Submillimeter Galaxies Research Articles

Hidden Giants in JWST's PEARLS: An Ultramassive z = 4.26 Submillimeter Galaxy that Is Invisible to HST

We present a multiwavelength analysis using the Submillimeter Array (SMA), James Clerk Maxwell Telescope, NOEMA, JWST, the Hubble Space Telescope (HST), and the Spitzer Space Telescope of two dusty strongly star-forming galaxies, 850.1 and 850.2, seen through the massive cluster lens A 1489. These SMA-located sources both lie at z = 4.26 and have bright dust continuum emission, but 850.2 is a UV-detected Lyman-break galaxy, while 850.1 is undetected at ≲ 2 μm, even with deep JWST/NIRCam observations. We investigate their stellar, interstellar medium, and dynamical properties, including a pixel-level spectral energy distribution analysis to derive subkiloparsec-resolution stellar-mass and A V maps. We find that 850.1 is one of the most massive and highly obscured, A V ∼ 5, galaxies known at z > 4 with M * ∼1011.8 M ⊙ (likely forming at z > 6), and 850.2 is one of the least massive and least obscured, A V ∼ 1, members of the z > 4 dusty star-forming population. The diversity of these two dust-mass-selected galaxies illustrates the incompleteness of galaxy surveys at z ≳ 3–4 based on imaging at ≲ 2 μm, the longest wavelengths feasible from HST or the ground. The resolved mass map of 850.1 shows a compact stellar-mass distribution, ∼1 kpc, but its expected evolution means that it matches both the properties of massive, quiescent galaxies at z ∼ 1.5 and ultramassive early-type galaxies at z ∼ 0. We suggest that 850.1 is the central galaxy of a group in which 850.2 is a satellite that will likely merge in the near future. The stellar morphology of 850.1 shows arms and a linear bar feature that we link to the active dynamical environment it resides within.

Submillimetre galaxies as laboratories for dust grain coagulation

ABSTRACT Coagulation in the dense interstellar medium (ISM) is an important process that determines the size of the largest grains. We use submillimetre galaxies (SMGs) as laboratories of grain coagulation, since some of them host the densest ISM on a galactic scale among various populations of galaxies known. We examine how large the grains can be in such dense environments based on the mean ISM density estimated from the observed typical dust mass density in SMGs. We also consider local density enhancement based on a model of supersonic turbulence, which is expected from strong stellar feedback. In the unlimited coagulation model, in which we do not impose any coagulation threshold velocity, grains as large as $\sim 30~\rm{\mu m}$ can form under the observationally estimated mean gas density if the Mach number of turbulence is $\mathcal {M}\gtrsim 3$. We exclude this possibility since the observed emissivity index β ≃ 2 in the far-infrared (FIR) indicates that such large grains cannot actively form in SMGs. This means that coagulation does not proceed in an unlimited way: 30-$\rm{\mu m}$ grains should have velocities larger than the coagulation threshold. If we use a coagulation threshold (upper limit) grain velocity (∼0.08 km s−1) taken from a theoretical study, grains likely grow only up to $\rm{\mu m}$ size, which is small enough not to affect the FIR emissivity index. The above results indicate that SMGs can be used to constrain the physical processes relevant to coagulation.

Obscuration beyond the nucleus: infrared quasars can be buried in extreme compact starbursts

ABSTRACT In the standard quasar model, the accretion disc obscuration is due to the canonical dusty torus. Here, we argue that a substantial part of the quasar obscuration can come from the interstellar medium (ISM) when the quasars are embedded in compact starbursts. We use an obscuration-unbiased sample of 578 infrared (IR) quasars at z ≈ 1–3 and archival Atacama Large Millimetre/submillimetre Array submillimetre host galaxy sizes to investigate the ISM contribution to the quasar obscuration. We calculate star formation rates (SFR) and ISM column densities for the IR quasars and a control sample of submillimetre galaxies (SMGs) not hosting quasar activity and show that: (1) the quasar obscured fraction is constant up to $\rm SFR\approx 300 \: {\rm M}_{\odot } \: yr^{-1}$, and then increases towards higher SFR, suggesting that the ISM obscuration plays a significant role in starburst host galaxies, and (2) at $\rm SFR\gtrsim 300 \: {\rm M}_{\odot } \: yr^{-1}$, the SMGs and IR quasars have similarly compact submillimetre sizes ($R_{\rm e}\approx 0.5{\!-\!}3\,\mathrm{ kpc}$) and consequently, the ISM can heavily obscure the quasar, even reaching Compton-thick ($N_{\rm H}\gt 10^{24} \rm \: cm^{-2}$) levels in extreme cases. Based on our results, we infer that ${\approx} 10{\!-\!}30~{{ \rm per\ cent}}$ of the IR quasars with $\rm SFR\gtrsim 300 \: {\rm M}_{\odot } \: yr^{-1}$ are obscured solely by the ISM.

