Low Surface Brightness Galaxies selected by different model fitting

Abstract

Abstract We present a study of low surface brightness galaxies (LSBGs) selection by fitting the images for all the galaxies in α.40 SDSS DR7 sample with two kinds of single-component model and two kinds of two-component model (disk+bulge): single exponential, single sérsic, exponential+deVaucular (exp+deV), and exponential+sérsic (exp+ser). Under the criteria of the B band disk central surface brightness µ0,disk(B) ⩾ 22.5 mag arcsec−2 and the axis ratio b/a > 0.3, we selected four none-edge-on LSBG samples from each of the models which contains 1105, 1038, 207, and 75 galaxies, respectively. There are 756 galaxies in common between LSBGs selected by exponential and sérsic models, corresponding to 68.42% of LSBGs selected by exponential model and 72.83% of LSBGs selected by sérsic model, the rest of the discrepancy is due to the difference in obtaining µ0 between the exponential and sérsic models. Based on the fitting, in the range of 0.5 ≤ n ≤ 1.5, the relation of µ0 from two models can be written as µ0,sersic − µ0,exp = −1.345(n − 1). The LSBGs selected by disk+bulge models (LSBG_2comps) are more massive than LSBGs selected by single-component models (LSBG_1comp), and also show a larger disk component. Though the bulges in the majority of our LSBG_2comps are not prominent, more than 60% of our LSBG_2comps will not be selected if we adopt a single-component model only. We also identified 31 giant low surface brightness galaxies (gLSBGs) from LSBG_2comps. They locate at the same region in the color-magnitude diagram as other gLSBGs. After we compared different criteria of gLSBGs selection, we find that for gas-rich LSBGs, M⋆ > 1010M⊙ is the best to distinguish between gLSBGs and normal LSBGs with bulge.