The mass-metallicity relation of interacting galaxies

MICHEL-DANSAC, L.; LAMBAS, D. G; ALONSO, M. S.; TISSERA, P. B.

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY

Año: 2007

0035-8711

We study the mass-metallicity relation of galaxies in pairs and in isolation taken from the Sloan Digital Sky Survey-Data Release 4 (SDSS-DR4) using the stellar masses and oxygen abundances derived by Tremonti et al. Close galaxy pairs, defined by projected separation rp < 25kpch-1 and radial velocity ΔV < 350kms-1, are morphologically classified according to the strength of the interaction signs. We find that only for pairs showing signs of strong interactions, the mass-metallicity relation differs significantly from that of galaxies in isolation. In such pairs, the mean gas-phase oxygen abundances of galaxies with low stellar masses (M* <~ 109Msolarh-1) exhibit an excess of 0.2dex. Conversely, at larger masses (M* >~ 1010Msolarh-1) galaxies have a systematically lower metallicity, although with a smaller difference (-0.05dex). Similar trends are obtained if g-band magnitudes are used instead of stellar masses. In minor interactions, we find that the less massive member is systematically enriched, while a galaxy in interaction with a comparable stellar mass companion shows a metallicity decrement with respect to galaxies in isolation. We argue that metal-rich starbursts triggered by a more massive component, and inflows of low-metallicity gas induced by comparable or less massive companion galaxies, provide a natural scenario to explain our findings.