The Snapshot Hubble U-Band Cluster Survey (SHUCS). II. The Star Cluster Population of NGC 2997
Larsen, S.; Bastian, N.; Smith, L. J.; Ryon, J. E.; Adamo, A.; Gallagher, J. S., III; Konstantopoulos, I. S.; Silva-Villa, E.; Zackrisson, E.
United States, Germany, Sweden, United Kingdom, Australia, Netherlands, Canada
Abstract
We study the star cluster population of NGC 2997, a giant spiral galaxy located at 9.5 Mpc and targeted by the Snapshot Hubble U-band Cluster Survey (SHUCS). Combining our U-band imaging from SHUCS with archival BVI imaging from the Hubble Space Telescope, we select a high confidence sample of clusters in the circumnuclear ring and disk through a combination of automatic detection procedures and visual inspection. The cluster luminosity functions in all four filters can be approximated by power laws with indices of -1.7 to -2.3. Some deviations from pure power-law shape are observed, hinting at the presence of a high-mass truncation in the cluster mass function. However, upon inspection of the cluster mass function, we find it is consistent with a pure power law of index -2.2 ± 0.2 despite a slight bend at ~2.5 × 104 M ⊙. No statistically significant truncation is observed. From the cluster age distributions, we find a low rate of disruption (ζ ~ -0.1) in both the disk and circumnuclear ring. Finally, we estimate the cluster formation efficiency (Γ) over the last 100 Myr in each region, finding 7% ± 2% for the disk, 12% ± 4% for the circumnuclear ring, and 10% ± 3% for the entire UBVI footprint. This study highlights the need for wide-field UBVI coverage of galaxies to study cluster populations in detail, though a small sample of clusters can provide significant insight into the characteristics of the population.