The galactic extinction towards Maffei 1

The extinction of Maffei 1 has been measured by two new techniques. First, BV aperture photometry has been performed to obtain the colour excess from standard aperture–colour relations for early-type galaxies. Secondly, millimetre and radio observations of galactic CO and H I have been used to calculate the total hydrogen column density along the line-of-sight, and thereby estimate the colour excess from the local dust-to-gas ratio. After consideration of all extinction measurements to date, it is concluded that A_v= 5.1 ± 0.2 mag. The isophotal diameter and the corrected apparent visual magnitude are estimated to be ∼ 15 arcmin and ∼ 6.3 respectively (assuming type E), making Maffei 1 one of the biggest and brightest galaxies in the sky. The distance is found to be $$2.1^{+1.3}_{-0.8}$$ Mpc, indicating that Maffei 1 is probably associated with the Ursa Major–Camelopardalis cloud, not the Local Group. The primary source of error in the distance is now the uncertainty in the central velocity dispersion.