A Near-infrared-faint, Far-infrared-luminous Dusty Galaxy at z ∼ 5 in COSMOS-Web

A growing number of far-infrared (FIR) bright sources completely invisible in deep extragalactic optical surveys hint at an elusive population of z > 4 dusty, star-forming galaxies. Cycle 1 JWST surveys are now detecting their rest-frame optical light, which provides key insight into their stellar properties and statistical constraints on the population as a whole. This work presents the JWST Near Infrared Camera (NIRCam) counterpart from the COSMOS-Web survey to an FIR SCUBA-2 and Atacama Large Millimeter/submillimeter Array (ALMA) source, AzTECC71, which was previously undetected at wavelengths shorter than 850 μm. AzTECC71, among the reddest galaxies in COSMOS-Web with F277W − F444W ∼ 0.9, is undetected in NIRCam/F150W and F115W and fainter in F444W than other submillimeter galaxies identified in COSMOS-Web by 2–4 magnitudes. This is consistent with the system having both a lower stellar mass and higher redshift than the median dusty, star-forming galaxy. With deep ground- and space-based upper limits combined with detections in F277W, F444W, and the FIR including ALMA Band 6, we find a high probability (99%) that AzTECC71 is at z > 4 with . This galaxy is massive () and infrared-luminous (), comparable to other optically undetected but FIR-bright dusty, star-forming galaxies at z > 4. This population of luminous, infrared galaxies at z > 4 is largely unconstrained but comprises an important bridge between the most extreme dust-obscured galaxies and more typical high-redshift star-forming galaxies. If further FIR-selected galaxies that drop out of the F150W filter in COSMOS-Web have redshifts z > 4 like AzTECC71, then the volume density of such sources may be ∼3–10 × greater than previously estimated.

Z-GAL: A NOEMA spectroscopic redshift survey of bright Herschel galaxies

The z-GAL survey observed 137 bright Herschel-selected targets with the IRAM Northern Extended Millimeter Array, with the aim to measure their redshift and study their properties. Several of them have been resolved into multiple sources. Consequently, robust spectroscopic redshifts have been measured for 165 individual galaxies in the range 0.8 < z < 6.5. In this paper we analyse the millimetre spectra of the z-GAL sources, using both their continuum and line emission to derive their physical properties. At least two spectral lines are detected for each source, including transitions of 12CO, [CI], and H2O. The observed 12CO line ratios and spectral line energy distributions of individual sources resemble those of local starbursts. In seven sources the para-H2O (211−202) transition is detected and follows the IR versus H2O luminosity relation of sub-millimetre galaxies. The molecular gas mass of the z-GAL sources is derived from their 12CO, [CI], and sub-millimetre dust continuum emission. The three tracers lead to consistent results, with the dust continuum showing the largest scatter when compared to 12CO. The gas-to-dust mass ratio of these sources was computed by combining the information derived from 12CO and the dust continuum and has a median value of 107, similar to star-forming galaxies of near-solar metallicity. The same combined analysis leads to depletion timescales in the range between 0.1 and 1.0 Gyr, which place the z-GAL sources between the ‘main sequence’ of star formation and the locus of starbursts. Finally, we derived a first estimate of stellar masses – modulo possible gravitational magnification – by inverting known gas scaling relations: the z-GAL sample is confirmed to be mostly composed by starbursts, whereas ∼25% of its members lie on the main sequence of star-forming galaxies (within ±0.5 dex).

