The Unusual Luminosity Function of the Globular Cluster M10

Abstract

We present the I-band luminosity function of the differentially reddened globular cluster M10. We combine photometric analysis derived from wide-field (23' x 23') images that include the outer regions of the cluster and high-resolution images of the cluster core. After making corrections for incompleteness and field star contamination, we find that the relative numbers of stars on the lower giant branch and near the main-sequence turnoff are in good agreement with theoretical predictions. However, we detect significant (> 6 σ) excesses of red giant branch stars above and below the red giant branch bump using a new statistic (a population ratio) for testing relative evolutionary timescales of main-sequence and red giant stars. The statistic is insensitive to assumed cluster chemical composition, age, and main-sequence mass function. The excess number of red giants cannot be explained by reasonable systematic errors in our assumed cluster chemical composition, age, or main-sequence mass function. Moreover, M10 shows excesses when compared to the cluster M12, which has nearly identical metallicity, age, and color-magnitude diagram morphology. We discuss possible reasons for this anomaly, finding that the most likely cause is a mass function slope that shows significant variations as a function of mass.

31 pages, 12 figures, accepted for ApJ

References in corpus (3)

• Chemical Abundances and Rotation Velocities of Blue Horizontal-Branch Stars in Six Globular Clusters
• The Initial Helium Abundance of the Galactic Globular Cluster System
• The Luminosity Function and Color-Magnitude Diagram of the Globular Cluster M12

Cited by in corpus (13)

• Accurate distances to Galactic globular clusters through a combination of Gaia EDR3, HST and literature data
• Homogeneous photometry VII. Globular clusters in the Gaia era
• Uncloaking globular clusters in the inner Galaxy
• Theoretical Uncertainties in Red Giant Branch Evolution: The Red Giant Branch Bump
• Star Counts in the Globular Cluster Omega Centauri. I. Bright Stellar Components
• The dynamical state of the Globular Cluster M10 (NGC 6254)
• A Re-Evaluation of the Evolved Stars in the Globular Cluster M13
• Light Element Abundances and Multiple Populations in M10
• Photometry of the Globular Cluster NGC 5466: Red Giants and Blue Stragglers
• A Census of Above-Horizontal-Branch Stars in Galactic Globular Clusters
• Carbon Isotope Ratios in M10 Giants
• Astrophysics in 2005
• Internal Kinematics of M10 and M71