Sign on

SAO/NASA ADS Astronomy Abstract Service

· Find Similar Abstracts (with default settings below)
· Electronic Refereed Journal Article (HTML)
· Full Refereed Journal Article (PDF/Postscript)
· arXiv e-print (arXiv:astro-ph/0112414)
· On-line Data
· References in the article
· Citations to the Article (21) (Citation History)
· Refereed Citations to the Article
· SIMBAD Objects (9)
· Also-Read Articles (Reads History)
·
· Translate This Page
Title:
A Proper-Motion Survey for White Dwarfs with the Wide Field Planetary Camera 2
Authors:
Nelson, C. A.; Cook, K. H.; Axelrod, T. S.; Mould, J. R.; Alcock, C.
Affiliation:
AA(Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, CA 94550; , .; Department of Physics, University of California, Berkeley, CA 94720.), AB(Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, CA 94550; , .; Center for Particle Astrophysics, University of California, 301 Le Conte Hall, Berkeley, CA 94720.), AC(Research School of Astronomy and Astrophysics, Mount Stromlo Observatory, Cotter Road, Weston, ACT 2611, Australia; .), AD(National Optical Astronomy Observatory, 950 North Cherry Avenue, Tucson, AZ, 85726; .), AE(Center for Particle Astrophysics, University of California, 301 Le Conte Hall, Berkeley, CA 94720.; Department of Physics and Astronomy, University of Pennsylvania, Philadelphia, PA 19104-6396 .)
Publication:
The Astrophysical Journal, Volume 573, Issue 2, pp. 644-661. (ApJ Homepage)
Publication Date:
07/2002
Origin:
UCP
ApJ Keywords:
Cosmology: Dark Matter, Galaxy: Halo, Galaxy: Structure, Stars: White Dwarfs
DOI:
10.1086/340759
Bibliographic Code:
2002ApJ...573..644N

Abstract

We have performed a search for halo white dwarfs as high proper motion objects in a second-epoch Wide Field Planetary Camera 2 image of the Groth-Westphal strip. The survey covers 74.8 arcmin2 and is complete to V~26.5. We identify 24 high proper motion objects with μ>0.014" yr-1. Five of these high proper motion objects are identified as strong white dwarf candidates on the basis of their position in a reduced proper motion diagram. We also identify two marginal candidates whose photometric errors place them within ~1 σ of the white dwarf region of the reduced proper motion diagram. We create a model of the Milky Way thin disk, thick disk, and stellar halo and find that this sample of white dwarfs is clearly an excess above the <=2 detections expected from these known stellar populations. The origin of the excess signal is less clear. Possibly, the excess cannot be explained without invoking a fourth galactic component: a white dwarf dark halo. Previous work of this nature has separated white dwarf samples into various galactic components based on kinematics; distances, and thus velocities, are unavailable for a sample this faint. Therefore, we present a statistical separation of our sample into the four components and estimate the corresponding local white dwarf densities using only the directly observable variables, V, (V-I), and μ. For all Galactic models explored, our five white dwarf sample separates into about three disk white dwarfs and two halo white dwarfs. However, the further subdivision into the thin and thick disk and the stellar and dark halo, and the subsequent calculation of the local densities, are sensitive to the input parameters of our model for each Galactic component. Using the lowest mean mass model for the dark halo and the five white dwarf sample, we find n0,thindisk=2.4+0.7-0.6×10- 2 pc-3, n0,thickdisk=0.0+7.6×10-4 pc-3, n0,stellarhalo=0.0+7.7×10-5 pc-3, and n0,darkhalo=1.0+0.4-0.4×10- 3 pc-3. This implies a 7% white dwarf halo and 6 times the canonical value for the thin disk white dwarf density (at marginal statistical significance), but possible systematic errors due to uncertainty in the model parameters likely dominate these statistical error bars. The white dwarf halo can be reduced to ~1.5% of the halo dark matter by changing the initial mass function slightly. The local thin disk white dwarf density in our solution can be made consistent with the canonical value by assuming a larger thin disk scale height of 500 pc.
Bibtex entry for this abstract   Preferred format for this abstract (see Preferences)
   

Find Similar Abstracts:

Use: Authors
Title
Keywords (in text query field)
Abstract Text
Return: Query Results Return    items starting with number
Query Form
Database: Astronomy
Physics
arXiv e-prints