2006ApJ...638L..79H

We present a study of a faint fuzzy star cluster system in the nearby SB0 galaxy NGC 5195 interacting with the famous spiral galaxy NGC 5194 (M51), based on HST ACS BVI mosaic images taken by the Hubble Heritage Team. We have found about 50 faint fuzzy star clusters around NGC 5195 that are larger than typical globular clusters with effective radii r_eff>7 pc and that are red with (V-I)>1.0. They are mostly fainter than M_V~-8.3 mag. From the comparison of BVI photometry of these clusters with the simple stellar population models, we find that they are as massive as ~10⁵ M_☉and older than 1 Gyr. Strikingly, most of these clusters are found to be scattered in an elongated region almost perpendicular to the northern spiral arm of NGC 5194, and the center of the region is slightly north of the NGC 5195 center, while normal compact red clusters of NGC 5195 are located around the bright optical body of the host galaxy. This is in contrast to the cases of NGC 1023 and NGC 3384 where the spatial distribution of faint fuzzy clusters shows a ring structure around the host galaxy. We suggest that at least some faint fuzzy clusters are experiencing tidal interactions with the companion galaxy NGC 5194 and must be associated with the tidal debris in the western halo of NGC 5195.