Bright submillimeter galaxies do trace galaxy protoclusters

There is controversy in the literature regarding whether distant, massive, and dusty starbursts selected at (sub)millimeter wavelengths can trace galaxy overdensities. We thus performed the first systematic search for distant protoclusters around a homogeneously selected sample of 12 spectroscopically confirmed submillimeter galaxies (SMGs) at z ∼ 1.2 − 5.3, which we selected from the GOODS-N field. We applied the well-established Poisson probability method (PPM) to search for megaparsec-scale overdensities around these SMGs, using three different photometric redshift catalogs. We robustly detect galaxy overdensities for 11 out of the 12 SMGs (i.e., 92%±8%), distributed over eight large-scale protoclusters. We confirm all three previously discovered protoclusters, and we detect five new ones around the SMGs SMM J123634 (z = 1.225), ID.19 (z = 2.047), SMM J123607 (z = 2.487), SMM J123606 (z = 2.505), and GN10 (z = 5.303). A wavelet-based analysis of the protocluster fields shows that the SMGs are located in protocluster cores with a complex morphology (compact, filamentary, or clumpy) and an average size of ∼(0.4 − 1) Mpc. By comparing the PPM results obtained using the three redshift catalogs independently, each of which trace different galaxy populations and redshift ranges, we speculate that we are possibly witnessing a transitioning phase at z ≳ 4 for the galaxy population of protoclusters. While z ≲ 4 protoclusters appear to be populated by dusty galaxies, those at the highest redshifts, z ∼ 5, are detected as overdensities of Lyman α emitters or Lyman break galaxies. Further investigation with larger samples is required to reach a definitive conclusion. We also find a good correlation between the molecular (H2) gas mass of the SMGs and the significance of the associated overdensity. To explain the overall phenomenology, we suggest that galaxy interactions in dense environments likely triggered the starburst and gas-rich phase of the SMGs. Altogether, our findings support the scenario that SMGs are excellent tracers of distant protoclusters. The ones presented in this work are excellent targets for the James Webb Space Telescope. Similarly, future surveys with forthcoming facilities (e.g., Euclid and LSST) can be tuned to detect even larger samples of distant protoclusters.

SCUBA-2 High Redshift Bright Quasar Survey. II. The Environment of z ∼ 6 Quasars at Submillimeter Band

The formation of the first supermassive black holes is expected to have occurred in some most pronounced matter and galaxy overdensities in the early universe. We have conducted a submillimeter wavelength continuum survey of 54 z ∼ 6 quasars using the Submillimeter Common-User Bolometre Array-2 on the James Clerk Maxwell Telescope to study the environments around z ∼ 6 quasars. We identified 170 submillimeter galaxies (SMGs) with above 3.5σ detections in 450 or 850 μm maps. Their far-IR luminosities are (2.2–6.4) × 1012 L ⊙, and their star formation rates are ∼400–1200 M ⊙ yr−1. We also calculated the SMGs’ differential and cumulative number counts in a combined area of ∼620 arcmin2. To a 4σ detection (at ∼5.5 mJy), SMGs’ overdensity is (±0.19), exceeding the blank-field source counts by a factor of 1.68. We find that 13/54 quasars show overdensities (at ∼5.5 mJy) of δ SMG ∼ 1.5–5.4. The combined area of these 13 quasars exceeds the blank-field counts with the overdensity to 5.5 mJy of δ SMG ∼ (±0.25) in the regions of ∼150 arcmin2. However, the excess is insignificant on the bright end (e.g., 7.5 mJy). We also compare results with previous environmental studies of Lyα emitters and Lyman break galaxies on a similar scale. Our survey presents the first systematic study of the environment of quasars at z ∼ 6. The newly discovered SMGs provide essential candidates for follow-up spectroscopic observations to test whether they reside in the same large-scale structures as the quasars and search for protoclusters at an early epoch.

