epoch of reionization.

The [C II] 158 μm line is one of the strongest IR emission lines, which has been shown to trace the star formation rate (SFR) of galaxies in the nearby Universe, and up to z ∼ 2. Whether this is also the case at higher redshift and in the early Universe remains debated. The ALPINE survey, which targeted 118 star-forming galaxies at 4.4 < z < 5.9, provides a new opportunity to examine this question with the first statistical dataset. Using the ALPINE data and earlier measurements from the literature, we examine the relation between the [C II] luminosity and the SFR over the entire redshift range from z ∼ 4 − 8. ALPINE galaxies, which are both detected in [C II] and in dust continuum, show good agreement with the local L([C II])–SFR relation. Galaxies undetected in the continuum by ALMA are found to be over-luminous in [C II] when the UV SFR is used. After accounting for dust-obscured star formation, by an amount of SFR(IR) ≈ SFR(UV) on average, which results from two different stacking methods and SED fitting, the ALPINE galaxies show an L([C II])–SFR relation comparable to the local one. When [C II] non-detections are taken into account, the slope may be marginally steeper at high-z, although this is still somewhat uncertain. When compared homogeneously, the z > 6 [C II] measurements (detections and upper limits) do not behave very differently to the z ∼ 4 − 6 data. We find a weak dependence of L([C II])/SFR on the Lyα equivalent width. Finally, we find that the ratio L([C II])/L_(IR) ∼ (1 − 3) × 10⁻³ for the ALPINE sources, comparable to that of “normal” galaxies at lower redshift. Our analysis, which includes the largest sample (∼150 galaxies) of [C II] measurements at z > 4 available so far, suggests no or little evolution of the [C II]–SFR relation over the last 13 Gyr of cosmic time.

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 similar or equal to 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 mu m rest-frame and total infrared (8-1000 mu m) LFs from z similar or equal to 0.5 to 6.Results. Our ALMA blind survey (860 mu m flux density range: similar to 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 similar or equal to 2.5 to z similar or equal to 6, and a "flat" slope up to the highest redshifts (i.e. 4.5 3.

We present dust attenuation properties of spectroscopically confirmed star forming galaxies on the main sequence at a redshift of similar to 4.4-5.8. Our analyses are based on the far infrared continuum observations of 118 galaxies at rest-frame 158 mu m obtained with the Atacama Large Millimeter Array (ALMA) Large Program to INvestigate [CII] at Early times (ALPINE). We study the connection between the ultraviolet (UV) spectral slope (beta), stellar mass (M-star), and infrared excess (IRX = L-IR/L-UV). Twenty-three galaxies are individually detected in the continuum at > 3.5 sigma significance. We perform a stacking analysis using both detections and nondetections to study the average dust attenuation properties at z similar to 4.4-5.8. The individual detections and stacks show that the IRX-beta relation at z similar to 5 is consistent with a steeper dust attenuation curve than typically found at lower redshifts (z 4. Similarly, we find that our galaxies have lower IRX values, up to 1 dex on average, at a fixed mass compared to previously studied IRX-M-star relations at z less than or similar to 4, albeit with significant scatter. This implies a lower obscured fraction of star formation than at lower redshifts. Our results suggest that dust properties of UV-selected star forming galaxies at z greater than or similar to 4 are characterised by (i) a steeper attenuation curve than at z less than or similar to 4, and (ii) a rapidly decreasing dust obscured fraction of star formation as a function of redshift. Nevertheless, even among this UV-selected sample, massive galaxies (log M-star/M-circle dot> 10) at z similar to 5-6 already exhibit an obscured fraction of star formation of similar to 45%, indicating a rapid build-up of dust during the epoch of reionization.

We report the detection of [C II] lambda 158 mu m emission from a system of three closely separated sources in the Cosmic Evolution Survey (COSMOS) field at z similar to 4.56 , as part of the Atacama Large Millimeter/submillimeter Array (ALMA) Large Program to INvestigate C II at Early times (ALPINE). The two most luminous sources are closely associated, both spatially (1.6 arcsec similar to 11 kpc) and in velocity (similar to 100 km s(-1)), while the third source is slightly more distant (2.8 arcsec similar to 18 kpc, similar to 300 km s(-1)). The second most luminous source features a slight velocity gradient, while no significant velocity gradient is seen in the other two sources. Using the observed [C II] luminosities, we derive a total log(10)(SFR[C II] [M-circle dot Yr(-1)]) = 2.8 +/- 0.2, which may be split into contributions of 59, 31, and 10 per cent from the central, east, and west sources, respectively. Comparison of these [C II] detections to recent zoom-in cosmological simulations suggests an ongoing major merger. We are thus witnessing a system in a major phase of mass build-up by merging, including an ongoing major merger and an upcoming minor merger, which is expected to end up in a single massive galaxy by z similar to 2.5.

