Horizontal Branch Morphology and Mass Loss in Globular Clusters

Abstract

The connection between mass loss on the red giant branch (RGB) and horizontal branch (HB) morphology in globular clusters (GCs) has long been acknowledged but the mechanisms governing mass loss remains poorly understood from a theoretical perspective. The present study uses synthetic HB models to demonstrate for the first time that alpha-enhancement and a simple relation between mass loss and metallicity can explain the entire range of HB morphology (characterized by the HB type index) observed in old, coeval GCs. The mass loss-metallicity relation accounts naturally for the fact that the most metal poor GCs ([Fe/H] < -2) have redder HBs than is typical of GCs with -2 < [Fe/H] < -1.5 without invoking younger ages. These results may prove useful in studying the contribution of HB stars to integrated light via stellar population synthesis.

13 pages, 5 figures, to appear in ApJ Letters (figure 2 may not display correctly in some PDF viewers)

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Cited by in corpus (21)

• The ACS Survey of Galactic Globular Clusters. IX. Horizontal Branch Morphology and the Second Parameter Phenomenon
• The second and third parameters of the Horizontal Branch in Globular Clusters
• The peculiar Horizontal Branch of NGC 2808
• Optical and Near-Infrared UBVRIJHK Photometry for the RR Lyrae stars in the Nearby Globular Cluster M4 (NGC 6121)
• Giants in the globular cluster omega Centauri: dust production, mass loss and distance
• Population Parameters of Intermediate-Age Star Clusters in the Large Magellanic Cloud. I. NGC 1846 and its Wide Main Sequence Turnoff
• CNO abundances in the globular clusters NGC 1851 and NGC 6752
• Fast Winds and Mass Loss from Metal-Poor Field Giants
• The effect of starspots on the radii of low-mass pre-main sequence stars
• Fake star formation bursts: blue horizontal branch stars masquerade as young stars in optical integrated light spectroscopy
• UV Properties of Galactic Globular Clusters with GALEX II. Integrated colors
• Unmixing the Galactic Halo with RR Lyrae tagging
• A Near-infrared RR Lyrae census along the southern Galactic plane: the Milky Way's stellar fossil brought to light
• The environment of formation as a second parameter for globular cluster classification
• Evolutionary and pulsation properties of Type II Cepheids
• Optimal Integrated Abundances for Chemical Tagging of Extragalactic Globular Clusters
• A Dearth of Close-In Stellar Companions to M-dwarf TESS Objects of Interest
• Comparison of Alpha-Element Enhanced Simple Stellar Population Models with Milky Way Globular Clusters
• Star Cluster Ages in the Gaia Era
• A search for period changes of eight short-period Type II Cepheids
• M dwarf stars in the light of (future) exoplanet searches