From the Top to the Bottom of the Main Sequence: A Complete Mass Function of the Young Open Cluster M35

Abstract

We present very deep and accurate photometry of the open cluster M35. We have observed this association in the Cousins R, I Ðlters, together with the Johnson V Ðlter. We have covered a region of 27.5]27.5 square arcmin, equivalent to a Ðfth of the total area of the cluster. The data range from to 23.5 mag, and the color intervals are Ic\12.5 values span from 1.6 down to the substellar limit, in the case of cluster members. By using the location of the stars on color-magnitude and color-color diagrams, we have selected candidate members of this cluster. We have merged our sample with previously published data and obtained a color- magnitude diagram for the complete stellar population of the cluster, covering the spectral range early BÈmid M. Based on the distribution of Ðeld and cluster stars in color-magnitude and color-color dia- grams, we estimate that two-thirds of these candidates are likely to be true members of M35. These stars approximately double the number of stars identiÐed as candidate members of this cluster (D2700). We provide the photometry and accurate positions of these stars. The deep photometry has allowed us to study the mass segregation within the cluster, the luminosity function, and mass function. We show that in the magnitude range M_ to higher mass stars, where the mass segregation is stronger. The luminosity function behaves essentially as the one characteristic of the Pleiades, presenting a peak at photometry with previous data corresponding to more massive stars, we Ðnd that the mass function increases monotonically, when plotted in a log-log form, until it reaches D0.8 to the substellar regime. These di†erent behaviors suggest that at least three mechanisms play a role in the formation of stellar and substellar objects. The total mass of the cluster is D1600 _), covered by this study.