SDSS J013127.34-032100.1: a candidate blazar with a 11 billion solar mass black hole at $z$=5.18

0.2 MB·English

by  G. Ghisellini

Mon.Not.R.Astron.Soc.000,1–6(2012) Printed13March2015 (MNLATEXstylefilev2.2)
SDSS J013127.34–032100.1: a candidate blazar with a 11 billion
z
solar mass black hole at =5.18
G. Ghisellini1, ⋆ G. Tagliaferri1, T. Sbarrato2, N. Gehrels3
1INAF–OsservatorioAstronomicodiBrera,viaE.Bianchi46,I–23807Merate,Italy
5 2Univ.diMilanoBicocca,Dip.diFisicaG.Occhialini,PiazzadellaScienza3,I–20126Milano,Italy
1 3NASA–GoddardSpaceFlightCenter,Greenbelt,Maryland2077,USA
0
2

r 13March2015
a
M
ABSTRACT

2 Theradio–loudquasarSDSSJ013127.34–032100.1ataredshiftz=5.18isoneofthemostdis-
1 tantradio–loudobjects.Theradiotoopticalfluxratio(i.e.theradio–loudness)ofthesource
islarge,makingitapromisingblazarcandidate.Itsoverallspectralenergydistribution,com-
]
pletedbytheX–rayfluxandspectralslopederivedthroughTargetofOpportunitySwift/XRT
E
observations,is interpretedby a non–thermaljet plusan accretiondisc and moleculartorus
H
model.We estimate thatits blackholemass is(1.1±0.2)×1010M⊙ foranaccretioneffi-
h. ciencyη =0.08,scalingroughlylinearlywithη.Althoughthereisafactor ∼> 2ofsystematic
p uncertainty,thisblackholemassisthelargestfoundattheseredshifts.We derivea viewing
- anglebetween3and5degrees.Thisimpliesthattheremustbeother(hundreds)sourceswith
o
thesameblackholemassofSDSSJ013127.34–032100.1,butwhosejetsarepointingaway
r
t fromEarth.Wediscusstheproblemsposedbytheexistenceofsuchlargeblackholemasses
s
atsuchredshifts,especiallyinjettedquasars.Infact,iftheyareassociatedtorapidlyspinning
a
[ blackholes,theaccretionefficiencyishigh,implyingaslowerpaceofblackholegrowthwith
respecttoradio–quietquasars.
2
v Keywords: quasars:general;quasars:supermassiveblackholes–X–rays:general
9
6
2
7
0 1 INTRODUCTION Uptonowthethreeblazarsknownatz >5areQ0906+6930
. (z = 5.47; Romanietal.2004),B21023+25(z = 5.3;Sbarrato
1 Yi et al. (2014, hereafter Yi14) discovered SDSS J013127.34–
etal.2012, 2013), andSDSSJ114657.79+403708.6 (z = 5.005;
0 032100.1 (hereafter SDSS0131–0321) as a radio–loud quasars a
Ghisellinietal.2014a).Allthesesourceshaveawellvisibleaccre-
5
aredshift z = 5.18 characterised by alargeradiotooptical flux
1 tiondisc emission in the IR–optical part of the observed spectral
ratio (i.e. the so–called radio–loudness) R ∼ 100. Yi14 selected
: energydistribution(SED),includingstrongbroademissionlines.A
v thesourcethroughoptical–IRselectioncriteriabasedonSDSSand
largeradio–loudnessRisagoodindicatorofthealignmentoftheir
i WISEphotometricdata(Wuetal.2012),andthenobserveditspec-
X jets with the line of sight, that boosts the non–thermal emission
troscopicallyintheopticalandtheIR.TheIRspectrumrevealedan
becauseofrelativisticbeaming.ValuesR>100,asinthecaseof
r absorbedbroadLyαlineandabroadMgIIline,thatallowedtoes-
a SDSS0131–0321(Yi14),makethesourceagoodblazarcandidate,
timatetheblackholemassoftheobjectsthoughthevirialmethod,
yieldingMBH = (2.7−4)×109M⊙.Ifthisweretherealblack tih.ee.abesaomuricnegwahnogsleej1e/tΓis,sweehneruendΓerisatvhieewbuinlkgaLnogrleenθtzvfsamctaolrleorfthtahne
holemass,thenthesourcewouldemitabovetheEddingtonlimit.
