[en] We report the results of a deep SCUBA-2 850 and 450 μm survey for dust-obscured ultra-/luminous infrared galaxies (U/LIRGs) in the field of the z = 1.46 cluster XCS J2215.9−1738. We detect a striking overdensity of submillimeter sources coincident with the core of this cluster: ∼3–4 × higher than expected in a blank field. We use the likely radio and mid-infrared counterparts to show that the bulk of these submillimeter sources have spectroscopic or photometric redshifts that place them in the cluster and that their multiwavelength properties are consistent with this association. The average far-infrared luminosities of these galaxies are (1.0 ± 0.1) × 10¹² $L_{\odot <!--\; ???\; -->}$, placing them on the U/LIRG boundary. Using the total star formation occurring in the obscured U/LIRG population within the cluster, we show that the resulting mass-normalized star formation rate for this system supports previous claims of a rapid increase in star formation activity in cluster cores out to $z\sim <!--\; ???\; -->1.5$, which must be associated with the ongoing formation of the early-type galaxies that reside in massive clusters today.

[en] We investigate the far-infrared (far-IR) properties of galaxies selected via deep, narrow-band imaging of the Hα emission line in four redshift slices from $z=0.40\text{--}2.23$ over ∼1 deg² as part of the High-redshift Emission Line Survey (HiZELS). We use a stacking approach in the Herschel PACS/SPIRE far-IR bands, along with $850\mathrm{\mu <!--\; ??\; -->}\mathrm{m}$ imaging from SCUBA-2 and Very Large Array 1.4 GHz imaging, to study the evolution of the dust properties of Hα-emitters selected above an evolving characteristic luminosity threshold, $0.2L_{\mathrm{H}\mathrm{\alpha <!--\; ??\; -->}}^{\star <!--\; ???\; -->}(z)$. We investigate the relationship between the dust temperatures, T _dust, and the far-infrared luminosities, L _IR, of our stacked samples, finding that our Hα-selection identifies cold, low-L _IR galaxies ($T_{\mathrm{d}\mathrm{u}\mathrm{s}\mathrm{t}}\sim <!--\; ???\; -->14$ K; $\mathrm{l}\mathrm{o}\mathrm{g}[L_{\mathrm{I}\mathrm{R}}/L_{\odot <!--\; ???\; -->}]\sim <!--\; ???\; -->9.9$) at z = 0.40, and more luminous, warmer systems ($T_{\mathrm{d}\mathrm{u}\mathrm{s}\mathrm{t}}\sim <!--\; ???\; -->34$ K; $\mathrm{l}\mathrm{o}\mathrm{g}[L_{\mathrm{I}\mathrm{R}}/L_{\odot <!--\; ???\; -->}]\sim <!--\; ???\; -->11.5$) at z = 2.23. Using a modified graybody model, we estimate “characteristic sizes” for the dust-emitting regions of Hα-selected galaxies of ∼0.5 kpc, nearly an order of magnitude smaller than their stellar continuum sizes, which may provide indirect evidence of clumpy interstellar medium structure. Lastly, we use measurements of the dust masses from our far-IR stacking along with metallicity-dependent gas-to-dust ratios (${\mathrm{\delta <!--\; ??\; -->}}_{\mathrm{G}\mathrm{D}\mathrm{R}}$) to measure typical molecular gas masses of $\sim <!--\; ???\; -->1\times <!--\; ??\; -->{10}^{10}{M}_{\odot <!--\; ???\; -->}$ for these bright Hα-emitters. The gas depletion timescales are shorter than the Hubble time at each redshift, suggesting probable replenishment of their gas reservoirs from the intergalactic medium. Based on the number density of Hα-selected galaxies, we find that typical star-forming galaxies brighter than $0.2L_{\mathrm{H}\mathrm{\alpha <!--\; ??\; -->}}^{\star <!--\; ???\; -->}(z)$ comprise a significant fraction (35 ± 10%) of the total gas content of the universe, consistent with the predictions of the latest state-of-the-art cosmological simulations.

