The star cluster population of M 51

Abstract

Abstract. We use archival Hubble Space Telescope observations of broad-band images from the ultraviolet (F255W-filter) through the near infrared (NICMOS F160W-filter) to study the star cluster population of the interacting spiral galaxy M 51. We obtain age, mass, extinction, and effective radius estimates for 1152 star clusters in a region of ∼7.3 × 8.1 kpc centered on the nucleus and extending into the outer spiral arms. In this paper we present the data set and exploit it to determine the age distribution and relationships among the fundamental parameters (i.e. age, mass, effective radius). We show the critical dependence of the age distribution on the sample selection, and confirm that using a constant mass cut-off, above which the sample is complete for the entire age range of interest, is essential. In particular, in this sample we are complete only for masses above 5 × 10 4 M for the last 1 Gyr. Using this dataset we find: i) that the cluster formation rate seems to have had a large increase ∼50−70 Myr ago, which is coincident with the suggested second passage of its companion, NGC 5195; ii) a large number of extremely young (<10 Myr) star clusters, which we interpret as a population of unbound clusters of which a large majority will disrupt within the next ∼10 Myr; and iii) that the distribution of cluster sizes can be well approximated by a power-law with exponent, −η = −2.2 ± 0.2, which is very similar to that of Galactic globular clusters, indicating that cluster disruption is largely independent of cluster radius. In addition, we have used this dataset to search for correlations among the derived parameters. In particular, we do not find any strong trends between the age and mass, mass and effective radius, nor between the galactocentric distance and effective radius. There is, however, a strong correlation between the age of a cluster and its extinction, with younger clusters being more heavily reddened than older clusters.

Imaging of star clusters in unperturbed spiral galaxies with the Advanced Camera for Surveys

“…In similar previous studies (e.g. Bastian et al 2005b;Larsen 2004), the relation between sizes and masses for young star clusters had already been investigated, and a slight trend was found toward more massive star clusters being more extended. We considered the masses derived assuming the metallicities from In the panels where a metallicity of Z = 0.02 is indicated, it corresponds to Z = 0.02 (GALEV) and Z = 0.019 (Girardi); therefore, the Δ log(Age/yr) corresponds to log(Age Z=0.02 /yr) − log(Age Z=0.019 /yr).…”

The Age, Mass, and Size Distributions of Star Clusters in M51

“…M51 is a nearby, grand-design spiral with a rich population of star clusters that has played a critical role in understanding cluster formation and evolution (e.g., Boutloukos & Lamers 2003;Bastian et al 2005;Gieles et al 2005;Scheepmaker et al 2007;Hwang & Lee 2010;Chandar et al 2011). In this work we present a catalog of compact star clusters selected from the beautiful mosaic images taken with the WFC camera on the Advanced Camera for Surveys (ACS).…”

The VMC survey – XVI. Spatial variation of the cluster formation activity in the innermost regions of the Large Magellanic Cloud

“…Fall, Chandar & Whitmore 2005;Bastian et al 2005;Fall 2006). This fast disruption mechanism, which is thought to disrupt up to 50-90% of the youngest clusters in a given cluster population (e.g.…”