Photometric properties of six Local Volume dwarf galaxies from deep near-infrared observations

Abstract

We have obtained deep near-infrared (NIR) J- (1.25 μm), H- (1.65 μm) and Ks-band (2.15 μm) imaging for a sample of six dwarf galaxies (MB≳−17 mag) in the Local Volume (LV; D≲ 10 Mpc). The sample consists mainly of early-type dwarf galaxies found in various environments in the LV. Two galaxies (LEDA 166099 and UGCA 200) in the sample are detected in the NIR for the first time. The deep NIR images allow for a detailed study of the photometric and structural properties of each galaxy. The surface brightness (SB) profiles of the galaxies are detected down to the ∼ 24 mag arcsec−2 isophote in the J and H bands, and 23 mag arcsec−2 in the Ks band. The total magnitudes of the galaxies are derived in the three wavelength bands. For the brightest galaxies (MB≲− 15.5 mag) in the sample, we find that the Two-Micron All-Sky Survey underestimates the total magnitudes of these systems by up to ≲0.5 mag. The radial SB profiles of the galaxies are fitted with an exponential (for those galaxies having a stellar disc) or Sérsic law to derive the structure of the underlying stellar component. In particular, the effective SB (μe) and effective radius (re) are determined from the analytic fits to the SB profile. The J−Ks colours for the galaxies have been measured to explore the luminosity–metallicity relation for early-type dwarfs. In addition, the B−Ks colours of the galaxies are used to assess their evolutionary state relative to other galaxy morphologies. The total stellar masses of the dwarf galaxies are derived from the H-band photometric measurements. These will later be compared to the dynamical mass estimates for the galaxies to determine their dark matter content.