Galactic structure studies with BATC star counts

Free access article

Issue		A&A Volume 407, Number 2, August IV 2003


Page(s)		541 - 549
Section		Stellar clusters and associations
DOI		http://dx.doi.org/10.1051/0004-6361:20030532

A&A 407, 541-549 (2003)
DOI: 10.1051/0004-6361:20030532

Galactic structure studies with BATC star counts

Cuihua Du¹, Xu Zhou¹, Jun Ma¹, Alfred Bing-Chih Chen², Yanbin Yang¹, Jiuli Li¹, Hong Wu¹, Zhaoji Jiang¹ and Jiansheng Chen¹

¹ National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012, PR China
e-mail: dch@vega.bac.pku.edu.cn
² Department of Physics, National Cheng Kung University, Taiwan 70148, Taiwan

(Received 16 January 2003/ Accepted 21 March 2003)

Abstract
We report the first results of star counts carried out with the National Astronomical Observatories (NAOC) 60/90 cm Schmidt Telescope in 15 intermediate-band filters from 3000 to 10 000 Å in the BATC survey. We analyze a sample of over 1400 main sequence stars ( $14\le V\le21$ ), which lie in the field with central coordinates ${\rm RA=09^h53^m13^s{\mbox{} .}30}$ and ${\rm Dec}=47^\circ49^{\prime}00^{\prime\prime}{\mbox{} .0}$ (J2000) (Galactic coordinates: $l=169.95^{\circ}, b=49.80^{\circ}$ ). The field of view is 0.95 deg ², and the spatial scale was $1\arcsec{\mbox{} .}67$ . Since star counts at high galactic latitudes are not strongly related to the radial distribution, they are well suited to study the vertical distribution of the Galaxy. In our model, the distribution of stars perpendicular to the plane of the Galaxy is given by two exponential disks (thin disk plus thick disk) and a de Vaucouleurs halo. Also, based on star counts, we derive the scale heights of the thin disk to be 320⁺¹⁴_-15 pc and of the thick disk to be 640⁺³⁰_-32 pc, respectively, with a local density of $7.0\pm1\%$ of the thin disk. The errors of scale heights and the corresponding space number density normalization are estimated at a $68\%$ confidential level. The density law for the Galactic halo population is also investigated. We find that the observed counts support an axial ratio of $c/a\le0.6$ for a de Vaucouleurs r^1/4 law, implying a more flattened halo. We consider that it is possible that the halo has two subpopulations-a flattened inner halo and a spherical outer halo in the Milky Way, and such a halo model might resolve many of the divergences in star count results. We also derive the stellar luminosity function (SLF) for the thin disk, and it partly agrees with the Hipparcos luminosity function.

Key words: Galaxy: structure -- stars: luminosity function, mass function

Offprint request: Cuihua Du, dch@vega.bac.pku.edu.cn

SIMBAD Objects

What is OpenURL?

The OpenURL standard is a protocol for transmission of metadata describing the resource that you wish to access. An OpenURL link contains article metadata and directs it to the OpenURL server of your choice. The OpenURL server can provide access to the resource and also offer complementary services (specific search engine, export of references...). The OpenURL link can be generated by different means.

If your librarian has set up your subscription with an OpenURL resolver, OpenURL links appear automatically on the abstract pages.
You can define your own OpenURL resolver with your EDPS Account. In this case your choice will be given priority over that of your library.
You can use an add-on for your browser (Firefox or I.E.) to display OpenURL links on a page (see http://www.openly.com/openurlref/). You should disable this module if you wish to use the OpenURL server that you or your library have defined.