Ram-pressure-induced star formation in low-mass galaxies infalling onto the Coma cluster: Insights from DESI

Résumé fourni par la source

Ram-pressure stripping is a key driver of galaxy morphological transformation in clusters, contributing to the formation of quenched, especially dwarf, populations. Ram-pressure compression can also induce a starburst prior to quenching and build up significant stellar mass in an initially gas-rich galaxy. The detailed physics of these processes remains poorly understood, especially in the low-mass regime. Here we demonstrate that the key factor for a ram-pressure-induced starburst in a low-mass galaxy is its angular momentum within a host cluster. In this study, we selected a sample of 39 post-starburst galaxies (PSGs) in the Coma cluster using the Dark Energy Spectroscopic Instrument Early Data Release (DESI EDR) spectroscopic data, extending to low luminosities (M_g < -14). This sample is at least 90% complete down to M_g ≈ -14.8, which enabled a systematic analysis of their properties. For each galaxy, we used projected cluster-centric distances and line-of-sight velocities to constrain the normalised orbital angular momentum and a 3D radial coordinate to the cluster centre, assuming zero orbital energy. The resulting probability distributions show that while star-forming galaxies are split into two populations favouring intermediate and high angular momentum, almost all PSGs prefer high angular momentum. Our analysis statistically demonstrates that ram-pressure-induced starbursts are likely to be more efficient on tangential orbits, where gas stripping proceeds slowly enough to allow substantial star formation before gas removal.

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