Astronomy & Astrophysics

Free access article

A&A 408, 127-134 (2003)
DOI: 10.1051/0004-6361:20030944

NTT infrared imaging of star cluster candidates towards the central parts of the Galaxy

C. M. Dutra^{1, 2}, S. Ortolani³, E. Bica⁴, B. Barbuy¹, M. Zoccali⁵ and Y. Momany³

¹ Universidade de São Paulo, Instituto de Astronomia, Geofísica e Ciências atmosféricas, CP 3386, São Paulo 01060-970, SP, Brazil
² Universidade Estadual do Rio Grande do Sul, Rua Bompland 512, São Borja 97670-000, RS, Brazil
³ Università di Padova, Dept. di Astronomia, Vicolo dell'Osservatorio 2, 35122 Padova, Italy
⁴ Universidade Federal do Rio Grande do Sul, Instituto de Física, CP 15051, Porto Alegre 91501-970, RS, Brazil
⁵ European Southern Observatory, Karl-Schwarzschild-Strasse 2, 85748 Garching bei München, Germany

(Received 20 December 2002 / Accepted 25 April 2003)

Abstract
We address the issue whether the central parts of the Galaxy harbour young clusters other than Arches, Quintuplet and the Nuclear Young Cluster. A large sample of centrally projected cluster candidates has been recently identified from the 2MASS J, H and $K_{\rm s}$ Atlas. We provide a catalogue of higher angular resolution and deeper images for 57 2MASS cluster candidates, obtained with the near-IR camera SOFI at the ESO NTT telescope. We classify 10 objects as star clusters, some of them deeply embedded in gas and/or dust clouds. Three other objects are probably star clusters, although the presence of dust in the field does not exclude the possibility of their being field stars seen through low-absorption regions. Eleven objects are concentrations of stars in areas of little or no gas, and are classified as dissolving cluster candidates. Finally, 31 objects turned out to be the blend of a few bright stars, not resolved as such in the low resolution 2MASS images. By combining the above results with other known objects we provide an updated sample of 42 embedded clusters and candidates projected within 7 $^{\circ}$ . As a first step we study Object 11 of Dutra & Bica (2000) projected at $\approx$ 1 $^{\circ}$ from the nucleus. We present H and $K_{\rm s}$ photometry and study the colour-magnitude diagram and luminosity function. Object 11 appears to be a less massive cluster than Arches or Quintuplet, and it is located at a distance from the Sun $d_{\odot} \approx$ 8 kpc, with a visual absorption $A_{V} \approx 15$ .

Key words: Galaxy: open clusters and associations -- ISM: dust, extinction

Offprint request: C. M. Dutra, dutra@astro.iag.usp.br

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