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We present a study of compact star clusters in the nearby pair of interacting galaxies NGC 5194/95 (M51), based on multifilter Hubble Space Telescope WFPC2 archival images. We have detected ~400 isolated clusters. Our requirement that clusters be detected based only on their morphology results in the selection of relatively isolated objects, and we estimate that we are missing the majority (by a factor 4-6) of <10 Myr clusters due to crowding. Hence we focus on the cluster population older than 10 Myr. An age distribution shows a broad peak between 100-500 Myr, which is consistent with the crossing times of NGC 5195 through the NGC 5194 disk estimated in both single and multiple-passage dynamical models. We estimate that the peak contains approximately 2.2-2.5 times more clusters than expected from a constant rate of cluster formation over this time interval. We estimate the effective radii of our sample clusters and find a median value of 3-4 pc. Additionally, we see correlations of increasing cluster size with cluster mass (with a best fit slope of 0.14pm0.03) at the 4sigma level, and with cluster age (0.06pm0.02) at the 3sigma level. Finally, we report for the first time the discovery of faint, extended star clusters in the companion, NGC 5195, an SB0 galaxy. These have red [(V-I)>1.0] colors, effective radii >7 pc, and are scattered over the disk of NGC 5195. Our results indicate that NGC 5195 is therefore currently the third known barred lenticular galaxy to have formed so-called faint fuzzy star clusters. (abridged)
We use UBVI,Ha images of the Whirlpool galaxy, M51, taken with the ACS and WFPC2 cameras on the Hubble Space Telescope (HST) to select star clusters, and to estimate their masses and ages by comparing their observed colors with predictions from popul
We exploit the superb resolution of the new HST/ACS mosaic image of M51 to select a large sample of young (< 1 Gyr) star clusters in the spiral disk, based on their sizes. The image covers the entire spiral disk in B, V, I and H_alpha, at a resolutio
We use HST/ACS observations of the spiral galaxy M51 in F435W, F555W and F814W to select a large sample of star clusters with accurate effective radius measurements in an area covering the complete disc of M51. We present the dataset and study the ra
The population of low-luminosity (< 10^35 erg/s) X-Ray Binaries (XRBs) has been investigated in our Galaxy and M31 but not further. To address this problem, we have used data from the Chandra X-Ray Observatory and the Hubble Space Telescope to invest
We present a new technique for empirically calibrating how the X-ray luminosity function (XLF) of X-ray binary (XRB) populations evolves following a star-formation event. We first utilize detailed stellar population synthesis modeling of far-UV to fa