Astron. Astrophys. 364, 455-466 (2000)

Reddenings and metallicities in the LMC and SMC from Strömgren CCD photometry ^* **

S.S. Larsen ^1,2, J.V. Clausen ¹ and J. Storm <sup>3

1</sup> Niels Bohr Institute for Astronomy, Physics and Geophysics, Astronomical Observatory, Juliane Maries Vej 30, 2100 Copenhagen O, Denmark (jvc@astro.ku.dk)
² University of California, UC Observatories / Lick Observatory, Santa Cruz, CA 95064, USA (soeren@ucolick.org)
³ Astrophysikalisches Institut Potsdam, An der Sternwarte 16, 14482 Potsdam, Germany (jstorm@aip.de)

Received 25 May 2000 / Accepted 11 October 2000

Abstract

The individual reddenings for B stars in two fields in the Small Magellanic Cloud (SMC) and two fields in the Large Magellanic Cloud (LMC) are determined by means of Strömgren uvby CCD photometry. In both LMC fields we find a foreground reddening of , and for the SMC fields we find . In addition to the foreground reddening we find contributions from reddening intrinsically in the Clouds up to . The intrinsic contribution is not correlated with position within our CCD fields but varies in an essentially random way. Unless the reddening is measured for a particular object, it will be uncertain by (best case, far from the central bars) to more than (close to the central bars).

The Strömgren vby photometry has been used to derive metallicities for GK giant stars in the observed fields. Adopting average reddenings we obtain mean metallicities which are consistent with those found from spectroscopic studies of F and G supergiants (Westerlund 1997), but with a considerable scatter in the derived metallicities, from [Fe/H] to [Fe/H] . A significant fraction of the scatter is, however, due to reddening variations rather than being intrinsic. The possible existence of high metallicity stars should be investigated further using spectroscopic methods.

Key words: galaxies: abundances galaxies: ISM galaxies: Magellanic Clouds galaxies: photometry

* Based on observations carried out with the Strömgren Automatic Telescope (SAT) and the Danish 1.54 meter telescope at ESO, La Silla
** The CCD uvby photometry is available in electronic form at the CDS via anonymous ftp to 130.79.128.5 or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/364/455 .

Send offprint requests to: S.S. Larsen

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Contents

• 1. Introduction
• 2. Observations and reductions
• 3. Reddenings
  • 3.1. Reddenings from Strömgren photometry
  • 3.2. Selection of B stars
  • 3.3. Foreground reddening
  • 3.4. The correlation of reddening with position.
  • 3.5. Discussion of reddenings
• 4. Metallicities
  • 4.1. Metallicities for GK giants
  • 4.2. Investigating the effect of reddening
  • 4.3. Ages
• 5. Summary and conclusions
• Acknowledgements
• References

© European Southern Observatory (ESO) 2000

Online publication: January 29, 2001
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