WFPC2 Observations of the Globular Cluster M30
Abstract
We describe images of the center of the dense globular cluster M30 (NGC 7099) obtained with the Hubble Space Telescope Wide Field/Planetary Camera 2 (HST WFPC2). Data taken in the F336W, F439W, and F555W filters (approximately U, B, and V) yield a color-magnitude diagram with photometric errors of 1 sigma = 0.05 mag for stars with V less than 17.5, and 1 sigma approximately 0.1 mag at V = 20, which is 1.5 mag fainter than the main-sequence turnoff. Simulations show that the star identifications are essentially complete for stars with V less than 19.5, even in the densest regions of the cluster. The projected radial distribution of stars can be represented by a power law distribution: N(r) approximately ralpha, with slope alpha = -0.4 +/- 0.15, into radii less than 0.4 sec (0.015 pc). The radial profile is also consistent with a flat core of any radius smaller than approximately 1.5 sec (0.05 pc), but inconsistent with any core radius larger than 2.5 sec (0.09 pc). A total of 30 blue straggler candidates within 20 sec of the cluster center have been identified from the three-color data. Their radial distribution is strongly centrally concentrated when compared to the horizontal branch, red giant branch, or main-sequence stars in the cluster. The abundance of blue stragglers (relative to red giants and subgiants) within r approximately less than 20 sec of the center of M30 is fBS = 0.19 =/- 0.04, about twice as high as in other dense clusters.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- November 1994
- DOI:
- 10.1086/187594
- Bibcode:
- 1994ApJ...435L..59Y
- Keywords:
-
- Blue Stars;
- Globular Clusters;
- Radial Distribution;
- Color-Magnitude Diagram;
- Computerized Simulation;
- Hubble Space Telescope;
- Power Series;
- Stellar Luminosity;
- Astronomy