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We analyze new SCUBA-2 submillimeter and archival SPIRE far-infrared imaging of a z = 1.62 cluster, Cl 0218.3–0510, which lies in the UKIRT Infrared Deep Sky Survey/Ultra-Deep Survey field of the SCUBA-2 Cosmology Legacy Survey. Combining these tracers of obscured star-formation activity with the extensive photometric and spectroscopic information available for this field, we identify 31 far-infrared/submillimeter-detected probable cluster members with bolometric luminosities ≳1012L☼ 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 ALMA submillimeter continuum observations, which cover 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-normalized 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, MH ∼ –23, the subsequent stronger fading of the more active galaxies means that they will evolve into passive systems at the present day that are less luminous than the descendants of those galaxies that were already passive at z ∼ 1.6 (MH ∼ –20.5 and MH ∼ –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 Cl 0218.3–0510 we are seeing continuing infall of less extreme, but still ultraluminous, star-forming galaxies onto a pre-existing structure. [ABSTRACT FROM AUTHOR]

We present the results of a gravitational lensing analysis of the bright zs = 2.957 submillimeter galaxy (SMG) HERMES found in the Herschel/SPIRE science demonstration phase data from the Herschel Multi-tiered Extragalactic Survey (HerMES) project. The high-resolution imaging available in optical and near-IR channels, along with CO emission obtained with the Plateau de Bure Interferometer, allows us to precisely estimate the intrinsic source extension and hence estimate the total lensing magnification to be µ = 10.9 ± 0.7. We measure the half-light radius Reff of the source in the rest-frame near-UV and V bands that characterize the unobscured light coming from stars and find Reff,* = [2.0 ± 0.1] kpc, in good agreement with recent studies on the SMG population. This lens model is also used to estimate the size of the gas distribution (Reff,gas = [1.1 ± 0.5] kpc) by mapping back in the source plane the CO (J = 5 → 4) transition line emission. The lens modeling yields a relatively large Einstein radius REin = 4".10 ± 0".02, corresponding to a deflector velocity dispersion of [483 ± 16] kms-1. This shows that HERMES is lensed by a galaxy group-size dark matter halo at redshift z1 ~ 0.6. The projected dark matter contribution largely dominates the mass budget within the Einstein radius with fdm (REin) ~ 80%. This fraction reduces to Fdm (Reff.G1 ≃ 4.5 kpc) ~ 47% within the effective radius of the main deflecting galaxy of stellar mass M*,GI = [8-5 ± 1.6] x 1011 M⊙. At this smaller scale the dark matter fraction is consistent with results already found for massive lensing ellipticals at z ~ 0.2 from the Sloan Lens ACS Survey. [ABSTRACT FROM AUTHOR]

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 hierarchical 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 overdensity of dusty, star-forming galaxies. We cannot rule out the presence of dusty neighbors with confidence, but deeper 450 μm 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. [ABSTRACT FROM AUTHOR]

We report the detection at 850 μm of the central source in SSA22-LAB1, the archetypal “Lyman-α Blob” (LAB), a 100 kpc scale radio-quiet emission-line nebula at z = 3.1. The flux density of the source, S850 = 4.6 ± 1.1 mJy, implies the presence of a galaxy or group of galaxies with a total luminosity of LIR ≈ 1012L☼. The position of an active source at the center of a ∼50 kpc radius ring of linearly polarized Lyα emission detected by Hayes et al. suggests that the central source is leaking Lyα photons preferentially in the plane of the sky, which undergo scattering in H I clouds at a large galactocentric radius. The Lyα morphology around the submillimeter detection is reminiscent of a biconical outflow, and the average Lyα line profiles of the two “lobes” are dominated by a red peak, which is expected for a resonant line emerging from a medium with a bulk velocity gradient that is outflowing relative to the line center. Taken together, these observations provide compelling evidence that the central active galaxy (or galaxies) is responsible for a large fraction of the extended Lyα emission and morphology. Less clear is the history of the cold gas in the circumgalactic medium being traced by Lyα: is it mainly pristine material accreting into the halo that has not yet been processed through an interstellar medium (ISM), now being blown back as it encounters an outflow, or does it mainly comprise gas that has been swept-up within the ISM and expelled from the galaxy? [ABSTRACT FROM AUTHOR]