JCMT/SCUBA-2 uncovers an excess of 850 μm counts on megaparsec scales around high-redshift quasars

We conducted a systematic survey of the environment of high-redshift quasars at submillimeter wavelengths to unveil and characterize the surrounding distribution of dusty submillimeter galaxies (SMGs). We took sensitive observations with the SCUBA-2 instrument on the James Clerk Maxwell Telescope for 3 enormous Lyman-alpha nebulae (ELANe) and 17 quasar fields in the redshift range 2 < z < 4.2 selected from recent Lyman alpha (Lyα) surveys. These observations uncovered 523 and 101 sources at 850 μm and 450 μm, respectively, with signal-to-noise ratios (S/N) > 4 or detected in both bands at S/N > 3. We ran self-consistent Monte Carlo simulations to construct 850 μm number counts and unveil an excess of sources in 75% of the targeted fields. Overall, regions around ELANe and quasars are overabundant with respect to blank fields by a factor of 3.4 ± 0.4 and 2.5 ± 0.2, respectively (weighted averages). Therefore, the excess of submillimeter sources is likely part of the megaparsec-scale environment around these systems. By combining all fields and repeating the count analysis in radial apertures, we find (at high significance, ≳5σ) a decrease in the overdensity factor from > 3 within ∼2 cMpc to ∼2 in the annulus at the edge of the surveyed field (∼10 cMpc), which suggests that the physical extent of the overdensities is larger than our maps. We computed preferred directions for the overdensities of SMGs from the positions of the sources and used them to orient and create stacked maps of source densities for the quasars’ environment. This stacking unveils an elongated structure reminiscent of a large-scale filament with a scale width of ≈3 cMpc. Finally, the directions of the overdensities are roughly aligned with the major axis of the Lyα nebulae, suggesting that the latter trace, on scales of hundreds of kiloparsecs, the central regions of the projected large-scale structure described by the SMGs on megaparsec scales. Confirming member associations of the SMGs is required to further characterize their spatial and kinematic distribution around ELANe and quasars.

Characterizing CO Emitters in the SSA22-AzTEC26 Field

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.

Observations of neutral carbon in 29 high-z lensed dusty star-forming galaxies and the comparison of gas mass tracers

Context. The nature and evolution of high-redshift dusty star-forming galaxies (high-z DSFGs) remain open questions. Their massive gas reservoirs play an important role in driving the intense star formation rates hosted in these galaxies. Aims. Our aim is to estimate the molecular gas content of high-z DSFGs by using various gas mass tracers, such as the [CI], CO, [CII] emission lines and the dust content. These tracers need to be well calibrated as they are all limited by uncertainties on factors such as αCO, XCI, α[CII], and δGDR, thereby affecting the accurate determination of the gas mass. The main goal of our work is to check the consistency between the gas mass tracers and to cross-calibrate the uncertain factors. Methods. We observed the two [CI] line transitions for 29 South Pole telescope Submillimeter Galaxies (SPT-SMGs) with the Atacama Large Millimeter/submillimeter Array–Atacama Compact Array (ALMA-ACA). Additionally, we also present new Atacama Pathfinder EXperiment (APEX) observations of [CII] line for nine of these galaxies. We combined our observations with the rich ancillary data of low- and mid-J CO lines, ancillary [CII] line, and dust mass estimations for these galaxies. Results. We find a nearly linear relation between the infrared luminosity and [CI] luminosity if we fit the starbursts and main-sequence galaxies separately. We measure a median [CI]-derived excitation temperature of 34.5 ± 2.1 K. We probed the properties of the interstellar medium (ISM), such as density and radiation field intensity, using [CI] to mid- or high-J CO lines and the [CI]-to-infrared luminosity ratio, and find similar values to the SMG populations in the literature. Finally, the gas masses estimated from [CI], CO, dust, and [CII] do not exhibit any significant trend with the infrared luminosity or the dust temperature. We provide the various cross-calibrations between these tracers. Conclusions. Our study confirms that [CI] is a suitable tracer of the molecular gas content, and shows an overall agreement between all the classical gas tracers used at high redshift. However, their absolute calibration, and thus the gas depletion timescale measurements, remain uncertain.

