We present high-resolution 870-um ALMA continuum maps of 30 bright sub-millimeter sources in the UKIDSS UDS field. These sources are selected from deep, 1-square degrees 850-um maps from the SCUBA--2 Cosmology Legacy Survey, and are representative of
the brightest sources in the field (median SCUBA2 flux S_850=8.7+/-0.4 mJy). We detect 52 sub-millimeter galaxies (SMGs) at >4-sigma significance in our 30 ALMA maps. In 61+/-17% of the ALMA maps the single-dish source comprises a blend of >=2 SMGs, where the secondary SMGs are Ultra--Luminous Infrared Galaxies (ULIRGs) with L_IR>10^12 Lo. The brightest SMG contributes on average 80+/-4% of the single-dish flux density, and in the ALMA maps containing >=2 SMGs the secondary SMG contributes 25+/-3% of the integrated ALMA flux. We construct source counts and show that multiplicity boosts the apparent single-dish cumulative counts by 20% at S_870>7.5mJy, and by 60% at S_870>12mJy. We combine our sample with previous ALMA studies of fainter SMGs and show that the counts are well-described by a double power-law with a break at 8.5+/-0.6mJy. The break corresponds to a luminosity of ~6x10^12Lsol or a star-formation rate of ~1000Mo/yr. For the typical sizes of these SMGs, which are resolved in our ALMA data with r=1.2+/-0.1kpc, this yields a limiting SFR density of ~100Msol/yr/kpc2. Finally, the number density of S_870>2mJy SMGs is 80+/-30 times higher than that derived from blank-field counts. An over-abundance of faint SMGs is inconsistent with line-of-sight projections dominating multiplicity in the brightest SMGs, and indicates that a significant proportion of these high-redshift ULIRGs must be physically associated.
We report the redshift of an unlensed, highly obscured submillimetre galaxy (SMG), HS1700.850.1, the brightest SMG (S850um =19.1 mJy) detected in the JCMT/SCUBA-2 Baryonic Structure Survey, based on the detection of its CO line emission. Using the IR
AM PdBI-WIDEX with 3.6GHz band width, we serendipitously detect an emission line at 150.6 GHz. From a search over 14.5 GHz in the 3-mm and 2-mm atmospheric windows, we confirm the identification of this line as CO(5-4) at z = 2.816, meaning that it does not reside in the z~2.30 proto-cluster in this field. Measurement of the 870um source size (<0.85) from the Sub-Millimeter Array (SMA) confirms a compact emission in a S870um =14.5mJy, LIR~10^13 Lsun component, suggesting an Eddington-limited starburst. We use the double-peaked CO line profile measurements along with the SMA size constraints to study the gas dynamics of a HyLIRG, estimating the gas and dynamical masses of HS1700.850.1. While HS1700.850.1 is one of the most extreme galaxies known in the Universe, we find that it occupies a relative void in the Lyman-Break Galaxy distribution in this field. Comparison with other extreme objects at similar epochs (HyLIRG Quasars), and cosmological simulations, suggests such an anti-bias of bright SMGs could be relatively common, with the brightest SMGs rarely occupying the most overdense regions at z=2-4.
We present deep MUSE integral-field unit (IFU) spectroscopic observations of the giant (~150 x 80 kpc) Ly-alpha halo around the z=4.1 radio galaxy TNJ J1338-1942. This 9-hr observation maps the two-dimensional kinematics of the Ly-alpha emission acro
ss the halo. We identify two HI absorbers which are seen against the Ly-alpha emission, both of which cover the full 150 x 80 kpc extent of the halo and so have covering fractions ~1. The stronger and more blue-shifted absorber (dv~1200 km/s) has dynamics that mirror that of the underlying halo emission and we suggest that this high column material (n(HI) ~ 10^19.4 /cm^2), which is also seen in CIV absorption, represents an out-flowing shell that has been driven by the AGN (or star formation) within the galaxy. The weaker (n(HI)~10^14 /cm^2) and less blue shifted (dv~500 km/s) absorber most likely represents material in the cavity between the out-flowing shell and the Ly-alpha halo. We estimate that the mass in the shell must be of order 10^10 Msol -- a significant fraction of the ISM from a galaxy at z=4. The large scales of these coherent structures illustrate the potentially powerful influence of AGN feedback on the distribution and energetics of material in their surroundings. Indeed, the discovery of high-velocity (~1000 km/s), group-halo-scale (i.e. >150 kpc) and mass-loaded winds in the vicinity of the central radio source are broadly in agreement with the requirements of models that invoke AGN-driven outflows to regulate star formation and black-hole growth in massive galaxies at early times.
