Galaxy formation and evolution

Abstract:

Studying samples of young star-forming regions allows us to statistically examine the evolution of their natal gas and dust along with the associated time-scales in the volatile early stages of their lives. With the Physics at High Angular resolution in Nearby GalaxieS survey data, we analyse the diversity of spectral energy distributions (SEDs) for the rich sample of massive star-forming regions found in NGC 1365. By combining unique detections across a variety of data sets from Hubble Space Telescope (HST), James Web Space Telescope (JWST), and Atacama Large Millimeter/sub-millimeter Array (ALMA) images, we produce a catalogue of 85 star-forming regions located in the central starbursting region of NGC 1365. Prior to analysis, we observe clear saturation effects in our four JWST Mid-Infrared Instrument (MIRI) images, and implement a saturation-correction method which allows us to recover data for 23 of 32 saturation-affected regions in these images. We then perform photometry in 13 HST & JWST images which are convolved to match the resolution of MIRI/F2100W (64 pc), allowing us to probe star clusters as well as their immediate surroundings. Upon deriving their properties from SED-fitting using Code Investigating GALaxy Emission, we observe that regions selected with progressively redder wavebands are younger and generally more reddened. We also identify three SED features correlated with age: (1) sources with a positive near-infrared slope [(F300W + F360M)/(2F200W)] are by median half the age of those with negative near-infrared slopes; turnover occurs around 6 Myr, (2) the relative strength of dust emission (F2100W/F200W), and (3) polycyclic aromatic hydrocarbon emission (F335M/F300M) both show that larger such ratios correlate with younger ages. Considering our working resolution, these features are robust to the inclusion of nearby emission surrounding star clusters.

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:

Supermassive black hole (SMBH) masses can be measured using molecular gas kinematics. Here we present high-angular-resolution (0.12 arcsec or pc) Atacama Large Millimeter/submillimeter Array observations of the CO(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 arcsec ( 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 an SMBH mass of M and an F160W-filter stellar mass-to-light ratio of M/L. 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 (CDM) 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 m imaging under fixed mass-to-light ratio () assumptions and are complemented, for the first time for a H i-selected sample, by spatially resolved , obtained from multiwavelength spectral energy distribution fitting. We examine the ratio of baryonic to observed rotation velocity () at the characteristic radius . Adopting a fixed yields a clear dependence of on galaxy luminosity, while adopting substantially weakens this trend. In contrast, the resolved 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 systematically shift galaxies relative to the theoretical stellar-to-halo mass and baryonic-to-halo mass relations, while the spatially varying yields the closest agreement with theoretical benchmarks within CDM. We therefore demonstrate that future investigations of the dark matter properties of galaxies using rotation curves need to account for varying across individual galaxy profiles and between galaxies in order to obtain accurate measurements of the dark matter, and therefore test CDM.