An ultra-deep multiband Very Large Array (VLA) survey of the faint radio sky (COSMOS-XS): new constraints on the cosmic star formation history

Large scale structure and cosmolog

An ultradeep multiband VLA survey of the faint radio sky (COSMOS-XS): source catalog and number counts

Galaxie

Ultra-red Galaxies Signpost Candidate Protoclusters at High Redshift

We present images obtained with LABOCA of a sample of 22 galaxies selected via their red Herschel SPIRE colors. We aim to see if these luminous, rare, and distant galaxies are signposting dense regions in the early universe. Our 870 μm survey covers an area of ≈1 deg2 down to an average rms of $3.9\,\mathrm{mJy}\,{\mathrm{beam}}^{-1}$, with our five deepest maps going ≈2× deeper still. We catalog 86 dusty star-forming galaxies (DSFGs) around our "signposts," detected above a significance of 3.5σ. This implies a ${100}_{-30}^{+30} \%$ overdensity of ${S}_{870}\gt 8.5\,\mathrm{mJy}$ (or {L}_{\mathrm{FIR}}=6.7\times {10}^{12}\mbox{--}2.9\times {10}^{13}\,{L}_{\odot }) DSFGs, excluding our signposts, when comparing our number counts to those in "blank fields." Thus, we are 99.93% confident that our signposts are pinpointing overdense regions in the universe, and ≈95% [50%] confident that these regions are overdense by a factor of at least ≥1.5 × [2×]. Using template spectral energy distributions (SEDs) and SPIRE/LABOCA photometry, we derive a median photometric redshift of z = 3.2 ± 0.2 for our signposts, with an inter-quartile range of z = 2.8–3.6, somewhat higher than expected for ~850 μm selected galaxies. We constrain the DSFGs that are likely responsible for this overdensity to within $| {\rm{\Delta }}z| \leqslant 0.65$ of their respective signposts. These "associated" DSFGs are radially distributed within (physical) distances of 1.6 ± 0.5 Mpc from their signposts, have median star formation rates (SFRs) of $\approx (1.0\pm 0.2)\times {10}^{3}\,{M}_{\odot }\,{\mathrm{yr}}^{-1}$ (for a Salpeter stellar inital mass function) and median gas reservoirs of $\sim 1.7\times {10}^{11}\,{M}_{\odot }$. These candidate protoclusters have average total SFRs of at least $\approx (2.3\pm 0.5)\times {10}^{3}\,{M}_{\odot }\,{\mathrm{yr}}^{-1}$ and space densities of ~9 × 10−7 Mpc−3, consistent with the idea that their constituents may evolve to become massive early-type galaxies in the centers of the rich galaxy clusters we see today

Kiloparsec-scale Imaging of the CO(1-0)-traced cold molecular gas reservoir in a z similar to 3.4 submillimeter galaxy

We present a high-resolution study of the cold molecular gas as traced by CO(1-0) in the unlensed z similar to 3.4 submillimeter galaxy SMM J13120+4242, using multiconfiguration observations with the Karl G. Jansky Very Large Array (JVLA). The gas reservoir, imaged on 0 ''.39 (similar to 3 kpc) scales, is resolved into two components separated by similar to 11 kpc with a total extent of 16 +/- 3 kpc. Despite the large spatial extent of the reservoir, the observations show a CO(1-0) FWHM linewidth of only 267 +/- 64 km s(-1). We derive a revised line luminosity of LCO(1-0)' = (10 +/- 3) x 10(10) K km s(-1) pc(2) and a molecular gas mass of M-gas = (13 +/- 3)x 10(10) (alpha(CO)/1) M-circle dot. Despite the presence of a velocity gradient (consistent with previous resolved CO(6-5) imaging), the CO(1-0) imaging shows evidence for significant turbulent motions that are preventing the gas from fully settling into a disk. The system likely represents a merger in an advanced stage. Although the dynamical mass is highly uncertain, we use it to place an upper limit on the CO-to-H-2 mass conversion factor a alpha(CO) of 1.4. We revisit the SED fitting, finding that this galaxy lies on the very massive end of the main sequence at z = 3.4. Based on the low gas fraction, short gas depletion time, and evidence for a central AGN, we propose that SMM J13120 is in a rapid transitional phase between a merger-driven starburst and an unobscured quasar. The case of SMM J13120 highlights how mergers may drive important physical changes in galaxies without pushing them off the main sequence.Galaxie

COLDz:: probing cosmic star formation with radio free-free emission

Galaxie

The ALMA REBELS Survey: dust continuum detections at z > 6.5

Galaxie

An ultra-deep multiband Very Large Array (VLA) survey of the faint radio sky (COSMOS-XS): new constraints on the cosmic star formation history

Large scale structure and cosmolog

The radio spectral turnover of radio-loud quasars at z > 5

Galaxie