Optical integral field spectroscopy and ROSAT X-ra

Mon.Not.R.Astron.Soc.000,000{000(0000)Printed24April1996(MNLATEXstylelev1.4)OpticalintegraleldspectroscopyandROSATX-rayimagingofIRAS09104+4109C.S.Crawford1;y&C.Vanderriest2;31.InstituteofAstronomy,MadingleyRoad,CambridgeCB30HA2.ObservatoiredeParis-Meudon(DAEC),92195MeudonCedex,France3.Canada-France-HawaiiTelescopeCorp,POBox1597,Kamuela96743,Hawaii,USAyVisitingobserver,Canada-France-HawaiiTelescope,whichisoperatedbytheNRCofCanada,CNRSofFrance,andtheUniversityofHawaii.24April1996ABSTRACTWepresentresultsfromalongobservationusingtheintegraleldspectrographAR-GUSoftheultra-luminousIRASsourceIRAS09104+4109,whichisassociatedwiththecentralgalaxyofarichclusterataredshiftz=0:44.Wemapthedistribution,kinematicsandionizationstateofitsextendedemission-lineregion,andshowthatboththenucleusandasecondarynorthernpeakinthenebulahaveratiosconsistentwithphoto-ionizationbyahidden,butluminousquasarcontinuum.Thekinematicsoftheionizedgassuggeststhatthegalaxyanditsnebulaformarelativelystaticsystemattheclustercore.Astronglyblueshiftedcomponentofemission-linegasaroundthenucleusrevealsacentraloutow,dueeithertoachangeinthecentralradiosource,oramassivesupernovawind.Wealsopresenta30ksecROSATHRIpointedobservationofIRAS09104+4109.TheX-rayimageisextended,andade-projectionanalysisconrmsthepresenceofa800-1100Myr1coolingowintheLX=2:91045ergs1cluster.AcentraldipisobservedintheX-rayimage,whichmaybecausedbytheoutowseenintheopticaldata.IRAS09104+4109ismostlikelyaveryhighly-absorbedquasar,andpresentsthermestcaseforastrongcool-ingcoolingowoccurringaroundaquasar,andtherstsodiscovereddirectlyfromtheX-rayimage.Keywords:galaxies:active{galaxies:clusters:coolingows{galaxies:individual(IRAS09104+4109){galaxies:quasars:general{infrared:galaxies{X-rays:galaxies1INTRODUCTIONIRAS09104+4109isoneofthemostluminousobjectsdiscoveredbytheIRASsatellite,andisidentiedwithacDgalaxyatthecentreofarich,attenedclusteratz=0:442(Kleinmannetal.1988,Hutchings&Ne1988;hereafterK88andHN88respectively).IthasanopticalspectrumcharacteristicofaSeyfert2,andanarrow-bandimagecentredonredshifted[OIII]resolvesasecondarypeak4arcsecnorthofthegalaxycoreatpositionangle25(K88).Thenarrowemissionlinesarerelativelybroad,withamarkedlyblue-asymmetricprole.AlthoughtherearenobroadcomponentstotheBalmerlinesinthespectrum,thereisplentyofevidencethatIRAS09104+4109containsapowerfulactivenucleus.IthasthemostpowerfulradiosourcefoundassociatedwithanIRAS-discoveredgalaxy,showingthestrongcoreanddouble-lobedstructureofaclas-sicalFRII(althoughitspowerat1.4GHzof1024:5WHz1isborderlineFRI/II;Hines&Wills1993hereafterHW93).Inaddition,theopticalspectrumofIRAS09104+4109showsanultravioletexcess,ahighlypolarizedcomponent(polar-izationof18percent,aftersubtractionofthestellarlight),andabroadMgIIline(HW93).Thescatteredlightcontin-uumischaracteristicofalow-luminosityQSO,althoughnotonethatisheavilyreddened.ThelargeIRexcessofthissourceisthusprobablyproducedbywarmdustobscuringtheactivenucleus.Thelowratioofnuclear-to-hostluminos-ity(HN88),thelackofreddeningandbroadBalmerlinesintheopticalspectrumallsuggeststhatthisdustislocatedbetweenthebroad-andnarrow-lineregions(HW93).AnASCAspectrumofIRAS09104+4109revealeditasapowerfulX-raysource,withapower-law-likespec-trumandastronglinefromHelium-likeiron(Fabianetal.1994).Afollow-upROSATHRI(HighResolutionImager)observationresolvedthesourceasspatiallyex-tended,witha0.1-2keV(observed)luminosityof2:9c0000RAS2C.S.CrawfordandC.Vanderriest09h13m42s44s46s48s50sRightAscension(2000)40°55′45″56′00″15″30″45″57′00″15″Declination(2000)09h13m42s44s46s48s50sRightAscension(2000)40°55′45″56′00″15″30″45″57′00″15″Declination(2000)Figure1.POSSimageofIRAS09104+4109(greyscale)overlaidwithcontoursofX-rayemission.TheX-rayimagehasbeenadap-tivelysmoothedtohaveaminimumof16countspersmoothingbin(Ebeling,White&Rangarajan1996),andthecontourlev-elsare:0.1,0.14,0.20,0.28,0.40,0.56.,0.79,1.12,1.58and2.24countspersquarearcsec.ThecentralcontourrepresentsadipintheX-rayintensity.1045ergs1(Fabian&Crawford1995,hereafterFC95).GiventhatIRAS09104+4109liesinarichcluster,andthesimilarityofthe(extrapolated)ASCAuxtothatinROSAT,itislikelythatthebulkoftheX-rayemissionisduetothermalbremsstrahlung.Indeed,theASCAspectrumwasbetterre-modelledasanabsorbedcoolingow,althoughthestrengthoftheironlinecouldindicateacontributionfromscatteringofahiddennucleus.IRAS09104+4109isaparticularlyinterestingsourcetostudyindetail,giventheevidenceforastrongQSOembed-dedindustatthecentreofarichcoolingowcluster.Itsimmediateenvironmentshowsmanyfaintercompanionob-jects(overelevenwithina7.5arcsecradius),whichhasalsoledtothesuggestionthatitisintheprocessoftidallyin-teracting(HN88).Inthispaperwepresenttwo-dimensionalspectroscopyofIRAS09104+4109,allowingdeterminationofthemorphology,ionizationstateandkinematicsofthewholeemission-linesystem,withtheaimofidentifyingthedominantprocessesoccurringinandaroundthisexceptionalgalaxy.2X-RAYOBSERVATIONSIRAS09104+4109wasobservedwiththeROSATHRIfor21,868sin1995April,andwasaddedtotheoriginalpointedHRIobservation(N