SCYON Abstract

Received on March 19 2008

Mass functions and photometric binaries in nine open clusters

AuthorsSaurabh Sharma (1), A.K. Pandey (1), K. Ogura (2), T. Aoki (3), Kavita Pandey (4), T.S. Sandhu (1,5), and R. Sagar (1)
Affiliation(1) Aryabhatta Research Institute of Observational Sciences, Nainital, India - 263 129
(2) Kokugakuin University, Higashi, Shibuya-ku, Tokyo 150-8440, Japan
(3) Kiso Observatory, School of Science, University of Tokyo, Mitake-mura, Kiso-gun, Nagano 397-0101, Japan
(4) Department of Physics, DSB Campus, Kumaun University, Nainital, India
(5) Department of Physics, Punjabi University, Patiala 147002, India
Accepted byAstronomical Journal
Contactsaurabh@aries.ernet.in
URL
Links Berkeley 62 / NGC 1528 / NGC 1960 / NGC 2287 / NGC 2301 / NGC 2323 / NGC 2420 / NGC 2437 / NGC 2548

Abstract

Using homogeneous CCD photometric data from the 105-cm Kiso Schmidt telescope covering a 50' x 50' field, we study the mass functions (MFs) of nine open clusters. The ages and Galactocentric distances of the target clusters vary from 16 - 2000 Myr and 9-10.8 kpc, respectively. The values of MF slopes vary from -1.1 to -2.1. The classical value derived by Salpeter (1955) for the slope of the IMF is Γ = -1.35. The MFs in the outer regions of the clusters are found to be steeper than in the inner regions, indicating the presence of mass segregation in the clusters.The MF slopes (in the outer region as well as the whole cluster) undergo an exponential decay with the evolutionary parameter τ (= age/relaxation time). It seems that the evaporation of low-mass members from outer regions of the clusters is not significant at larger Galactocentric distances. It is concluded that the initial mass function (IMF) in the anticentre direction of the Galaxy might have been steeper than the IMF in the opposite direction. A comparison of the observed CMDs of the clusters with synthetic CMDs gives a photometric binary content of ~40%.