Journal Article

Disentangling the Galaxy at low Galactic latitudes

M. Cignoni, M. Tosi, A. Bragaglia, J. S. Kalirai and D. S. Davis

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 386, issue 4, pages 2235-2241
Published in print June 2008 | ISSN: 0035-8711
Published online April 2008 | e-ISSN: 1365-2966 | DOI:
Disentangling the Galaxy at low Galactic latitudes

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We have used the field stars from the open cluster survey BOCCE (Bologna Open Clusters Chemical Evolution), to study three low-latitude fields imaged with the Canada–France–Hawaii telescope (CFHT), with the aim of better understanding the Galactic structure in those directions. Because of the deep and accurate photometry in these fields, they provide a powerful discriminant among Galactic structure models. In the present paper we discuss if a canonical star count model, expressed in terms of thin and thick disc radial scales, thick disc normalization and reddening distribution, can explain the observed colour–magnitude diagrams (CMDs). Disc and thick disc are described with double exponentials, the spheroid is represented with a De Vaucouleurs density law. In order to assess the fitting quality of a particular set of parameters, the colour distribution and luminosity function of synthetic photometry is compared to that of target stars selected from the blue sequence of the observed CMDs. Through a Kolmogorov–Smirnov test, we find that the classical decomposition halo-thin/thick disc is sufficient to reproduce the observations – no additional population is strictly necessary. In terms of solutions common to all three fields, we have found a thick disc scalelength that is equal to (or slightly longer than) the thin disc scale.

Keywords: Hertzsprung–Russell (HR) diagram; dust, extinction; Galaxy: disc; Galaxy: stellar content; Galaxy: structure

Journal Article.  4743 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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