DEEP NEAR-INFRARED SURFACE PHOTOMETRY OF 57 GALAXIES IN THE LOCAL SPHERE OF INFLUENCE

We present H-band (1.65 mu m) surface photometry of 57 galaxies drawn from the Local Sphere of Influence (LSI), with distances of less than 10 Mpc from the Milky Way. The images, with a typical surface brightness limit 4 mag fainter than the Two Micron All Sky Survey (2MASS) (24.5 mag arcsec(-2) < mu(lim) < 26 mag arcsec-2), have been obtained with the Infrared Imager and Spectrograph 2 on the 3.9 m Anglo-Australian Telescope. A total of 22 galaxies that remained previously undetected in the near-infrared (NIR), and potentially could have been genuinely young galaxies, were found to have an old stellar population with a star density 1-2 mag below the 2MASS detection threshold. The cleaned NIR images reveal the morphology and extent of many of the galaxies for the first time. For all program galaxies, we derive radial luminosity profiles, ellipticities, and position angles, together with global parameters such as total magnitude, mean effective surface brightness, and half-light radius. Our results show that 2MASS underestimates the total magnitude of galaxies with eff between 18 and 21 mag arcsec(-2) by up to 2.5 mag. The Sersic parameters that best describe the observed surface brightness profiles are also presented. By adopting accurate galaxy distances and an H-band mass-to-light ratio of Gamma(H)(*) = 1.0 +/- 0.4, the LSI galaxies are found to cover a stellar-mass range of 5.6 < log(10)(M-stars) < 11.1. The results are discussed along with previously obtained optical data. Our sample of low-luminosity galaxies is found to closely follow the optical-infrared B-versus-H luminosity relation defined by brighter galaxies, with a slope of 1.14 +/- 0.02 and a scatter of 0.3 mag. Finally, we analyze the luminosity-surface brightness relation to determine an empirical mass-to-light ratio of Gamma(H)(*) = 0.78 +/- 0.08 for late-type galaxies in the H band.