Low Surface Brightness Galaxies selected by different model fitting

Abstract

We present a study of low surface brightness galaxies (LSBGs) selected by fitting the images for all the galaxies in $\alpha$.40 SDSS DR7 sample with two kinds of single-component models and two kinds of two-component models (disk+bulge): single exponential, single s\'{e}rsic, exponential+deVaucular (exp+deV), and exponential+s\'{e}rsic (exp+ser). Under the criteria of the B band disk central surface brightness $\mu_{\rm 0,disk}{\rm (B) \geqslant 22.5\ mag\ arcsec^{-2}}$ and the axis ratio $\rm b/a > 0.3$, we selected four none-edge-on LSBG samples from each of the models which contain 1105, 1038, 207, and 75 galaxies, respectively. There are 756 galaxies in common between LSBGs selected by exponential and s\'{e}rsic models, corresponding to 68.42% of LSBGs selected by the exponential model and 72.83% of LSBGs selected by the s\'{e}rsic model, the rest of the discrepancy is due to the difference in obtaining $\mu_{0}$ between the exponential and s\'{e}rsic models. Based on the fitting, in the range of $0.5 \leqslant n \leqslant 1.5$, the relation of $\mu_{0}$ from two models can be written as $\mu_{\rm 0,s\acute{e}rsic} - \mu_{\rm 0,exp} = -1.34(n-1)$. 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 are located 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, $M_{\star} > 10^{10}M_{\odot}$ is the best to distinguish between gLSBGs and normal LSBGs with bulge.