The energetics and mass loss of the dwarf starburst Markarian 33

We present ROSAT HRI X-ray data and optical imaging of the important dwarf starburst Markarian 33. We find an extended, complex, shell-like morphology in the X-ray emission, with an extent of ~2.3×1.9kpc², coincident with the bright star-forming regions at the centre of the galaxy. The physical extent of this X-ray emission from Mrk 33 is very similar to the observed Hα emission, and suggests that the bulk of the X-ray emission is coming from an expanding superbubble. We estimate the age and mass of Mrk 33's starburst to be 5.8Myr and 6.9×10⁶M_solar respectively, with the energy injection rate in the central regions of the galaxy being ~10⁴¹ergs^-1, while the associated mass-loss rate from the star-forming regions is estimated to be ~0.2M_solaryr^-1. We suggest that the X-ray emission is predominantly powered by starburst-type activity, and argue that a blow-out in the form of a galactic wind is the most likely fate for Mrk 33, resulting in the loss of most of the galaxy's metal-enriched material and a small fraction (<1 per cent) of the ISM.