have $\mu_0(B)$ within 22-23 mag arcsec$^{-2}$, thus $A_V$=0.6 is acceptable to be their dust extinction. Also $A_V$=0.8 is reasonable to be the dust extinction of HSBGs.

Figure \[Fig2\] shows the resulted SED fittings (left panel for one example of LSBGs; middle panel for one example of HSBGs) and the histogram distributions of the derived ages of the galaxies (the right panel, where the shaded region is for LSBGs and the dashed-line is for HSBGs). The right panel shows that the ages of most of the LSBGs are 1-5 Gyr with median (mean) value of 1.63 (1.75) Gyr. This means that the majority of their stars were formed quite recently. However, about 3% of the LSBGs have larger ages, 5-8 Gyr. This small part of galaxies could probably form their stars at earlier time. Similarly, the ages of most of HSBGs are 1-5 Gyr as well with the median value of 1.47 (mean as 1.59) Gyr. About 3% of them have larger ages as 5-8 Gyr. This similarity may mean that the LSBGs and HSBGs could have no much different star formation history. This result is consistent with the metallicity estimates of similar samples presented in Liang et al. (2010). But 