the right panel shows the histogram distributions of the derived ages of LSBGs (shade region) and HSBGs (dashed-line) with bin of 0.2 Gyr. []{data-label="Fig2"}](ms471fig2b.eps "fig:"){width="4.8cm" height="4.8cm"} ![The fitting results with PEGASE model and constant dust extinction ($A_V$=0.6 for LSBGs and $A_V$=0.8 for HSBGs) for our sample galaxies. The left panel shows the SED fitting for one example of LSBGs (RA=8.06543, DEC=0.90616 in 2000 epoch, the derived age is 1.57 Gyr), the middle panel shows the SED fitting for one example of HSBGs (RA=6.75941, DEC=-9.63505 in 2000 epoch, the derived age is 1.44 Gyr)), and the right panel shows the histogram distributions of the derived ages of LSBGs (shade region) and HSBGs (dashed-line) with bin of 0.2 Gyr. []{data-label="Fig2"}](ms471fig2c.eps "fig:"){width="4.6cm" height="4.2cm"}

Varying dust extinction {#sect:analysis2}
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Now we adopt $A_V$ as a varying parameter from 0.1 to 1.6 in the fittings. This range of $A_V$ values is reasonable for LSBGs and HSBGs by following Liang et al. (2010), and 1.6 is almost the upper limit of the sample (also see Liang et al. 2007 for the SDSS star forming galaxies).

Figure \[Fig3\] shows the resulted SED fittings of two example galaxies (the left panel for the same example of LSBGs, and 