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We present rest-frame optical JWST Near-infrared Spectrograph (NIRSpec) integral field unit (IFU) spectroscopy of TN J1338−1942 at z  = 4.1, one of the most luminous galaxies in the early universe with powerful extended radio jets. Previous observations showed evidence for strong, large-scale outflows based on its large (∼150 kpc) halo detected in Ly α, and high-velocity [O  ii ] emission features detected in ground-based spectroscopy. Our NIRSpec/IFU observations spatially resolve the emission line properties across the host galaxy. We find at least five concentrations of strong line emission, coinciding with discrete continuum features previously detected in imaging from Hubble Space Telescope and JWST , over an extent of ∼2 arcsec (∼15 kpc). The spectral diagnostics unambiguously trace active galactic nuclei (AGN) activity plus interaction between the interstellar medium and the radio jet as the dominant mechanisms for the ionization state and kinematics of the gas in the system. A secondary region of very high ionization lies at roughly 5 kpc away from the nucleus, and within the context of an expanding cocoon enveloping the radio lobe, this may be explained by strong shock-ionization of the entrained gas. However, it could also signal the presence of a second obscured AGN, which may offer an explanation for an intriguing outflow feature seen perpendicular to the radio axis. The presence of a dual supermassive black holes system in this galaxy would support that large galaxies in the early Universe quickly accumulated their mass through the merging of smaller units, at the centres of large overdensities. The inferred black hole mass to stellar mass ratio of 0.01−0.1 for TNJ1338 points to a more rapid assembly of black holes compared to the stellar mass of galaxies at high redshifts, consistent with other recent observations. [ABSTRACT FROM AUTHOR]

Spectral energy distribution (SED) fitting has been extensively used to determine the nature of the faint radio source population. Recent efforts have combined fits from multiple SED-fitting codes to account for the host galaxy and any active nucleus that may be present. We show that it is possible to produce similar-quality classifications using a single energy-balance SED fitting code, prospector , to model up to 26 bands of UV–far-infrared aperture-matched photometry for ∼31 000 sources in the ELAIS-N1 field from the LOFAR Two-Metre Sky Survey (LoTSS) deep fields first data release. One of a new generation of SED-fitting codes, prospector accounts for potential contributions from radiative active galactic nuclei (AGN) when estimating galaxy properties, including star formation rates (SFRs) derived using non-parametric star formation histories. Combining this information with radio luminosities, we classify 92 per cent of the radio sources as a star-forming galaxy, high-/low-excitation radio galaxy, or radio-quiet AGN and study the population demographics as a function of 150 MHz flux density, luminosity, SFR, stellar mass, redshift, and apparent r -band magnitude. Finally, we use prospector SED fits to investigate the SFR–150 MHz luminosity relation for a sample of ∼133 000 3.6 μm-selected z < 1 sources, finding that the stellar mass dependence is significantly weaker than previously reported, and may disappear altogether at |$\log _{10} (\mathrm{SFR}/M_\odot \, \mathrm{yr}^{-1}) \gt 0.5$|⁠. This approach makes it significantly easier to classify radio sources from LoTSS and elsewhere, and may have important implications for future studies of star-forming galaxies at radio wavelengths. [ABSTRACT FROM AUTHOR]

We present the first JWST observations of the z  = 4.11 luminous radio galaxy TN J1338–1942, obtained as part of the 'Prime Extragalactic Areas for Reionization and Lensing Science' ('PEARLS') project. Our NIRCam observations, designed to probe the key rest-frame optical continuum and emission line features at this redshift, enable resolved spectral energy distribution modelling that incorporates both a range of stellar population assumptions and radiative shock models. With an estimated stellar mass of log10(M /M⊙) ∼ 10.9, TN J1338–1942 is confirmed to be one of the most massive galaxies known at this epoch. Our observations also reveal extremely high equivalent-width nebular emission coincident with the luminous AGN jets that is best fit by radiative shocks surrounded by extensive recent star formation. We estimate the total star-formation rate (SFR) could be as high as |$\sim 1600\, \text{M}_{\odot }\, \text{yr}^{-1}$| , with the SFR that we attribute to the jet induced burst conservatively |$\gtrsim 500\, \text{M}_{\odot }\, \text{yr}^{-1}$|. The mass-weighted age of the star-formation, t mass < 4 Myr, is consistent with the likely age of the jets responsible for the triggered activity and significantly younger than that measured in the core of the host galaxy. The extreme scale of the potential jet-triggered star-formation activity indicates the potential importance of positive AGN feedback in the earliest stages of massive galaxy formation, with our observations also illustrating the extraordinary prospects for detailed studies of high-redshift galaxies with JWST. [ABSTRACT FROM AUTHOR]

