The Luminosity Function and Mass Function in the Galactic Bulge
Abstract
We present deep photometry obtained with the Hubble Space Telescope (HST) in a field in Baade's Window in the Galactic bulge. We derive a luminosity function down to I ~ 24.3, or V ~ 27.5, corresponding to M ~ 0.3 Msun. The luminosity function from the turnoff down to this level appears remarkably similar to that observed in the solar neighborhood. We derive a mass function using both an empirical local mass-luminosity relation and a mass-luminosity relation from recent stellar model calculations, allowing for the presence of binaries and photometric errors. The mass function has a power law form with dN/dM proportional to M^{-2.2} for M >~ 0.7 Msun. However, we find strong evidence for a break in the mass function slope around 0.5-0.7 Msun, with a significantly shallower slope at lower masses. The value of the slope for the low masses depends on the assumed binary fraction and the accuracy of our completeness correction. This mass function should directly reflect the initial mass function.
Keywords
Cite
@article{arxiv.astro-ph/9801321,
title = {The Luminosity Function and Mass Function in the Galactic Bulge},
author = {Jon A. Holtzman and Alan M. Watson and William A. Baum and Carl J. Grillmair and Edward J. Groth and Robert M. Light and Roger Lynds and Earl J. O'Neil},
journal= {arXiv preprint arXiv:astro-ph/9801321},
year = {2009}
}
Comments
26 pages, 9 figures, to be published in the Astronomical Journal