2mass-allsky

Theodoros Bitsakis -- Galaxy evolution in compact groups from the UV to the infrared

February
6
S M T W T F S

We present our results on the impact of the environment of compact galaxy groups to the evolution of their members. We performed multiwavelength analysis, from the UV to the far-IR, for the 32 Hickson compact groups (HCGs) for which high quality Spitzer mid-IR maps were available. To expand our analysis we have used a larger more complete sample of 1770 compact groups defined by applying the Hickson's criteria to the whole SDSS database. We have fitted the SEDs of all galaxies of the first sample, using the state-of-the-art model of Da Cunha et al. (2008) and accurately estimated their stellar masses, star formation rates (SFRs), and extinction, as well as their IR luminosity and dust content. We have also performed UV/GALEX photometry and obtained the near-IR/2MASS and mid-IR/WISE fluxes of all galaxies in SDSS groups in order to examine how their surface brightnesses (SBs), SFRs and nuclear activity vary as a function of their environment. As comparison/control samples we have used field, early-stage interacting pair, and cluster galaxies. We find that classifying the evolutionary state of compact groups as dynamically ``young'' (``old'') depending on whether (or not) they contain less than 25% of early-type galaxies is physical and consistent with past classifications. Late-type galaxies in ``young'' groups have specific SFR, as well as NUV-r and mid-IR colors, which are similar to those of field and interacting pairs. However, late-type galaxies in ``old'' groups have redder colors, as they had built-up their stellar masses due to numerous tidal encounters in the past. Yet, the mass distributions of late-type galaxies hosting an AGN are independent of the dynamical state of their group. Finally, we find that the SB profiles of the late-type galaxies evolve into earlier type systems before their SFR is reduced substantially. We suggest an evolutionary scenario in which it takes time for the group environment to visibly affect the properties of its members. The effects of tidal torques and minor merging shape the morphology and star formation history of the group galaxies, leading to an increase of the fraction of early-type members and a rapid built-up of the stellar mass in the remaining late-type galaxies.

Date: February 6th, 2013
Location: MR LCR