jet.Thisdefinitionissomewhatarbitrary,buthasthemerittodivide
Averylargeblackholemassfoundinajettedquasaratsuch
inasimplewayblazarsfromtheirparent population,i.e.quasars
large redshifts is somewhat puzzling. This is because it is com-
monlybelievedthatthejetisassociatedwithrapidlyspinningblack withjetspointingawayfromus.Thedivideatθv = 1/Γimplies
that for each blazar there are other 2Γ2 sources of similarintrin-
holes, in order to let the Blandford & Znajek (1977) mechanism
sicpropertiesbutpointingelsewhere.However,theradio–loudness
work. But ifthiswerethecase, theefficiencyof accretionwould
alonedoesnotguaranteetheclassificationofthesourceasablazar:
be large, implying that less mass is required to emit a given lu-
minosity. The black hole would then grow at a slower rate, and R>100couldinfactcorrespondtoasourceseenatθv >1/Γ,but
withaparticularlyweakintrinsicopticalluminosity,or,vice–versa,
itbecomesproblematictoexplainlargeblackholemassesathigh
withaparticularstrongintrinsicradio–luminosity. Toconfirmthe
redshifts(seee.g.Ghisellinietal.2013).Thismotivatesourinterest
blazar nature of these high–redshift powerful sources we require
injettedquasarsathighredshiftswithlargeblackholemasses.
alsoastrongandhardX–rayflux,becauseitisanadditionalsigna-
tureofasmallviewingangle(duetothespecificemissionmecha-
nismthoughtoproducetheX–rayemission,seeDermer1995and
⋆ E–mail:[email protected]
(cid:13)c 2012RAS
2 G. Ghiselliniet al.
Sbarratoetal.2015).Forthisreason,weaskedandobtainedatar-
get of opportunity observation in the X–ray band with the Swift
satellite.Inthisletterwediscussthesedatainthebroadercontext
oftheentireSED,derivingarobustestimateontheblackholemass
andonthepossiblerangeofviewingangles.
Inthiswork,weadoptaflatcosmologywithH0 =70kms−1
Mpc−1andΩM =0.3.
2 SDSS0131–0321ASABLAZARCANDIDATE
SDSS0131–0321wasselectedbyYi14asahigh–zquasarsonthe
basisoftheSloanDigitalSkySurvey(SDSS)andtheWide–Field
InfraredSurveyExplorer(WISE)photometricdata.Theopticaland
nearinfraredspectroscopyperformedbyYi14showedabroadLyα
and a MgII line, at z = 5.18. FromtheFIRST(Faint Images of
theRadioSkyatTwenty-cm;Becker,White&Helfand,1995)cat-
alogtheradiofluxis33mJyat1.4GHz,correspondingtoaνLν
luminosityof1.3×1044ergs−1.Yi14measuredaradioloudness
of∼100,byassumingthattheradio–to–opticalspectrumfollowsa
Fν ∝ν−0.5powerlaw,andcalculatingthiswaythefluxattherest
framefrequencies of5GHzand4400 A˚ (Kellermanetal.1989). Figure1. Optical–UVSEDof0131–0321intherestframe,togetherwith
ThesourceisnotdetectedbytheLargeAreaTelescope(LAT)on- modelsofstandard accretion discemission.Thegreystripeindicates the
board the Fermi satellite. In high–z and powerful radio sources, νLνpeakluminosityofthedisc,estimatedasLd=10×LBLR(seetext).
