The Extinction and Distance of Maffei 2 and a New View of the IC 342/Maffei Group

Abstract

We have obtained spectra of HII regions in the heavily obscured spiral galaxy Maffei 2. The observations have allowed for a determination of the Galactic extinction of this galaxy using a correlation between extinction and hydrogen column density observed among spirals. The technique reveals that the optical depth of Galactic dust at 1 µm obscuring Maffei 2 is τ 1 = 2.017 ± 0.211, which implies that A V = 5.58 ± 0.58 mag, significantly higher than observed for the giant elliptical Maffei 1 despite its similar latitude. For comparison, we apply the same technique to IC 342, a neighbouring spiral to Maffei 2 but with more moderate obscuration by Galactic dust, owing to its higher Galactic latitude. For this galaxy, we obtain τ 1 = 0.692 ± 0.066, which agrees within errors with the value of 0.639±0.102 derived from the reddening estimate of Schlegel et al. (1998). We therefore adopt the weighted mean of τ 1 = 0.677 ± 0.056 for the extinction of IC 342, which implies that A V = 1.92 ± 0.16 mag. A new distance estimate for Maffei 2 of 3.34±0.56 Mpc is obtained from a self-consistent Tully-Fisher relation in I adjusted to the NGC 4258 maser zero-point. With our new measurement of M I , Maffei 2 joins Maffei 1 and IC 342 as one of three giant members of the nearby IC 342/Maffei group of galaxies. We present the revised properties of all three galaxies based on the most accurate extinction and distance estimates to date, accounting for shifts in the effective wavelengths of broadband filters as this effect can be significant for highly reddened galaxies. The revised distances are consistent with what would be suspected for the Hubble Flow, making it highly unlikely that the galaxies interacted with the Local Group since the Big Bang.

An Hα Imaging Survey of Galaxies in the Local 11 Mpc Volume

“…We adopted independently measured foreground extinctions from the literature for three galaxies that lie near the Galactic plane (IC 10, Maffei 2, Circinus), because the Schlegel et al values become unreliable in these regions. Sources were Richer et al (2001) for IC 10, Fingerhut et al (2003Fingerhut et al ( , 2007 for Maffei 1 and 2, respectively, and Freeman et al (1977) for Circinus.…”

Spatially Resolved Chemistry in Nearby Galaxies. Ii. The Nuclear Bar in Maffei 2

“…The Sb galaxy Maffei 2 is one of the nearest and brightest extragalactic molecular line sources, at a distance of only 3.3 Mpc (1 ′′ ∼15 pc, Fingerhut et al 2007, see discussion in MTH08). A strongly barred and somewhat asymmetric galaxy, Maffei 2 has undergone a recent interaction with a small companion that has driven a large quantity of gas into the nucleus, building up a compact central bulge seen in the NIR (Hurt et al 1993(Hurt et al , 1996.…”

Dense gas in nearby galaxies

“…In addition, in peak B, which is close to the continuum emission peak, the NH 3 (2, 2) is seen in absorption against the 1.3 cm continuum in the velocity range between −20 and 100 km s −1 . Maffei 2 is located close to the Galactic plane and the line of sight material causes a visual extinction of 5.6 mag (Fingerhut et al 2007). The NH 3 absorption we observe is most likely from gas within Maffei 2 and not from intervening gas in our own Milky Way since a) the observed lines are much wider than a few km s −1 and b) the velocities expected from gas in this quadrant of the Milky Way would be at negative velocities.…”