Age and Metallicity of Merging Galaxies and Merger Remnants in the SDSS
American Astronomical Society, AAS Meeting #217, #335.34; Bulletin of the American Astronomical Society, Vol. 43, 2011
Published in Jan 2011
We study the stellar ages and metallicities of major mergers and post-merger remnants among massive galaxies in the local universe. The ages and metallicities are excellent records of the star formation and chemical enrichment histories of galaxies, and major merging between comparable mass systems is postulated to be a central mechanism in explaining the assembly and growth of spheroids over cosmic time. Starting with a volume-limited (z LE 0.08) and stellar mass-limited (M GE 1e10 Msun) sample of 36,000 galaxies with SDSS spectra having median S/N > 20 we identified over 600 galaxies in pairs (mergers), and 100 individual systems (remnants), with tidal signatures associated with major merging activity. Using previously derived median-likelihood estimates of stellar metallicity, light-weighted age and stellar mass, we compare mergers and remnants to each other and to the underlying galaxy population. We confirm that the lower metallicity (Zstar < -0.1 Zsun) population has a higher fraction of isolated disturbed galaxies (remnants) compared to the majority of galaxies with typical stellar metal abundances (> -0.1 Zsun). Comparing mergers and remnants, we find that the remnant population has a higher percentage of low metallicity members than does the merger population. We further explore the stellar metallicity distributions of galaxies involved in spiral-spiral, spiral-elliptical and elliptical-elliptical mergers. Last, we find that remnants have younger light-weighted ages on average than either galaxies involved in ongoing major interactions or non-merging systems. This result connects evidence of recent star formation with visible tidal signatures as expected in the aftermath of a gas-rich major merger.
(c) 2011: American Astronomical Society