Galaxy formation and evolution

Abstract:

Early-type galaxies (ETGs) show a bimodal distribution in key structural properties like stellar specific angular momentum, kinematic morphology, shape, and nuclear surface brightness profiles. Slow rotator ETGs, mostly found in the densest regions of galaxy clusters, become common when the stellar mass exceeds a critical value of around M ∗ crit ≈2×1011 M ⊙, or more precisely when lg(R e/kpc)≳12.4−lg(M ∗/M ⊙). These galaxies have low specific angular momentum, spheroidal shapes, and stellar populations that are old, metal-rich, and α-enhanced. In contrast, fast rotator ETGs form a continuous sequence of properties with spiral galaxies. In these galaxies, the age, metallicity, and α-enhancement of the stellar population correlate best with the effective stellar velocity dispersion σ e ∝ M ∗ / R e (i.e., properties are similar for R e ∝ M ∗), or with other proxies approximating their bulge mass fraction. This sequence spans from star-forming spiral disks to quenched, passive, spheroid-dominated fast rotator ETGs. Notably, at a fixed σ e, younger galaxies show lower metallicity. The structural differences and environmental distributions of ETGs suggest two distinct formation pathways: slow rotators undergo early intense star formation followed by rapid quenching via their dark halos and supermassive black holes, and later evolve through dry mergers during hierarchical cluster assembly; fast rotators, on the other hand, develop more gradually through gas accretion and minor mergers, becoming quenched by internal feedback above a characteristic lg(σ e crit/km s−1) ≳ 2.3 (in the local Universe) or due to environmental effects.

Abstract:

We combine the power of blind integral field spectroscopy from the Hobby–Eberly Telescope (HET) Dark Energy Experiment (HETDEX) with sources detected by the Low Frequency Array (LOFAR) to construct the HETDEX-LOFAR Spectroscopic Redshift Catalog. Starting from the first data release of the LOFAR Two-metre Sky Survey, including a value-added catalog with photometric redshifts, we extracted 28,705 HETDEX spectra. Using an automatic classifying algorithm, we assigned each object a star, galaxy, or quasar label along with a velocity/redshift, with supplemental classifications coming from the continuum and emission-line catalogs of the internal, fourth data release from HETDEX (HDR4). We measured 9087 new redshifts; in combination with the value-added catalog, our final spectroscopic redshift sample is 9710 sources. This new catalog contains the highest substantial fraction of LOFAR galaxies with spectroscopic redshift information; it improves archival spectroscopic redshifts and facilitates research to determine the [O ii] emission properties of radio galaxies from 0.0 < z < 0.5, and the Lyα emission characteristics of both radio galaxies and quasars from 1.9 < z < 3.5. Additionally, by combining the unique properties of LOFAR and HETDEX, we are able to measure star formation rates (SFRs) and stellar masses. Using the Visible Integral-field Replicable Unit Spectrograph, we measure the emission lines of [O iii], [Ne iii], and [O ii] and evaluate line-ratio diagnostics to determine whether the emission from these galaxies is dominated by active galactic nuclei or star formation and fit a new SFR–L 150MHz relationship.

Abstract:

Over the past two decades, tight correlations between black hole masses (M•) and their host galaxy properties have been firmly established for massive galaxies (with stellar mass log(M*/M⊙)≳10 ) at low-z (z < 1), indicating coevolution of supermassive black holes and galaxies. However, the situation at high-z, especially beyond cosmic noon (z ≳ 2.5), is controversial. With a combination of JWST Near Infrared Camera (NIRCam)/wide field slitless spectroscopy (WFSS) from FRESCO, CONGRESS and deep multiband NIRCam/image data from JADES in the GOODS fields, we study the black-hole-to-galaxy mass relation at z ∼ 1–4. After identifying 18 broad-line active galactic nuclei (AGNs) at 1 < z < 4 (with 8 at z > 2.5) from the WFSS data, we measure their black hole masses based on broad near-infrared lines (Paα, Paβ, and He i λ10833 Å), and constrain their stellar masses from AGN-galaxy image decomposition or spectral energy distribution decomposition. Taking account of the observational biases, the intrinsic scatter of the M•−M* relation, and the errors in mass measurements, we find no significant difference in the M•/M* ratio for 2.5 < z < 4 compared to that at lower redshifts (1 < z < 2.5), suggesting no evolution of the M•−M* relation at log(M*/M⊙)≳10 up to z ∼ 4.

Abstract:

The morphology of a galaxy reflects the mix of physical processes occurring within and around it, offering indirect clues to its formation and evolution. We apply both visual classification and computer vision to test the suspected connection between galaxy mergers and active galactic nucleus (AGN) activity, as evidenced by a close/merging galaxy pair, or tidal features surrounding an apparently singular system. We use JADES JWST/NIRCam imagery of a complete, multiwavelength AGN sample recently expanded with JWST/Mid-Infrared Instrument (MIRI) photometry. This 0.9–25 μm data set enables constraints on the host-galaxy morphologies of a broad range of AGN beyond z ∼ 1, including heavily obscured examples missing from previous studies. Our primary AGN sample consists of 243 lightly to highly obscured X-ray-selected AGN and 138 presumed Compton-thick, mid-infrared-bright/X-ray-faint AGN revealed by MIRI. Utilizing the shape asymmetry morphology indicator, AS, as the metric for disturbance, we find that 88% of the Seyferts sampled are strongly spatially disturbed (AS > 0.2). The experimental design we employ reveals a ≳3σ obscuration–merger (NH–AS) correlation at 0.6 < z < 2.4, and also recovers a physical distinction between the X-ray- and mid-IR-detected AGN suggestive of their link to a common evolutionary scenario. Placing the observed pattern of disturbances in the context of the other average host-galaxy properties, we conclude that mergers are common among obscured AGN. This finding presents tension with the leading model on AGN fueling that requires Seyfert AGN with subquasar luminosities (Lbol < 1045 erg s−1) to evolve only through nonmerger mechanisms.