Spatial Distributions of Dust and Polycyclic Aromatic Hydrocarbons in the Nearby Elliptical Galaxy NGC4589 Observed with AKARI

摘要

Wereportonnear-tofar-infrared(IR)observationsofthenearbyellipticalgalaxyNGC4589byAKARI.NGC4589hasacomplexstellarrotationfieldwithapositionangledifferenceof45$$^{circ}$$betweenthekinematicandmorphologicalaxes,althoughitsmorphologyshowsasmoothopticalprofilethatcloselyfollowsthedeVaucouleurslaw.Thegalaxyhasaminor-axisdustlane,whichistwistedtowardthemainstellarrotation.Thesepropertiesstronglysupportthatthegalaxyisarelativelyoldmergerremnant.Wehaveobtainedthespatialdistributionsofdustfromfar-IRemissionandnear-IRabsorption,separately.Wehavealsoestimatedthedistributionofpolycyclicaromatichydrocarbons(PAHs)fromthedifferencebetweenimagesinthemid-IRbands.ThespatialdistributionsofthedustandPAHsresembleeachother,bothshowingsignificantdeviationsfromthesmoothstellardistribution.Theyextendtothemainstellarrotationandthedirectionofthetwistedinnerdustlane,thusfollowingtherelicsofthemerger.Therefore,alargefractionofthedustandPAHsinNGC4589arelikelytooriginatefromapastmergerevent.