Sub-millimetre galaxies with Webb

We utilised the unprecedented depth and resolution of recent early-release science (ERS) JWST observations to define the near-infrared counterparts of sub-millimetre galaxies (SMGs). We identified 45 SCUBA-2 SMG positions within the Cosmic Evolution Early Release Science (CEERS) survey JWST/NIRCam fields. Through an analysis of multi-wavelength p-values, NIRCam colours and predicted SCUBA-2 fluxes, we define 43 JWST/NIRCam counterparts to the SCUBA-2 SMGs, finding a 63 per cent agreement with those identified in prior HST studies. Using EaZy-py, we fitted the available HST and JWST observations to quantify the photometric redshifts of the NIRCam-SMGs, establishing a broad range of redshift from z ≈ 0.2–5.4 with a median of z ≈ 2.29, in agreement with other studies of SMGs. We identified significant variations in the morphology of the NIRCam-SMGs from isolated discs and spheroidal galaxies to irregular interacting systems. We analysed their rest-frame optical and near-infrared morphological properties (e.g. effective radius (Re), Sérsic index (n), concentration (C), asymmetry (A), clumpiness (S), as well as the Gini and M20 parameters), finding, on average, late-type disc-like morphologies with large scatter into the intermediate and merger regions of the non-parametric parameter space. For the non-merging galaxies, we find a median rest-frame optical size and Sérsic index (and 1σ scatter) of Re = 3.10 ± 1.67 kpc and n = 0.96 ± 0.66. Whilst in the rest-frame near-infrared, we establish more compact, higher Sérsic index morphologies (Re = 1.64 ± 0.97, n = 1.85 ± 0.63). We further establish that both the rest-frame optical and near-infrared effective radii correlate negatively (at a 2σ level) with redshift, whilst the Sérsic index remains constant with cosmic time. Our results are consistent with the picture of inside-out galaxy evolution, with more centrally concentrated older stellar populations, and more extended, younger star-forming regions whose stellar emission is heavily attenuated in the central regions.

Cosmic Sands: The Origin of Dusty, Star-forming Galaxies in the Epoch of Reionization

We present the Cosmic Sands suite of cosmological zoom-in simulations based on the simba galaxy formation model in order to study the buildup of the first massive and dusty galaxies in the early universe. Residing in the most massive halos, we find that the compact proto-massive galaxies undergo nearly continuous mergers with smaller subhalos, boosting star formation rates (SFRs) and the buildup of stellar mass. The galaxies are already appreciably chemically evolved by z = 7, with modeled dust masses comparable to those inferred from observations in the same epoch, except for the most extreme systems. We track gas accretion onto the galaxies to understand how extreme SFRs can be sustained by these early systems. We find that smooth gas accretion can maintain SFRs above 250 M ⊙ yr−1, but to achieve SFRs that boost galaxies well above the main sequence, a larger perturbation like a gas-rich major merger is necessary to trigger a starburst episode. Post-processing the Cosmic Sands simulations with dust RT, we find that, while the infrared luminosities of the most-dust-rich galaxies are comparable to local ULIRGs, they are substantially dimmer than classical z = 2 submillimeter galaxies. We end with a discussion on the possible reasons for this discrepancy at the highest masses and the future work we intend to carry out to study the chemical enrichment of the earliest dusty galaxies.

Lightning: An X-Ray to Submillimeter Galaxy SED-fitting Code with Physically Motivated Stellar, Dust, and AGN Models

We present an updated version of Lightning, a galaxy spectral energy distribution (SED) fitting code that can model X-ray to submillimeter observations. The models in Lightning include the options to contain contributions from stellar populations, dust attenuation and emission, and active galactic nuclei (AGNs). X-ray emission, when utilized, can be modeled as originating from stellar compact binary populations with the option to include emission from AGNs. We have also included a variety of algorithms to fit the models to observations and sample parameter posteriors; these include adaptive Markov Chain Monte Carlo (MCMC), affine-invariant MCMC, and Levenberg–Marquardt gradient-descent (MPFIT) algorithms. To demonstrate some of the capabilities of Lightning, we present several examples using a variety of observational data. These examples include (1) deriving the spatially resolved stellar properties of the nearby galaxy M81, (2) demonstrating how X-ray emission can provide constraints on the properties of the supermassive black hole of a distant AGN, (3) exploring how to rectify the attenuation effects of inclination on the derived the star formation rate of the edge-on galaxy NGC 4631, (4) comparing the performance of Lightning to similar Bayesian SED-fitting codes when deriving physical properties of the star-forming galaxy NGC 628, and (5) comparing the derived X-ray and UV-to-IR AGN properties from Lightning and CIGALE for a distant AGN. Lightning is an open-source application developed in IDL and is available at https://github.com/rafaeleufrasio/lightning.

