Galaxy formation and evolution

Abstract:

Abstract We re-analysed ALMA observations of the [O iii] λ88μm emission line in JADES-GS-z14-0, so one of the most distant spectroscopically confirmed galaxy at z=14.18. Our analysis shows a tentative detection of a velocity gradient of [O iii] λ88μm using three independent tests: (1) construction of moment maps; (2) extraction of integrated spectra from a grid of apertures; and (3) spectro-astrometry in both the image and uv planes, confirming the presence of the velocity gradient at 3σ significance. We performed kinematical fitting using the KinMS code and estimated a dynamical mass of log10(Mdyn/$\rm M_\odot$)= 9.4$^{+0.8}_{-0.4}$, with the bulk of the uncertainties due to the degeneracy between dynamical mass and inclination. We measure an upper limit on the velocity dispersion (σv) of <40 km s−1 which results in an estimate of Vrot/σ > 2.5. This result, if confirmed with higher-resolution observations, would imply that kinematically cold discs are already in place at z ∼ 14. Comparison with mock observations from the SERRA cosmological simulations confirms that even low-resolution observations are capable of detecting a velocity gradient in z > 10 galaxies as compact as JADES-GS-z14-0. This work shows that deeper ALMA or JWST/NIRSpec IFS observations with high spatial resolution will be able to estimate an accurate dynamical mass for JADES-GS-z14-0, providing an upper limit to the stellar mass of this over-luminous galaxy.

Abstract:

We present measurements of the masses associated with ∼18,​​​​​000 H ii regions across 19 nearby star-forming galaxies by combining data from JWST, Hubble Space Telescope, MUSE, Atacama Large Millimeter/submillimeter Array, Very Large Array, and MeerKAT from the multiwavelength PHANGS survey. We report 10 pc-scale measurements of the mass of young stars, ionized gas, and older disk stars coincident with each H ii region, as well as the initial and current mass of molecular gas, atomic gas, and swept-up shell material, estimated from lower-resolution data. We find that the mass of older stars dominates over young stars at ≳10 pc scales, and ionized gas exceeds the stellar mass in most optically bright H ii regions. Combining our mass measurements for a statistically large sample of H ii regions, we derive 10 pc-scale star formation efficiencies of ≈6%–17% for individual H ii regions. Comparing each region’s self-gravity with the ambient interstellar medium (ISM) pressure and total pressure from presupernova stellar feedback, we show that most optically bright H ii regions are overpressured relative to their own self-gravity and the ambient ISM pressure and that they are hence likely expanding into their surroundings. Larger H ii regions in galaxy centers approach dynamical equilibrium. The self-gravity of regions is expected to dominate over presupernova stellar feedback pressure at ≳130 and 60 pc scales in galaxy disks and centers, respectively, but is always subdominant to the ambient ISM pressure on H ii region scales. Our measurements have direct implications for the dynamical evolution of star-forming regions and the efficiency of stellar feedback in ionizing and clearing cold gas.

Abstract:

Recent studies of gas kinematics at high redshift have reported discy systems that appear to challenge models of galaxy formation, but it is unclear whether they are representative of the underlying galaxy population. We present the first statistical sample of spatially resolved ionized gas kinematics at high redshift, comprised of 213 H emitters in GOODS-S and GOODS-N at redshifts , observed with James Webb Space Telescope/NIRCam slitless spectroscopy and imaging from JADES, FRESCO, and CONGRESS. The sample probes two orders of magnitude in stellar mass () and star formation rate (), and is representative down to . Using a novel inference tool, geko, we model the grism data to measure morphological and kinematic properties of the ionized gas, as probed by H . Our results are consistent with a decrease of the rotational support and increase of the velocity dispersion with redshift, when compared to , with km s and at . We study the relations between and , and different star formation tracers and find a large scatter and diversity, with the most significant correlation between and SFR. We find no evolution of the fraction of rotationally supported systems () from to , measured at in both redshift bins, for galaxies with masses . Overall, discs do not dominate the turbulent high-redshift galaxy population in the mass range probed by this work, but they remain a sizeable population. When placed in the context of studies up to cosmic noon, our results are consistent with a needed increase of disc-like systems with cosmic time.