The rich information on (sub)millimeter dust continuum emission from distant galaxies in the public Atacama Large Millimeter/submillimeter Array (ALMA) archive is contained in thousands of inhomogeneous observations from individual PI-led programs. To increase the usability of these data for studies deepening our understanding of galaxy evolution, we have developed automated mining pipelines for the ALMA archive in the COSMOS field (A³COSMOS) that efficiently exploit the available information for large numbers of galaxies across cosmic time and keep the data products in sync with the increasing public ALMA archive: (a) a dedicated ALMA continuum imaging pipeline, (b) two complementary photometry pipelines for both blind source extraction and prior source fitting, (c) a counterpart association pipeline utilizing the multiwavelength data available (including quality assessment based on machine-learning techniques), (d) an assessment of potential (sub)millimeter line contribution to the measured ALMA continuum, and (e) extensive simulations to provide statistical corrections to biases and uncertainties in the ALMA continuum measurements. Application of these tools yields photometry catalogs with ~1000 (sub)millimeter detections (spurious fraction ~8%–12%) from over 1500 individual ALMA continuum images. Combined with ancillary photometric and redshift catalogs and the above quality assessments, we provide robust information on redshift, stellar mass, and star formation rate for ~700 galaxies at redshifts 0.5–6 in the COSMOS field (with undetermined selection function). The ALMA photometric measurements and galaxy properties are released publicly within our blind extraction, prior fitting, and galaxy property catalogs, plus the images. These products will be updated on a regular basis in the future.

We present the discovery of HLock01-LAB, a luminous and large Lyα nebula at z = 3.326. Medium-band imaging and long-slit spectroscopic observations with the Gran Telescopio Canarias reveal extended emission in the Lyα 1215 Å, C IV 1550 Å, and He II 1640 Å lines over ∼100 kpc, and a total luminosity LLyα = (6.4 ± 0.1)×1044 erg s−1. HLock01-LAB presents an elongated morphology aligned with two faint radio sources contained within the central ∼8 kpc of the nebula. The radio structures are consistent with faint radio jets or lobes of a central galaxy, whose spectrum shows nebular emission characteristic of a type-II active galactic nucleus (AGN). The continuum emission of the AGN at short wavelengths is however likely dominated by stellar emission of the host galaxy, for which we derive a stellar mass M* ≃ 2.3 × 1011 M⊙. Our kinematic analysis shows that the ionized gas is perturbed almost exclusively in the inner region between the radio structures, probably as a consequence of jet–gas interactions, whereas in the outer regions the ionized gas appears more quiescent. The detection of extended emission in C IV and C III] indicates that the gas within the nebula is not primordial. Feedback may have enriched the halo at at least 50 kpc from the nuclear region. Using rest-frame UV emission-line diagnostics, we find that the gas in the nebula is likely heated by the AGN. Nevertheless, at the center of the nebula we find extreme emission line ratios of Lyα/C IV ∼60 and Lyα/He II ∼80, one of the highest values measured to date, and well above the standard values of photoionization models (Lyα/He II ∼30 for case B photoionization). Our data suggest that jet-induced shocks are likely responsible for the increase of the electron temperature and, thus, the observed Lyα enhancement in the center of the nebula. This scenario is further supported by the presence of radio structures and perturbed kinematics in this region. The large Lyα luminosity in HLock01-LAB is likely due to a combination of AGN photoionization and jet-induced shocks, highlighting the diversity of sources of energy powering Lyα nebulae. Future follow-up observations of HLock01-LAB will help to reveal the finer details of the excitation conditions of the gas induced by jets and to investigate the underlying cooling and feedback processes in this unique object.

