Galaxy formation and evolution

Abstract:

We present JWST observations of the radio galaxy TGSSJ1530+1049, spectroscopically confirmed at $z=4.0$ . NIRCam images and NIRSpec/IFU spectroscopy ( $R=2700$ ) show that TGSSJ1530+1049 is part of one of the densest-known structures of continuum and line-emitting objects found at these redshifts. NIRCam images show a number of distinct continuum objects and evidence of interactions traced by diffuse emission, and the NIRSpec IFU cube reveals further strong line emitting regions. We identify six continuum and four additional strong Halpha emitting sources with weaker or no underlying continuum within the 3’‘x3’’ IFU field. From spatial alignment with high-resolution radio data and emission line profiles, the radio AGN host galaxy is clearly identified. The bright Halpha emission (but not the optical components) is distributed remarkably linearly along the radio axis, suggestive of a biconical illumination zone by a central obscured AGN. The emission line kinematics indicate jet-gas interactions on scales of a few kpc. However, due to large relative velocities and presence of underlying continuum, the alignment with the radio structure appears to be, at least partly, caused by a particular configuration of interacting galaxies. At least four objects within a 10x10 (projected) kpc area which includes the radio source have high stellar masses (log( $M_{\star }/M_{\odot })>10.3$ ) and star formation rates in the range 70-163 $M_{\odot }$ yr. Using a stellar mass-based analysis, we predict a total dark matter halo mass of $\approx {10}^{13}{M}_{\odot }$ . Based on the physical separations and velocity differences between the galaxies, it is expected that these galaxies will merge to form a massive galaxy within a few Gyr. The system qualitatively resembles the forming brightest cluster galaxies in cosmological simulations that form early through a rapid succession of mergers.

Abstract:

Abstract Supermassive black hole (SMBH) masses can be measured using molecular gas kinematics. Here we present high angular resolution (0.12 arcsec or ≈11 pc) Atacama Large Millimeter/submillimeter Array observations of the 12CO(2–1) line emission of the early-type galaxy NGC 1387. The observations reveal a face-on, regularly-rotating central molecular gas disc with a diameter of ≈18 arcsec (≈1.7 kpc) and a central depression slightly larger than the SMBH sphere of influence. We forward model the CO data cube in a Bayesian framework with the Kinematic Molecular Simulation code, and use Hubble Space Telescope data to constrain the stellar gravitational potential contribution to the molecular gas kinematics. We infer a SMBH mass of $1.10^{+1.71}_{-0.95}[\textrm{stat},3\sigma ]^{+2.45}_{-1.09}[\textrm{sys}]\times 10^8$ M⊙ and a F160W-filter stellar mass-to-light ratio of $0.90^{+0.44}_{-0.35}[\textrm{stat}, 3\sigma ]^{+0.46}_{-0.36}[\textrm{sys}]$ M⊙/L⊙, F160W. This SMBH mass is consistent with the SMBH mass – stellar velocity dispersion relation.

Abstract:

Measuring galaxy rotation curves is critical for inferring the properties of dark-matter haloes in the Lambda Cold Dark Matter (ΛCDM) paradigm. We present H i rotation curves and mass models for 20 galaxies from the MIGHTEE survey. Using extended H i kinematics, we construct resolved mass models that include stellar, gaseous, and dark-matter components. Stellar masses are derived using 3.6 μm imaging under fixed mass-to-light ratio (ϒ* = M/L) assumptions and are complemented, for the first time for a H I-selected sample, by spatially resolved M/L, obtained from multi-wavelength SED fitting. We examine the ratio of baryonic to observed rotation velocity (Vbar/Vobs) at the characteristic radius R2.2. Adopting a fixed ϒ⋆ = 0.5 M⊙/L⊙ yields a clear dependence of V2.2/Vobs on galaxy luminosity, while adopting ϒ⋆ = 0.2 M⊙/L⊙ substantially weakens this trend. In contrast, the resolved M/L analysis preserves the luminosity dependence while modifying the stellar contribution on a galaxy-by-galaxy basis, providing a more accurate representation of the underlying relation. We model the dark-matter haloes using Navarro–Frenk–White profiles and find that the different assumptions for a fixed a M/L systematically shift galaxies relative to the theoretical stellar-to-halo mass and baryonic-to-halo mass relations, while the spatially varying M/L yields the closest agreement with theoretical benchmarks within ΛCDM. We therefore demonstrate that future investigations of the dark matter properties of galaxies using rotation curves need to account for varying M/L across individual galaxy profiles and between galaxies in order to obtain accurate measurements of the dark matter, and therefore test ΛCDM.

Abstract:

We present results of Population III (Pop III) formation in the megatron suite of simulations, which self-consistently follows radiation and non-equilibrium chemistry, and resolves gas at near-pc resolution in a Milky Way-mass progenitor at Cosmic Dawn. While the very first Pop III stars form in haloes with masses well below the atomic cooling limit, the majority of Pop III stars form in more massive systems above the K atomic cooling threshold as a Lyman–Werner (LW) background of is rapidly established. We find that the global Pop III star formation rate stabilizes to a value of at . Among the three processes that quench Pop III star formation in minihaloes, the LW background, gas starvation, and external chemical enrichment, the LW background is most important. A small fraction of haloes undergo multiple episodes of Pop III star formation when the earlier forming stars all directly collapse to black holes. If the haloes become massive enough, they can form up to Pop III stars in a single burst, which may be observable by James Webb Space Telescope with moderate gravitational lensing. Pop III stars form at a wide range of distances from UV-bright galaxies, with only per cent of Pop III stars forming within the virial radius of galaxies with . Finally, by tracking Pop III star remnants down to , we find that per cent reside in the stellar halo of our simulated Milky Way analogue, while the remainder are gravitationally bound to lower mass systems, including satellite haloes.