The relevance of ram pressure stripping for the evolution of blue cluster galaxies as seen at optical wavelengths

TL;DR

This study assesses the prevalence of ram pressure stripping in blue, late-type cluster galaxies at optical wavelengths, finding that approximately 35% show signs of stripping, highlighting its significant role in galaxy evolution within clusters.

Contribution

It provides the first comprehensive optical morphological census of ram pressure stripping signs in a large sample of low-redshift cluster galaxies, including unwinding features.

Findings

About 35% of infalling blue late-type galaxies show signs of stripping.

Both traditional debris and unwinding features are important indicators of stripping.

Almost all bright blue late-type cluster galaxies likely undergo a stripping phase during their evolution.

Abstract

Ram pressure stripping is one of the most efficient mechanisms able to affect the gas reservoir in cluster galaxies and in the last decades many studies have characterized the properties of stripped galaxies. A definite census of the importance of this process in local clusters is though still missing. Here we characterize the fraction of galaxies showing signs of stripping at optical wavelengths, using the data of 66 clusters from the WINGS and OMEGAWINGS surveys. We focus on the infalling galaxy population and hence only consider blue, bright (B<18.2) late-type spectroscopically confirmed cluster members within 2 virial radii. In addition to "traditional" stripping candidates (SC) -- i.e. galaxies showing unilateral debris and tails -- we also consider unwinding galaxies (UG) as potentially stripped galaxies. Recent work has indeed unveiled a connection between unwinding features and ram pressure stripping and even though only integral field studies can inform on how often these features are indeed due to ram pressure, it is important to include them in the global census. We performed a visual inspection of B-band images and here we release a catalog of 143 UG. SC and UG each represent ~15-20% of the inspected sample. If we make the assumption that they both are undergoing ram pressure stripping, we can conclude that at any given time in the low-z universe about 35% of the infalling cluster population show signs of stripping in their morphology at optical wavelengths. These fractions depend on color, mass, morphology, and little on clustercentric distance. Making some rough assumptions on the duration of the tail visibility and on the time cluster galaxies can maintain blue colors, we infer that almost all bright blue late-type cluster galaxies undergo a stripping phase during their life, boosting the importance of ram pressure stripping in cluster galaxy evolution.