Alpha Enhancement and the Metallicity Distribution Function of Plaut's Window

Abstract

We present Fe, Si, and Ca abundances for 61 giants in Plaut's Window (l=-1,b=-8.5) and Fe abundances for an additional 31 giants in a second, nearby field (l=0,b=-8) derived from high resolution (R~25,000) spectra obtained with the Blanco 4m telescope and Hydra multifiber spectrograph. The median metallicity of red giant branch (RGB) stars in the Plaut field is ~0.4 dex lower than those in Baade's Window, and confirms the presence of an iron abundance gradient along the bulge minor axis. The full metallicity range of our (biased) RGB sample spans -1.5<[Fe/H]<+0.3, which is similar to that found in other bulge fields. We also derive a photometric metallicity distribution function for RGB stars in the (l=-1,b=-8.5) field and find very good agreement with the spectroscopic metallicity distribution. The radial velocity and dispersion data for the bulge RGB stars are in agreement with previous results of the BRAVA survey, and we find evidence for a decreasing velocity dispersion with increasing [Fe/H]. The [alpha/Fe] enhancement in Plaut field stars is nearly identical to that observed in Baade's window, and suggests that an [alpha/Fe] gradient does not exist between b=-4 and -8. Additionally, a subset of our sample (23 stars) appear to be foreground red clump stars that are very metal--rich, exhibit small metallicity and radial velocity dispersions, and are enhanced in alpha elements. While these stars likely belong to the Galactic inner disk population, they exhibit [alpha/Fe] ratios that are enhanced above the thin and thick disk.

Accepted for publication in ApJ. 38 pages, 11 figures, and 2 tables. Requests for higher resolution figures and electronic versions of tables 1 and/or 2 in advance of publication may be sent to cijohnson[at]astro.ucla.edu

References in corpus (15)

• alpha-, r-, and s-process element trends in the Galactic thin and thick disks
• Chemical Abundances for 855 Giants in the Globular Cluster Omega Centauri (NGC 5139)
• Oxygen, Sodium, Magnesium and Aluminium as tracers of the Galactic Bulge Formation
• Chemical similarities between Galactic bulge and local thick disk red giant stars
• Stellar Proper Motions in the Galactic Bulge from deep HST ACS/WFC Photometry
• Insights on the Milky Way bulge formation from the correlations between kinematics and metallicity
• Kinematics at the Edge of the Galactic Bulge: Evidence for Cylindrical Rotation
• The Bulge Radial Velocity Assay (BRAVA): I. Sample Selection and a Rotation Curve
• Chemical Evolution of the Galactic Bulge as Derived from High-Resolution Infrared Spectroscopy of K and M Red Giants
• Formation & evolution of the Galactic bulge: constraints from stellar abundances
• The First Detailed Abundances for M giants in the inner Bulge from Infrared Spectroscopy
• High resolution infrared spectroscopy of the old open cluster NGC6791
• Fe and Al Abundances for 180 Red Giants in the Globular Cluster Omega Centauri (NGC 5139)
• Proper Motions in the Galactic Bulge: Plaut's Window
• The Extinction Toward the Galactic Bulge from RR Lyrae Stars

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