Astron. Astrophys. 326, 442-448 (1997)

Cepheids as tracers of star formation in M 31 ^*

II. NGC 206: evidence for spiral arm interactions

E.A. Magnier ^{1, 2, 3, 4, 5}, S. Prins ^{1, 2}, T. Augusteijn ^{1, 2, 6}, J. van Paradijs ^{1, 2, 7} and W.H.G. Lewin <sup>5

1</sup> Astronomical Institute "Anton Pannekoek", Kruislaan 403, 1098 SJ Amsterdam, The Netherlands
² Center for High Energy Astrophysics, Kruislaan 403, 1098 SJ Amsterdam, The Netherlands
³ University of Illinois, Astronomy Dept. Bldg. 103, 1002 W. Green St., Urbana, IL 61801, USA
⁴ Astronomy Dept. 351580, University of Washington, Seattle, WA 98195, USA
⁵ Massachusetts Institute of Technology, Room 37-624, Cambridge, MA 02139, USA
⁶ European Southern Observatory, Casilla 19001, Santiago 19, Chile
⁷ Physics Department, University of Alabama in Huntsville, Huntsville, AL 35899, USA

Received 14 November 1996 / Accepted 2 April 1997

Abstract

NGC 206 in the Andromeda Galaxy (M 31) is the largest and perhaps the most massive region in the Local Group with coherent star formation taking place on a timescale of 30 Myr. We have incorporated observations of the HI emission and blue stars with our new identifications of Cepheid variables and those from observations by Baade and collaborators to study the star formation history in this region in comparison with the rest of M 31. We find that NGC 206 represents the latest phase of an enhanced level of star formation in the southern region of M 31. NGC 206 is located at the intersection of two spiral arms, suggesting that the interaction between the spiral arms is responsible for the enhanced levels of star formation. The locations of the Cepheid variables demonstrate the motion of the interaction point. We find a relative velocity of 32 km sec^-1 between the velocity of the stars in M 31 and the velocity of the spiral arm pattern.

Key words: stars: variables: Cepheids stars: formation galaxies: individual: M 31 galaxies: stellar content cosmology: distant scale

* Based on observations made with the Isaac Newton Telescope operated on the island of La Palma by the Royal Greenwich Observatory in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canarias.

Send offprint requests to: E.A. Magnier (gene@astro.uva.nl)

SIMBAD Objects

Contents

• 1. Introduction
• 2. Galaxy texture
• 3. NGC 206 as a superassociation
• 4. Observational data
  • 4.1. Cepheids as age indicators
  • 4.2. Observations of Cepheids in M 31
• 5. NGC 206 as the result of an interaction
• Acknowledgements
• References

© European Southern Observatory (ESO) 1997

Online publication: October 15, 1997
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