The IMF and star formation history of the stellar clusters in the Vela D cloud

Free access article

Issue		A&A Volume 448, Number 3, March IV 2006


Page(s)		1007 - 1022
Section		Galactic structure, stellar clusters and populations
DOI		http://dx.doi.org/10.1051/0004-6361:20053836

A&A 448, 1007-1022 (2006)
DOI: 10.1051/0004-6361:20053836

The IMF and star formation history of the stellar clusters in the Vela D cloud

F. Massi¹, L. Testi¹ and L. Vanzi²

¹ INAF - Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy
e-mail: fmassi@arcetri.astro.it
² ESO, Alonso de Cordova 3107, Vitacura, Casilla 19001, Santiago 19, Chile

(Received 15 July 2005 / Accepted 8 November 2005 )

Abstract
Aims.We present the results of a Near-Infrared deep photometric survey of a sample of six embedded star clusters in the Vela-D molecular cloud, all associated with luminous ( ${\sim} 10^{3}$ $L_{\odot}$ ) IRAS sources. The clusters are unlikely to be older than a few 10⁶ yrs, since all are still associated with molecular gas.
Methods.We employed the fact that all clusters lie at the same distance and were observed with the same instrumental setting to derive their properties in a consistent way, being affected by the same instrumental and observational biases. We extracted the clusters' K Luminosity Functions and developed a simple method to correct them for extinction, based on colour-magnitude diagrams. The reliability of the method has been tested by constructing synthetic clusters from theoretical tracks for pre-main sequence stars and a standard Initial Mass Function. The clusters' Initial Mass Functions have been derived from the dereddened K Luminosity Functions by adopting a set of pre-main sequence evolutionary tracks and assuming coeval star formation.
Results.All clusters are small ( ${\sim} 100$ members) and compact (radius ${\sim} 0.1{-}0.2$ pc); their most massive stars are intermediate-mass ( ${\sim} 2{-}10$ $M_{\odot}$ ) ones. The dereddened K Luminosity Functions are likely to arise from the same distribution, suggesting that the selected clusters have quite similar Initial Mass Functions and star formation histories. The Initial Mass Functions are consistent with those derived for field stars and clusters. Adding them together we found that the "global" Initial Mass Function appears steeper at the high-mass end and exhibits a drop-off at ${\sim} 10$ $M_{\odot}$ . In fact, a standard Initial Mass Function would predict a star with M > 22.5 $M_{\odot}$ within one of the clusters, which is not found. Hence, either high-mass stars need larger clusters to be formed, or the Initial Mass Function of the single clusters is steeper at the high-mass end because of the physical conditions in the parental gas.

Key words: stars: formation -- stars: pre-main sequence -- ISM: individual objects: Vela Molecular Ridge -- infrared: stars

SIMBAD Objects

What is OpenURL?

The OpenURL standard is a protocol for transmission of metadata describing the resource that you wish to access. An OpenURL link contains article metadata and directs it to the OpenURL server of your choice. The OpenURL server can provide access to the resource and also offer complementary services (specific search engine, export of references...). The OpenURL link can be generated by different means.

If your librarian has set up your subscription with an OpenURL resolver, OpenURL links appear automatically on the abstract pages.
You can define your own OpenURL resolver with your EDPS Account. In this case your choice will be given priority over that of your library.
You can use an add-on for your browser (Firefox or I.E.) to display OpenURL links on a page (see http://www.openly.com/openurlref/). You should disable this module if you wish to use the OpenURL server that you or your library have defined.