SuperCLASS - II. Photometric redshifts and characteristics of spatially resolved mu Jy radio sources

We present optical and near-infrared imaging covering a similar to 1.53 deg(2) region in the Super-Cluster Assisted Shear Survey (SuperCLASS) field, which aims to make the first robust weak lensing measurement at radio wavelengths. We derive photometric redshifts for approximate to 176 000 sources down to i'(AB) similar to 24 and present photometric redshifts for 1.4 GHz expanded Multi-Element Radio Linked Interferometer Network (e-MERLIN) and Karl G. Jansky Very Large Array (VLA) detected radio sources found in the central 0.26 deg(2). We compile an initial catalogue of 149 radio sources brighter than S-1.4 > 75 mu Jy and find their photometric redshifts span 0 = 0.55 and = 1.9 x 10(23) WHz(-1), respectively. We find 95 per cent of the mu Jy radio source sample (141/149) have spectral energy distributions (SEDs) best fit by star-forming templates while 5 per cent (8/149) are better fit by active galactic nuclei (AGN). Spectral indices are calculated for sources with radio observations from the VLA and Giant Metrewave Radio Telescope (GMRT) at 325 MHz, with an average spectral slope of alpha = 0.59 +/- 0.04. Using the full photometric redshift catalogue, we construct a density map at the redshift of the known galaxy clusters, z = 0.20 +/- 0.08. Four of the five clusters are prominently detected at > 7 sigma in the density map and we confirm the photometric redshifts are consistent with previously measured spectra from a few galaxies at the cluster centres

SuperCLASS - III. Weak lensing from radio and optical observations in Data Release 1

We describe the first results on weak gravitational lensing from the SuperCLASS survey: the first survey specifically designed to measure the weak lensing effect in radio-wavelength data, both alone and in cross-correlation with optical data. We analyse 1.53 deg(2) of optical data from the Subaru telescope and 0.26 deg(2) of radio data from the e-MERLIN and VLA telescopes (the DR1 data set). Using standard methodologies on the optical data only we make a significant (10 sigma) detection of the weak lensing signal (a shear power spectrum) due to the massive supercluster of galaxies in the targeted region. For the radio data we develop a new method to measure the shapes of galaxies from the interferometric data, and we construct a simulation pipeline to validate this method. We then apply this analysis to our radio observations, treating the e-MERLIN and VLA data independently. We achieve source densities of 0.5 arcmin(-2) in the VLA data and 0.06 arcmin(-2) in the e-MERLIN data, numbers which prove too small to allow a detection of a weak lensing signal in either the radio data alone or in cross-correlation with the optical data. Finally, we show preliminary results from a visibility-plane combination of the data from e-MERLIN and VLA which will be used for the forthcoming full SuperCLASS data release. This approach to data combination is expected to enhance both the number density of weak lensing sources available, and the fidelity with which their shapes can be measured

Uncovering a Massive z~7.65 Galaxy Hosting a Heavily Obscured Radio-Loud QSO Candidate in COSMOS-Web

In this letter, we report the discovery of the highest redshift, heavily obscured, radio-loud QSO candidate selected using JWST NIRCam/MIRI, mid-IR, sub-mm, and radio imaging in the COSMOS-Web field. Using multi-frequency radio observations and mid-IR photometry, we identify a powerful, radio-loud (RL), growing supermassive black hole (SMBH) with significant spectral steepening of the radio SED ($f_{1.32 \mathrm{GHz}} \sim 2$ mJy, $q_{24\mu m} = -1.1$, $\alpha_{1.32-3\mathrm{GHz}}=-1.2$, $\Delta \alpha = -0.4$). In conjunction with ALMA, deep ground-based observations, ancillary space-based data, and the unprecedented resolution and sensitivity of JWST, we find no evidence of QSO contribution to the UV/optical/NIR data and thus infer heavy amounts of obscuration (N$_{\mathrm{H}} > 10^{23}$ cm$^{-2}$). Using the wealth of deep UV to sub-mm photometric data, we report a singular solution photo-z of $z_\mathrm{phot}$ = 7.65$^{+0.4}_{-0.3}$ and estimate an extremely massive host-galaxy ($\log M_{\star} = 11.92 \pm 0.06\,\mathrm{M}_{\odot}$). This source represents the furthest known obscured RL QSO candidate, and its level of obscuration aligns with the most representative but observationally scarce population of QSOs at these epochs.Comment: Submitted to ApJL, Comments welcom

