3 Distance discussion

The distance may be worth a special consideration, due to the role that it plays in Figs. 2 and 3. Some galaxies have relatively well-known distance, as NGC 224, NGC 598, IC 1613, WLM, Sext A of Local Group, or NGC 3109. For galaxies belonging to the M 81 group (NGC 2366, NGC 2403, NGC 3034, NGC 3077, NGC 4236, IC 2574 and HoII), the adopted distance is 3.25 Mpc. The Canes Venatici Group (NGC 4144, NGC 4258, NGC 4395, NGC 4449, NGC 4736, DDO 125) seems to be located between 4.5 and 7 Mpc, although the more generally accepted distance is 6.6 Mpc (adopted here). The galaxy belonging to the NGC 5128 group (NGC 5236) has an adopted distance of 4 Mpc. The M101 group (NGC 5055, NGC 5457 and NGC 5474) is located between 7 and 7.2 Mpc (the distance adopted here is 7 Mpc). For the Circinus galaxy, we adopt the value given by Freeman et al. (1977). The distance given in the literature for NGC 1560 varies between 2.9 and 3.7 Mpc; we adopt an intermediate value of 3.3 Mpc. For galaxies in the Virgo Cluster, even with low velocities, we adopt a distance of 16.8 Mpc. Sculptor group galaxies have been located by different authors between 1.6 and 3.5 Mpc (Huchtmeier & Seiradakis 1985; Carignan & Puche 1990; Puche et al. 1991; Hummel et al. 1986). Because of the contrast between nearest and furthest positions assumed for the galaxies of this Group (NGC 55 and NGC 247), we do not adopt any distance, but we kept the lower and higher values to estimate the parameters that depend on distance. This issue also happens for the galaxies: NGC 6946, DDO 154, IC 10, A0355+66, IC 342 and DDO 69 (Leo A). The remaining galaxies have velocities (referred to the Local Group) greater than 400 km s^-1, therefore we calculate their distances with the Hubble constant (H₀=75 Mpc/km s^-1).