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

Abstract

We present a new catalog of 3816 compact star clusters in the grand design spiral galaxy M51 based on observations taken with the Hubble Space Telescope. The age distribution of the clusters declines starting at very young ages, and can be represented by a power law,, with g = - 0.65 0.15. No significant changes in the shape of the age distribution at different masses is observed. The mass function of the clusters younger than t » 400 Myr can also be described by a power law, µ b dN dM M , with b » - 2.1 0.2. We compare these distributions with the predictions from various cluster disruption models, and find that they are consistent with models where clusters disrupt approximately independent of their initial mass, but not with models where lower mass clusters are disrupted earlier than their higher mass counterparts. We find that the half-light radii of clusters more massive than »´ M M 3 10 4and with ages between 100 and 400 Myr are larger by a factor of ≈3-4 than their counterparts that are younger than 10 7 years old, suggesting that the clusters physically expand during their early life.

The PdBI Arcsecond Whirlpool Survey (PAWS): The Role of Spiral Arms in Cloud and Star Formation

“…Based on the high derived star formation rate surface density, Bastian et al (2005) classify C2 as a localized starburst. The difference in the spatial distribution of young stellar clusters between spurs and the arm is also evident in the amount of (young) stellar mass per area, where Lee et al 2011), and young stellar clusters (from Chandar et al 2016) present in the region under study. Objects residing in our gas spiral arm (blue) and gas spurs (red) are color-coded: (a) GMCs from the catalog of Colombo et al (2014a), where the size of the symbols corresponds to their respective mass (from small to large: Lee et al (2011), where the size of the symbols corresponds to their respective Hα luminosity (from small to large: log(L Hα )<37.5, 37.5log (L Hα )<39.0, log(L Hα )39.0); and (c) stellar clusters younger than 10 Myr from the catalog of Chandar et al (2016), where the size of the symbols corresponds to their respective stellar mass (from small to large:…”

“…The remaining columns give the logarithm of the mean age in column (3), the mean stellar mass in column (4), and the mean stellar mass density (from clusters) in column (5). The properties of the individual stellar clusters are listed in Table 8 and are taken from the catalog of Chandar et al (2016). The mean for all properties of young stellar clusters found in the individual spurs is given in the second last column, and the corresponding properties for the arm segment are listed in the last row.…”

“…About 3500 stellar clusters with a 90% completeness level down to m V ≈23 have been identified in a summed HST BVI image by applying certain selection criteria on morphology (Chandar et al , 2016. The ages and masses are estimated using U, B, V, I, and (non-continuum-subtracted) Hα aperture photometry, together with population synthesis models (for a more detailed discussion of the young stellar clusters, see Calzetti et al 2010).…”

“…In addition, we use the catalog of 1507 GMCs identified in the PAWS area (Colombo et al 2014a), the catalog of 7215 grouped H II regions (i.e., giant H II regions identified via a friends-of-friends algorithm; Lee et al 2011), and the catalog of 3812 stellar clusters identified in and characterized by HST a + UVBI H imaging (Chandar et al 2016). …”

“…A quantitative analysis of star formation in the different zones of the selected spiral arm region is made utilizing catalogs of (giant) H II regions (Lee et al 2011) and young (10 Myr) stellar clusters (Chandar et al 2016) identified in HST images (see Section 3.2.2).…”