A New Method to Constrain the Appearance and Disappearance of Observed Jellyfish Galaxy Tails

TL;DR

This paper introduces a new Bayesian method to determine when and where Jellyfish galaxy tails first appear and disappear during galaxy infall, using observational data and modeling of tail directions and velocities.

Contribution

The paper presents a novel, flexible Bayesian approach to constrain the timing and location of Jellyfish galaxy tail visibility relative to galaxy orbits, validated with mock data and applied to real observations.

Findings

Radio tails appear at about three quarters of r200 during first infall.

Tails remain visible for a few hundred million years after pericenter.

Lower mass galaxies in massive hosts lose tails more quickly.

Abstract

We present a new approach to observationally constrain where the tails of Jellyfish (JF) galaxies in groups and clusters first appear and how long they remain visible with respect to the moment of their orbital pericenter. This is accomplished by measuring the distribution of their tail directions with respect to their host's center, and their distribution in a projected velocity-radius phase-diagram. We then model these observed distributions using a fast and flexible approach where JF tails are painted onto dark matter halos according to a simple parameterised prescription, and perform a Bayesian analysis to estimate the parameters. We demonstrate the effectiveness of our approach using observational mocks, and then apply it to a known observational sample of 106 JF galaxies with radio continuum tails located inside 68 hosts such as groups and clusters. We find that, typically, the radio continuum tails become visible on first infall when the galaxy reaches roughly three quarters of r$_{200}$, and the tails remain visible for a few hundred Myr after pericenter passage. Lower mass galaxies in more massive hosts tend to form visible tails further out and their tails disappear more quickly after pericenter. We argue that this indicates they are more sensitive to ram pressure stripping. With upcoming large area surveys of JF galaxies in progress, this is a promising new method to constrain the environmental conditions in which visible JF tails exist.