Deep Hubble Space Telescope observations of star clusters in NGC 1275

被引:86
作者
Carlson, MN
Holtzman, JA
Watson, AM
Grillmair, CJ
Mould, JR
Ballester, GE
Burrows, CJ
Clarke, JT
Crisp, D
Evans, RW
Gallagher, JS
Griffiths, RE
Hester, JJ
Hoessel, JG
Scowen, PA
Stapelfeldt, KR
Trauger, JT
Westphal, JA
机构
[1] New Mexico State Univ, Dept Astron, Dept 4500, Las Cruces, NM 88003 USA
[2] Univ Nacl Autonoma Mexico, Astron Inst, Morelia 58090, Michoacan, Mexico
[3] CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA
[4] Australian Natl Univ, Mt Stromlo & Siding Spring Observ, Weston Creek, ACT 2611, Australia
[5] Univ Michigan, Dept Atmospher Ocean & Space Sci, Ann Arbor, MI 48109 USA
[6] Space Telescope Sci Inst, Baltimore, MD 21218 USA
[7] European Space Agcy, Div Astrophys, Dept Space Sci, F-75738 Paris 15, France
[8] Univ Wisconsin, Dept Astron, Madison, WI 53706 USA
[9] Carnegie Mellon Univ, Dept Phys, Pittsburgh, PA 15213 USA
[10] Arizona State Univ, Dept Phys & Astron, Tempe, AZ 85287 USA
[11] CALTECH, Dept Geol & Planetary Sci, Pasadena, CA 91125 USA
关键词
galaxies; active; star clusters;
D O I
10.1086/300334
中图分类号
P1 [天文学];
学科分类号
0704 ;
摘要
We present an analysis of compact star clusters in deep Hubble Space Telescope Wide Field Planetary Camera 2 images of NGC 1275. B- and R-band photometry of roughly 3000 clusters shows a bimodality in the B-R colors, suggesting that distinct old and young cluster populations are present. The small spread in the colors of the blue clusters is consistent with the hypothesis that they are a single-age population, with an inferred age of 0.1 to 1 Gyr. The luminosity function shows increasing numbers of blue clusters to the limit of our photometry, which reaches several magnitudes past the turnover predicted if the cluster population is identical to current Galactic globular clusters seen at a younger age. The blue clusters have a spatial distribution that is more centrally peaked than that of the red clusters. The individual clusters are slightly resolved, with core radii less than or similar to 0.75 pc if they have modified Hubble profiles. We estimate the specific frequencies of the old and young populations and discuss the uncertainties in these estimates. We find that the specific frequency of the young population in NGC 1275 is currently larger than that of the old population and will remain so as the young population evolves, even if the majority of the low-mass clusters are eventually destroyed. If the young population formed during a previous merger, this suggests that mergers can increase the specific frequency of globular clusters in a galaxy. However, the presently observed young population likely contains too few clusters to have a significant impact on the overall specific frequency as it will be observed in the future.
引用
收藏
页码:1778 / 1790
页数:13
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