Color-Magnitude Diagram of Palomar 4: CCD Photometry
Abstract
Photometry of the globular cluster Pal 4 was obtained with the RCA CCD camera on the 3.6 m Canada-France-Hawaii Telescope on Mauna Kea. The color-magnitude diagram of the cluster shows a well-defined red horizontal branch, typical of outer halo systems, and an asymptotic giant branch well separated from the giant branch. The population of Pal 4 has been sampled to the main-sequence turnoff region (V = 25), allowing a detailed comparison of this distant object with theoretical models. The cluster parameters consistent with the CCD data are (m - M)0 = 20.1 + or - 0.1 mag, E(B - V) = 0.02 + or - 0.02, and Fe/H forbidden line = -1.7 + or - 0.1 with Y =0.2. The age of the cluster, determined by comparison with the isochrones of VandenBerg and Bell (1985) is consistent with an age of 15 + or - 1 Gyr, similar to inner halo globular clusters with ages determined in the same way.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- April 1986
- DOI:
- 10.1086/164067
- Bibcode:
- 1986ApJ...303..216C
- Keywords:
-
- Astronomical Photometry;
- Charge Coupled Devices;
- Color-Magnitude Diagram;
- Globular Clusters;
- Stellar Evolution;
- Asymptotic Giant Branch Stars;
- Horizontal Branch Stars;
- Main Sequence Stars;
- Metallicity;
- Tables (Data);
- Astrophysics;
- CLUSTERS: GLOBULAR;
- PHOTOMETRY;
- STARS: EVOLUTION