INFRARED SURFACE BRIGHTNESS FLUCTUATIONS - K'-BAND OBSERVATIONS OF M31, M32, AND THE DISTANCE TO MAFFEI-1

We have taken 2.1 mum infrared K'-band images of the Local Group galaxies M31 and M32 and the nearby elliptical galaxy Maffei 1 using a 256 x 256 pixel HgCdTe infrared array. Measurement of the amplitude of the K'-band surface brightness fluctuations (SBFs) for M31 has enabled us to calibrate the K'-band fluctuations absolute magnitude, M(K')BAR, -5.61 +/- 0.09, taking M31 to be 0.77 Mpc distant. This agrees with theoretical predictions. The exceptional brightness of M(K')BAR, combined with the extremely red color of the fluctuations compared to background globular clusters and galaxies [(M(V)BAR - M(K')BAR) approximately 7 whereas (V - K')bkgnd approximately 31, suggests that K'-band SBF can be used out to much greater distances than optical 1-band SBFs, although we find that K'BAR may be more sensitive to stellar populations, and is anomalously bright in M32 if M32 is at the same distance as M31. Using our value for M(K')BAR in M31, we have determined the distance to Maffei 1, an elliptical galaxy that lies at low galactic latitude and is heavily obscured by dust. We measure a distance modulus of 28.1 +/- 0.25 corresponding to a distance of d(SBF) = 4.2 +/- 0.5 Mpc. We find a gradient in K'BAR with radius whereby the fluctuation amplitude increases by about 0.13 mag per factor of 2 increase in radius. Our infrared images allow the first accurate determination of the Hubble type for Maffei 1 which we find to be a true giant elliptical (E4) with a total K' absolute magnitude of M(K')TBAR = -24.25 corresponding to about 1 L*, consistent with its velocity dispersion. We have also determined the distance to Maffei 1 using the technique D(n)-sigma and find d(Dnsigma) = 4.2 +/- 1.1 Mpc (assuming H0 = 80 km s-1 Mpc-1), in close agreement with the SBF distance. Our distance of 4.2 Mpc places Maffei 1 well outside the boundary of the Local Group and indicates that Maffei 1 plays no role in Local Group dynamics.