The impact of large-scale structure on the anisotropic quenching of satellites

TL;DR

This study uses the IllustrisTNG simulation to show that anisotropic satellite galaxy quenching is primarily driven by the infall of young satellites along filaments aligned with the central galaxy's major axis, influenced by large-scale structure.

Contribution

It demonstrates that large-scale filaments influence satellite infall directions and the resulting anisotropic quenching, highlighting the role of external large-scale structure in galaxy evolution.

Findings

Young satellites infall along the central galaxy's major axis.

ASGQ appears at satellite infall, outside R200.

Old satellites show no anisotropic quenching signature.

Abstract

Galaxies within groups exhibit characteristics different from those of galaxies that reside in regions of average density (the field). Galaxy properties also depend on their location within the host structure and orientation with respect to the central galaxy: galaxies in the inner regions that are aligned to the major axis of the central galaxy tend to be more quenched and redder than galaxies in the outskirts and with random orientation. This phenomenon, called anisotropic satellite galaxy quenching (ASGQ), can be explained in two different ways: invoking either external influences (large-scale distribution of matter) or internal factors (black hole activity of the central galaxy). In this work, we study the impact of filaments in shaping the ASGQ in the local Universe, exploiting the magneto-hydrodynamic (MHD) simulation IllustrisTNG. We separated all surviving satellites into young and old populations depending on their infall times. We show that only young satellites contribute to the observed ASGQ. These satellites preferentially infall along the major axis of the central galaxy, which tends to have the same direction of the filament feeding the groups. We demonstrate that old satellites were quenched inside their hosts and do not exhibit signatures of ASGQ. We show that the ASGQ emerges at the time of the infall of the young satellites and is also visible outside $\rm R_{200}$. In contrast, there is no sign of anisotropic distribution in the inner regions ($R<0.5 R_{200}$). We argue that our results support a scenario in which a large-scale structure is imprinted on the ASGQ.