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ABSTRACT Cold quasars are a rare population of luminous, unobscured quasars associated with host galaxies that have a high star formation rate. We aimed to study the host galaxies of 64 of these cold quasars in order to probe how the supermassive black holes and host galaxies were co-evolving. We compiled data from the XMM-XXL survey and cross-matched with the VHS, WISE, and HerMES surveys to obtain multiwavelength photometry spanning the X-ray to the infrared and including optical spectroscopy. From the data, we calculated the supermassive black hole’s mass using broad emission from the Mg ii and Hbeta lines. We compared this with the stellar mass of the entire galaxy and found that the black holes are significantly more massive than would be predicted by local relations, indicating that the majority of black hole growth precedes the bulk of the the stellar mass formation. In addition to this, we created a spectral energy distribution for each galaxy to calculate the star formation rate. We compared the star formation rate with the black hole accretion rate and find that the stellar mass is rapidly increasing at a relative rate faster than the black hole growth, supporting the picture where the black hole grows first. 

ABSTRACT We aim to determine the intrinsic far-Infrared (far-IR) emission of X-ray-luminous quasars over cosmic time. Using a 16 deg2 region of the Stripe 82 field surveyed by XMM-Newton and Herschel Space Observatory, we identify 2905 X-ray luminous (LX > 1042 erg/s) active galactic nuclei (AGN) in the range z ≈ 0–3. The IR is necessary to constrain host galaxy properties such as star formation rate (SFR) and gas mass. However, only 10 per cent of our AGN are detected both in the X-ray and IR. Because 90 per cent of the sample is undetected in the far-IR by Herschel, we explore the mean IR emission of these undetected sources by stacking their Herschel/SPIRE images in bins of X-ray luminosity and redshift. We create stacked spectral energy distributions from the optical to the far-IR, and estimate the median SFR, dust mass, stellar mass, and infrared luminosity using a fitting routine. We find that the stacked sources on average have similar SFR/Lbol ratios as IR detected sources. The majority of our sources fall on or above the main sequence line suggesting that X-ray selection alone does not predict the location of a galaxy on the main sequence. We also find that the gas depletion time scales of our AGN are similar to those of dusty star forming galaxies. This suggests that X-ray selected AGN host high star formation and that there are no signs of declining star formation. 

Abstract The 3D geometries of high-redshift galaxies remain poorly understood. We build a differentiable Bayesian model and use Hamiltonian Monte Carlo to efficiently and robustly infer the 3D shapes of star-forming galaxies in James Webb Space Telescope Cosmic Evolution Early Release Science observations with $\log M_{*}/M_{\odot }=9.0–10.5$atz= 0.5–8.0. We reproduce previous results from the Hubble Space Telescope Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey in a fraction of the computing time and constrain the mean ellipticity, triaxiality, size, and covariances with samples as small as ∼50 galaxies. We find high 3D ellipticities for all mass–redshift bins, suggesting oblate (disky) or prolate (elongated) geometries. We break that degeneracy by constraining the mean triaxiality to be ∼1 for $\log M_{*}/M_{\odot }=9.0–9.5$dwarfs atz> 1 (favoring the prolate scenario), with significantly lower triaxialities for higher masses and lower redshifts indicating the emergence of disks. The prolate population traces out a “banana” in the projected $b/a–\log a$diagram with an excess of low-b/a, large- $\log a$galaxies. The dwarf prolate fraction rises from ∼25% atz= 0.5–1.0 to ∼50%–80% atz= 3–8. Our results imply a second kind of disk settling from oval (triaxial) to more circular (axisymmetric) shapes with time. We simultaneously constrain the 3D size–mass relation and its dependence on 3D geometry. High-probability prolate and oblate candidates show remarkably similar Sérsic indices (n∼ 1), nonparametric morphological properties, and specific star formation rates. Both tend to be visually classified as disks or irregular, but edge-on oblate candidates show more dust attenuation. We discuss selection effects, follow-up prospects, and theoretical implications. 

Abstract We present rest-frame optical emission-line flux ratio measurements for fivez> 5 galaxies observed by the James Webb Space Telescope Near-Infared Spectrograph (NIRSpec) in the SMACS 0723 Early Release Observations. We add several quality-control and post-processing steps to the NIRSpec pipeline reduction products in order to ensure reliablerelativeflux calibration of emission lines that are closely separated in wavelength, despite the uncertainabsolutespectrophotometry of the current version of the reductions. Compared toz∼ 3 galaxies in the literature, thez> 5 galaxies have similar [Oiii]λ5008/Hβratios, similar [Oiii]λ4364/Hγratios, and higher (∼0.5 dex) [NeIII]λ3870/[OII]λ3728 ratios. We compare the observations to MAPPINGS V photoionization models and find that the measured [NeIII]λ3870/[OII]λ3728, [Oiii]λ4364/Hγ, and [Oiii]λ5008/Hβemission-line ratios are consistent with an interstellar medium (ISM) that has very high ionization ( $\log \left(Q\right)\simeq 8-9$, units of cm s⁻¹), low metallicity (Z/Z_⊙≲ 0.2), and very high pressure ( $\log \left(P/k\right)\simeq 8-9$, units of cm⁻³). The combination of [Oiii]λ4364/Hγand [Oiii]λ(4960 + 5008)/Hβline ratios indicate very high electron temperatures of $4.1<\log \left(T_e/\mathrm{K}\right)<4.4$, further implying metallicities ofZ/Z_⊙≲ 0.2 with the application of low-redshift calibrations for “T_e-based” metallicities. These observations represent a tantalizing new view of the physical conditions of the ISM in galaxies at cosmic dawn.