We present Keck spectroscopic observations and redshifts for a sample of 767 Herschel-SPIRE selected galaxies (HSGs) at 250, 350, and 500 μm, taken with the Keck I Low Resolution Imaging Spectrometer and the Keck II DEep Imaging Multi-Object Spectrograph. The redshift distribution of these SPIRE sources from the Herschel Multitiered Extragalactic Survey peaks at z = 0.85, with 731 sources at z < 2 and a tail of sources out to z ∼ 5. We measure more significant disagreement between photometric and spectroscopic redshifts (〈 Δz/(1 + zspec)〉 = 0.29) than is seen in non-infrared selected samples, likely due to enhanced star formation rates and dust obscuration in infrared-selected galaxies. The infrared data are used to directly measure integrated infrared luminosities and dust temperatures independent of radio or 24 μm flux densities. By probing the dust spectral energy distribution (SED) at its peak, we estimate that the vast majority (72%-83%) of z < 2 Herschel-selected galaxies would drop out of traditional submillimeter surveys at 0.85-1 mm. We find that dust temperature traces infrared luminosity, due in part to the SPIRE wavelength selection biases, and partially from physical effects. As a result, we measure no significant trend in SPIRE color with redshift; if dust temperature were independent of luminosity or redshift, a trend in SPIRE color would be expected. Composite infrared SEDs are constructed as a function of infrared luminosity, showing the increase in dust temperature with luminosity, and subtle change in near-infrared and mid-infrared spectral properties. Moderate evolution in the far-infrared (FIR)/radio correlation is measured for this partially radio-selected sample, with qIR∝(1 + z)–0.30 ± 0.02 at z < 2. We estimate the luminosity function and implied star formation rate density contribution of HSGs at z < 1.6 and find overall agreement with work based on 24 μm extrapolations of the LIRG, ULIRG, and total infrared contributions. This work significantly increased the number of spectroscopically confirmed infrared-luminous galaxies at z ≫ 0 and demonstrates the growing importance of dusty starbursts for galaxy evolution studies and the build-up of stellar mass throughout cosmic time. [ABSTRACT FROM AUTHOR]

We present spectroscopic observations for a sample of 36 Herschel-SPIRE 250-500 μm selected galaxies (HSGs) at 2 < z < 5 from the Herschel Multi-tiered Extragalactic Survey. Redshifts are confirmed as part of a large redshift survey of Herschel-SPIRE-selected sources covering ∼0.93 deg2 in six extragalactic legacy fields. Observations were taken with the Keck I Low Resolution Imaging Spectrometer and the Keck II DEep Imaging Multi-Object Spectrograph. Precise astrometry, needed for spectroscopic follow-up, is determined by identification of counterparts at 24 μm or 1.4 GHz using a cross-identification likelihood matching method. Individual source luminosities range from log (LIR/L☼) = 12.5-13.6 (corresponding to star formation rates (SFRs) 500-9000 M☼ yr–1, assuming a Salpeter initial mass function), constituting some of the most intrinsically luminous, distant infrared galaxies discovered thus far. We present both individual and composite rest-frame ultraviolet spectra and infrared spectral energy distributions. The selection of these HSGs is reproducible and well characterized across large areas of the sky in contrast to most z > 2 HyLIRGs in the literature, which are detected serendipitously or via tailored surveys searching only for high-z HyLIRGs; therefore, we can place lower limits on the contribution of HSGs to the cosmic star formation rate density (SFRD) at (7 ± 2) × 10–3M☼ yr–1h3 Mpc–3 at z ∼ 2.5, which is >10% of the estimated total SFRD of the universe from optical surveys. The contribution at z ∼ 4 has a lower limit of 3 × 10–3M☼ yr–1h3 Mpc–3, ≳20% of the estimated total SFRD. This highlights the importance of extremely infrared-luminous galaxies with high SFRs to the buildup of stellar mass, even at the earliest epochs. [ABSTRACT FROM AUTHOR]