Backsplash galaxies and their impact on galaxy evolution: a three-stage, four-type perspective

RUIZ, A.N.; MARTÍNEZ, HÉCTOR J.; COENDA, V.; MURIEL, H.; CORA, S. A.; DE LOS RIOS, MARTÍN; VEGA-MARTINEZ, C. A.

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 2023

0035-8711

We study the population of backsplash galaxies at z = 0 in the outskirts of massive, isolatedclusters of galaxies taken from the mdpl2-sag semi-analytic catalogue. We consider four typesof backsplash galaxies according to whether they are forming stars or passive at three stages intheir lifetimes: before entering the cluster, during their first incursion through the cluster, andafter they exit the cluster. We analyse several geometric, dynamic, and astrophysical aspectsof the four types at the three stages. Galaxies that form stars at all stages account for themajority of the backsplash population (58%) and have stellar masses typically below M⋆ ∼3 × 1010h−1M⊙ that avoid the innermost cluster’s regions and are only mildly affected by it. Ina similar mass range, galaxies that become passive after exiting the cluster (26%) follow orbitscharacterised by small pericentric distance and a strong deflection by the cluster potentialwell while suffering a strong loss of both dark matter and gas content. Only a small fractionof our sample (4%) become passive while orbiting inside the cluster. These galaxies haveexperienced heavy pre-processing and the cluster’s tidal stripping and ram pressure providethe final blow to their star formation. Finally, galaxies that are passive before entering thecluster for the first time (12%) are typically massive and are not affected significantly bythe cluster. Using the bulge/total mass ratio as a proxy for morphology, we find that a singleincursion through a cluster do not result in significant morphological changes in all four types.