No Increase of the Red-Giant-Branch Tip Luminosity Toward the Center of M31

Abstract

We present observations with the Hubble Space Telescope Wide Field Planetary Camera 2 of three fields centered on super-metal-rich globular clusters in the bulge of M31. Our (I,V-I) color-magnitude diagrams reach as faint as I ~ 26.5 mag and clearly reveal the magnitude of the first ascent red giant branch (RGB) tip. We find that the apparent I magnitude of the RGB tip does not become brighter near the center of M31 as concluded by previous investigators. Our observations and artificial star experiments presented in this study strongly support the idea that previous very bright stars were likely the result of spurious detections of blended stars due to crowding in lower resolution images. On the contrary, our observations indicate that, at a mean projected galactocentric distance of 1.1 kpc, the RGB tip is some 1.3 magnitudes fainter than it is at 7 kpc. An analysis of this difference in RGB tip magnitude suggests that the M31 bulge stellar population has a mean metallicity close to that of the Sun.

arXiv commentAccepted for publication in ApJ, June 20, 1999 issue

References in corpus (7)

• Maps of Dust IR Emission for Use in Estimation of Reddening and CMBR Foregrounds
• Hubble Space Telescope Observations of M32: The Color-Magnitude Diagram
• The Stellar Populations of Pixels and Frames
• Deep HST V- and I-Band Observations of the Halo of M31: Evidence for Multiple Stellar Populations
• Deep HST V- and I-Band Observations of Two Globular Clusters in the Halo of M31
• The Hubble Space Telescope Extragalactic Distance Scale Key Project. X. The Cepheid Distance to NGC 7331
• No Increase of the Red-Giant-Branch Tip Luminosity Toward the Center of M31

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• The Wendelstein Calar Alto Pixellensing Project(WeCAPP): First MACHO Candidates
• The Metallicity Distribution Function of Field Stars in M31's Bulge
• The Star Formation Histories of the Bulge and Disk of M31 from Gemini North+NIRI/Altair and HST/NICMOS
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• The Angstrom Project: a microlensing survey of the structure and composition of the bulge of the Andromeda galaxy
• The Brightest AGB Stars in the Inner Bulge of M31
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• The Wendelstein Calar Alto Pixellensing Project (WeCAPP): The M31 Variable Star Catalogue
• HST-NICMOS Observations of M31's Metal Rich Globular Clusters and Their Surrounding Fields: II. Results
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• Cluster-Cluster Microlensing as a Probe of Intracluster Stars, MACHOs, and Remnants of the First Generation Stars
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