The Structure and Morphology of the Ionized Gas in Starburst Galaxies NGC52535236

(Abridged) We investigate the interplay between starbursts and host galaxies by studying the structure and physical characteristics of the ionized gas surrounding the central starbursts in the two nearby galaxies NGC5253 and NGC5236. The two systems repres

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aTheStructureandMorphologyoftheIonizedGasinStarburstGalaxies:NGC5253/5236.1DanielaCalzettiSpaceTelescopeScienceInstitute,3700SanMartinDr.,Baltimore,MD21218,USA;e-mail:calzetti@stsci.eduChristopherJ.ConseliceandJohnS.GallagherIIIDept.ofAstronomy,UniversityofWisconsin,475N.CharterSt.,Madison,WI53706,USA;e-mail:chris@astro.wisc.edu,jsg@astro.wisc.eduandAnneL.KinneySpaceTelescopeScienceInstitute,3700SanMartinDr.,Baltimore,MD21218,USA;e-mail:kinney@stsci.eduABSTRACTWeinvestigatetheinterplaybetweenstarburstsandhostgalaxiesbystudyingthestructureandphysicalcharacteristicsoftheionizedgassurroundingthecentralstarburstsinthetwonearbygalaxiesNGC5253andNGC5236.Thetwosystemsformapairwhichpresumablyinteractedabout1Gyrago.Theyrepresentverydi erentgalacticenvironments,NGC5253beingametal-poordwarf,andNGC5236beingametal-rich,massive,grand-designspiral.Wepresentimagesofthestarburstregionsinthesetwogalaxiesinthelightofthelineemission[OIII],Hα,and[SII],andincontinuumU,V,R.ForNGC5253,theimagesaredeepenoughthatwecandetectfaintHαarchesand lamentsoutto～1.9kpcand[SII] lamentsoutto～1kpcfromthemain

ionizingcluster.Theground-basedlineimagesarecomplementedwithanarchivalHST-WFPC2Hβimage.Lineratiomaps[OIII]/Hβand[SII]/Hαshowthatintheouterregionsthedi useionizedgasispartiallyexcitedbyanon-photoionizationprocess(‘shocks’).The‘shocked’gasismostlyconcentratedsouth-westofthegalaxy’scenter,incoincidencewiththepositionofHαbubblesandwithextendedsoftX-rayemission.TheHαemissionfromtheshock-excitedgasis≈1–2%ofthetotaland≈10–20%ofthedi useionizedgasemission,althoughthemechanicalinputfromthestarburstwouldbesu cienttosupportashockedHαluminosity～3timestheobservedone.About80–90%ofthedi usegasisconsistentwithbeingphotoionized,requiringthatabout10%oftheionizingphotonsescapefromthestarburstsite.The

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