The anomalous properties of Markarian 1460

We present and discuss optical, near-infrared and HI measurements of the galaxy Markarian 1460 at a distance of 19 Mpc in the Ursa Major Cluster. This low-luminosity (M_B = -14) galaxy is unusual because (i) it is blue (B-R=0.8) and has the spectrum of an HII galaxy, (ii) it has a light profile that is smooth and well fit by an r^{1/4} and not an exponential function at all radii larger than the seeing, and (iii) it has an observed central brightness of about mu_B = 20 mag arcsec^{-2}, intermediate between those of elliptical galaxies (on the bright mu_B side) and normal low-luminosity dwarf irregular (on the low mu_B side) galaxies. No other known galaxy exhibits all these properties in conjunction. On morphological grounds this galaxy looks like a normal distant luminous elliptical galaxy, since the fundamental plane tells us that higher luminosity normal elliptical galaxies tend to have lower surface-brightnesses. Markarian 1460 has 2 X 10^7 M_sun of HI and a ratio M(HI)/L_B of 0.2, which is low compared to typical values for star-forming dwarf galaxies. From the high surface brightness and r^{1/4} profile, we infer that the baryonic component of Markarian 1460 has become self-gravitating through dissipative processes. From the colours, radio continuum, HI and optical emission line properties, yet smooth texture, we infer that Markarian 1460 has had significant star formation as recently as about 1 Gyr ago but not today.