AGNandGalacticBlackHoleSpectra
TodaysBestAdvertisingforAGN-RyanHickox
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• Differential Keplerian rotation • Viscosity : gravity → heat • Thermal emission: L = AσT4 • Temperature increases inwards • GR last stable orbit gives
minimum radius Rms
Spectra of accretion flow: disc- C. Done Review
Log ν
Log
ν f(ν)
Log ν
Log
ν f(ν)
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• GR last stable orbit gives minimum radius Rms
• a=0: Tmax = (M/M� )-1/4 (L/LEdd )1/4
• 1 keV (107 K) for 10 M� if L=LEdd
• 10 eV (105 K) for 108 M� " "
• a=0.998 Tmax ~ 2.2 Tmax (a=0) • AGN: UV disc, ISM absorption,
mass more uncertain. XRB…
Spectra of accretion flow: disc- C. Done Review
Log ν
Log
ν f(ν)
Log ν
Log
ν f(ν)
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Relativisticeffects-C.Done
Fabian et al. 1989
Energy (keV) flu
x
• Relativisticeffects(specialandgeneral)affectallemission(Cunningham1975)
• Hardtoeasilyspotoncontinuumcomponents
• FeKα linefromirradiateddisc–broadandskewed!(Fabianetal1989)
• BroadeninggivesanindependentmeasureofRin–sospinifISO(Laor1991)
• Modelspredictincreasingwidthasgofromlow/hardtohigh/softstates
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WhatDoBroadBandSpectraofBlackHolesLookLike
Log(flu
x)
Log(frequency)
Thermalemissionfromaccretiondisk(softX-raysforGBHC;UVforAGN)
X-ray�tail�- not due to the accretion disk
T~(M/MEdd)1/4M-1/4
How Hot is a Black Hole?? Lets go back to the accretion disk spectrum- Longair 14.52-14.54 T(R)=[3GMM/8πR3]1/4(R/Rin)]-3/4
Temperature at fixed number of Rs decreases as M-1/4
- disks around more massive black holes are cooler at a fixed R/RS and M/MEdd now recasting in terms of the Eddington limit where MEdd is the mass accretion rate for the Eddington limit and we assume that the conversion efficiency of mass into energy is 10% and M8 is the BH mass in units of 108 M¤ T~6.3x105[M/MEdd]1/4[M/M8]-1/4(R/Rin)]-3/4k-UV T~6.3x107[M/MEdd]1/4[M/M!]-1/4(R/Rin)]-3/4k-Xray
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GalacticBlackHoles• Relativelylowmassandsothe
diskare'hot'
L~ 7x1038 f(M10)2(Tin)4 erg/s Where M10 is the mass in units of 10 M� and Tin is in keV f is a factor taking some complex physics into account !
AdaptedfromMilleretal2003
DiskBB
"Powerlaw"
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GalacticBlackHoles-GBH
• Relativelylowmassandsothediskare'hot'-mostofthefluxappearinginthex-rays
0.1 1.0 Tin (keV)
L x104
0 ergs/sec
AdaptedfromMilleretal2003
GBHULX
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ReminderofAccretionDiskSpectrum• Derivationofpreviouseq• L=2πRin2f(cosi)-1;fisthefluxfromthesurfaceofthedisk,Ristheradius• Usingtheblackbodylaw L=4πσR2Tin4σ istheStefan-Boltmannconstant
InfittingthespectrumTinisdirectlyobservableWecanthustakethe2equationstogettheinnermostradius
Rin=sqrt(L/4πσTin4)andTin~3M10
-1/4keV T(r)=6.3x105 (M/MEdd)1/4M8
-1/4(r/rs)-3/4(MEdd is the accretion rate in Eddington units, T=Tinforr=rs)
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RealObjects• Dataforgalactic
blackholesagreeswiththesimpletheory
• E.gassumethatMBHdoesnotchangeandallchangesluminosityduetochangesinM-ifsothenexpectTin~M 1/4~L1/4
Makishimaetal2000
FittedTin
Diskbolom
etricluminosity
x10
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Miller(2013)
kT(Kev)
Diskflux
blackholetransient
ModificationstoDiskBlackBody
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Miller(2013)
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• CanFitAGNUV-opticaldatawithaccretiondiskmodels
MalkanandSun1989
Effectsofinclinationondiskspectrumfor5x108M¤BH
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AGN• AGNareverymassiveand
sothepredictedspectrumoftheaccretiondiskis'cool'-peakinginUV-EUV
• T~8x104kforaEddingtonlimitedM~108M¤blackhole
• ProblemswithobservingintheEUVandsodonotobservehighenergyexponentialcutoff
FitofSSADmodelstoAGNspectrum(MalkanandSun1989
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FittedParametersforUVDiskFits
• Resultsare'reasonable'butnotunique
• Nowhaveindependentmassestimates-resultscanbechecked– Findthatvaluesarenotquite
right-needmorecomplexaccretiondiskmodels(surfaceisnotsimpleBB,needtoinclude
relativisticeffects)
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EffectsofStrongGravity(Spin),
InclinationAngleonSpectrumofDisk(Merloni2010)
aisspininGRunits
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RelativisticEffects• Lightraysarebentbystronggravity-makingthegeometry
rathercomplicated
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• Possiblestrongeffectoflightbending.
