We report the discovery of three optical open clusters in the Milky Way. Two clusters are in Scutum (Cluster 1 at ℓ=18.44° and b=-0.42o, and Cluster 2 at ℓ=19.60° and b=-1.02o), thus projected not far from the Galactic center direction, and the other is in Canis Major (Cluster 3 at ℓ=235.61° and b=-4.10o), 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 t=25 ± 5 Myr, a reddening E(B-V)=2.18 ± 0.03 and a distance from the Sun d☉=1.64 ± 0.19 kpc; for Cluster 2, t=500 ± 100 Myr, E(B-V)=0.91 ± 0.03 and d☉=2.19 ± 0.21 kpc; finally for Cluster 3, t=32-100 Myr, E(B-V)=0.94 ± 0.03 and d☉=3.93 ± 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 147 M☉ and 89 M☉, respectively. Estimated total masses, by extrapolating the mass functions to 0.08 M☉, amount to 382 M☉ and 614 M☉ for the two clusters. Cluster 3 has an observed mass of ∼55 M☉. The present results indicate that further searches in the optical might still reveal new open clusters, especially in the infrared bands.
Astronomy and Astrophysics
- Pub Date:
- August 2004
- Galaxy: open clusters and associations: general;
- Galaxy: structure;
- accepted to Astronomy and Astrophysics, 9 figures