We present results on the star-formation activity of an optically obscured region containing an embedded cluster ( S255-IR ) and molecular gas between two evolved H ii regions S255 and S257 .
We have studied the complex using optical , near-infrared ( NIR ) imaging , optical spectroscopy and radio continnum mapping at 15 GHz , along with Spitzer -IRAC results .
It is found that the main exciting sources of the evolved H ii regions S255 and S257 and the compact H ii regions associated with S255-IR are of O9.5 - B3 V nature , consistent with previous observations .
Our NIR observations reveal 109 likely young stellar object ( YSO ) candidates in an area of \sim 4 ^ { \prime } .9 \times 4 ^ { \prime } .9 centered on S255-IR , which include 69 new YSO candidates .
To see the global star formation , we constructed the V - I / V diagram for 51 optically identified IRAC YSOs in an area of \sim 13 ^ { \prime } \times 13 ^ { \prime } centered on S255-IR .
We suggest that these YSOs have an approximate age between 0.1 - 4 Myr , indicating a non-coeval star formation .
Using spectral energy distribution ( SED ) models , we constrained physical properties and evolutionary status of 31 and 16 YSO candidates outside and inside the gas ridge , respectively .
The models suggest that the sources associated within the gas ridge are of younger population ( mean age \sim 1.2 Myr ) than the sources outside the gas ridge ( mean age \sim 2.5 Myr ) .
The positions of the young sources inside the gas ridge at the interface of the H ii regions S255 and S257 , favor a site of induced star formation .