A morphological analysis of the galaxy cluster XLSSC 122 at z = 1.98

Abstract

ABSTRACT We present a morphological analysis of 29 spectroscopically confirmed members of XLSSC 122, a massive galaxy cluster at $z=1.98$. We perform photometry using statmorph on images of the cluster members from the Hubble Space Telescope (HST) Wide Field Camera (WFC3) in the F140W band. We visually assess the images and compute non-parametric morphological measures, namely the concentration C, asymmetry A, Gini, and $M_{20}$ values and use them to classify cluster members as either being bulge-dominated, disc-dominated or presenting possible merger features. The morphological properties of the XLSSC 122 members show clear evidence of bimodality. The bulge-dominated galaxies are redder, older, and are found in the denser regions of the cluster, while the galaxies showing disturbed features are bluer, younger and are found towards the outskirts of the cluster. XLSSC 122 is also found to be deficient in blue and disturbed galaxies compared to field galaxy populations from the Cosmic Assembly Near-IR Extragalactic Legacy Survey (CANDELS)/3D-HST surveys. An analysis of merger events occurring in numerical simulations suggest that galaxy interactions generating a population of morphologically disturbed galaxies in XLSSC 122 may have occurred over the interval $2\lt z\lt 3$, that is, prior to their infall into the virial core of the cluster.