Connections between central intensity ratio and hot gas properties of early-type galaxies

Abstract

ABSTRACT We report strong connections between central intensity ratio (CIR) and hot gas properties of Early-type galaxies (ETGs) in the nearby ($D\lt 30\, \mathrm{Mpc}$) Universe. We find new strong correlations between (optical) CIR and X-ray gas luminosity (LX, GAS) as well as X-ray gas temperature (TGAS). These correlations suggest that higher the central gas temperature lower will be the (central) star formation process in ETGs. Correlations of CIR separately with K-band magnitude and age of the sample galaxies further support suppression of star formation in the central region of ETGs as they grow in mass and age. The systematic and tight variation of CIR with LX, GAS not only shows its remarkable potential to estimate LX, GAS from simple photometry but also helps in transforming the core-coreless dichotomy into a gradual one.