Kinematics and Structure of the Starburst Galaxy NGC 7673

The morphology and kinematics of the luminous blue starburst galaxy NGC 7673 are explored using the WIYN 3.5m telescope. Signs of a past kinematic disturbance are detected in the outer galaxy; the most notable feature is a luminous ripple located 1.55 arc

KinematicsandStructureoftheStarburstGalaxyNGC7673

N.L.HomeierandJ.S.Gallagher

DepartmentofAstronomy,UniversityofWisconsin-Madison

ABSTRACT

arXiv:astro-ph/9904197v1 15 Apr 1999ThemorphologyandkinematicsoftheluminousbluestarburstgalaxyNGC7673areexploredusingtheWIYN3.5mtelescope.Signsofapastkinematicdisturbancearedetectedintheoutergalaxy;themostnotablefeatureisaluminousripplelocated1.55arcminutesfromthecenterofNGC7673.Sub-arcsecondimaginginBandR ltersalsorevealsreddustlanesandbluestarclustersthatdelineatespiralarmsinthebrightinnerdiskandnarrowbandHαimagingshowsthattheluminousstarclustersareassociatedwithgiantHIIregions.TheHαkinematicsmeasuredwithechelleimagingspectroscopyusingtheWIYNDensePak berarrayimplythattheseHIIregionsarecon nedtoasmoothlyrotatingdisk.Thevelocitydispersioninionizedgasinthediskisσ～24kms 1,whichsetsanupperboundonthedispersionofyoungstellarpopulations..Broademissioncomponentswithσ～63kms 1foundinsomeregionsarelikelyproducedbymechanicalpowersuppliedbymassive,youngstars;aviolentstarburstisoccurringinakinematicallycalmdisk.Althoughtheasymmetricouterfeaturespointtoamergerorinteractionasthestarbursttrigger,theinnerdiskstructureconstrainsthestrengthoftheeventtothescaleofaminormergerorweakinteractionthatoccurredatleastanouterdiskdynamicaltimescaleinthepast.Subjectheadings:Galaxies:Evolution,Galaxies:KinematicsandDynamics,Galaxies:Starburst,Galaxies:Individual,ISM:HIIregions

1.Introduction

Highsurfacebrightnessbluegalaxieshavebeenacuriosityinsamplesofnearbygalaxiesformorethan40years(e.g.SandageWhilethesetypesofcompactgalaxieswereoftenexcludedfromtraditionalsamplesofgalaxiesthatchoseobjectsonthebasisofangularsize(seetheycanbereadilyfoundinsurveysthatselectforbluecolorsorstrongopticalemissionlines.Follow-upstudiestotheMarkariansurvey,forexample,haveshownthatthesehighsurfacebrightnessgalaxiesconsistofsystemswithAGNsand/orwithextraordinarilyhighstarformationrates(SFRs),i.e.thestarburstgalaxies(e.g.,HuchraRecentlyinterestinbluehighSFRgalaxieshasbeenstimulatedbytheirspectroscopicandmorphologicalsimilaritiestoclassesofgalaxieswhicharecommonlyfoundatmoderatetohighredshifts(seeGallagher1990,Ellis1997,

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