Feedback from low-excitation radio galaxies (LERGs) plays a key role in the lifecycle of massive galaxies in the local Universe; their evolution, and the impact of these active galactic nuclei on early galaxy evolution, however, remain poorly understood. We use a sample of 10 481 LERGs from the first data release of the LOFAR two-metre Sky Survey Deep Fields, covering ∼25 deg2, to present the first measurement of the evolution of the radio luminosity function (LF) of LERGs out to z ∼ 2.5; this shows relatively mild evolution. We split the LERGs into those hosted by quiescent and star-forming galaxies, finding a new dominant population of LERGs hosted by star-forming galaxies at high redshifts. The incidence of LERGs in quiescent galaxies shows a steep dependence on stellar mass out to z ∼ 1.5, consistent with local Universe measurements of accretion occurring from cooling of hot gas haloes. The quiescent-LERGs dominate the LFs at z < 1, showing a strong decline in space density with redshift, tracing that of the available host galaxies, while there is an increase in the characteristic luminosity. The star-forming LERG LF increases with redshift, such that this population dominates the space densities at most radio-luminosities by z ∼ 1. The incidence of LERGs in star-forming galaxies shows a much weaker stellar-mass dependence, and increases with redshift, suggesting a different fuelling mechanism compared to their quiescent counterparts, potentially associated with the cold gas supply present in the star-forming galaxies. [ABSTRACT FROM AUTHOR]

In this paper, we present photometric redshift (photo- z) estimates for the Dark Energy Spectroscopic Instrument (DESI) Legacy Imaging Surveys, currently the most sensitive optical survey covering the majority of the extragalactic sky. Our photo- z methodology is based on a machine-learning approach, using sparse Gaussian processes augmented with Gaussian mixture models (GMMs) that allow regions of parameter space to be identified and trained separately in a purely data-driven way. The same GMMs are also used to calculate cost-sensitive learning weights that mitigate biases in the spectroscopic training sample. By design, this approach aims to produce reliable and unbiased predictions for all parts of the parameter space present in wide area surveys. Compared to previous literature estimates using the same underlying photometry, our photo- z s are significantly less biased and more accurate at z  > 1, with negligible loss in precision or reliability for resolved galaxies at z < 1. Our photo- z estimates offer accurate predictions for rare high-value populations within the parent sample, including optically selected quasars at the highest redshifts (z  > 6), as well as X-ray or radio continuum selected populations across a broad range of flux (densities) and redshift. Deriving photo- z estimates for the full Legacy Imaging Surveys Data Release 8, the catalogues provided in this work offer photo- z estimates predicted to be of high quality for ≳9 × 108 galaxies over |${\sim}19\, 400\, \text{deg}^{2}$| and spanning 0 < z ≲ 7, offering one of the most extensive samples of redshift estimates ever produced. [ABSTRACT FROM AUTHOR]

In this work we report the discovery of the hyperluminous galaxy HELP_J100156.75 + 022344.7 at a photometric redshift of |$z$| ≈ 4.3. The galaxy was discovered in the Cosmological Evolution Survey (COSMOS) field, one of the fields studied by the Herschel Extragalactic Legacy Project (HELP). We present the spectral energy distribution (SED) of the galaxy and fit it with the CYprus models for Galaxies and their NUclear Spectra (CYGNUS) multi-component radiative transfer models. We find that its emission is dominated by an obscured quasar with a predicted total 1–1000 μm luminosity of |$3.91^{+1.69}_{-0.55} \times 10^{13}\, \mathrm{ L}_\odot$| and an active galactic nucleus (AGN) fraction of |$\sim 89{{\ \rm per\ cent}}$|⁠. We also fit HELP_J100156.75 + 022344.7 with the cigale(code investigating galaxy emission) code and find a similar result. This is only the second |$z$| > 4 hyperluminous obscured quasar discovered to date. The discovery of HELP_J100156.75 + 022344.7 in the ∼2 deg2 COSMOS field implies that a large number of obscured hyperluminous quasars may lie in the HELP fields, which cover ∼1300 deg2. If this is confirmed, tension between supermassive black hole evolution models and observations will be alleviated. We estimate the space density of objects like HELP_J100156.75 + 022344.7 at |$z$| ≈ 4.5 to be ∼1.8 × 10−8 Mpc−3. This is slightly higher than the space density of coeval hyperluminous optically selected quasars, suggesting that the obscuring torus in |$z$| > 4 quasars may have a covering factor |$\gtrsim 50{{\ \rm per\ cent}}$|⁠. [ABSTRACT FROM AUTHOR]