[en] The ALESS survey has followed up on a sample of 122 sub-millimeter sources in the Extended Chandra Deep Field South at 870 μm with the Atacama Large Millimeter Array (ALMA), allowing us to pinpoint the positions of sub-millimeter galaxies (SMGs) to ∼0.3 arcsec and to find their precise counterparts at different wavelengths. This enabled the first compilation of the multi-wavelength spectral energy distributions (SEDs) of a statistically reliable survey of SMGs. In this paper, we present a new calibration of the magphys SED modeling code that is optimized to fit these ultraviolet-to-radio SEDs of $z><!--\; >\; -->1$ star-forming galaxies using an energy balance technique to connect the emission from stellar populations, dust attenuation, and dust emission in a physically consistent way. We derive statistically and physically robust estimates of the photometric redshifts and physical parameters (such as stellar masses, dust attenuation, star formation rates (SFRs), and dust masses) for the ALESS SMGs. We find that the ALESS SMGs have median stellar mass $M_{\ast <!--\; ???\; -->}=8.9\pm <!--\; ??\; -->0.1\times <!--\; ??\; -->{10}^{10}{M}_{\odot <!--\; ???\; -->}$, median SFR $=280\pm <!--\; ??\; -->70M_{\odot <!--\; ???\; -->}{\mathrm{y}\mathrm{r}}^{-<!--\; ???\; -->1}$, median overall V-band dust attenuation $A_V=1.9\pm <!--\; ??\; -->0.2$ mag, median dust mass $M_{\mathrm{d}\mathrm{u}\mathrm{s}\mathrm{t}}=(5.6\pm <!--\; ??\; -->1.0)\times <!--\; ??\; -->{10}^8{M}_{\odot <!--\; ???\; -->}$, and median average dust temperature $T_{\mathrm{d}\mathrm{u}\mathrm{s}\mathrm{t}}\simeq <!--\; ???\; -->40$ K. We find that the average intrinsic SED of the ALESS SMGs resembles that of local ultra-luminous infrared galaxies in the infrared range, but the stellar emission of our average SMG is brighter and bluer, indicating lower dust attenuation, possibly because they are more extended. We explore how the average SEDs vary with different parameters (redshift, sub-millimeter flux, dust attenuation, and total infrared luminosity), and we provide a new set of SMG templates that can be used to interpret other SMG observations. To put the ALESS SMGs into context, we compare their stellar masses and SFRs with those of less actively star-forming galaxies at the same redshifts. We find that at $z\simeq <!--\; ???\; -->2$, about half of the SMGs lie above the star-forming main sequence (with SFRs three times larger than normal galaxies of the same stellar mass), while half are consistent with being at the high-mass end of the main sequence. At higher redshifts ($z\simeq <!--\; ???\; -->3.5$), the SMGs tend to have higher SFRs and stellar masses, but the fraction of SMGs that lie significantly above the main sequence decreases to less than a third.

[en] We present high-resolution (0.''3) Atacama Large Millimeter Array 870 μm imaging of 52 sub-millimeter galaxies (SMGs) in the Ultra Deep Survey field to investigate the size and morphology of the sub-millimeter (sub-mm) emission on 2-10 kpc scales. We derive a median intrinsic angular size of FWHM = 0.''30 ± 0.''04 for the 23 SMGs in the sample detected at a signal-to-noise ratio (S/N) >10. Using the photometric redshifts of the SMGs we show that this corresponds to a median physical half-light diameter of 2.4 ± 0.2 kpc. A stacking analysis of the SMGs detected at S/N <10 shows they have sizes consistent with the 870 μm bright SMGs in the sample. We compare our results to the sizes of SMGs derived from other multi-wavelength studies, and show that the rest-frame ∼250 μm sizes of SMGs are consistent with studies of resolved ¹²CO (J = 3-2 to 7-6) emission lines, but that sizes derived from 1.4 GHz imaging appear to be approximately two times larger on average, which we attribute to cosmic ray diffusion. The rest-frame optical sizes of SMGs are around four times larger than the sub-millimeter sizes, indicating that the star formation in these galaxies is compact relative to the pre-existing stellar distribution. The size of the starburst region in SMGs is consistent with the majority of the star formation occurring in a central region, a few kiloparsecs in extent, with a median star formation rate surface density of 90 ± 30 M _☉ yr^–1 kpc^–2, which may suggest that we are witnessing an intense period of bulge growth in these galaxies

