Distance to M31 with the Hubble Space Telescope and Hipparcos red clump stars

摘要

Following the approach by Paczynski & Stanek, we compare the red clump stars with parallaxes known to better than 10/100 in the Hipparcos catalog with the red clump stars observed in three fields in M31 using the Hubble Space Telescope. There are ～600 and ～6300 such stars in the two data sets, respectively. The local red Clump luminosity function is well represented by a Gaussian with the peak at M_I,m = -0.23 and the dispersion σ_RC ≈0.2 mag. This allows a single-step determination of the distance modulus to M31, μ_0,M31 = 24.471± 0. 035±0.045 mag(statistical plus systematic error), and the corresponding distance, R_M31 = 784±13±17 kpc.