Paper detail

The effects of UV photometry and binary interactions on photometric redshift and galaxy morphology

Using the Hyperz code and a template spectral library which consists of 4 observed galaxy spectra from Coleman, Wu & Weedman (CWW, 1980) and 8 spectral families built with evolutionary population synthesis models, we present photometric redshift estimates (photo-z) for a spectroscopic sample of 6,531 galaxies, and morphologies for a morphological sample of 1,502 bright galaxies. All galaxies are matched with the SDSS DR7 and GALEX DR4. The inclusion of Fuv or Nuv or both photometry decreases the number of catastrophic identifications (CIs, |z_phot -z_spec| > 1.0). If CIs are removed, the inclusion of both Fuv and Nuv photometry mainly increases the number of non-CIs in the low redshift, g-r < 0.8 and fainter r-magnitude regions. The inclusion of binary interactions (BIs) mainly increases the number of non-CIs and decreases the deviations in the 0.3 < g-r < 0.8 region in the case of only using optical photometry. The inclusion of UV photometry would decrease and increase the probability that early types are classified as Burst and E types, respectively, and increase that late types are classified as CWW-Sbc and CWW-Scd types. If CIs are excluded, the inclusion of UV data mainly raises the identifications of late types in all redshift, bluer g-r and r > 14 regions. Moreover, BIs mainly affect the determinations of E and S0 types. Nuv -u = 1.94 and 5.77-1.47(u-r) = Fuv discriminators can be used as morphology selection indicators. These two criteria have comparable reliability and completeness for selecting early- and late-type galaxies to C=2.6 criterion and higher completeness for early-type selection than u-r=2.22 criterion.