Eric Rohr, Annalisa Pillepich, Dylan Nelson, Elad Zinger, Gandhali D Joshi, Mohammadreza Ayromlou

Jellyfish galaxies with the IllustrisTNG simulations – when, where, and for how long does ram pressure stripping of cold gas occur?

  • Space and Planetary Science
  • Astronomy and Astrophysics

ABSTRACT Jellyfish galaxies are prototypical examples of satellite galaxies undergoing strong ram pressure stripping (RPS). We analyse the evolution of 512 unique, first-infalling jellyfish galaxies from the TNG50 cosmological simulation. These have been visually inspected to be undergoing RPS sometime in the past 5 Byr (since z = 0.5), have satellite stellar masses $M_\star ^{\rm sat}\sim 10^{8\!-\!10.5}\, {\rm M}_\odot$, and live in hosts with $M_{\rm 200c}\sim 10^{12\!-\!14.3}\, {\rm M}_\odot$ at z = 0. We quantify the cold gas (T ≤ 104.5 K) removal using the tracer particles, confirming that for these jellyfish, RPS is the dominant driver of cold gas loss after infall. Half of these jellyfish are completely gas-less by z = 0, and these galaxies have earlier infall times and smaller satellite-to-host mass ratios than their gaseous counterparts. RPS can act on jellyfish galaxies over long time-scales of ≈1.5–8 Gyr. Jellyfish in more massive hosts are impacted by RPS for a shorter time span and, at a fixed host mass, jellyfish with less cold gas at infall and lower stellar masses at z = 0 have shorter RPS time spans. While RPS may act for long periods of time, the peak RPS period – where at least 50 per cent of the total RPS occurs – begins within ≈1 Gyr of infall and lasts ≲2 Gyr. During this period, the jellyfish are at host-centric distances ∼0.2–2R200c, illustrating that much of RPS occurs at large distances from the host galaxy. Interestingly, jellyfish continue forming stars until they have lost ≈98 per cent of their cold gas. For groups and clusters in TNG50 $(M_{\rm 200c}^{\rm host}\sim 10^{13\!-\!14.3}\, {\rm M}_\odot)$, jellyfish galaxies deposit more cold gas ($\sim 10^{11\!-\!12}\, {\rm M}_\odot$) into haloes than what exists in them at z = 0, demonstrating that jellyfish, and in general satellite galaxies, are a significant source of cold gas accretion.

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