Anisotropic quenching of satellite galaxies and novel galaxy cluster detection – Dr John Stott

This talk was part of the UH Centre for Astrophysics Research (CAR) 2023-2024 seminar series. For the ongoing programme, please see: https://www.herts.ac.uk/research/cent...

Date: 17 Apr 2024
Speaker: Dr John Stott – Lancaster University
Title: Anisotropic quenching of satellite galaxies and novel galaxy cluster detection

Abstract: A recent observational result finds that the quenching of satellites in galaxy groups at z = 0.1 has an angular dependence relative to the semi-major axis of the central galaxy. This observation is described as 'anisotropic quenching' or 'angular conformity'. Here, I present the variation in the colour of a mass-limited sample of satellite galaxies relative to their angle from the major axis of the brightest cluster galaxy in the CLASH clusters up to z ~ 0.5, 4 Gyr further in lookback time. The same result is found: galaxies close to the major axis are more quenched than those along the minor axis. I also find that the star-forming galaxies tend to avoid a region +/- 45 degrees from the major axis. Simulations predict that this quenching signal is driven by AGN outflows along the minor axis, reducing the density of the intergalactic medium and thus the strength of ram pressure. I will discuss potential alternative mechanisms. In addition, I will describe 2 separate projects using quasars and machine learning in order to discover new galaxy clusters.