DIRECT Distances to Local Group Galaxies

The two nearby galaxies, M31 and M33, are stepping stones for most of our current efforts to understand the evolving universe at large scales. We are undertaking a long term project, called DIRECT, to improve the direct distance estimate to M31 and M33. The massive photometry we have obtained as part of our project over the past 3 years provides us with very good light curves for known and new Cepheid variables, a large number of eclipsing binaries and other variable stars. 1. Distances to Local Group Galaxies The distances to nearby Local Group galaxies are not known very well, especially with the new demands of extragalactic stellar astrophysics which are only likely to increase with the advent of several 8-m class telescopes (e.g., Aparicio, Herrero, & Sanchez 1998). Nearby galaxies are also crucial calibrators to techniques for establishing the extragalactic distance scale and determining the value of H0 (Mould et al. 1999). Two important spiral galaxies in our nearest neighbourhood are M31 and M33. Yet, their distances are now known to no better than 10-15%, as there are discrepancies of 0.2 − 0.3 mag between various distance indicators (e.g. Huterer, Sasselov & Schechter 1995; Holland 1998; Stanek & Garnavich 1998) (see Fig. 1). Direct distances to M31 and M33 are now achieveable, by the use of geometric techniques, with detached eclipsing binaries and Cepheids, and the use of 8−10-m class telescopes for the required spectroscopy. Such direct distances are the ultimate goal of project DIRECT, which we started three years ago (Kaluzny et al. 1998, 1999; Stanek et al. 1998, 1999). The identification of variables suitable for direct study was accomplished by massive photometry; much of it still continues. In this review I describe some results from the massive photometry by project DIRECT in M31 and M33.