On the nature of Small Galaxy Systems

DUPLANCIC, FERNANDA; GEORGINA COLDWELL; ALONSO, SOL; DIEGO G. LAMBAS

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 2018 vol. 481 p. 2458 - 2469

0035-8711

We aim at defining homogeneous selection criteria of small galaxy systems in order to build catalogues suitable to compare main properties of pairs, triplets, and groups with four or more members. To this end we use spectroscopic and photometric SDSS data to identify systems with a low number of members. We study global properties of these systems and theproperties of their member galaxies finding that galaxies in groups are systematically redder and with lower star formation activity indicators than galaxies in pairs which have a higher fraction of star forming galaxies. Triplet galaxies present intermediate trends between pairsand groups. We also find an enhancement of star formation activity for galaxies in small systems with companions closer than 100 kpc, irrespective the number of members. We have tested these analysis on SDSS mock catalogues derived from the Millennium simulation, finding as conservative thresholds 76% completeness and a contamination of 23% in small galaxy systems, when considering an extreme case of incompleteness due to fiber collisions. Nevertheless, we also found that the results obtained are not likely affected by projection effects. Ourstudies suggest that an extra galaxy in a system modify the properties of the member galaxies. In pairs, galaxy-galaxy interactions increases gas density and trigger starbursts. However, repeated interactions in triplets and groups can generate gas stripping, turbulence and shocksquenching the star formation in these systems.