The evolution of brightest cluster galaxies in the nearby Universe II: The star-formation activity and the stellar mass from spectral energy distribution

We study the star-formation activity in a sample of similar to 56 000 brightest cluster galaxies (BCGs) at 0.05 < z < 0.42 using optical and infra-red data from SUSS and WISE. We estimate stellar masses and star-formation rates (SFR) through SED fitting and study the evolution of the SFR with redshift as well as the effects of BCG stellar mass, cluster halo mass, and cooling time on star formation. Our BCGs have SFR = 1.4 x 10(-3) - 275.2 [M-circle dot yr(-1)] and sSFR = 5 x 10(-15) - 6 x 10(-10) [yr(-1)]. We find that star-forming BCGs are more abundant at higher redshifts and have higher SFR than at lower redshifts. The fraction of star-forming BCGs (f(SF)) varies from 30 per cent to 80 per cent at 0.05 < z < 0.42. Despite the large values of f(SF), we show that only 13 per cent of the BCGs lie on the star-forming main sequence for field galaxies at the same redshifts. We also find that f(SF) depends only weakly on M-200, while it sharply decreases with M*. We finally find that the SFR in BCGs decreases with increasing t(cool), suggesting that star formation is related to the cooling of the intracluster medium. IIowever, we also find a weak correlation of M* and M-200 with t(cool )suggesting that AGNs are heating the intracluster gas around the BCGs. We compare our estimates of SFR with the predictions from empirical models for the evolution of the SFR with redshift, finding that the transition from a merger dominated to a cooling-dominated star formation may happen at z < 0.6.