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 similar to 2.3 x 1.9 kpc(2), 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 H alpha 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 5.8 Myr and 6.9 x 10(6) M-. respectively, with the energy injection rate in the central regions of the galaxy being similar to 10(41) erg s(-1), while the associated mass-loss rate from the star-forming regions is estimated to be similar to0.2 M-. yr(-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.