CALIBRATION OF THE LUMINOSITY FUNCTION OF BRIGHT BLUE STARS AS A DISTANCE INDICATOR FOR LATE-TYPE GALAXIES

Published data for 38 galaxies are used to construct the differential luminosity functions of the brightest blue stars with (B-V)(0) < 0.4. The magnitude V(5)(0), for which the value of the luminosity function is equal to five stars in a 0(m).5 interval, is calibrated as a distan ce indicator. The calibration of the relation between the distance mod ulus (m-M)(0) and the total magnitude of the galaxy B(g)(0) and V(5)(0 ) is constructed for 15 nearby galaxies: (m-M)(0) = 1.08 - 0.87B(g)(0) + 1.85V(5)(0), sigma = 0(m).39. This calibration is applied to 27 oth er galaxies. For 18 dwarf galaxies, the distance moduli obtained by th e brightest-star and luminosity-function methods are in agreement with 0(m).35 accuracy. Dwarf galaxies with an excess (the LMC, NGC 2366, S extans A, GR 8, DDO 187) and a deficit (Sextans B, Pegasus) of blue st ars have been identified. In contrast to the brightest-star method, th e luminosity-function method is less sensitive to the presence of nons tellar and chance blue objects.