We report the blind detection of 12CO emission from a Distant Red Galaxy, HS1700.DRG55. We have used the IRAM PdBI-WIDEX, with its 3.6GHz of instantaneous dual-polarization bandwidth, to target 12CO(3--2) from galaxies lying in the proto-cluster at z
=2.300 in the field HS1700+64. If indeed this line in DRG55 is 12CO(3--2), its detection at 104.9GHz indicates a z_CO=2.296. None of the other eight known z~2.30 proto-cluster galaxies lying within the primary beam (PB) are detected in 12CO, although the limits are ~2x worse towards the edge of the PB where several lie. The optical/near-IR magnitudes of DRG55 (R_AB>27, K_AB=22.3) mean that optical spectroscopic redshifts are difficult with 10m-class telescopes, but near-IR redshifts would be feasible. The 24um-implied SFR (210 M_odot yr-1), stellar mass (~10^11 M-odot) and 12CO line luminosity (3.6x10^10 K km s-1 pc^2) are comparable to other normal 12CO-detected star forming galaxies in the literature, although the galaxy is some ~2 mag (~6x) fainter in the rest-frame UV than 12CO-detected galaxies at z>2. The detection of DRG55 in 12CO complements three other 12CO detected UV-bright galaxies in this proto-cluster from previous studies, and suggests that many optically faint galaxies in the proto-cluster may host substantial molecular gas reservoirs, and a full blind census of 12CO in this overdense environment is warranted.
We analyse HST WFC3/$H_{160}$-band observations of a sample of 48 ALMA-detected submillimeter galaxies (SMGs) in the Extended Chandra Deep Field South field, to study their stellar morphologies and sizes. We detect 79$pm$17% of the SMGs in the $H_{16
0}$-band imaging with a median sensitivity of 27.8 mag, and most (80%) of the non-detections are SMGs with 870$mu$m fluxes of $S_{870} < $3 mJy. With a surface brightness limit of $mu_H sim $26 mag arcsec$^{-2}$, we find that 82$pm$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 Sersic fit to the $H_{160}$ surface-brightness profiles we derive a median Sersic index of $n = $1.2$pm$0.3 and a median half-light radius of $r_e = $4.4$^{+1.1}_{-0.5}$ kpc for our SMGs at $z = $1-3. We also find significant displacements between the positions of the $H_{160}$-component and 870$mu$m emission in these systems, suggesting that the dusty star-burst regions and less-obscured stellar distribution are not co-located. We find significant differences in the sizes and the Sersic index between our $z = $2-3 SMGs and $z sim $2 quiescent galaxies, suggesting a major transformation of the stellar light profile is needed in the quenching processes if SMGs are progenitors of the red-and-dead $zsim$2 galaxies. Given the short-lived nature of SMGs, we postulate that the majority of the $z = $2-3 SMGs with $S_{870} gtrsim $2 mJy are early/mid-stage major mergers.
We present high-resolution (0.3) ALMA 870um imaging of 52 sub-millimeter galaxies (SMGs) in the Ultra Deep Survey (UDS) field and investigate the size and morphology of the sub-millimeter (sub-mm) emission on 2-10kpc scales. We derive a median intrin
sic angular size of FWHM=0.30$pm$0.04 for the 23 SMGs in the sample detected at a signal-to-noise ratio (SNR) >10. Using the photometric redshifts of the SMGs we show that this corresponds to a median physical half-light diameter of 2.4$pm$0.2kpc. A stacking analysis of the SMGs detected at an SNR <10 shows they have sizes consistent with the 870um-bright SMGs in the sample. We compare our results to the sizes of SMGs derived from other multi-wavelength studies, and show that the rest-frame ~250um sizes of SMGs are consistent with studies of resolved 12CO (J=3-2 to 7-6) emission lines, but that sizes derived from 1.4GHz imaging appear to be approximately two times larger on average, which we attribute to cosmic ray diffusion. The rest-frame optical sizes of SMGs are around four times larger than the sub-millimeter sizes, indicating that the star formation in these galaxies is compact relative to the pre-existing stellar distribution. The size of the starburst region in SMGs is consistent with the majority of the star formation occurring in a central region, a few kpc in extent, with a median star formation rate surface density of 90$pm$30Msol/yr/kpc$^2$, which may suggest that we are witnessing an intense period of bulge growth in these galaxies.
We describe a search for submillimeter emission in the vicinity of one of the most distant, luminous galaxies known, HerMES FLS3 at z=6.34, exploiting it as a signpost to a potentially biased region of the early Universe, as might be expected in hier
archical structure formation models. Imaging to the confusion limit with the innovative, wide-field submillimeter bolometer camera, SCUBA-2, we are sensitive to colder and/or less luminous galaxies in the surroundings of HFLS3. We use the Millennium Simulation to illustrate that HFLS3 may be expected to have companions if it is as massive as claimed, but find no significant evidence from the surface density of SCUBA-2 galaxies in its vicinity, or their colors, that HFLS3 marks an over-density of dusty, star-forming galaxies. We cannot rule out the presence of dusty neighbours with confidence, but deeper 450-um imaging has the potential to more tightly constrain the redshifts of nearby galaxies, at least one of which likely lies at z>~5. If associations with HFLS3 can be ruled out, this could be taken as evidence that HFLS3 is less biased than a simple extrapolation of the Millennium Simulation may imply. This could suggest either that it represents a rare short-lived, but highly luminous, phase in the evolution of an otherwise typical galaxy, or that this system has suffered amplification due to a foreground gravitational lens and so is not as intrinsically luminous as claimed.