Resolving a merger in a hyperluminous submillimeter galaxy at z = 2.82

ABSTRACT We present the resolved properties of the z = 2.82 hyperluminous infrared Galaxy (HyLIRG) HS1700.850.1, the brightest 850 $\mu$m source found in the SCUBA-2 followup to the Keck Baryonic Structure Survey fields (S850$\mu$m =19.5 mJy), and amongst the most luminous starbursts known at any redshift.- Using the IRAM-NOEMA interferometer in the highest resolution A-configuration, we resolve the source into two components separated by ∼8 kpc, visible as blue shifted and red shifted 12CO(5–4) lines, exhibiting the expected kinematic properties of a major merger between two gas rich Galaxies. The combined merger system is traced over 2.3 arcsec or 18.4 kpc. Each component of the merger shows ordered gas motions suggestive of a massive turbulent disc. We measure the dynamical masses of the blue and red discs as (1.5 ± 0.2) × 1011 and (0.71 ± 0.22) × 1011 M⊙, respectively. The more massive disc component shows broad wings in the CO line, offset by ∼3 kpc from the disc centroid along the major axis, and extending to velocities ∼±1000 km $\rm {s^{-1}}$ from systemic velocity. We interpret this as either a possible bipolar outflowing component, or more likely a warping or tidal structure in the CO disc. Comparing the properties of HS1700.850.1 to other submillimeter detected galaxies with comparably bright 850 $\mu$m luminosities suggests that ongoing gas-rich mergers, or at least a clustered/group environment lead to these most extreme starburst phases.

A massive quiescent galaxy at redshift 4.658

The extremely rapid assembly of the earliest galaxies during the first billion years of cosmic history is a major challenge for our understanding of galaxy formation physics1–5. The advent of the James Webb Space Telescope (JWST) has exacerbated this issue by confirming the existence of galaxies in substantial numbers as early as the first few hundred million years6–8. Perhaps even more surprisingly, in some galaxies, this initial highly efficient star formation rapidly shuts down, or quenches, giving rise to massive quiescent galaxies as little as 1.5 billion years after the Big Bang9,10. However, due to their faintness and red colour, it has proven extremely challenging to learn about these extreme quiescent galaxies, or to confirm whether any existed at earlier times. Here we report the spectroscopic confirmation of a massive quiescent galaxy, GS-9209, at redshift, z = 4.658, just 1.25 billion years after the Big Bang, using the JWST Near-Infrared Spectrograph (NIRSpec). From these data we infer a stellar mass of M* = 3.8 ± 0.2 × 1010 M⊙, which formed over a roughly 200 Myr period before this galaxy quenched its star-formation activity at z={6.5}_{-0.5}^{+0.2}, when the Universe was approximately 800 Myr old. This galaxy is both a likely descendent of the highest-redshift submillimetre galaxies and quasars, and a likely progenitor for the dense, ancient cores of the most massive local galaxies.

Exploring the environment, magnetic fields, and feedback effects of massive high-redshift galaxies with [C II

