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Deep Multi-Colour Starcounts

Published online by Cambridge University Press:  26 July 2016

I.N. Reid
Affiliation:
Palomar Observatory, California Institute of Technology, Pasadena, CA 91125, U.S.A.
S.R. Majewski
Affiliation:
Observatories of the Carnegie Institute of Washington, Santa Barbara Street, Pasadena, CA 91101-1292, U.S.A.

Extract

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Starcounts remain one of the most effective methods of probing the structure of the Galactic stellar populations. However, studies of the distribution at large distances above the Plane demand accurate photometry extending to faint magnitudes (V > 20), and such datasets are still rare. We (Reid & Majewski 1993) have analyzed data from one field — Majewski's (1992) UJF observations of SA57, the North Galactic Pole field. Our results revealed significant discrepancies with the standard model of the Galaxy (see refs. in Reid & Majewski), notably a paucity in the number of halo stars by a factor of two and the presence of a factor of two more disk stars than predicted — sufficient stars that the disk is the majority stellar population, outnumbering halo stars 2:1 even at V = 21. Majewski et al. (1993) has obtained UJFN photographic data for several other fields, and Fig. 1 shows a preliminary comparison of these observations with the predictions of the best-fitting SA57 model. Given that none of the parameters have been modified, the agreement is surprisingly good.

Type
Part Nine: Galactic Structure
Copyright
Copyright © Kluwer 1994 

References

Gilmore, G.F. and Reid, I.N., 1983. Mon. Not. R. astron. Soc., 202, 1025.CrossRefGoogle Scholar
Majewski, S.R., 1992. Astrophys. J. Suppl., 78, 76.Google Scholar
Majewski, S.R., Reid, I.N., Kron, R.G., Munn, J.A. and Koo, D.C., 1994. In preparation.Google Scholar
Reid, I.N. and Majewski, S.R., 1993. Astrophys. J., 409, 635.CrossRefGoogle Scholar