Jellyfish galaxies with the IllustrisTNG simulations -- Citizen-science results towards large distances, low-mass hosts, and high redshifts

Abstract

We present the ``Cosmological Jellyfish'' project - a citizen-science classification program to identify jellyfish galaxies within the IllustrisTNG cosmological simulations. Jellyfish (JF) are satellite galaxies that exhibit long trailing gas features -- `tails' -- extending from their stellar body. Their distinctive morphology arises due to ram-pressure stripping (RPS) as they move through the background gaseous medium. Using the TNG50 and TNG100 simulations, we construct a sample of $\sim 80,000$ satellite galaxies spanning an unprecedented range of stellar masses, $10^{8.3-12.3}{\mathrm{M}}_{\odot }$, and host masses of $M_{200,\mathrm{c}}=10^{10.4-14.6}{\mathrm{M}}_{\odot }$ back to $z=2$ \citep[extending the work of][]{yun_jellyfish_2019}. Based on this sample, $\sim 90,000$ galaxy images were presented to volunteers in a citizen-science project on the Zooniverse platform who were asked to determine if each galaxy image resembles a jellyfish. Based on volunteer votes, each galaxy was assigned a score determining if it is a JF or not. This paper describes the project, the inspected satellite sample, the methodology, and the classification process that resulted in a dataset of $5,307$ visually-identified jellyfish galaxies. We find that JF galaxies are common in nearly all group- and cluster-sized systems, with the JF fraction increasing with host mass and decreasing with satellite stellar mass. We highlight JF galaxies in three relatively unexplored regimes: low-mass hosts of $M_{200,\mathrm{c}}\sim 10^{11.5-13}{\mathrm{M}}_{\odot }$, radial positions within hosts exceeding the virial radius $R_{200,\mathrm{c}}$, and at high redshift up to $z=2$. The full dataset of our jellyfish scores is publicly available and can be used to select and study JF galaxies in the IllustrisTNG simulations.

submitted to MNRAS ; See additional jellyfish companion papers today on astro-ph: Rohr et al. and Goeller et al.; Jellyfish image gallery: https://www.tng-project.org/explore/gallery/zinger23/