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

¹ Dipartimento di Fisica e Astronomia Galileo Galilei, Università degli studi di Padova, Vicolo dell’Osservatorio, 3, I-35122 Padova, Italy
² INAF – Osservatorio astronomico di Padova, Vicolo dell’Osservatorio, 5, I-35122 Padova, Italy
³ School of Physics and Astronomy, University of Birmingham, Birmingham B15 2TT, UK
⁴ INAF – Osservatorio Astronomico di Trieste, Via Tiepolo 11, I-34131 Trieste, Italy
⁵ IFPU – Institute for Fundamental Physics of the Universe, via Beirut 2, 34151 Trieste, Italy

^⋆ Corresponding author; dzakharovaa@gmail.com

Received: 18 September 2024
Accepted: 4 December 2024

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 R₂₀₀. In contrast, there is no sign of anisotropic distribution in the inner regions (R < 0.5R₂₀₀). We argue that our results support a scenario in which a large-scale structure is imprinted on the ASGQ.