The ARAUCARIA project. Discovery of Cepheid Variables in NGC 300 from a Wide-Field Imaging Survey

Abstract

Based on observations of NGC 300, obtained with the Wide-Field Camera at the 2.2 m ESO/MPI telescope during 29 nights spread over a 5.3 month interval, 117 Cepheids and 12 Cepheid candidates were found which cover the period range from 115 to 5.4 days. We present a catalog which provides equatorial coordinates, period, time of maximum brightness, and intensity mean B and V magnitudes for each variable, and we show phased B and V light curves for all the Cepheids found. We also present the individual B and V observations for each Cepheid in our catalog. We find very good agreement between our photometry and that obtained by Freedman et al. from ground-based CCD data for common stars. The Cepheids delineate the spiral arms of NGC 300, and a couple of them were detected very close to the center of the galaxy. From the color-magnitude diagram of NGC 300 constructed from our data, we expect that our Cepheid detection is near-complete for variables with periods larger than about 10 days. We present plots of the PL relations in the B and V bands obtained from our data, which clearly demonstrate the presence of a Malmquist bias for periods below about 10 days. A thorough discussion of the distance to NGC 300 will be presented in a forthcoming paper which will include the analysis of photometry in longer-wavelength bands.