• ifweonlyknewwherethex-rayscomefrom(hs~rs)fromtimevariabilityarguments
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EffectsofStrongGravity(Spin),InclinationAngleonSpectrumofDisk(Merloni2010)
ToppanelisADspectrumvsenergyforfixedinclinationangle,spinvariesBottompanelfixedspin,inclinationanglevaries.
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Next...
• AccretionDiskfitstoAGNspectra
• Broadbandspectraarenotsosimple-what'sthereinadditiontotheaccretiondisk– thegeometryoftheinnermostregions– briefreviewofComptonization
• Effectsof'reprocessing'-thedisk'sees'thehardx-rayradiationandtherearemeasurableeffects
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LifeisNotSoSimple
• ThebroadbandspectraofbothAGNandGalacticblackholeshavemajordeviationsfromdiskspectra
AdaptedfromPolettaetal2007
Emissionfromdust?
diskemission
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AGN• Ahugeamountofwork
hasgoneintoobservingAGNacrosstheentireelectromagneticspectrum
• Thereisastrongrelationshipbetweentheoptical-UVandthex-ray
Brusaetal2009
diskemission
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X-raytoUVRelationship• Over103in
luminositytheUVandx-raytrackeachintypeIAGN
• Directconnectionofdiskemission(seeninUV)tox-rays
Lussoetal2010LUV
L xray
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• AverageSpectralEnergyDistributionsfor2ClassesofObjectsSelectedasX-rayEmittingAGNinagivenx-rayluminositybin(Pollettaetal2007)
Effectofreddeningbydust
x-ray
GeneralShapeoftheOptical-X-
raySED
• Astheluminosityofthesourceincreasestheratioofx-raytoopticalluminosity(αox)decreasesslightly
• e.gmoreluminousAGNarex-ray'quieter"
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Coffeyetal2019
αox=[log(Fx)-log(FUV)]/2.605
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EffectsofDustCanBeDominant• RememberfortheM~108
T~5x105Kso'rollover'isintheFUV–effectsofdustaremaximumintheUV
• Emax~3kT~1016hz• Theeffectsofdust(Reddening)
goatλ-2
• muchbiggereffectsatshorter(UV)wavelengths-majoreffectondeterminationoftemperatureofaccretiondiskfitstoquasars.
Laor1990
averageamountofreddeningintheMilkywayatb=500
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AGN-SummaryofSpectralComponents• 3Broadbandsofenergy• Diskdominatesinoptical-UV• ComptonizationinX-ray• ReprocessedradiationinIR
Magdziarz et al 1998
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AGN• AGNareverymassiveand
sothepredictedspectrumoftheaccretiondiskis'cool'-peakinginUV-EUV
• T~8x104kforaEddingtonlimitedM~108M¤blackhole
• ProblemswithobservingintheEUVandsodonotobservehighenergyexponentialcutoff
FitofSSADmodelstoAGNspectrum(MalkanandSun1989
ConnectionofFeKlineandtheReprocessingRegions• Themostprominentspectral
featuresinmostx-rayAGNspectraare– theFeKlinecomplex– TheComptonreflection�hump�
• Wherearetheseregions• Howaretheyconnected• Whatdowelearnaboutthegeometryandchemicalabundanceofthecentralregions?
• Whatisthephysicalstateofthegasandhowisitconnectedtoother�places�-e.gtheregionsresponsibleforproducingtheoptical/UV/IRradiation
• Whatcanwelearnaboutaccretion
X-ray source
reflection
MCG-5-23-16Suzakudata(Reevesetal2006
Cartoonorreality??
Comptonhump
FeKcomplex
MoreComplexity• ComptonizationandX-rayAGNSpectra
• X-raySpectralComponentsandreprocessing
• Directevidencefordisksandsmallx-raysizefromgravlensing
• BroadFeKLinesandSpin
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Optically-thickpartoftheaccretiondiskemitsthermalspectrum…blackbodyradiationwith
X-ray�tail�probablycomesfromahotcoronax-raysproducedbyinverseComptonscatteringofthermaldiskemissionbyelectronswithT~109K
WheredotheSpectralComponentsArise?
