Metallicities and ages of stellar populations at a high Galactic latitude field |
| |
| Authors: | Michael H Siegel Yüksel Karata&#; I Neill Reid |
| |
| Institution: | Pennsylvania State University, 525 Davey Laboratory, State College, PA 16801, USA;Istanbul University Science Faculty, Department of Astronomy and Space Sciences, 34119 University-Istanbul, Turkey;Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA |
| |
| Abstract: | We present an analysis of UBVRI data from the selected area SA 141. By applying recalibrated methods of measuring ultraviolet excess (UVX), we approximate abundances and absolute magnitudes for 368 stars over 1.3 deg2 out to distances over 10 kpc. With the density distribution constrained from our previous photometric parallax investigations and with sufficient accounting for the metallicity bias in the UVX method, we are able to compare the vertical abundance distribution to those measured in previous studies. We find that the abundance distribution has an underlying uniform component consistent with previous spectroscopic results that posit a monometallic thick disc and halo with abundances of Fe/H]=?0.8 and ?1.4, respectively. However, there are a number of outlying data points that may indicate contamination by more metal-rich halo streams. The absence of vertical abundance gradients in the Galactic stellar populations and the possible presence of interloping halo streams would be consistent with expectations from merger models of Galaxy formation. We find that our UVX method has limited sensitivity in exploring the metallicity distribution of the distant Galactic halo, owing to the poor constraint on the UBV properties of very metal-poor stars. The derivation of metallicities from broad-band UBV photometry remains fundamentally sound for the exploration of the halo but is in need of both improved calibration and superior data. |
| |
| Keywords: | stars: abundances stars: Population II Galaxy: evolution |
|
|
