The star cluster Collinder 232 in the Carina complex and its relation to Trumpler 14/16

Free access article

Issue		A&A Volume 418, Number 2, May I 2004


Page(s)		525 - 537
Section		Galactic structure, stellar clusters and populations
DOI		http://dx.doi.org/10.1051/0004-6361:20034335

A&A 418, 525-537 (2004)
DOI: 10.1051/0004-6361:20034335

The star cluster Collinder 232 in the Carina complex and its relation to Trumpler 14/16

G. Carraro^{1, 2}, M. Romaniello², P. Ventura³ and F. Patat²

¹ Dipartimento di Astronomia, Università di Padova, vicolo dell'Osservatorio 2, 35122, Padova, Italy
² European Southern Observatory, Karl-Schwarzschild-Str 2, 85748 Garching b. München, Germany
³ Osservatorio Astronomico di Roma, Via di Frascati 33, 00040, Monte Porzio Catone, Italy

(Received 17 September 2003 / Accepted 7 January 2004 )

Abstract
In this paper we present and analyze new CCD UBVRI photometry down to $V\approx21$ in the region of the young open cluster Collinder 232, located in the Carina spiral arm, and discuss its relationship to Trumpler 14 and Trumpler 16, the two most prominent young open clusters located in the core of NGC 3372 (the Carina Nebula). First of all we study the extinction pattern in the region. We find that the total to selective absorption ratio R_V differs from cluster to cluster, being $3.48\pm0.11$ , $4.16\pm0.07$ and $3.73\pm0.01$ for Trumpler 16, Trumpler 14 and Collinder 232, respectively. Then we derive individual reddenings and intrinsic colours and magnitudes using the method devised by Romaniello et al. (2002). Ages, age spreads and distances are then estimated by comparing the Colour Magnitude Diagrams and the Hertzsprung-Russel diagram with post and pre-main sequence tracks and isochrones. We find that Trumpler 14 and Collinder 232 lie at the same distance from the Sun (about 2.5 kpc), whereas Trumpler 16 lies much further out, at about 4 kpc from the Sun. As for the age, we find that Trumpler 16 is older than both Trumpler 14 and Collinder 232. For all the clusters we indicate the existence of a significant age dispersion, whose precise value is hampered by our inability to properly distinguish members from non-members. We finally suggest that Collinder 232 is a physical aggregate and provide estimates of its basic parameters.

Key words: stars: Hertzsprung-Russell (HR) and C-M -- Galaxy: open clusters and associations: individual: Trumpler 14

Offprint request: G. Carraro, giovanni.carraro@unipd.it

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