Hubble Space Telescope WFPC2 and VLA observations of the ionized gas in the dwarf starburst galaxy NGC 4214

We present new Ha and [O III] lambda 5007 narrowband images of the starburs ting dwarf galaxy NGC 4214, obtained with the Wide Field and Planetary Came ra (WFPC2) on board the Hubble Space Telescope (HST), together with VLA obs ervations of the same galaxy. The HST images resolve features down to physi cal scales of 2-5 pc, revealing several young (<10 Myr) star-forming comple xes of various ionized gas morphologies (compact knots, complete or fragmen tary shells) and sizes (<similar to>10-200 pc). Our results are consistent with a uniform set of evolutionary trends: The youngest, smaller, filled re gions that presumably are those just emerging from dense star-forming cloud s tend to be of high excitation and are highly obscured. Evolved, larger sh ell-like regions have lower excitation and are less extincted owing to the action of stellar winds and supernovae. In at least one case we find eviden ce for induced star formation, which has led to a two-stage starburst. Age estimates based on W(H alpha) measurements do not agree with those inferred from wind-driven shell models of expanding H II regions. The most likely e xplanation for this effect is the existence of an approximate to2 Myr delay in the formation of superbubbles caused by the pressure exerted by the hig h-density medium in which massive stars are born. We report the detection o f a supernova remnant embedded in one of the two large H II complexes of NG C 4214. The dust in NGC 4214 is not located in a foreground screen but is p hysically associated with the warm ionized gas.