Abstract
ABSTRACT A recent observational result finds that the quenching of satellites in groups at z = 0.08 has an angular dependence relative to the semimajor axis of the central galaxy. This observation is described as ‘anisotropic quenching’ or ‘angular conformity’. In this paper, I study 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○ from the major axis. This quenching signal is thought to be driven by AGN outflows along the minor axis, reducing the density of the intergalactic medium and thus the strength of ram pressure. Here, I will discuss potential alternative mechanisms. Finally, I note that the advent of the Legacy Survey of Space and Time (LSST) and Euclid surveys will allow for a more detailed study of this phenomenon and its evolution.
Highlights
Dense environments are known to quench the star formation within galaxies, which leads to the observation that a higher fraction of galaxies in massive clusters are passive early-types compared with the field (e.g. Dressler 1980; Peng et al 2010)
The main goal of this paper was to study the relationship between how quenched a satellite galaxy is and its angle on the sky compared with the major axis of the central galaxy
The clusters within the samples still had a range of redshifts (z = 0.206 − 0.352 and z = 0.391 − 0.545) and so the probed rest-frame colour was affected by k correction and potentially galaxy evolution across these ranges
Summary
Dense environments are known to quench the star formation within galaxies, which leads to the observation that a higher fraction of galaxies in massive clusters are passive early-types compared with the field (e.g. Dressler 1980; Peng et al 2010). The force of the ICM gas on the cold gas in the disc of the galaxy removes this gas from the galaxy and the fuel for star formation (Gunn & Gott 1972). This may temporarily increase the star formation rate, causing a star burst (Dressler & Gunn 1983), with star formation induced in both the gas compressed on the leading edge and that which is disturbed and pulled out into a tail behind (Fumagalli et al 2014; Poggianti et al 2017). Ram pressure stripping is thought to lead to rapid quenching on a timescale of ∼ 1 Gyr regardless of whether the gas is removed and/or partially used up in a starburst (Roberts et al 2019)
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