arXiv subjects

Harrison J. Souchereau

Publications and source records attributed to Harrison J. Souchereau.

3 recordsLinked to original sources

arXiv2026

ALMA-JELLY II. Constraining the radial profiles of the quenching timescales in ram-pressure-stripped galaxies

We investigate the environmental quenching histories and spatial progression of ram-pressure stripping in 11 galaxies in the nearby Coma, Norma, and A1367 clusters. As part of the ALMA-JELLY large program, we combine high-sensitivity VLT/MUSE integral-field spectroscopy with ultraviolet-to-far-infrared photometry in 37 spatially resolved disc apertures. The sample spans $\log(M_*/\mathrm{M}\odot)\sim7.5-10.5$ and includes galaxies undergoing active or recent ram-pressure stripping, identified through prominent H$α$ or UV tails. We use Bayesian spectrophotometric modelling with exponentially declining star-formation histories and show with mock data that combining spectra and photometry breaks parameter degeneracies and improves quenching-age constraints. All galaxies show quenched outer discs and relatively old ($\lesssim1$ Gyr) stellar populations. Massive galaxies ($\log(M_*/\mathrm{M}_\odot)>9.5$) exhibit clear outside-in quenching: inner regions quench about 500 Myr later than their outskirts. The small scatter in quenching age with distance from the truncation radius, despite differences in environment and stripping geometry, points to a common evolutionary sequence. Low-mass and dwarf galaxies instead show weak radial gradients, with quenching occurring more rapidly, typically within 300 Myr.

astro-ph.GA↗

arXiv2026

Up, Up, and Away? Quantifying ISM Fallback using Ram Pressure Stripping Simulations

The evolution of the cold interstellar medium (ISM) in satellite galaxies orbiting through massive hosts is an important factor in how they evolve while experiencing ram pressure stripping (RPS), as cold molecular gas clouds are the most difficult ISM component to fully strip and serve as the sites of star formation. We investigate ISM evolution using a suite of hydrodynamical wind tunnel simulations with an intermediate mass ($M_* = 10^{9.7}$ M$_\odot$) galaxy orbiting in a Coma cluster-like environment, varying the disk-wind angle. Even if the ultimate fate of a ram pressure stripped galaxy is complete gas removal, we find that cold gas evolves through cycles of outflow and inflow (fallback). We show that fallback can be identified at a wide range of wind angles, but is elevated for angles closer to edge-on and occurs predominantly in a specific quadrant (trailing side, rotating into the wind). Most inflow occurs in gas that never leaves an ``inner tail" region that extends to $\sim20$ kpc. We discuss possible reasons for when and why fallback occurs using simple idealized simulations. For a highly inclined disk, offset rotational motion is a major driver of fallback, while disk shadowing and cloud growth can act at all wind angles. Lastly, we discuss the relative importance of each mechanism at different stages of a galaxy's evolution under ram pressure, and compare our findings with instances of ISM fallback detected in observed RPS galaxies.

astro-ph.GA↗

arXiv2025

ALMA-JELLY I: High Resolution CO(2-1) Observations of Ongoing Ram Pressure Stripping in NGC 4858 Reveal Asymmetrical Gas Tail Formation and Fallback

We present new CO(2-1) observations (resolution $\sim1" = 460$pc) of the Coma cluster jellyfish galaxy NGC 4858 obtained from the ALMA-JELLY large program. Analyzing this data alongside complimentary Subaru H$α$ and HST (F600LP / F350LP) observations, we find numerous structural and kinematic features indicative of the effects from strong, inclined ram pressure, including an asymmetric inner gas tail. We estimate a highly-inclined disk-wind angle of $ϕ_{DW} = 75^{+10}_{-27}$. By subtracting a simple circular velocity model, we find (1): gas clumps that are being accelerated by ram pressure, and (2): signatures of gas clumps that had been previously pushed out of the disk but are now falling inwards. We also discuss head-tail morphologies in star complexes within the stellar disk that appear to be RPS-influenced. Lastly, we compare this galaxy to state-of-the-art galaxy ``wind tunnel'' simulations. We find that this galaxy is one of the best nearby examples of strong and inclined ram pressure gas stripping, and of gas that is perturbed by ram pressure but not fully stripped and falls back. We emphasize the importance of torques due to ram pressure in highly-inclined interactions, which help drive gas inwards on the side rotating against the wind, contributing to the formation of asymmetric inner RPS tails.

astro-ph.GA↗