1994A&A...289...39K

The structure of the halo of the dwarf irregular galaxy MCG 06-30-025 is here investigated using data from a co-added array of digitised Schmidt plates. MCG 06-30-025 is a probable member of the NGC 5128 (Centaurus A) group of galaxies, at a distance of about 5 Mpc. Its inner regions show traces of spiral structure. Normal and high-contrast images of this galaxy are presented. The halo of MCG 06-30-025 is seen to have a diameter of at least 10 kpc. Ellipses were fitted to the isophotes of this galaxy. The equivalent radius surface brightness profile of MCG 06-30-025 is of an exponential disk form, with possible flattening at the faintest levels (∼2% of the sky brightness). The position angle of the major axis of this galaxy changes from ∼100deg in the central regions to ∼40deg for the outer isophotes. At an equivalent radius of about 5 kpc the ellipticity of the halo of MCG 06-30-025 is about 0.025. The very irregular central regions of this galaxy may then be embedded in an extensive fairly spherical halo. The SMC appears to have a similar general structure, with its young irregularly-distributed populations being in the central regions, and its older populations having a spheroidal, less centrally-concentrated distribution. The age distribution of the populations of MCG 06-30-025 may be similar to that of the SMC.