We analyse new SCUBA-2 submillimeter and archival SPIRE far-infrared imaging of a z=1.62 cluster, Cl0218.3-0510, which lies in the UKIDSS/UDS field of the SCUBA-2 Cosmology Legacy Survey. Combining these tracers of obscured star formation activity wi
th the extensive photometric and spectroscopic information available for this field, we identify 31 far-infrared/submillimeter-detected probable cluster members with bolometric luminosities >1e12 Lo and show that by virtue of their dust content and activity, these represent some of the reddest and brightest galaxies in this structure. We exploit Cycle-1 ALMA submillimeter continuum imaging which covers one of these sources to confirm the identification of a SCUBA-2-detected ultraluminous star-forming galaxy in this structure. Integrating the total star-formation activity in the central region of the structure, we estimate that it is an order of magnitude higher (in a mass-normalised sense) than clusters at z~0.5-1. However, we also find that the most active cluster members do not reside in the densest regions of the structure, which instead host a population of passive and massive, red galaxies. We suggest that while the passive and active populations have comparable near-infrared luminosities at z=1.6, M(H)~-23, the subsequent stronger fading of the more active galaxies means that they will evolve into passive systems at the present-day which are less luminous than the descendants of those galaxies which were already passive at z~1.6 (M(H)~-20.5 and M(H)~-21.5 respectively at z~0). We conclude that the massive galaxy population in the dense cores of present-day clusters were already in place at z=1.6 and that in Cl0218.3-0510 we are seeing continuing infall of less extreme, but still ultraluminous, star-forming galaxies onto a pre-existing structure.
MS$,$0451.6$-$0305 is a rich galaxy cluster whose strong lensing is particularly prominent at submm wavelengths. We combine new SCUBA-2 data with imaging from Herschel SPIRE and PACS and HST in order to try to understand the nature of the sources bei
ng lensed. In the region of the giant submm arc, we uncover seven multiply imaged galaxies (up from the previously known three), of which six are found to be at a redshift of $zsim2.9$, and possibly constitute an interacting system. Using a novel forward-modelling approach, we are able to simultaneously deblend and fit SEDs to the individual galaxies that contribute to the giant submm arc, constraining their dust temperatures, far infrared luminosities and star formation rates. The submm arc first identified by SCUBA can now be seen to be composed of at least five distinct sources, four of these within the galaxy group at $zsim2.9$. The total unlensed luminosity for this galaxy group is $(3.1pm0.3) times 10^{12},mathrm{L}_odot$, which gives an unlensed star formation rate of $(450pm50)$ M$_odot$ yr$^{-1}$. From the properties of this system, we see no evidence of evolution towards lower temperatures in the dust temperature versus far-infrared luminosity relation for high redshift galaxies.
We exploit ALMA 870um (345GHz) observations of submillimetre sources in the Extended Chandra Deep Field South to investigate the far-infrared properties of high-redshift submillimetre galaxies (SMGs). Using the precisely located 870um ALMA positions
of 99 SMGs, together with 24um and radio imaging of this field, we deblend the Herschel/SPIRE imaging of this region to extract their far-infrared fluxes and colours. The median photometric redshifts for ALMA LESS (ALESS) SMGs which are detected in at least two SPIRE bands increases with wavelength of the peak in their SEDs, with z=2.3+/-0.2, 2.5+/-0.3 and 3.5+/-0.5 for the 250, 350 and 500-um peakers respectively. We find that 34 ALESS SMGs do not have a >3-sigma counterpart at 250, 350 or 500-um. These galaxies have a median photometric redshift of z=3.3+/-0.5, which is higher than the full ALESS SMG sample; z=2.5+/-0.2. Using the photometric redshifts together with the 250-870um photometry, we estimate the far-infrared luminosities and characteristic dust temperature of each SMG. The median infrared luminosity of the S_870um>2mJy SMGs is L_IR=(3.0+/-0.3)x10^{12}Lo(SFR=300+/-30Mo/yr). At a fixed luminosity, the characteristic dust temperature of these high-redshift SMGs is 2-3K lower than comparably luminous galaxies at z=0, reflecting the more extended star formation occurring in these systems. By extrapolating the 870um number counts to S_ 870um=1mJy, we show that the contribution of S_870um>1mJy SMGs to the cosmic star formation budget is 20% of the total over the redshift range z~1-4. We derive a median dust mass for these SMGs of M_d=(3.6+/-0.3)x10^8Mo and by adopting an appropriate gas-to-dust ratio, we estimate an average molecular mass of M_H2=(4.2+/-0.4)x10^{10}Mo. Finally, we use our estimates of the H2 masses to show that SMGs with S_870um>1mJy contain ~10% of the z~2 volume-averaged H2 mass density at this epoch.