The e-MERLIN SuperCLASS legacy survey : photometric redshifts and characteristics of spatially resolved [mu] Jy radio sources

We present optical and near-infrared imaging covering a ~1.53 deg² region in the Super-Cluster Assisted Shear Survey (SuperCLASS) field, which aims to make the first robust weak lensing measurement at radio wavelengths. We derive photometric redshifts for [approximately equal to] 176,000 sources down to i'[subscript AB]~24 and present photometric redshifts for 1.4 GHz e-MERLIN and VLA detected radio sources found in the central 0.26 deg². We compile an initial catalog of 149 radio sources brighter than S₁.₄ > 75 µJy and find their photometric redshifts span 0 = 0.55 and =1.9 x 10²³ W Hz⁻¹ respectively. We find 95% of the µJy radio source sample (141/149) have SEDs best fit by star-forming templates while 5% (8/149) are better fit by AGN. Spectral indices are calculated for sources with radio observations from VLA and GMRT at 325 MHz, with an average spectral slope of α=0.59±0.04. Using the full photometric redshift catalog we construct a density map at the redshift of the known galaxy clusters, z=0.20±0.08. Four of the five clusters are prominently detected at > 7 σ in the density map and we confirm the photometric redshifts are consistent with previously measured spectra from a few galaxies at the cluster centers.Astronom

Physical Characterization of an Unlensed, Dusty Star-forming Galaxy at z = 5.85

We present a physical characterization of MM J100026.36+021527.9 (a.k.a. "Mambo-9"), a dusty star-forming galaxy (DSFG) at z = 5.850 \ub1 0.001. This is the highest-redshift unlensed DSFG (and fourth most distant overall) found to date and is the first source identified in a new 2 mm blank-field map in the COSMOS field. Though identified in prior samples of DSFGs at 850 μm to 1.2 mm with unknown redshift, the detection at 2 mm prompted further follow-up as it indicated a much higher probability that the source was likely to sit at z > 4. Deep observations from the Atacama Large Millimeter and submillimeter Array (ALMA) presented here confirm the redshift through the secure detection of 12CO(J = 6→5) and p-H2O (21,1 → 20,2). Mambo-9 is composed of a pair of galaxies separated by 6 kpc with corresponding star formation rates of 590 M o˙ yr-1 and 220 M o˙ yr-1, total molecular hydrogen gas mass of (1.7 \ub1 0.4) 7 1011 M o˙, dust mass of (1.3 \ub1 0.3) 7 109 M o˙, and stellar mass of (3.2-1.5+1.0) 7 109 M o˙. The total halo mass, (3.3 \ub1 0.8) 7 1012 M o˙, is predicted to exceed 1015 M o˙ by z = 0. The system is undergoing a merger-driven starburst that will increase the stellar mass of the system tenfold in τ depl = 40-80 Myr, converting its large molecular gas reservoir (gas fraction of 96-2+1) into stars. Mambo-9 evaded firm spectroscopic identification for a decade, following a pattern that has emerged for some of the highest-redshift DSFGs found. And yet, the systematic identification of unlensed DSFGs like Mambo-9 is key to measuring the global contribution of obscured star formation to the star formation rate density at z ⪆ 4, the formation of the first massive galaxies, and the formation of interstellar dust at early times (≲1 Gyr)

Characterization of Two 2 mm detected Optically Obscured Dusty Star-forming Galaxies

