Distribution and Kinematics of Molecular Gas in Barred Spiral Galaxies. I. NGC 3504

摘要

WepresenttheresultsofCOmappingobservationsofthebarredspiralgalaxyNGC3504withtheNobeyama45-mtelescope.ThedistributionofthemoleculargasshowsoffsetridgeswhichcorrespondtothedistributionofHIIregionsalongthebar.Thevelocityperpendiculartothebardecreasesabruptlyattheridge.Thevelocitychangeimpliesthatthemoleculargaschangesthedirectionofitsmotiontoparalleltothebarattheridge.SincethepositionangleofthemajoraxisofthebarandthelineofnodesarealmostthesameinNGC3504,anupperlimittothepatternspeedofthebarcanbederiveddirectlyfromtheradialvelocity.Theresultantupperlimitis41kmsa?’1kpca?’1,whichismuchsmallerthanthatderivedbasedonanassumptionthatthecorotationradiusislocatedattheendofthebar(77kmsa?’1kpca?’1).Thecorotationradiusderivedfromourupperlimitismorethantwo-timeslargerthanthelengthofthesemi-majoraxisofthebarinNGC3504.