Unveiling the Behavior of the Ionized Gas in Irregular Galaxies

We present the results of a detailed kinematical and dynamical analysis performed in two highly interesting gas-rich Irregular galaxies (Irrs): IC 1613 and NGC 4449. The analysis has been accomplished by means of optical Fabry-Perot interferometry mapping

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aDisksofGalaxies:Kinematics,DynamicsandPerturbationsASPConferenceSeries,Vol.iii,2002E.Athanassoula&A.Bosma,eds.UnveilinggalaxiesthebehavioroftheionizedgasinirregularMargaritaValdez–Guti´errezInstitutoNacionaldeAstrof´ sica,OpticayElectr´onica,Tonantzintla,Puebla,M´exicoMargaritaRosadoInstitutodeAstronom´ a–UNAM,M´exico,City,M´exico1.ResultsandDiscussionWepresenttheresultsofadetailedkinematicalanddynamicalanalysisper-formedintwohighlyinterestinggas–richIrregulargalaxies(Irrs):IC1613andNGC4449.TheanalysishasbeenaccomplishedbymeansofopticalFabry–PerotinterferometrymappingtheHαand[SII]lines.Ourinterestwascenteredonglobalandlocalscalesinbothgalaxies.Theresultsfocusedontheglobalradialvelocity eldinbothgalaxiesshowthattheyaredi erentfromeachother.IC1613displaysahighlyperturbedvelocity eldduetolocalmotionscausedbysuperbubbles.NGC4449showsavelocity eldwhichisrelativelywellbehavedwithaweakdecreasingrangeinradialvelocities(～60kms 1)fromNEtoSW.Onlocalscales,wefoundthattheHIIregionpopulationforbothgalaxiesdis-playsavelocitydispersionmeanvalueof～20kms 1,whichdoesnotre ecttheenvironmentofthehostgalaxyineachcase.TheHIIregionpopulationinthesegalaxiesdisplaystandardvaluesaccordingtotheirdiameterdistribu-tionandluminosityfunctions(D0=30–65pc;α=1.5–1.9).ThesuperbubblepopulationinIC1613displaysexpansionvelocities(20–40kms 1),sizes(100–320pc),dynamicalages(0.7–2Myr)andmechanicalenergies(0.6–8×1050ergs)whichcanbeexplained–intheframeworkofthestandardmodel–intermsoftheactivityderivedfromthemassivestars(stellarwindsandsupernovaexplo-

sions)atthoselocations.Basedonourresults(Valdez–Guti´errezetal.2001,2002,Rosadoetal.2001),weconcludethattheimpressivedistributionandkinematical/dynamicalbehavioroftheionizedgasinthesetwogas–richIrrshasbeenmoulded–onglobalandlocalscales–bytheactivityoftheirmassivestars;i.e.suchactivityhas“etched”globallyandlocallythegalaxiesastheylooktoday.Duetothenatureofthepresentwork–andasfarasweknow–,thisisthe rsttimethatthekinematicsanddynamics(onglobalandlocalscales)oftheionizedgasinnearbygas–richIrrsisunveiledinsuchdetail.References

Valdez–Guti´errez,M.etal.2001,A&A,366,35

Valdez–Guti´errez,M.etal.2002,AJ,submitted

Rosado,M.etal.2001,AJ,122,194

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