The observed empirical relation between the star formation rates (SFR) of low-redshift galaxies and their radio continuum luminosity offers a potential means of measuring SFR in high-redshift galaxies that is unaffected by dust obscuration. In this study, we make the first test for redshift evolution in the SFR-radio continuum relation at high redshift using dust-corrected H α SFR. Our sample consists of 178 galaxies from the MOSFIRE Deep Evolution Field (MOSDEF) Survey at 1.4 < z < 2.6 with rest-frame optical spectroscopy and deep 1.5 GHz radio continuum observations from the Karl G. Jansky Very Large Array (VLA) GOODS North field. Using a stacking analysis, we compare the observed radio continuum luminosities with those predicted from the dust-corrected H α SFR assuming a range of z  ∼ 0 relations. We find no evidence for a systematic evolution with redshift, when stacking the radio continuum as a function of dust-corrected H α SFR and when stacking both optical spectroscopy and radio continuum as a function of stellar mass. We conclude that locally calibrated relations between SFR and radio continuum luminosity remain valid out to z  ∼ 2. [ABSTRACT FROM AUTHOR]

We present an optical to near-infrared (NIR) selected astronomical catalogue covering 1270 deg2. This is the first attempt to systematically combine data from 23 of the premier extragalactic survey fields – the product of a vast investment of telescope time. The fields are those imaged by the Herschel Space Observatory that form the Herschel Extragalactic Legacy Project (HELP). Our catalogue of 170 million objects is constructed by a positional cross-match of 51 public surveys. This high-resolution optical, NIR, and mid-infrared catalogue is designed for photometric redshift estimation, extraction of fluxes in lower resolution far-infrared maps, and spectral energy distribution modelling. It collates, standardizes, and provides value added derived quantities including corrected aperture magnitudes and astrometry correction over the Herschel extragalactic wide fields for the first time. |$grizy$| fluxes are available on all fields with g -band data reaching |$5\sigma$| point-source depths in a 2 arcsec aperture of 23.5, 24.4, and 24.6 (AB) mag at the 25th, 50th, and 75th percentiles, by area covered, across all HELP fields. It has K or |$K_s$| coverage over 1146 deg2 with depth percentiles of 20.2, 20.4, and 21.0 mag, respectively. The IRAC Ch 1 band is available over 273 deg2 with depth percentiles of 17.7, 21.4, and 22.2 mag, respectively. This paper defines the 'masterlist' objects for the first data release (DR1) of HELP. This large sample of standardized total and corrected aperture fluxes, uniform quality flags, and completeness measures provides large well-understood statistical samples over the full Herschel extragalactic sky. [ABSTRACT FROM AUTHOR]

Building on the first paper in this series (Duncan et al. 2018), we present a study investigating the performance of Gaussian process photometric redshift (photo-z) estimates for galaxies and active galactic nuclei (AGNs) detected in deep radio continuum surveys. A Gaussian process redshift code is used to produce photo-z estimates targeting specific subsets of both the AGN population -- infrared (IR), X-ray, and optically selected AGNs -- and the general galaxy population. The new estimates for the AGN population are found to perform significantly better at z > 1 than the template-based photo-z estimates presented in our previous study. Our new photo-z estimates are then combined with template estimates through hierarchical Bayesian combination to produce a hybrid consensus estimate that outperforms both of the individual methods across all source types. Photo-z estimates for radio sources that are X-ray sources or optical/IR AGNs are significantly improved in comparison to previous template- only estimates -- with outlier fractions and robust scatter reduced by up to a factor of -4. The ability of our method to combine the strengths of the two input photo-z techniques and the large improvements we observe illustrate its potential for enabling future exploitation of deep radio continuum surveys for both the study of galaxy and black hole coevolution and for cosmological studies. [ABSTRACT FROM AUTHOR]