International audienceThe 2 mm Mapping Obscuration to Reionization with ALMA (MORA) Survey was designed to detect high-redshift (z ≳ 4), massive, dusty star-forming galaxies (DSFGs). Here we present two likely high-redshift sources, identified in the survey, whose physical characteristics are consistent with a class of optical/near-infrared (OIR)-invisible DSFGs found elsewhere in the literature. We first perform a rigorous analysis of all available photometric data to fit spectral energy distributions and estimate redshifts before deriving physical properties based on our findings. Our results suggest the two galaxies, called MORA-5 and MORA-9, represent two extremes of the "OIR-dark" class of DSFGs. MORA-5 ( ${z}_{\mathrm{phot}}={4.3}_{-1.3}^{+1.5}$ ) is a significantly more active starburst with a star formation rate (SFR) of ${830}_{-190}^{+340}$ M ⊙ yr-1 compared to MORA-9 ( ${z}_{\mathrm{phot}}={4.3}_{-1.0}^{+1.3}$ ), whose SFR is a modest ${200}_{-60}^{+250}$ M ⊙ yr-1. Based on the stellar masses (M ⋆ ≍ 1010-11 M ⊙), space density (n ~ (5 ± 2) × 10-6 Mpc-3, which incorporates two other spectroscopically confirmed OIR-dark DSFGs in the MORA sample at z = 4.6 and z = 5.9), and gas depletion timescales (<1 Gyr) of these sources, we find evidence supporting the theory that OIR-dark DSFGs are the progenitors of recently discovered 3 < z < 4 massive quiescent galaxies

Mapping Obscuration to Reionization with ALMA (MORA): 2 mm Efficiently Selects the Highest-redshift Obscured Galaxies

International audienceWe present the characteristics of 2 mm selected sources from the largest Atacama Large Millimeter/submillimeter Array (ALMA) blank-field contiguous survey conducted to date, the Mapping Obscuration to Reionization with ALMA (MORA) survey covering 184 arcmin2 at 2 mm. Twelve of 13 detections above 5σ are attributed to emission from galaxies, 11 of which are dominated by cold dust emission. These sources have a median redshift of $\langle {z}_{2\,\mathrm{mm}}\rangle ={3.6}_{-0.3}^{+0.4}$ primarily based on optical/near-infrared photometric redshifts with some spectroscopic redshifts, with 77% ± 11% of sources at z > 3 and 38% ± 12% of sources at z > 4. This implies that 2 mm selection is an efficient method for identifying the highest-redshift dusty star-forming galaxies (DSFGs). Lower-redshift DSFGs (z 3 yet are likely to drop out at 2 mm. MORA shows that DSFGs with star formation rates in excess of 300 M ⊙ yr-1 and a relative rarity of ~10-5 Mpc-3 contribute ~30% to the integrated star formation rate density at 3 2. Analysis of MORA sources' spectral energy distributions hint at steeper empirically measured dust emissivity indices than reported in typical literature studies, with $\langle \beta \rangle ={2.2}_{-0.4}^{+0.5}$ . The MORA survey represents an important step in taking census of obscured star formation in the universe's first few billion years, but larger area 2 mm surveys are needed to more fully characterize this rare population and push to the detection of the universe's first dusty galaxies

Mapping Obscuration to Reionization with ALMA (MORA): 2 mm Efficiently Selects the Highest-redshift Obscured Galaxies

We present the characteristics of 2 mm selected sources from the largest Atacama Large Millimeter/submillimeter Array (ALMA) blank-field contiguous survey conducted to date, the Mapping Obscuration to Reionization with ALMA (MORA) survey covering 184 arcmin2 at 2 mm. Twelve of 13 detections above 5σ are attributed to emission from galaxies, 11 of which are dominated by cold dust emission. These sources have a median redshift of primarily based on optical/near-infrared photometric redshifts with some spectroscopic redshifts, with 77% ± 11% of sources at z > 3 and 38% ± 12% of sources at z > 4. This implies that 2 mm selection is an efficient method for identifying the highest-redshift dusty star-forming galaxies (DSFGs). Lower-redshift DSFGs (z 3 yet are likely to drop out at 2 mm. MORA shows that DSFGs with star formation rates in excess of 300 M ⊙ yr−1 and a relative rarity of ∼10−5 Mpc−3 contribute ∼30% to the integrated star formation rate density at 3 2. Analysis of MORA sources’ spectral energy distributions hint at steeper empirically measured dust emissivity indices than reported in typical literature studies, with . The MORA survey represents an important step in taking census of obscured star formation in the universe’s first few billion years, but larger area 2 mm surveys are needed to more fully characterize this rare population and push to the detection of the universe’s first dusty galaxies