We present sub-arcsecond ( FWHM \sim 0″.7 ) , near-infrared ( NIR ) JHK _ { s } -band images and a high sensitivity radio continuum image at 1280 MHz , using SIRIUS on UH 88-inch telescope and GMRT .
The NIR survey covers an area of \sim 24 arcmin ^ { 2 } with 10 \sigma limiting magnitudes of \sim 19.5 , 18.4 , and 17.3 in J , H , and K _ { s } -band , respectively .
Our NIR images are deeper than any JHK surveys to date for the larger area of NGC 7538 star forming region .
We construct JHK color-color and J-H/J and H-K/K color-magnitude diagrams to identify young stellar objects ( YSOs ) and to estimate their masses .
Based on these color-color and color-magnitude diagrams , we identified a rich population of YSOs ( Class I and Class II ) , associated with the NGC 7538 region .
A large number of red sources ( H-K > 2 ) have also been detected around NGC 7538 .
We argue that these red stars are most probably pre-main sequence stars with intrinsic color excesses .
Most of YSOs in NGC 7538 are arranged from the north-west toward south-east regions , forming a sequence in age : the diffuse H II region ( north-west , oldest : where most of the Class II and Class I sources are detected ) ; the compact IR core ( center ) ; and the regions with the extensive IR reflection nebula and a cluster of red young stars ( south-east and south ) .
We find that the slope of the K _ { s } -band luminosity function of NGC 7538 is lower than the typical values reported for the young embedded clusters , although equally low values have also been reported in the W3 Main star forming region .
From the slope of the K _ { s } -band luminosity function and the analysis by Megeath et al .
( 1996 ) , we infer that the embedded stellar population is comprised of YSOs with an age of \sim 1 Myr .
Based on the comparison between models of pre-main sequence stars with the observed color-magnitude diagram we find that the stellar population in NGC 7538 is primarily composed of low mass pre-main sequence stars similar to those observed in the W3 Main star forming region .
The radio continuum image from the GMRT observations at 1280 MHz shows an arc-shaped structure due to the interaction between the H II region and the adjacent molecular cloud .
The ionization front at the interface between the H II region and the molecular cloud is clearly delineated by comparing the radio continuum , molecular line , and near-infrared images .