aradio–loudness equal orlargerof100stronglysuggeststhatwe Weshowthespectrumofthreeaccretiondiscmodelswithdifferentblack
seethejetradiationwithasmallviewingangle.ThismakesSDSS holemasses:MBH/M⊙ = 1.4×1010 (reddashed),1.1×1010 (solid
0131–0321agoodblazarcandidate,butinordertoconfirmit,we blueanddarkgreen)and9×109(dashed,lightgreen).Outsidethisrangeof
masses,themodelcannotfitsatisfactorilythedata.TheWISElowfrequency
needtocheckifitsX–rayemission,producedbythejet,isstrong
pointisfittedassumingthat,besidesthetorusemissionenvisaged bythe
relativeto theoptical, and if itsslope isharder than the one of a
Ghisellini&Tavecchio(2009)model,thereisanother,hotter(T ∼1300K)
typicalaccretiondisccorona(i.e.αX <0.8–1). toruscomponent,asfoundinCalderoneetal.(2013).
2.1 Swiftobservations
onceduringtheobservationofNovember12,2014foratotalexpo-
ToconfirmtheblazarnatureofSDSS0131–0321weaskedtoob- suresof223and512s,respectively.Thesourcewasneverdetected.
serve the source with the Swift satellite (Gehrels et al. 2004). In Forthev filterwederivea3σ upperlimitofv ∼ 20.5mag,cor-
fact the X–ray spectra of blazars beamed towards us are partic- responding toafluxF < 0.023 mJy, without accounting for the
ularly bright and hard, with an energy spectral index αx ∼ 0.5 likelyabsorptionalongthelineofsightduetointerveningmatter.
[F(ν) ∝ ν−αx](seee.g.Ghisellinietal.2010, Wuetal.2013).
TheobservationswereperformedbetweenOctober23andDecem-
2.2 Theaccretiondiscluminosity
ber9,2014(ObsIDs:00033480001–00033480014).
DataoftheX–rayTelescope(XRT,Burrowsetal.2005)and Fig.1showstheIR–UVpartoftheSED,thatcanbewelldescribed
the UltraViolet Optical Telescope (UVOT, Roming et al. 2005) asthermalemissionfromanaccretiondisc.Thepeakofthisther-
weredownloadedfromHEASARCpublicarchive,processedwith malemissionliesredwardof thehydrogen Lyαfrequency (verti-
thespecificSwiftsoftwareincludedinthepackageHEASoft v. calocherline),implyingthatitisnotanartefactoftheabsorption
6.13andanalysed.ThecalibrationdatabasewasupdatedonJune, duetointerveningLyαclouds.Thisallowstoderivetheluminosity
2014. We did not consider the data of the Burst Alert Telescope ofthediscratheraccurately:Ld = 4.1×1047 ergs−1.The(rest
(BAT,Barthelmyetal.2005),giventheweakX–rayflux. frame)peakfrequencyofthediscemissionisνd,peak∼1.7×1015
FromalltheXRTobservations weextractasinglespectrum Hz.NotethatLdisroughlyhalfofthebolometricluminosityLbol
with total exposure of 20.2 ks. The mean count rate was (2.3± estimatedbyYi14onthebasisofthe(restframe)3000A˚ contin-
0.3)×10−3.Giventhelowstatistics,thefitwithapowerlawmodel uumluminosity,usingtheprescriptionsuggestedbyRichardsetal.
withGalacticabsorption(NH =3.7×1020 cm−2,Kalberlaetal. (2006):Lbol = 5.18L(3000A˚).AsdiscussedinCalderoneetal.
2005)wasdonebyusingthelikelihoodstatistic(Cash1979). (2013),LbolconsideredbyRichardsetalal.(2006)includestheIR
The output parameters of the model were a spectral slope ri–emissionbythetorusandtheX–rayemission,whilethe“pure”
Γx = (αx +1) = 1.56±0.38 and an integrated de–absorbed discluminosityisLd ∼0.5Lbol.
