No abstract

We have obtained low-and high-resolution spectra of the core of the highly reddened elliptical galaxy Maffei 1. From these data, we have obtained the first measurement of the Mg 2 index and have measured the velocity dispersion and radial velocity with improved accuracy. To evaluate the extinction, a correlation between the Mg 2 index and effective VÀI color has been established for elliptical galaxies. Using a new method for correcting for effective wavelength shifts, the VÀI color excess reveals that the optical depth of Galactic dust at 1 lm is 1:69 AE 0:07. Thus, A V ¼ 4:67 AE 0:19 mag, which is lower by 0.4 mag than previously thought. To establish the distance, the fundamental plane for elliptical galaxies has been constructed in I. The velocity dispersion of Maffei 1, measured to be 186:8 AE 7:4 km s À1 , in combination with modern widefield photometry in I, leads to a distance of 2:92 AE 0:37 Mpc. The D n -relation, which is independently calibrated, gives 3:08 AE 0:85 and 3:23 AE 0:67 Mpc from photometry in B and K 0 , respectively. The weighted mean of the three estimates is 3:01 AE 0:30 Mpc, which is lower than distances judged with reference to M32 and the bulge of M31 from the brightest stars seen at K 0 . Since the luminosity of asymptotic giant branch stars at K 0 is strongly dependent on age, the lower distance suggests that the last epoch of star formation in Maffei 1 occurred farther in the past than in these other systems. The distance and luminosity make Maffei 1 the nearest giant elliptical galaxy. In the absence of extinction, the galaxy would be among the brightest in the sky and would have an apparent size 2 3 that of the full Moon. The radial velocity of Maffei 1 is +66:4 AE 5:0 km s À1 , significantly higher than the accepted value of À10 km s À1 . The Hubble distance corresponding to the mean velocity of Maffei 1, Maffei 2, and IC 342 is 3.5 Mpc. Thus, it is unlikely that Maffei 1 has had any influence on Local Group dynamics.

Aims. Star-forming dwarfs are studied to elucidate the physical underpinnings of their fundamental plane. Processes controlling dynamics are evaluated, connections between quiescent and bursting dwarfs are examined, and the viability of using structural properties of dwarfs to determine distances is assessed. Methods. Deep surface photometry in K s is presented for 19 star-forming dwarfs. The data are amalgamated with previously published observations to create a sample of 66 galaxies suitable for exploring how global properties and kinematics are connected. Results. It is confirmed that residuals in the Tully-Fisher relation are correlated with surface brightness, but that even after accomodating the surface brightness dependence through the dwarf fundamental plane, residuals in absolute magnitude are far larger than expected from observational errors. Rather, a more fundamental plane is identified which connects the potential to HI line width and surface brightness. Residuals correlate with the axis ratio in a way which can be accommodated by recognizing the galaxies to be oblate spheroids viewed at varying angles. Correction of surface brightnesses to face-on leads to a correlation among the potential, line width, and surface brightness for which residuals are entirely attributable to observational uncertainties. The mean mass-to-light ratio of the diffuse component of the galaxies is constrained to be 0.88±0.20 in K s . Blue compact dwarfs lie in the same plane as dwarf irregulars. The dependence of the potential on line width is less strong than expected for virialized systems, but this may be because surface brightness is acting as a proxy for variations in the mass-to-light ratio from galaxy to galaxy. Altogether, the observations suggest that gas motions are predominantly disordered and isotropic, that they are a consequence of gravity, not turbulence, and that the mass and scale of dark matter haloes scale with the amount and distribution of luminous matter. The tight relationship between the potential and observables offers the promise of determining distances to unresolved star-forming dwarfs to an accuracy comparable to that provided by the Tully-Fisher relation for spirals.

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.

We present deep near-infrared (K s ) images and surface photometry for 80 dwarf irregular galaxies (dIs) within ∼5 Mpc of the Milky Way. The galaxy images were obtained at five different facilities between 2004 and 2006. The image reductions and surface photometry have been performed using methods specifically designed for isolating faint galaxies from the high and varying near-infrared sky level. Fifty-four of the 80 dIs have surface brightness profiles which could be fit to a hyperbolic-secant (sech) function, while the remaining profiles could be fit to the sum of a sech and a Gaussian function. From these fits, we have measured central surface brightnesses, scale lengths, and integrated magnitudes. This survey is part of a larger study of the connection between largescale structure and the global properties of dIs, the hypothesized building-blocks of more massive galaxies.