Cepheids as tracers of star formation in M 31 ^*,**

I. Observations and identifications

¹ 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, U.S.A.
⁴ Astronomy Dept. 351580, University of Washington, Seattle, WA 98195, U.S.A.
⁵ Massachusetts Institute of Technology, Room 37-624, Cambridge, MA 02139, U.S.A.
⁶ European Southern Observatory, Casilla 19001, Santiago 19, Chile
⁷ Physics Department, University of Alabama in Huntsville, Huntsville, AL 35899, U.S.A.

Send offprint request to: E.A. Magnier

Received: 14 November 1996
Accepted: 2 April 1997

Abstract

Cepheid variables can be used for more than just a distance indicator. Since the age can be determined from the period, they can be used to trace the star formation history of a galaxy. We have identified 130 new Cepheid variable candidates in M 31, particularly along the spiral arm regions in the north-east of the galaxy. These areas had not been searched for Cepheids in the previous study by Baade and collaborators. The contamination of our sample by other types of variables is low (<3%). For , the completeness is ~ 53%. These Cepheids will be used to explore the star formation history in M 31.