Context. Massive galaxies are expected to grow through different transformative evolutionary phases. High-redshift starburst galaxies and quasars are thought to be such phases and thus provide insight into galaxy evolution. Several physical mechanisms are predicted to play an important role in driving these phases; for example, interaction with companion galaxies, active galactic nuclei feedback, and possibly magnetic fields. Aims. Our aim is to characterize the physical properties and the environment of the submillimeter galaxy AzTEC-3 at z = 5.3 and the lensed quasar BRI 0952−0115 at z = 4.4, and to set a limit on the polarization properties of the two sources. We intend to place these two sources in the broader context of galaxy evolution, specifically star formation and mass growth through cosmic time. Methods. We used full polarization, sub-arcsecond-resolution, ALMA band-7 observations of both BRI 0952−0115 and AzTEC-3. We detect [C II] (2P3/2−2P1/2) line emission towards both BRI 0952−0115 and AzTEC-3, along with companions in each field. We present an updated gravitational lensing model for BRI 0952−0115 for correction of gravitational magnification. Results. We present infrared luminosities, star-formation rates, and [C II] line to infrared luminosity ratios for each source. The [C II] emission line profile for both BRI 0952−0115 and AzTEC-3 exhibit a broad, complex morphology, indicating the possible presence of outflows. We present evidence of a “gas bridge” between AzTEC-3 and a companion source. Modified blackbody spectral energy distribution fitting is used to analyze the properties of [C II] detected companion sources in the field of both the submillimeter galaxy and the quasar. We investigated the possible role of the detected companions in outflow signatures. Using a simple dynamical mass estimate for the sources, we suggest that both systems are undergoing minor or major mergers. No polarization is detected for the [C II], placing an upper limit below that of theoretical predictions. Conclusions. Our results show that high-velocity wings are detected, indicating possible signs of massive outflows; however, the presence of companion galaxies can affect the final interpretation. Furthermore, the results provide additional evidence in support of the hypothesis that massive galaxies form in overdense regions, growing through minor or major mergers with companion sources. Finally, strong, ordered magnetic fields are unlikely to exist at the kiloparsec scale in the two studied sources.

CEERS Key Paper. IV. A Triality in the Nature of HST-dark Galaxies

The new capabilities that JWST offers in the near- and mid-infrared (IR) are used to investigate in unprecedented detail the nature of optical/near-IR-faint, mid-IR-bright sources, with HST-dark galaxies among them. We gather JWST data from the CEERS survey in the Extended Groth Strip, jointly with HST data, and analyze spatially resolved optical-to-mid-IR spectral energy distributions to estimate photometric redshifts in two dimensions and stellar population properties on a pixel-by-pixel basis for red galaxies detected by NIRCam. We select 138 galaxies with F150W − F356W > 1.5 mag and F356W < 27.5 mag. The nature of these sources is threefold: (1) 71% are dusty star-forming galaxies (SFGs) at 2 < z < 6 with and a variety of specific SFRs (<1 to >100 Gyr−1); (2) 18% are quiescent/dormant (i.e., subject to reignition/rejuvenation) galaxies (QGs) at 3 < z < 5, with and poststarburst mass-weighted ages (0.5–1.0 Gyr); and (3) 11% are strong young starbursts with indications of high equivalent width emission lines (typically, [O iii]+Hβ) at 6 < z < 7 (XELG-z6) and . The sample is dominated by disk-like galaxies with remarkable compactness for XELG-z6 (effective radii smaller than 0.4 kpc). Large attenuations in SFGs, 2 < A(V) < 5 mag, are found within 1.5 times the effective radius, approximately 2 kpc, while QGs present A(V) ∼ 0.2 mag. Our SED-fitting technique reproduces the expected dust emission luminosities of IR-bright and submillimeter galaxies. This study implies high levels of star formation activity between z ∼ 20 and z ∼ 10, where virtually 100% of our galaxies had already formed 108 M ⊙, 60% had assembled 109 M ⊙, and 10% up to 1010 M ⊙ (in situ or ex situ).

A NOEMA Molecular Line Scan of the Hubble Deep Field North: Improved Constraints on the CO Luminosity Functions and Cosmic Density of Molecular Gas

We present measurements of the CO luminosity functions (LFs) and the evolution of the cosmic molecular gas density out to z ∼ 6 based on an 8.5 arcmin2 spectral scan survey at 3 mm of the iconic Hubble Deep Field North (HDF-N) observed with the NOrthern Extended Millimeter Array (NOEMA). We use matched filtering to search for line emission from galaxies and determine their redshift probability distributions exploiting the extensive multiwavelength data for the HDF-N. We identify the seven highest-fidelity sources as CO emitters at 1 < z < 6, including the well-known submillimeter galaxy HDF 850.1 at z = 5.18. Four high-fidelity 3 mm continuum sources are found to be radio galaxies at z ≤ 1, plus HDF 850.1. We constrain the CO LFs in the HDF-N out to z ∼ 6, including a first measurement of the CO(5–4) LF at 〈z〉 = 5.0. The relatively large area and depth of the NOEMA HDF-N survey extends the existing LFs at 1 < z < 4 above the knee, yielding a somewhat lower density by 0.15–0.4 dex at the overlap region for the CO(2–1) and CO(3–2) transitions, attributed to cosmic variance. We perform a joint analysis of the CO LFs in the HDF-N and Hubble Ultra Deep Field from ASPECS, finding that they can be well described by a single Schechter function. The evolution of the cosmic molecular gas density from a joint analysis is in good agreement with earlier determinations. This implies that the impact of cosmic field-to-field variance on the measurements is consistent with previous estimates, adding to the challenges for simulations that model galaxies from first principles.

