Abundance and Star Formation Determinations in MARK galaxies from SDSS Spectra

Abstract

We analyse the oxygen and nitrogen abundance and specific star formation rates (sSFR) in Markarian galaxies from Sloan Digital Sky Survey (SDSS) spectra. The Data Release 7 (DR7) of SDSS contains photometric data for more there 1000 and spectral information for more than 700 Markarian objects. The Mrk sample has played a central role in the task of distinguishing between the astrophysical different types of phenomena that occur in AGNs. In the course of the Markarian survey, more than 200 Seyfert galaxies, and hundreds of starburst, blue compact, and H II galaxies were discovered. The Markarian survey remains perhaps the best-known source of such objects in the local universe. We have measured their line fluxes and derived the O and N abundances using recent calibrations. We have compared the oxygen and nitrogen abundances derived from global emission-line Sloan Digital Sky Survey (SDSS) spectra of galaxies using (1) the Te method and (2) two recent strong-line calibrations: the ON and NS calibrations. The behaviour of the [N/H] ratio in under abundant regions gives strong support to a partially primary origin of nitrogen. The star formation rate (SFR) is one of the main parameters used to analyse the evolution of galaxies through time. In the local Universe, the Hα luminosity derived from IFS observations can be used to measure SFR, at least in statistically significant, optically-selected galaxy samples, once stellar continuum absorption and dust attenuation effects are accounted for.