fluxF0.3−10keV =(1.4±0.5)×10−13ergcm−2s−1.Thevalue TheWISElowfrequencydetectionpointliesin–betweenthe
ofthelikelihoodwas43.9for45dof.TheX–raydatadisplayedin contributionof theaccretion discandthetorusemission asmod-
theSED(Fig.2)havebeenrebinnedtohaveatleast3σineachbin. elled by Ghisellini & Tavecchio (2009), who considered that the
The source was not expected to be detected in any of the torusemitsasasimpleblack–bodyatthetemperatureofTtorus =
UVOT filters, therefore the various observations were performed 370K.Inreality,thetorusemissionismorecomplex,withemis-
withdifferentfilters(i.e.theobservationswereperformedwiththe sionuptothesublimationdusttemperatureTsubl ∼ 2000K(e.g.
set-up “filter of the day”), usually W1 or M2 UV–filters. In four Peterson1997).Calderoneetal.(2012)foundthatcompositeWISE
casesalsotheufilterwasused,whilethebandvfilterswereused data of a large sample of quasars were consistent with the sum
(cid:13)c 2012RAS,MNRAS000,1–6
SDSSJ0131–0321:11billionsolarmassblackholeat z=5.18 3
of two black–bodies with average temperatures T=308 and 1440
K and similar luminosities. We have added a black–body with
T =1300KtothemodelSED,havingaluminositysimilartothe
colder black–body of 370K. Thisscenario isprobably stillover-
simplified,butcanaccountfortheobserveddata.
Fig. 1 shows also that the Two Micron All Sky Survey
(2MASS,Skrutskieetal.2006)pointatlog(ν/Hz) ∼ 15.05(rest
frame) is above the modelled disc emission. This discrepancy is
duetotheMgIIbroademissionline(at2800A˚ restframe),falling
intheHbandfilterof2MASS(Cohenetal.2003).
The grey stripe in Fig. 1 shows the Ld value inferred from
the Lyα and MgII broad lines. We assumed that Ld ∼ 10LBLR
(Baldwin&Netzer,1978;Smithetal.,1981),whereLBLR isthe
luminosityoftheentirebroadlineregion,thatwederivefollowing
thetemplatebyFranciset al.(1991): settingto100thecontribu-
tion of the Lyα line, the broad MgII contribution is 34, and the
entire LBLR is 555. For the template calculated by Vanden Berk
(2001)thecontributionofallbroadlinestoLBLR issimilar,with
theexceptionoftheLyαwhosecontributionisabouthalftheone
calculatedbyFrancisetal.(1991).
We then took the logarithmic average of the values derived
separately for the MgII and the Lyα line (see data in Yi14), as- Figure2. SEDofSDSSJ0131–0321togetherwiththreeone–zoneleptonic
sumingthatweseeonlyhalfofit(i.e.thenonabsorbedpart).We models,correspondingtoθv=3◦,Γ=13(greenlongdashedline);θv=
assumedanuncertaintyof0.2dexonthisestimateofLd. 5◦,Γ = 13(solidblueline)andθv = 5◦,Γ = 10(shortdashedblack
line).ParametersinTab.1.Thelowerboundofthegreystripecorrespond
totheLATupperlimitsfor5years,5σ.