The Ly α, C iv, and He iinebulae around J1000+0234: a galaxy pair at the centre of a galaxy overdensity atz = 4.5

ABSTRACTLy α λ1216 (Ly α) emission extending over $\gtrsim \, \rm 10\, kilo\,parsec\, (kpc)$ around dusty, massive starbursts at z ≳ 3 might represent a short-lived phase in the evolution of present-day, massive quiescent galaxies. To obtain empirical constraints on this emerging scenario, we present Ly α, C ivλ1550 (C iv), and He ii λ1640 (He ii) observations taken with the Multi-Unit Spectroscopic Explorer towards J1000+0234: a galaxy pair at z = 4.5 composed of a low-mass starburst (J1000+0234−South) neighbouring a massive Submillimeter Galaxy (SMG; J1000+0234−North) that harbours a rotationally supported gas disc. Based on the spatial distribution and relative strength of Ly α, C iv, and He ii, we find that star formation in J1000+0234−South and an active galactic nucleus in J1000+0234−North are dominant factors in driving the observed 40 kiloparsec-scale Ly α blob (LAB). We use the non-resonant He ii line to infer kinematic information of the LAB. We find marginal evidence for two spatially and spectrally separated He ii regions, which suggests that the two-peaked Ly α profile is mainly a result of two overlapping and likely interacting H i clouds. We also report the serendipitous identification of three Ly α emitters spanning over a redshift bin Δz ≤ 0.007 (i.e. $\lesssim 380\, \rm km\, s^{-1}$) located at $\lesssim 140\, \rm kpc$ from J1000+0234. A galaxy overdensity analysis confirms that J1000+0234 lies near the centre of a Megaparsec-scale galaxy overdensity at z = 4.5 that might evolve into a galaxy cluster at z = 0. The properties of J1000+0234 and its large-scale environment strengthen the link between SMGs within LABs, tracing overdense regions, as the progenitors of local massive ellipticals in galaxy clusters.

The JCMT SCUBA-2 Survey of the James Webb Space Telescope North Ecliptic Pole Time-Domain Field

The James Webb Space Telescope Time-Domain Field (JWST-TDF) is an ∼14′ diameter field near the North Ecliptic Pole that will be targeted by one of the JWST Guaranteed Time Observations programs. Here, we describe our James Clerk Maxwell Telescope SCUBA-2 850 μm imaging of the JWST-TDF and present the submillimeter source catalog and properties. We also present a catalog of radio sources from Karl J. Jansky Very Large Array 3 GHz observations of the field. These observations were obtained to aid JWST's study of dust-obscured galaxies that contribute significantly to cosmic star formation at high redshifts. Our deep 850 μm map covers the JWST-TDF at a noise level of σ 850µm = 1.0 mJy beam−1, detecting 83/31 sources in the main/supplementary signal-to-noise ratio (S/N > 4 / S/N = 3.5–4) sample, respectively. The 3 GHz observations cover a 24′ diameter field with a 1σ noise of 1 μJy beam−1 at a 0.″7 FWHM. We identified eighty-five 3 GHz counterparts to sixty-six 850 μm sources and then matched these with multiwavelength data from the optical to the mid-infrared wave bands. We performed spectral energy distribution fitting for 61 submillimeter galaxies (SMGs) matched with optical/near-infrared data, and found that SMGs at S/N > 4 have a median value of z phot = 2.22 ± 0.12, star formation rates of 300 ± 40 M ⊙ yr−1 (Chabrier initial mass function), and typical cold dust masses of 5.9 ± 0.7 × 108 M ⊙, in line with bright SMGs from other surveys. The large cold dust masses indicate correspondingly large cool gas masses, which we suggest are a key factor necessary to drive the high star formation rates seen in this population.