Studies of Hot B Subdwarfs. XI. A Redetermination of the Density of Hot, Hydrogen-rich Subdwarfs in the Galactic Plane
Abstract
We have reanalyzed the statistical properties of the sample of hydrogen-rich hot subdwarfs identified in the Kitt Peak-Downes survey in order to derive an improved value of the density D0 of these stars in the plane of the Galaxy. Our analysis is based on photoelectric Strömgren photometry for 22 of these stars, all brighter than V ∼ 15.0. The value of the average absolute magnitude of the KPD objects we redetermine is at least 1 mag brighter than that derived in the initial investigation. Three methods are then considered to derive D0, under the assumption of an exponential distribution of stars in the direction perpendicular to the Galactic plane: fits to the number of stars as a function of apparent brightness and as a function of vertical distance above the plane, as well as the 1/V'm method. We find that the distribution of hot, hydrogen-rich subdwarf stars can be satisfactorily reproduced with a midplane space density D0 = 3.8 ±1.7 × 10-7 pc-3, a factor of ∼5 lower than initial estimates, but in agreement with the recent determination of Villeneuve et al. based on the Palomar-Green sample at high galactic latitudes.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- September 1995
- DOI:
- 10.1086/176189
- Bibcode:
- 1995ApJ...450..851V
- Keywords:
-
- STARS: EARLY-TYPE;
- STARS: STATISTICS;
- STARS: SUBDWARFS