2.3 Theblackholemass
3 OVERALLSPECTRALENERGYDISTRIBUTION
WecansetalowerlimittotheblackholemassofSDSS0131–0321
byassumingthatitsdiscemitsatorbelowtheEddingtonlevel.This The overall SED of SDSS 0131–0321 from radio to X–rays is
impliesMBH >3.2×109M⊙.Yi14,usingthevirialmethod(e.g. showninFig.2.Toguidetheeye,thedashedlineintheradiodo-
Wandel1997;Petersonetal.2004)appliedtotheMgIIbroadline, mainshow aradiospectrum Fν ∝ ν0. The5yearslimitingsen-
derivedMBH =(2.7−4.0)×109,andconcludedthatthesource sitivityofFermi/LATisshownbythelowerboundaryofthegrey
isemittingatasuper–Eddingtonrate(theyalsoconsideredLbolas hatched area. The solid and long–dashed lines correspond to the
thediscluminosity). one–zone,leptonicmodeldescribedindetailinGhisellini&Tavec-
The IR–optical SED of the source shows a peak and has a chio(2009).Themodelassumesmostoftheemissionisproduced
low frequency slope consistent with the emission from a simple, atadistanceRdissfromtheblackhole,wherephotonsproducedby
Shakura&Sunyaevdisc(1973)model.Fig.2showsthatthenon– theBLRandbythetorusarethemostimportantseedsforthein-
thermal,possiblyhighlyvariable,continuumisnotcontributingto verseComptonscatteringprocess,thatdominatesthehighenergy
theIR–UVflux.Sincetheaccretiondiscismuchlessvariablethan luminosity.TheregionmoveswithabulkLorentzfactorΓandhas
thejetemission,weexpect thattheIR–UVdata,althoughnot si- atangled magneticfieldB.Thedistributionof theemittingelec-
multaneous,giveagooddescriptionofthediscemission.Thisde- tronsisderivedthroughacontinuityequation,assumingcontinuos
pendsonlyonMBH andthemassaccretionrateM˙.Thelatteris injection,radiativecooling,possiblepairproductionandpairemis-
tracedbythetotaldiscluminosityLd =ηM˙c2,whereηistheeffi- sion,andiscalculatedatatimer/cafterthestartoftheinjection,
ciency,thatdependsonthelaststableorbit,henceontheblackhole where r = ψRdiss is the size of the source, and ψ (=0.1 rad) is
spin(withη = 0.057andη = 0.3appropriateforanonrotating thesemi–apertureangleofthejet,assumedconical.Theaccretion
andamaximallyspinningblackhole,respectively;Thorne1974). diskcomponentisaccountedfor,aswelltheinfraredemissionre-
HavingalreadymeasuredLd(henceM˙,assumingη∼0.08), processedbyadustytorusandtheX–rayemissionproducedbya
theonlyfreeparameterisMBH,whosevaluedeterminesthepeak hotthermalcoronasandwichingtheaccretiondisc.
frequencyofthediscemission.ForafixedM˙,alargerMBH im- ThethreemodelsshowninFig.2,whoseparametersarelisted
plies a larger disc surface, hence a lower maximum temperature. inTab.1,differmainlyfromthevalueofθvandΓ.Thishighlights
ThereforealargerMBHshiftsthepeaktolowerfrequencies.Then howthepredictedSEDchanges,especiallyinthehardX–rayband,
thebestagreementwiththedatafixesMBH (e.g.Calderoneetal. byvaryingθvevenbyasmallamount.Thetwoθv =5◦casesindi-
2013).Fig.1showsthediscemissionforthree(slightly)different catethemaximumviewinganglethatcanwellexplaintheexisting
values of MBH: 9, 11 and 14 billions solar masses. Outside this data. The θv = 5◦, Γ = 10 and the θv = 3◦ cases correspond
rangewedonotsatisfactorilyaccountfortheobserveddata,while toaviewinganglesmallerthan1/Γ,thatwouldallowtoclassify
theagreementbetweenthedataandthemodelisrathergoodwithin SDSS0131–0321ablazar.Torefineourpossiblechoicesweneed
thismassrange.Weconcludethattheblackholemassiswelldeter- observationsinthehardX–rayband,suchastheonethattheNu-
minedandisMBH =(1.1±0.2)×1010M⊙forη=0.08.Weob- clearSpectroscopicTelescopeArraysatellite(NuSTAR,Harrisonet
tainMBH =8×109M⊙forη=0.057andMBH =2×1010M⊙ al.2013)canprovide.AsinthecaseofB21023+25(Sbarratoetal.
