Shoko Sakai et al. 1997 ApJ 478 49 doi:10.1086/303768
Shoko Sakai1, Barry F. Madore2, Wendy L. Freedman3, Tod R. Lauer4, Edward A. Ajhar4 and William A. Baum5
Show affiliationsWe report the detection of individually resolved stars in the elliptical galaxy NGC 3379, a luminous member of the Leo I Group. The bright end of the stellar luminosity function has a logarithmic slope that is consistent with these stars being Population II red giants. An abrupt discontinuity in the apparent luminosity function at I = 26.30 ± 0.09 mag is identified with the tip of the first-ascent red giant branch (TRGB). Adopting MI(TRGB) = -4.0 ± 0.1 mag gives a distance modulus of 30.30 mag ± 0.14 (random errors) ± 0.23 (systematic errors) corresponding to a linear distance to NGC 3379 of 11.5 ± 1.6 Mpc. The TRGB distance compares very well with the Cepheid distance of 11.9 ± 0.9 Mpc (30.37 ± 0.16 mag) to another group member M96 (=NGC 3368). The distance to NGC 3379 can be used in turn to calibrate the zero points of four other distance indicators: surface brightness fluctuations, planetary nebula luminosity functions, globular cluster luminosity functions and the Dn - σ method. We apply two approaches to measuring the Hubble constant: (1) using a simple Virgocentric infall model and (2) stepping out from Leo I to the Coma cluster using the previously measured relative distance between the two clusters. These give values of the Hubble constant in the range H0 = 60-68 km s-1 Mpc-1, each having a 20% uncertainty. The largest systematic errors could potentially increase this value to H0 = 74 ± 14 km s-1 Mpc-1.
galaxies: distances and redshifts; galaxies: individual (M105); galaxies: stellar content; stars: AGB and post-AGB
Issue 1 (1997 March 20)
Received 1996 June 13, accepted for publication 1996 October 11
Shoko Sakai et al. 1997 ApJ 478 49