arXiv:astro-ph/0312576v2 11 Jan 2004SUBMITTEDTOAPJ–DEC21,2003PreprinttypesetusingLATEXstyleemulateapjv.11/26/03
REFLECTIONSOFAGNOUTBURSTSINTHEGASEOUSATMOSPHEREOFM87
W.FORMAN1,P.NULSEN1,2,S.HEINZ3,F.OWEN4,J.EILEK5,A.VIKHLININ1,6,M.MARKEVITCH1,R.KRAFT1,E.CHURAZOV7,6,C.JONES1
SubmittedtoApJ–Dec21,2003
ABSTRACT
WecombineddeepChandra,ROSATHRI,andXMM-NewtonobservationsofM87tostudytheimpactof
AGNoutburstsonitsgaseousatmosphere.ManyX-rayfeaturesappeartobeadirectresultofrepetitiveAGN
outbursts.Inparticular,theX-raycavitiesaroundthejetandcounterjetarelikelyduetotheexpansionof
radioplasma,whileringsofenhancedemissionat14and17kpcareprobablyshockfrontsassociatedwith
outburststhatbegan1−2×107yearsago.Theeffectsoftheseshocksarealsoseeninbrighteningswithin
theprominentX-rayarms.Onlargerscales,∼50kpcfromthenucleus,depressionsinthesurfacebrightness
mayberemnantsofearlieroutbursts.AssuggestedforthePerseuscluster(Fabianetal.),ouranalysisofthe
energeticsoftheM87outburstsarguesthatshocksmaybethemostsignificantchannelforAGNenergyinput
intothecoolingflowatmospheresofgalaxies,groups,andclusters.ForM87,themeanpowerdrivingthe
shockoutburst,2.4×1043ergss−1,isthreetimesgreaterthantheradiativelossesfromtheentire“cooling
flow”.Thus,evenintheabsenceofotherenergyinputs,outburstsevery3×107yearsaresufficienttoquench
theflow.
Subjectheadings:galaxies:active-galaxies:individual(M87,NGC4486)-X-rays:galaxies
1.INTRODUCTION
M87(NGC4486)providesauniquelaboratorytostudythe
interactionbetweenenergygeneratedbyasupermassiveblack
holeandthehotintraclustermedium.Itsproximityallowed
thedisksurroundingitsactivenucleustoberesolvedbyHST
providingameasureforthemassofthecentralblackholeof
3.2×109M⊙(Harmsetal.1993,Fordetal.1994,Macchetto
etal.1997).M87’sproximityalsoprovidesauniqueview
ofitsjet,detectedinoptical,X-ray,andradio(e.g.,Sparks,
Biretta,&Macchetto1996,Perlmanetal.2001,Marshallet
al.2002,Harrisetal.2003).
M87isthecentralellipticalintherichVirgoclusterand
issurroundedbyanextensivegaseousatmospherewitha
meantemperatureof∼2−2.5keV(Mathews1978,Bahcall&
Sarazin1977,Fabricant&Gorenstein1983,Böhringeretal.
2001,Matsushitaetal.2002).X-raystructureinthegaseous
haloofM87wasfirstreportedbyFeigelsonetal.(1987)using
EinsteinObservatoryobservations.UsingROSATandXMM-
Newtonobservations,Böhringeretal.(1995),Churazovetal.
(2001)andBelsoleetal.(2001)discussedtherelationship
betweentheobservedX-raystructureandtheradioemission.
Likemanyotheropticallyluminousgalaxiesatthecenters
ofclusters,M87hasbeenconsideredtobeaclassicexample
ofa“coolingflow”system,wherethegascoolingtimeisrela-
tivelyshortcomparedtotheageofthesystem(e.g.,Stewartet
al.1984,Nulsen&Böhringer1995,Böhringeretal.2001).
However,observationswithXMM-Newtonhaveshownthat
coolingflows,likethataroundM87,depositcooledgasat
muchlowerratesthanexpectedinthestandardcoolingflow
1SmithsonianAstrophysicalObservatory,Harvard-SmithsonianCenterforAstrophysics,60GardenSt.,Cambridge,MA02138;wrf@cfa.harvard.edu2OnleavefromtheUniversityofWollongong3MIT,Cambridge,MA4NationalRadioAstronomyObservatory,Socorro,NM878015NewMexicoTech.,Socorro,NM878016SpaceResearchInstitute(IKI),Profsoyuznaya84/32,Moscow117810,Russia7MPIfürAstrophysik,Karl-Schwarzschild-Strasse1,85740Garching,Germanymodel(Fabian1994;Petersonetal.2003andreferences
therein).Thisrequiresconsiderableenergyinputtocompen-
sateforradiativelosses.M87,withitsproximity,itsactive
nucleus,jet,andextensivesystemofradiolobes,providesan
idealsystemforstudyingtheenergyinputfromtheAGNto
thehot,coolinggas.
Usingradiostudies,Owen,Eilek&Kassim(2000;see
alsoBinney1999)pioneeredtheviewthatthemechanical
powerproducedbythesupermassiveblackholeatthecenter
ofM87wasmorethansufficienttocompensatefortheen-
ergyradiatedinX-rays.Tabor&Binney(1993)andBinney
&Tabor(1995)developedmodelswithoutmassdeposition
andincludedenergyinjectionfromthecentralAGN.Heinz,
Reynolds&Begelman(1998;seealsoReynolds,Heinz&
Begelman2001)modelledshockheatingoftheIGMbyanex-
pandingradiosource.Churazovetal.(2001;seealsoKaiser
&Binney2003,Bruggen2003,DeYoung2003,Kaiser2003)
arguedthatthemorphologyoftheX-rayandradioobserva-
tionscouldbeexplainedbyradioemittingplasmabubbles
buoyantlyrisingthroughthehotX-rayemittinggas.These
buoyantbubblescouldupliftthecoolestgasandprovideen-
ergyinputasbubbleenthalpyisconvertedtokineticenergy,
thenthermalizedintothegasinthebubblewake.
Theresultsoutlinedabovereliedprimarilyonpre-Chandra
observationsofM87thatlackedsufficientangularresolution
toallowdetailedcomparisontotheradiostructuresshownin
theOwenetal.(2000)study.Young,Wilson&Mundell
(2002)useda37ksecChandraobservationtoconfirmpre-
viousstructures,aswellastodescribeseveralnewfeatures
includingtwonearlyspherical“edges”at∼45′′and∼3′
thattheyattributetoactivityinthenucleusassociatedwith
jetproduction.TheChandraimagesalsoshowcavitiesand
filamentsintheeasternandsouthwesternX-rayarms.Young
etal.arguedthatthearmswereoverpressurizedandmulti-
temperature.Molendi(2002)usedXMM-Newtonobserva-
tionstoshowthattheX-rayarmsrequiredtwo-temperature
modelswithgastemperaturesintherangekT∼0.8−1keV
andkT∼1.6−2.5keV.
Inthispaper,wecombinedeepChandra,ROSATHRI,and
