Distances to nearby galaxies around IC 342

Abstract

We present an analysis of Hubble Space Telescope/WFPC2 images of six nearby galaxies in the projected vicinity of IC 342: Cas dSph, KK 35, UGCA 86, Cam A, NGC 1560, and Cam B. We derive distances to five of them from the luminosity of the tip of the red giant branch stars with a typical accuracy of ∼10%. The galaxy distances are 0.79 Mpc (Cas dSph), 3.16 Mpc (KK 35), 3.93 Mpc (Cam A), 3.45 Mpc (NGC 1560), and 3.34 Mpc (Cam B). Two other observed galaxies, MB 2 and Cam C = KK 26, turn out to be Galactic cirrus and a Galactic H II region, respectively. Cas dSph belongs to the Local Group and is a companion of M 31. Combining our data with literature results, we find that there are seven dwarf galaxies associated with the giant spiral galaxy IC 342. This group is characterized by an average distance of (3.28 ± 0.15) Mpc, an average radial velocity of (229 ± 23) km s-1, a projected radius of 322 kpc, a radial velocity dispersion of 60 km s-1, and a total blue luminosity of 3.43 × 1010 L⊙. The derived virial and orbital mass-to-luminosity ratios are 20 and 28 M⊙/L⊙, respectively. The galaxy group around Maffei 1 has so far a less reliable distance of ∼ 3.0 Mpc and an average radial velocity of (309 ± 22) km s-1. This group consists of eight galaxies and is characterized by a projected radius of 112 kpc, a radial velocity dispersion of 59 km s-1, and a total blue luminosity of 2.97 × 1010 L⊙. For the Maffei group we estimate mass-to-light ratios of Mvir/LB = 16 and Morb/LB = 5 in solar units. The sum of the virial (119 × 1010 M⊙) and orbital (109 × 1010 M⊙) masses of both groups agree well with their total mass, (107 ± 33) 1010 M⊙, derived from the radius of the "zero velocity surface", R0 = (0.9 ± 0.1) Mpc, which separates the IC 342/Maffei complex from the Hubble flow.