[en] We present a multi-wavelength analysis of 52 submillimeter galaxies (SMGs), identified using ALMA 870 μm continuum imaging in a pilot program to precisely locate bright SCUBA-2-selected submillimeter sources in the UKIDSS Ultra Deep Survey (UDS) field. Using the available deep (especially near-infrared) panoramic imaging of the UDS field at optical-to-radio wavelengths we characterize key properties of the SMG population. The median photometric redshift of the bright ALMA/SCUBA-2 UDS (AS2UDS) SMGs that are detected in a sufficient number of wavebands to derive a robust photometric redshift is z = 2.65 ± 0.13. However, similar to previous studies, 27% of the SMGs are too faint at optical-to-near-infrared wavelengths to derive a reliable photometric redshift. Assuming that these SMGs lie at z ≳ 3 raises the median redshift of the full sample to z = 2.9 ± 0.2. A subset of 23 unlensed, bright AS2UDS SMGs have sizes measured from resolved imaging of their rest-frame far-infrared emission. We show that the extent and luminosity of the far-infrared emission are consistent with the dust emission arising from regions that are, on average, optically thick at a wavelength of ${\mathrm{\lambda <!--\; ??\; -->}}_0⩾<!--\; ???\; -->75\mathrm{\mu <!--\; ??\; -->}\mathrm{m}$ (1σ dispersion of 55–90 μm). Using the dust masses derived from our optically thick spectral energy distribution models, we determine that these galaxies have a median hydrogen column density of N _H = 9.8${}_{-<!--\; ???\; -->0.7}^{+1.4}$ × 10²³ cm⁻², or a corresponding median V-band obscuration of A _v = 540${}_{-<!--\; ???\; -->40}^{+80}$ mag, averaged along the line of sight to the source of their rest-frame ∼200 μm emission. We discuss the implications of this extreme attenuation by dust for the multi-wavelength study of dusty starbursts and reddening-sensitive tracers of star formation.

[en] We study the sub-millimeter properties of color-selected galaxies via a stacking analysis applied for the first time to interferometric data at sub-millimeter wavelengths. We base our study on 344 GHz ALMA continuum observations of ∼20''-wide fields centered on 86 sub-millimeter sources detected in the LABOCA Extended Chandra Deep Field South (ECDFS) Sub-millimeter Survey. We select various classes of galaxies (K-selected, star-forming sBzK galaxies, extremely red objects, and distant red galaxies) according to their optical/near-infrared fluxes. We find clear, >10σ detections in the stacked images of all these galaxy classes. We include in our stacking analysis Herschel/SPIRE data to constrain the dust spectral energy distribution of these galaxies. We find that their dust emission is well described by a modified blackbody with T _dust ≈ 30 K and β = 1.6 and infrared luminosities of (5-11) × 10¹¹ L _☉ or implied star formation rates of 75-140 M _☉ yr^–1. We compare our results with those of previous studies based on single-dish observations at 870 μm and find that our flux densities are a factor 2-3 higher than previous estimates. The discrepancy is observed also after removing sources individually detected in ALESS maps. We report a similar discrepancy by repeating our analysis on 1.4 GHz observations of the whole ECDFS. Hence, we find tentative evidence that galaxies that are associated in projected and redshift space with sub-mm bright sources are brighter than the average population. Finally, we put our findings in the context of the cosmic star formation rate density as a function of redshift.

[en] We analyze Hubble Space Telescope WFC3/H ₁₆₀-band observations of a sample of 48 Atacama Large Millimeter/submillimeter Array detected submillimeter galaxies (SMGs) in the Extended Chandra Deep Field South field, to study their stellar morphologies and sizes. We detect 79% ± 17% of the SMGs in the H ₁₆₀-band imaging with a median sensitivity of 27.8 mag, and most (80%) of the nondetections are SMGs with 870 μm fluxes of S ₈₇₀ < 3 mJy. With a surface brightness limit of μ _H ∼ 26 mag arcsec^–2, we find that 82% ± 9% of the H ₁₆₀-band-detected SMGs at z = 1-3 appear to have disturbed morphologies, meaning they are visually classified as either irregulars or interacting systems, or both. By determining a Sérsic fit to the H ₁₆₀ surface brightness profiles, we derive a median Sérsic index of n = 1.2 ± 0.3 and a median half-light radius of r_e = 4.4_−0.5^+1.1 kpc for our SMGs at z = 1-3. We also find significant displacements between the positions of the H ₁₆₀ component and 870 μm emission in these systems, suggesting that the dusty starburst regions and less-obscured stellar distribution are not colocated. We find significant differences in the sizes and the Sérsic index between our z = 2-3 SMGs and z ∼ 2 quiescent galaxies, suggesting that a major transformation of the stellar light profile is needed in the quenching processes if SMGs are progenitors of the red-and-dead z ∼ 2 galaxies. Given the short-lived nature of SMGs, we postulate that the majority of the z = 2-3 SMGs with S ₈₇₀ ≳ 2 mJy are early/mid-stage major mergers

