Discovery of three optical open clusters in the Galaxy

¹ Universidade Federal do Rio Grande do Sul, Instituto de Física, CP 15051, Porto Alegre 91501-970, RS, Brazil e-mail: charles@if.ufrgs.br
² Universidade Estadual do Rio Grande do Sul, Unidade São Borja, Rua Bompland 512, São Borja 97670-000, RS, Brazil

Received: 14 January 2004
Accepted: 31 March 2004

Abstract

We report the discovery of three optical open clusters in the Milky Way. Two clusters are in Scutum (Cluster 1 at and , and Cluster 2 at and ), thus projected not far from the Galactic center direction, and the other is in Canis Major (Cluster 3 at and ), near the anti-center direction. Cluster 3 is less populous than Clusters 1 and 2, but presents evidence of being a physical system. The objects were found optically by inspecting maps obtained from the Guide Star Catalogue and images from the Digitized Sky Survey. No previous identification of a cluster has been reported in any of these areas so far. The analysis was carried out with 2MASS photometry in J and H. For Cluster 1 we derive an age of  ± 5 Myr, a reddening  ± 0.03 and a distance from the Sun  ± 0.19 kpc; for Cluster 2,  ± 100 Myr,  ± 0.03 and  ± 0.21 kpc; finally for Cluster 3,  Myr,  ± 0.03 and  ± 0.35 kpc. Luminosity and mass functions are derived for Clusters 1 and 2 which, in turn, allow us to estimate their observed masses as and , respectively. Estimated total masses, by extrapolating the mass functions to , amount to  and for the two clusters. Cluster 3 has an observed mass of ~. The present results indicate that further searches in the optical might still reveal new open clusters, especially in the infrared bands.