A deep multiwavelength study of young stellar population in Cygnus OB2

Circumstellar disk evolution plays a key role in the growth of stars and formation of planetary systems. Deep, large-scale studies of various star-forming regions are required to understand the effect of cluster environment on disk evolution, their dispersal and hence, on the planet formation. At 1.6 kpc distance from the Sun and with  200 OB-stars, Cygnus OB2 is an ideal laboratory to study the role of feedback-driven environment on disk evolution. We have obtained the deepest and the widest optical photometry with 8m Subaru Hyper Suprime-Cam (HSC) of a 1. diameter region centred at Cygnus OB2. These are the pioneering wide-field and highly sensitive optical observations of a Galactic cluster available so far. We perform the statistical field decontamination of the central 18’ region and estimate the age of the cluster as  5  2 Myrs. We combine our deep optical photometry with near-IR (UKIDSS) and mid-IR (Spitzer) photometry to study the pre-main sequence population ( 1 sources) reaching down to brown-dwarf limit including a significant census of disk-bearing  and diskless objects. We identify circumstellar disk population in the target region and classify them into the class I and class II sources based on their IR excess. We calculate the disk fraction in the central 18’ region to be ~14% and observe the spatial variation of disk fraction across the region as a function of incident UV flux. We further aim to identify the sub-stellar population and obtain the IMF in the low-mass regime in one of the most massive regions outside the solar neighborhood.