Star formation in the blue compact dwarf Mrk 900

We disentangle two different stellar components in Mrk 900: a young population, which resolves into individual stellar clusters with ages ~5.5-6.6Myr and extends about 1 kpc along the galaxy minor axis, is placed on top of a rather red and regular shaped underlying stellar host, several Gyr old. We find evidence of a substantial amount of dust and an inhomogeneous extinction pattern, with a dust lane crossing the central starburst.

Mrk 900 displays overall rotation, although distorted in the central, starburst regions; the dispersion velocity map is highly inhomogeneous, with values increasing up to 60km/s at the periphery of the SF regions, where we also find hints of the presence of shocks. Our observational results point to an interaction or merger with a low-mass object or infalling gas as plausible trigger mechanisms for the present starburst event.