One of the last missing pieces in the puzzle of galaxy formation and evolution through cosmic history is a detailed picture of the role of the cold gas supply in the star-formation process. Cold gas is the fuel for star formation, and thus regulates the buildup of stellar mass, both through the amount of material present through a galaxy's gas mass fraction, and through the efficiency at which it is converted to stars. Over the last decade, important progress has been made in understanding the relative importance of these two factors along with the role of feedback, and the first measurements of the volume density of cold gas out to redshift 4, (the "cold gas history of the Universe") has been obtained. To match the precision of measurements of the star formation and black-hole accretion histories over the coming decades, a two orders of magnitude improvement in molecular line survey speeds is required compared to what is possible with current facilities. Possible pathways towards such large gains include significant upgrades to current facilities like ALMA by 2030 (and beyond), and eventually the construction of a new generation of radio-to-millimeter wavelength facilities, such as the next generation Very Large Array (ngVLA) concept., 7 pages, 2 figures, Science White paper submitted to Astro2020 Decadal Survey

The goal of this science case is to address the use of a ngVLA as a CO redshift machine for dust-obscured high-redshift galaxies which lack of clear counterparts at other wavelengths. Thanks to its unprecedentedly large simultaneous bandwidth and sensitivity, the ngVLA will be able to detect low--J CO transitions at virtually any $z>1$. In particular, at $z>4.76$ two CO transitions will be covered in a single frequency setting, thus ensuring unambiguous line identification. The ngVLA capabilities fill in a redshift range where other approaches (e.g., photometric redshifts, search for optical/radio counterparts, etc) typically fail due to the combination of intrinsically faint emission and increasing luminosity distance. This will allow us to explore the formation of massive galaxies in the early cosmic times., To be published in the ASP Monograph Series, "Science with a Next-Generation VLA", ed. E. J. Murphy (ASP, San Francisco, CA)

The goal of this science case is to study physical conditions of the interstellar medium (ISM) in distant galaxies. In particular, its densest component is associated with the inner cores of clouds -- this is where star formation takes place. Carbon monoxide is usually used to trace molecular gas emission; however, its transitions are practically opaque, thus preventing astronomers from piercing through the clouds, into the deepest layers that are most intimately connected with the formation of stars. Other dense gas tracers are required, although they are typically too faint and/or at too low frequencies to be effectively observed in high redshift galaxies. The ngVLA will offer for the first time the sensitivity at radio frequencies that is needed to target [CI]$_{1-0}$ (at $z>5$), as well as the ground transitions of dense gas tracers of the ISM such as HCN, HNC, HCO+ (at various redshifts $z>1$), beyond the tip of the iceberg of the hyper-luminous sources that could be studied up to now. These new tools will critically contribute to our understanding of the intimate interplay between gas clouds and star formation in different environments and cosmic epochs., To be published in the ASP Monograph Series, "Science with a Next-Generation VLA", ed. E. J. Murphy (ASP, San Francisco, CA). arXiv admin note: text overlap with arXiv:1510.06411

The goal of this science case is to accurately pin down the molecular gas content of high redshift galaxies. By targeting the CO ground transition, we circumvent uncertainties related to CO excitation. The ngVLA can observe the CO(1-0) line at virtually any $z>1.5$, thus exposing the evolution of gaseous reservoirs from the earliest epochs down to the peak of the cosmic history of star formation. The order-of-magnitude improvement in the number of CO detections with respect to state-of-the-art observational campaigns will provide a unique insight on the evolution of galaxies through cosmic time., To be published in the ASP Monograph Series, "Science with a Next-Generation VLA", ed. E. J. Murphy (ASP, San Francisco, CA). arXiv admin note: substantial text overlap with arXiv:1510.06411

We present the detailed science case, and brief descriptions of the telescope design, site, and first light instrument plans for a new ultra-wide field submillimeter observatory, CCAT-prime, that we are constructing at a 5600 m elevation site on Cerro Chajnantor in northern Chile. Our science goals are to study star and galaxy formation from the epoch of reionization to the present, investigate the growth of structure in the Universe, improve the precision of B-mode CMB measurements, and investigate the interstellar medium and star formation in the Galaxy and nearby galaxies through spectroscopic, polarimetric, and broadband surveys at wavelengths from 200 um to 2 mm. These goals are realized with our two first light instruments, a large field-of-view (FoV) bolometer-based imager called Prime-Cam (that has both camera and an imaging spectrometer modules), and a multi-beam submillimeter heterodyne spectrometer, CHAI. CCAT-prime will have very high surface accuracy and very low system emissivity, so that combined with its wide FoV at the unsurpassed CCAT site our telescope/instrumentation combination is ideally suited to pursue this science. The CCAT-prime telescope is being designed and built by Vertex Antennentechnik GmbH. We expect to achieve first light in the spring of 2021., Presented at SPIE Millimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy IX, June 14th, 2018

