An inventory of galaxies in cosmic filaments feeding galaxy clusters: galaxy groups, backsplash galaxies, and pristine galaxies

Kuchner, Ulrike; Haggar, Roan; Aragón-Salamanca, Alfonso; Pearce, Frazer R; Gray, Meghan E; Rost, Agustín; Cui, Weiguang; Knebe, Alexander; Yepes, Gustavo

Abstract

Galaxy clusters grow by accreting galaxies from the field and along filaments of the cosmic web. As galaxies are accreted they are affected by their local environment before they enter (pre-processing), and traverse the cluster potential. Observations that aim to constrain pre-processing are challenging to interpret because filaments comprise a heterogeneous range of environments including groups of galaxies embedded within them and backsplash galaxies that contain a record of their previous passage through the cluster. This motivates using modern cosmological simulations to dissect the population of galaxies found in filaments that are feeding clusters, to better understand their history, and aid the interpretation of observations. We use zoom-in simulations from TheThreeHundred project to track halos through time and identify their environment. We establish a benchmark for galaxies in cluster infall regions that supports the reconstruction of the different modes of pre-processing. We find that up to 45% of all galaxies fall into clusters via filaments (closer than 1 −1 Mpc from the filament spine). 12% of these filament galaxies are long-established members of groups and between 30 and 60% of filament galaxies at 200 are backsplash galaxies. This number depends on the cluster's dynamical state and sharply drops with distance. Backsplash galaxies return to clusters after deflecting widely from their entry trajectory, especially in relaxed clusters. They do not have a preferential location with respect to filaments and cannot collapse to form filaments. The remaining pristine galaxies (∼30-60%) are environmentally effected by cosmic filaments alone.

Citation

Kuchner, U., Haggar, R., Aragón-Salamanca, A., Pearce, F. R., Gray, M. E., Rost, A., …Yepes, G. (2022). An inventory of galaxies in cosmic filaments feeding galaxy clusters: galaxy groups, backsplash galaxies, and pristine galaxies. Monthly Notices of the Royal Astronomical Society, 510(1), 581-592. https://doi.org/10.1093/mnras/stab3419

• Journal Article Type: Article
• Acceptance Date: Nov 21, 2021
• Online Publication Date: Nov 27, 2021
• Publication Date: 2022-02
• Deposit Date: Nov 26, 2021
• Publicly Available Date: Nov 26, 2021
• Journal: Monthly Notices of the Royal Astronomical Society
• Print ISSN: 0035-8711
• Electronic ISSN: 1365-2966
• Peer Reviewed: Peer Reviewed
• Volume: 510
• Issue: 1
• Pages: 581-592
• DOI: https://doi.org/10.1093/mnras/stab3419
• Keywords: Space and Planetary Science; Astronomy and Astrophysics
• Public URL: https://nottingham-repository.worktribe.com/output/6790486
• Publisher URL: https://academic.oup.com/mnras/article/510/1/581/6445057?login=true
• Additional Information: This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©2022 The Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.