On the Full Spectrum Fitting of Luminous Red Galaxies by Using ULySS and STARLIGHT

Abstract: In this paper, we select a sample of quiescent luminous red galaxies (LRGs) from Sloan Digital Sky Survey Data Release 7 (SDSS DR7) with signal-to-noise ratio (S/N) substantially high to study the consistency of the full spectrum fitting method by using different packages, mainly, ULySS and STARLIGHT. The spectrum of each galaxy in the sample is fitted by the full spectrum fitting packages ULySS and STARLIGHT, respectively. We find: (1) for spectra with higher S/Ns, the ages of stellar populations obtained from ULySS are slightly older than that from STARLIGHT, and metallicities derived from ULySS are slightly richer than that from STARLIGHT. In general, both packages can give roughly consistent fitting results. (2) for low S/N spectra, it is possible that the fitting by ULySS can be trapped some local minimum parametric regions during execution and thus may give unreliable results, while STARLIGHT can still give reliable results. Based on the fitting results of LRGs, we further analyse their star formation history (SFH) and the relation between their age and velocity dispersion, and find that those highly agrees with conclusions from others' previous work.