Stellar populations and ionized gas in central spheroidal galaxies

We investigate the stellar populations and ionized gas properties of a sample of central spheroidal galaxies in order to better constrain their history of star formation and gas excitation mechanism. We select galaxies from Spheroids Panchromatic Investigation in Different Environmental Regions (SPIDER) catalogue and separate these  galaxies in different regimes of halo and galaxy mass. To characterize the stellar population properties of these galaxies we use the stellar population synthesis method with the Starlight code, and the presence of ionized gas is identified by measurements of the Hα equivalent width. We analyze how these properties behave as a function of the galaxy stellar mass and the parent halo mass. A trend is observed in the sense of increased ionized gas emission for low-mass centrals in high-mass halos. We interpret this trend in a scenario of intracluster medium (ICM) cooling versus active galactic nuclei (AGN) feedback.