Age Constraints for an M31 Globular Cluster from Main Sequence Photometry

Abstract

We present a color-magnitude diagram (CMD) of the globular cluster SKHB-312 in the Andromeda galaxy (M31), obtained with the Advanced Camera for Surveys on the Hubble Space Telescope. The cluster was included in deep observations taken to measure the star formation history of the M31 halo. Overcoming a very crowded field, our photometry of SKHB-312 reaches V ~ 30.5 mag, more than 1 mag below the main sequence turnoff. These are the first observations to allow a direct age estimate from the turnoff in an old M31 cluster. We analyze its CMD and luminosity function using a finely-spaced grid of isochrones that have been calibrated using observations of Galactic clusters taken with the same camera and filters. The luminosity difference between the subgiant and horizontal branches is ~0.2 mag smaller in SKHB-312 than in the Galactic clusters 47 Tuc and NGC 5927, implying SKHB-312 is 2-3 Gyr younger. A quantitative comparison to isochrones yields an age of 10 +2.5/-1 Gyr.

References in corpus (16)

• Maps of Dust IR Emission for Use in Estimation of Reddening and CMBR Foregrounds
• Correcting for the Effects of Interstellar Extinction
• Stellar population models of Lick indices with variable element abundance ratios
• Numerical Methods of Star Formation History Measurement and Applications to Seven Dwarf Spheroidals
• Distances and ages of NGC 6397, NGC 6752 and 47 Tuc
• A Globular Cluster Metallicity Scale Based on the Abundance of Fe II
• A Method for Determining the Star Formation History of a Mixed Stellar Population
• Evidence for a Significant Intermediate-Age Population in the M31 Halo from Main Sequence Photometry
• Photometry and the Metallicity Distribution of the Outer Halo of M31
• Integrated Spectroscopy of Bulge Globular Clusters and Fields I. The Data Base and Comparison of Individual Lick Indices in Clusters and Bulge
• The White Dwarf Distance to the Globular Cluster 47 Tucanae and its Age
• Parameter Estimation in Astronomy with Poisson-Distributed Data. I. The Chi-Square-Gamma Statistic
• RR Lyrae Stars in the Andromeda Halo from Deep Imaging with the Advanced Camera for Surveys
• New Photometry for the Intermediate-age LMC Globular Cluster NGC 2121 and the Nature of the LMC Age Gap
• Deep HST V- and I-Band Observations of Two Globular Clusters in the Halo of M31
• Testing population synthesis models with globular cluster colors

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