Cepheids as tracers of star formation in M 31. I. Observations and identifications

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 V < 21, the completeness is ~53%. These Cepheids will be used to explore the star formation history in M 31. 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. Table 1 and Figures 5 to 10 are only available in electronic form at CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or vai http://cdsweb.u-strasbg.f/Abstract.html