The Second Byurakan Survey Galaxies in Close Pairs

Abstract

418 pairs containing galaxies from the Second Byurakan Survey (SBS) with dV < 800 km/s and Dp < 100 kpc are selected for study of the dependence of star formation rates and nuclear activity on the kinematics of the pairs and on the morphologies and masses of the paired galaxies. The following basic results are obtained: SBS galaxies with neighbors do not differ spectral type from isolated SBS galaxies. The SBS galaxies are brighter than their neighbors by 0m.5 on the average, but there is no statistically significant difference in their colors, morphologies, and star formation rates. There is a weak, but statistically significant correlation between the morphologies of the paired galaxies. The neighbors of the SBS galaxies have a lower fraction of star forming galaxies and a higher fraction of galaxies in all the other spectral types. The specific (relative) star formation rate (SSFR) is higher for galaxies that are closer to a neighboring galaxy for galaxies of all morphological types. The enhancement is the greatest for galaxies of earlier types (by 1 dex) and less for galaxies of later morphological types. There is an increase of SSFR of galaxies within all ranges of masses. Both major and minor interactions can increase the SSFR by 0.7 dex, but the effect is greater for major interactions, while in the case of minor interactions the SSFR increases only in the massive members of the pairs. The existence of neighbor galaxy of earlier morphological types does not enhance the SSFR, neighbor galaxies of the same morphological types produce a moderate increase in the SSFR, while neighboring galaxies of later morphological types cause a significant increase in the SSFR.