Wide Field CCD photometry around nine open clusters

In this paper we study the evolution of core and corona of nine open clusters using the projected radial density profiles derived from homogeneous CCD photometric data obtained through the 105-cm Kiso Schmidt telescope. The age and galactocentric distance of the target clusters varies from 16 Myr to 2000 Myr and 9 kpc to 10.8 kpc respectively. Barring Be 62, which is young open cluster, other clusters show a uniform reddening across the cluster region. The reddening in Be 62 varies from E(B−V )min= 0.70 mag to E(B−V )max= 1.00 mag. The corona of six of the clusters in the present sample is found to be elongated, however on the basis of the present sample it is not possible to establish any correlation between the age and shape of the core. The elongated core in the case of young cluster Be 62 may reflect the initial conditions in the parental molecular cloud. The other results of the present study are (i) Core radius ‘rc’ and corona size ‘rcn’/cluster radius ‘rcl’ are linearly correlated. (ii) The rc/rcn/rcl are linearly correlated with the number of stars in that region. (iii) In the age range 10-1000 Myr, the core and corona shrink with age. (iv) We find that in the galactocentric distance range 9 10 kpc, the core and corona/cluster extent of the clusters increase with the galactocentric distance. Subject headings: open clusters and associations: general — techniques: photometric