We present a study of photometric redshift performance for galaxies and active galactic nuclei detected in deep radio continuum surveys. Using two multiwavelength data sets, over the NOAO Deep Wide Field Survey Boötes and COSMOS fields, we assess photometric redshift (photo-z) performance for a sample of ∼4500 radio continuum sources with spectroscopic redshifts relative to those of ∼63 000 non-radio-detected sources in the same fields. We investigate the performance of three photometric redshift template sets as a function of redshift, radio luminosity and infrared/X-ray properties.We find that no single template library is able to provide the best performance across all subsets of the radio-detected population, with variation in the optimum template set both between subsets and between fields. Through a hierarchical Bayesian combination of the photo-z estimates from all three template sets, we are able to produce a consensus photo-z estimate that equals or improves upon the performance of any individual template set. [ABSTRACT FROM AUTHOR]

We use a large sample of ∼350 000 galaxies constructed by combining the UKIDSS UDS, VIDEO/CFHT-LS, UltraVISTA/COSMOS and GAMA survey regions to probe the major (1:4 stellar mass ratio) merging histories of massive galaxies (>1010M☉) at 0.005 < z < 3.5. We use a method adapted from that presented in López-Sanjuan et al., using the full photometric redshift probability distributions, tomeasure pair fractions of flux-limited, stellarmass selected galaxy samples using close-pair statistics. The pair fraction is found to weakly evolve as α (1 + z)0.8 with no dependence on stellar mass.We subsequently derive major merger rates for galaxies at >1010M☉ and at a constant number density of n > 10-4 Mpc-3 and find rates a factor of 2-3 smaller than previous works, although this depends strongly on the assumed merger time-scale and likelihood of a close-pair merging. Galaxies undergo approximately 0.5 major mergers at z < 3.5, accruing an additional (1-4) x 1010M☉ in the process. On average, this represents an increase in stellar mass of 20-030 per cent (40-70 per cent) for constant stellar mass (constant number density) samples. Major merger accretion rate densities of ∼2 x 10-4 M☉ yr-1 Mpc-3 are found for number density selected samples, indicating that direct progenitors of local massive (>1011M☉) galaxies have experienced a steady supply of stellar mass via major mergers throughout their evolution. While pair fractions are found to agree with those predicted by the Henriques et al. semi-analytic model, the Illustris hydrodynamical simulation fails to quantitatively reproduce derived merger rates. Furthermore, we find that major mergers become a comparable source of stellar mass growth compared to star formation at z < 1, but is 10-100 times smaller than the star formation rate density at higher redshifts. [ABSTRACT FROM AUTHOR]

Low radio frequency surveys are important for testing unified models of radio-loud quasars and radio galaxies. Intrinsically similar sources that are randomly oriented on the sky will have different projected linear sizes. Measuring the projected linear sizes of these sources provides an indication of their orientation. Steep-spectrum isotropic radio emission allows for orientation-free sample selection at low radio frequencies. We use a new radio survey of the Boötes field at 150MHz made with the Low-Frequency Array (LOFAR) to select a sample of radio sources. We identify 60 radio sources withpowers P> 1025.5 WHz--1 at at 150MHz using cross-matched multiwavelength information from the AGN and Galaxy Evolution Survey, which provides spectroscopic redshifts and photometric identification of 16 quasars and 44 radio galaxies. When considering the radio spectral slope only, we find that radio sources with steep spectra have projected linear sizes that are on average 4.4 ± 1.4 larger than those with flat spectra. The projected linear sizes of radio galaxies are on average 3.1 ± 1.0 larger than those of quasars (2.0 ± 0.3 after correcting for redshift evolution). Combining these results with three previous surveys, we find that the projected linear sizes of radio galaxies and quasars depend on redshift but not on power. The projected linear size ratio does not correlate with either parameter. The LOFAR data are consistent within the uncertainties with theoretical predictions of the correlation between the quasar fraction and linear size ratio, based on an orientation-based unification scheme [ABSTRACT FROM AUTHOR]