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EvenMorePossibleGeometries
FromC.Done
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RealDataForGalacticBH
Wheredothehighenergyphotonsarise?InbothAGNandBlackHolebinariesitisthoughtthatthisspectralcomponentisduetoComptonizationofa'seedphoton'populationoffofhighlyenergeticelectronsproduced'above'thedisk
disknotdisk
Possiblegeometries-blueisx-rayemittingregion
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ComptonizedSpectraLongair9.4.1
Done2007
n y~4kT/mec2(maxτ,τ2)n slopeα~-3/2+(9/4+y)1/2
• Thefreeparameterforthepowerlawslopeisywhichcontrolsthespectralslope
• Howeverthesmallerτis,thelargerThastobetogetthesameslope-the'bumpier'thespectraare
• spectrumsteepsathighE(maxT)
• y~1istheusualcase• seeUnwrappingtheX-ray
SpectraofActiveGalacticNucleiC.ReynoldsarXiv:1510.07638
•
ThermalComptonizedContinuum• Thedetailedsolutionisabitmessy
(Zdziarski,Johnson&Magdziarz(1996)butfory>1oneformsaspectrumwhichcanbeapproximatedbyapowerlawofslopeΓwithahighenergycutoffrelatedtothetemperatureofthehotelectrons.
• power-lawindexofthephotoncountrateasafunctionof
energy,dN(E)/dE � E−Γ,
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ThermalComptonizedContinuum• Thedetailed
solutionisabitmessy(Zdziarski,Johnson&Magdziarz(1996)butfory>1oneformsaspectrumwhichcanbeapproximatedbyapowerlawofslopeΓwithahighenergycutoffrelatedtothetemperatureofthehotelectrons.
• , 37
Typicalslopesare~-2whichgivesτe~1andy =3/4y=4kTemec2max(τe,τ2e)typicaltemperaturesare50-300keV
ThermalComptonizedSpectra• Typicalslopesare~-2
• whichgivesτe~1andy =3/4
y=4kTemec2max(τe,τ2e)• typicaltemperaturesare50-300keV
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NumericalcalculationsofComptonizedspectrafordifferentT,τ combinations
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AGN-SummaryofSpectralComponents
Hickok & Alexander 2018
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MoreOnBHSpectra• Relationshipofcomponents• Whydowethinkdiskexists• Geometryofcentralregions• Reprocessing-howcanwelearnaboutthe
materialinandaroundtheblackholefromspectralandtemporalsignaturesinthespectra
• Spinanditsinfluence
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Howdoweknowthattherereallyisadisk??
• RecentmicrolensingobservationsofafewQSOshave'resolved'thex-rayandopticalsources
• Theopticalsourcesizeanddependenceofluminosityonwavelengthareconsistentwithstandarddisktheory-e.g.
• Microlensingperturbationstothefluxratiosofgravitationallylensedquasarimagescanvarywithwavelengthbecauseofthechromaticdependenceofthesourcesapparentsize.
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MicroLensing• AswesawlasttimeinadiskT(r)~Tmaxr-3/4
• Writingitoutinfull• Teff(r)={(3G2MBH
2mpfEdd)/2cσSBεr3)}1/4(1-rin/r)1/4– fEddistheEddingtonratio,MBHistheBHmass,σSBtheStefanBoltzman
constant,ε istheefficiency
• Thusthediskemitsmostofitsshortwavelengthlightatsmallradiiandlongwavelengthlightatlargeradii
• Integratingthedisktemperatureprofile(Blackburneetal2010)onegetsthatthehalflightradiusasafunctionofsizeis
r1/2~1.7x1016cm(MBH/109M�)2/3(fEdd/ε)1/3 (λ/µ)4/3• Inotherwordstheeffectivesize~λ4/3
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• ThesizeofthediskisinEinsteinradiusunitswhichareconvertedtocgsunitswithamodelofthegravpotentialofthelensinggalaxy
• Sourceisbiggeratlongerwavelengths-lineiswhataSSdiskshouldbe
• Tocomparetomodeldisks,havetoassumeMBH,fEdd/ε
SizeofPG1115inEinsteinradiusunits
logr(cm
)
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X-rayMicroLensingAlso
• Probabilitydistributionofopticalandx-raysourcesize(Zimmeretal2010,Chartasetal2008)-x-rayisMUCHsmaller
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ResultsareInRoughAgreementWithTheory• X-raysareemittingnear
theSchwarzschildradius
• Optical~10xfurtherout
Chartas2008
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