Star clusters in M 33

Free access article

Issue		A&A Volume 366, Number 2, February I 2001


Page(s)		498 - 507
Section		Stellar clusters and associations
DOI		http://dx.doi.org/10.1051/0004-6361:20000263

A&A 366, 498-507 (2001)
DOI: 10.1051/0004-6361:20000263

IV. A new survey from deep HST images

R. Chandar¹, L. Bianchi^{1, 2} and H. C. Ford¹

¹ Department of Physics & Astronomy, The Johns Hopkins University, 3701 San Martin Dr., Baltimore, MD 21218, USA
e-mail: rupali@pha.jhu.edu; bianchi@pha.jhu.edu; ford@pha.jhu.edu
² Astronomical Observatory of Torino, 10025 Pino Torinese, TO, Italy

(Received 2 June 2000 / Accepted 14 November 2000)

Abstract
We have detected 102 star clusters in M 33, from 35 deep Hubble Space Telescope (HST) WFPC2 fields taken from our program and from the HST archive. Twenty-eight fields have V and I band imaging, and an additional seven fields are imaged in a single V filter. Eighty-two of the clusters were previously unknown. Integrated photometry reveals that 25 clusters have (V-I) colors typical of those found in Galactic globular clusters (only ten of these objects were previously known). Our discovery of 15 new globular cluster candidates increases previous estimates of the old cluster population in M 33 by $\sim$ 60% . An additional eleven objects (only two were previously known) have colors expected for intermediate age clusters. The new clusters have a range of ages from 6 million years to >15 Gyrs, and masses between $10^{2} M_{\odot}{-}10^{6} M_{\odot}$ , although these parameters are estimated from only one color. The number of new clusters detected more than doubles our previous sample (Papers I and II), and extends coverage to older objects and new off-spiral arm locations in M 33. The luminosity function for old M 33 clusters shows a peak at $M_{V}\sim-7.0$ , nearly half a magnitude fainter than found in the Galactic and M 31 globular cluster populations. The luminosity function for intermediate age objects shows no turnover down to $M_{V}\sim-6.6$ . We estimate the total number of globular clusters in M 33 to be $75\pm14$ . This gives a specific frequency, $S_{\rm N}$ , of $2.07\pm0.39$ -significantly higher than found for other late-type spiral galaxies, but in the range found for ellipticals.

Key words: galaxies: individual (M 33) -- galaxies: star clusters -- galaxies: evolution

Offprint request: R. Chandar

SIMBAD Objects
Tables at the CDS

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.