Interacting galaxies: corotating and counter-rotating systems with tidal tails

MESA, VALERIA; DUPLANCIC, FERNANDA; ALONSO, MA. SOL; COLDWELL, GEORGINA; GARCÍA LAMBAS, DIEGO

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 2014 vol. 438 p. 1784 - 1793

0035-8711

We analyse interacting galaxy pairs with evidence of tidal features in the Sloan Digital Sky Survey Data Release 7 (SDSS-DR7). The pairs were selected within $z<0.1$ by requiring a projected separation $r_p < 50 \kpc$  and relative radial velocity$\Delta V < 500 \kms$. We complete spectroscopic pairs using galaxies with photometric redshifts considering $\Delta V_{phot} < 6800 \kms$, taking into account the mean photometric redshift uncertainty. We classify by visual inspection pairs of spirals into co-rotating and counter-rotating systems.  For a subsample of non-AGN galaxies, counter-rotating pairs have larger star formation rates, and a higher fraction of young, star-forming galaxies. These effects are enhanced by restricting to $r_p < 12 \kpc$.The distributions of $C$, $D_n(4000)$ and $(M_u-M_r)$ for AGN galaxies show that counter-rotating hosts have bluer colours and younger stellar population than the co-rotating galaxies although  the relative fractions of Seyfert, Liner, Composite and Ambiguous AGN  are similar. Also, counter-rotating hosts have more powerful AGN as revealed by enhanced $Lum[OIII]$  values.  The number of co-rotating systems is approximately twice the number of counter-rotating pairs which could be owed to a more rapid evolution of counter-rotating systems, besides possible different initial conditions of these interacting pairs.