Dust-enshrouded, starbursting, submillimeter galaxies (SMGs) at z >= 3 have been proposed as progenitors of z >= 2 compact quiescent galaxies (cQGs). To test this connection, we present a detailed spatially resolved study of the stars, dust, and stellar mass in a sample of six submillimeter-bright starburst galaxies at z similar to 4.5. The stellar UV emission probed by HST is extended and irregular and shows evidence of multiple components. Informed by HST, we deblend Spitzer/IRAC data at rest-frame optical, finding that the systems are undergoing minor mergers with a typical stellar mass ratio of 1:6.5. The FIR dust continuum emission traced by ALMA locates the bulk of star formation in extremely compact regions (median r(e) = 0.70 +/- 0.29 kpc), and it is in all cases associated with the most massive component of the mergers (median log(M-*/M-circle dot)= 10.49 +/- 0.32). We compare spatially resolved UV slope (beta) maps with the FIR dust continuum to study the infrared excess (IRX = L-IR/L-UV)-beta relation. The SMGs display systematically higher IRX values than expected from the nominal trend, demonstrating that the FIR and UV emissions are spatially disconnected. Finally, we show that the SMGs fall on the mass-size plane at smaller stellar masses and sizes than the cQGs at z = 2. Taking into account the expected evolution in stellar mass and size between z = 4.5 and z = 2 due to the ongoing starburst and mergers with minor companions, this is in agreement with a direct evolutionary connection between the two populations.

ASP Conference Series (ASPCS), Monograph 7

The goal of this chapter is to address the use of the ngVLA as a CO redshift machine for dust-obscured high-redshift galaxies which lack of clear counterparts at other wavelengths. Thanks to its unprecedented large simultaneous bandwidth and sensitivity, the ngVLA will be able to detect multiple low-J CO transitions at all redshifts > 1. In particular, at z ≥ 4.76 two CO transitions will be covered in a single frequency setting, thus ensuring unambiguous line identification. The ngVLA capabilities fill in a redshift range where other approaches (e.g., photometric redshifts, search for optical/radio counterparts, etc.) typically fail due to the combination of intrinsically faint emission and increasing luminosity distance. This will allow us to explore the formation of massive galaxies in the early cosmic times.

The goal of this chapter is to accurately pin down the molecular gas content of high redshift galaxies. By targeting the CO ground transition, we circumvent uncertainties related to CO excitation. The ngVLA can observe the CO(1-0) line at all redshifts, thus exposing the evolution of gaseous reservoirs from the earliest epochs down to the peak of the cosmic history of star formation. The order-of-magnitude improvement in the number of CO detections with respect to state-of-the- art observational campaigns will provide a unique insight on the evolution of galaxies through cosmic time. We show that the ngVLA will perform a precision measurement of the dense gas history of the Universe, the fuel for star formation, back to the epoch of cosmic reionization and the formation of the first galaxies.

Until recently, determining the rotational properties of galaxies in the early universe (z > 4, universe age

We have combined the wide-area Herschel-ATLAS far-IR survey with spectroscopic redshifts from GAMA and SDSS to define a sample of 21 low--redshift ($z_{\rm spec} < 0.5$) analogs of submm galaxies (SMGs). These have been selected because their dust temperatures and total IR luminosities are similar to those for the classical high-redshift SMG population. As well as presenting the sample, in this paper we report $^{12}$CO(2-1) and $^{12}$CO(1-0) observations of 16 low-redshift analogs of SMGs taken with the IRAM-30m telescope. We have obtained that low-redshift analogs of SMGs represent a very diverse population, similar to what has been found for high-redshift SMGs. A large variety in the molecular gas excitation or $^{12}$CO(2-1)/$^{12}$CO(1-0) line ratio is seen, meaning that extrapolations from $J \geq 2$ CO lines can result in very uncertain molecular gas mass determinations. Our sources with $^{12}$CO(1-0) detections follow the dust--gas correlation found in previous work at different redshifts and luminosities. The molecular gas mass of low-redshift SMGs has an average value of $M_{\rm H_2} \sim 1.6 \times 10^{10}\,M_\odot$ and will be consumed in $\sim 100 \, {\rm Myr}$ . We also find a wide range of molecular gas fractions, with the highest values being compatible with those found in high-redshift SMGs with $^{12}$CO(1-0) detections, which are only the most luminous. Low-redshift SMGs offer a unique opportunity to study the properties of extreme star formation in a detail not possible at higher redshifts., Submitted to ApJ. Comments welcome