[en] We present spectroscopic redshifts of $S_{870\mathrm{\mu <!--\; ??\; -->}\mathrm{m}}\gtrsim <!--\; ???\; -->2$ mJy submillimeter galaxies (SMGs), which have been identified from the ALMA follow-up observations of 870 μm detected sources in the Extended Chandra Deep Field South (the ALMA-LESS survey). We derive spectroscopic redshifts for 52 SMGs, with a median of z = 2.4  ±  0.1. However, the distribution features a high-redshift tail, with ∼23% of the SMGs at $z⩾<!--\; ???\; -->3$. Spectral diagnostics suggest that the SMGs are young starbursts, and the velocity offsets between the nebular emission and UV ISM absorption lines suggest that many are driving winds, with velocity offsets of up to 2000 km s⁻¹. Using the spectroscopic redshifts and the extensive UV-to-radio photometry in this field, we produce optimized spectral energy distributions (SEDs) using Magphys, and use the SEDs to infer a median stellar mass of $M_{\star <!--\; ???\; -->}$ = (6 ± 1)× 10¹⁰ M ${}_{\odot <!--\; ???\; -->}$ for our SMGs with spectroscopic redshift. By combining these stellar masses with the star formation rates (measured from the far-infrared SEDs), we show that SMGs (on average) lie a factor of ∼5 above the so-called “main sequence” at $z\sim <!--\; ???\; -->2$. We provide this library of 52 template fits with robust and uniquely well-sampled SEDs as a resource for future studies of SMGs, and also release the spectroscopic catalog of ∼2000 (mostly infrared-selected) galaxies targeted as part of the spectroscopic campaign.

[en] We present detailed studies of a z = 2.12 submillimeter galaxy, ALESS67.1, using sub-arcsecond resolution ALMA, adaptive optics-aided VLT/SINFONI, and Hubble Space Telescope (HST)/CANDELS data to investigate the kinematics and spatial distributions of dust emission (870 μm continuum), ¹²CO(J = 3–2), strong optical emission lines, and visible stars. Dynamical modeling of the optical emission lines suggests that ALESS67.1 is not a pure rotating disk but a merger, consistent with the apparent tidal features revealed in the HST imaging. Our sub-arcsecond resolution data set allows us to measure half-light radii for all the tracers, and we find a factor of 4–6 smaller sizes in dust continuum compared to all the other tracers, including ¹²CO; also, ultraviolet (UV) and Hα emission are significantly offset from the dust continuum. The spatial mismatch between the UV continuum and the cold dust and gas reservoir supports the explanation that geometrical effects are responsible for the offset of the dusty galaxy on the IRX–β diagram. Using a dynamical method we derive an ${\mathrm{\alpha <!--\; ??\; -->}}_{\mathrm{C}\mathrm{O}}=1.8\pm <!--\; ??\; -->1.0$, consistent with other submillimeter galaxies (SMGs) that also have resolved CO and dust measurements. Assuming a single ${\mathrm{\alpha <!--\; ??\; -->}}_{\mathrm{C}\mathrm{O}}$ value we also derive resolved gas and star formation rate surface densities, and find that the core region of the galaxy ($\lesssim <!--\; ???\; -->5$ kpc) follows the trend of mergers on the Schmidt–Kennicutt relationship, whereas the outskirts ($\gtrsim <!--\; ???\; -->5$ kpc) lie on the locus of normal star-forming galaxies, suggesting different star formation efficiencies within one galaxy. Our results caution against using single size or morphology for different tracers of the star formation activity and gas content of galaxies, and therefore argue the need to use spatially resolved, multi-wavelength observations to interpret the properties of SMGs, and perhaps even for $z><!--\; >\; -->1$ galaxies in general.

[en] We report the discovery of a 10 comoving megaparsec (cMpc)-scale structure traced by massive submillimeter galaxies (SMGs) at z ∼ 4.6. These galaxies are selected from an emission line search of ALMA Band 7 observations targeting 184 luminous submillimeter sources (S _850μm ≥ 6.2 mJy) across 1.6 degrees² in the COSMOS field. We identify four [C ii] emitting SMGs and two probable [C ii] emitting SMG candidates at z = 4.60–4.64 with velocity-integrated signal-to-noise ratio of S/N > 8. Four of the six emitters are near-infrared blank SMGs. After excluding one SMG whose emission line is falling at the edge of the spectral window, all galaxies show clear velocity gradients along the major axes that are consistent with rotating gas disks. The estimated rotation velocities of the disks are 330–550 km s⁻¹ and the inferred host dark-matter halo masses are ∼2–8 × 10¹² M _⊙. From their estimated halo masses and [C ii] luminosity function, we suggest that these galaxies have a high (50%–100%) duty cycle and high (∼0.1) baryon conversion efficiency (SFR relative to baryon accretion rate), and that they contribute ≃2% to the total star formation rate density at z = 4.6. These SMGs are concentrated within just 0.3% of the full survey volume, suggesting they are strongly clustered. The extent of this structure and the individual halo masses suggest that these SMGs will likely evolve into members of a ∼10¹⁵ M _⊙ cluster at z = 0. This survey reveals a synchronized dusty starburst in massive halos at z > 4, which could be driven by mergers or fed by smooth gas accretion.