forη=0.15(seealso§4).Thereisthusafactorof ∼> 2ofsystem- 2013),NuSTARcouldrevealaveryhardspectrum,thatcouldmake
aticuncertainty. ustochoosethelargeΓandsmallθvsolution.Tab.1reportsalso,
(cid:13)c 2012RAS,MNRAS000,1–6
4 G. Ghiselliniet al.
Name z Rdiss MBH RBLR Pi′ Ld LLEddd B Γ θv γb γmax Pr PB Pe Pp
[1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16] [17]
0131–0321 5.18 2310 1.1e10 2031 0.02 47.62 0.25 1.6 13 5 70 3e3 46.3 47.2 44.9 47.6
0131–0321 5.18 2310 1.1e10 2031 0.02 47.62 0.25 2.1 10 5 70 3e3 46.0 47.2 44.8 47.4
0131–0321 5.18 2310 1.1e10 2031 9e–3 47.62 0.25 1.1 13 3 300 3e3 46.0 46.9 44.0 46.5
1146+430 5.005 900 5e9 1006 7e–3 47.00 0.15 1.4 13 3 230 3e3 45.9 46.3 44.0 46.5
0906+693 5.47 630 3e9 822 0.02 46.83 0.17 1.8 13 3 100 3e3 46.3 46.2 44.6 47.1
1023+25 5.3 504 2.8e9 920 0.01 46.95 0.25 2.3 13 3 70 4e3 46.0 46.2 44.5 46.9
Table1.ListofparametersadoptedfororderivedfromthemodelfortheSEDof0131–0321,comparedwiththesetofparametersusedfortheothertwo
blazarsatz >5.Col.[1]:name;Col.[2]:redshift;Col.[3]:dissipationradiusinunitsof1015cm;Col.[4]:blackholemassinsolarmasses;Col.[5]:size
oftheBLRinunitsof1015cm;Col.[6]:powerinjectedintheblobcalculatedinthecomovingframe,inunitsof1045ergs−1;Col.[7]:logarithmofthe
accretiondiskluminosity(inergs−1);Col.[8]:LdinunitsofLEdd;Col.[9]:magneticfieldinGauss;Col.[10]:bulkLorentzfactoratRdiss;Col.[11]:
viewingangleindegrees;Col.[12]and[13]:breakandmaximumrandomLorentzfactorsoftheinjectedelectrons;Col.[14]–[17]:logarithmofthejetpower
(inergs−1)indifferentforms:Col.[14]powerspentbythejettoproducethenon–thermalbeamedradiation;Col.[15]:jetPoyntingflux;Col.[16]:power
inbulkmotionofemittingelectrons;Col.[17]:powerinbulkmotionofcoldprotons,assumingoneprotonperemittingelectron.ThetotalX–raycorona
luminosityisassumedtobeintherange10–30percentofLd.Itsspectralshapeisassumedtobealways∝ν−1exp(−hν/150keV).
4 DISCUSSIONANDCONCLUSIONS
Althoughwecannotdecide(yet)ifSDSS0131–0321canbeclas-
sifiedas ablazar ina strict sense (i.e.a source withθv < 1/Γ),
wecan nevertheless conclude that θv issmall, and therefore it is
very likely that there exist other sources like SDSS 0131–0321
pointinginotherdirections.Assumingtwooppositelydirectedjets,
Γ = 13 and θv = 5◦, we can estimate the presence of other
1/(1−cos5◦)=260sourcessharingthesameintrinsicproperties
ofSDSS0131–0321 inthesameskyarea(about1/4oftheentire
sky)coveredbytheSDSS+FIRSTsurvey.IffutureNuSTARobser-
vationsdetectahighhardX–rayflux,thentheΓ = 13,θv = 3◦
solution is preferred, and the total number of sources like SDSS
0131–0321shouldbe2Γ2 =338(Γ/13)2 inthesameskyarea.
We believe that the black hole mass we found through the
disc–fittingmethodisveryreliable,sincewedoseethepeakofthe
accretion disc emission red–ward of the Lyα limit. The only un-
certaintyconcernstheuseofasimpleShakuraandSunyaev(1973)
model,thatassumesano(oramodestly)spinningblackhole.On
theotherhandtheresultingfitisgood,andwestressthatinthecase
ofafastlyspinningblackhole,withacorrespondinghighaccretion
Figure3.TheSEDofSDSS0131–0321iscomparedtotheSEDsofthe efficiencyη,wewouldderivealargerblackholemass.Thisisbe-
otherknownblazarsatz >5.SDSS0131–0321standsoutbyhavingthe cause,foragivenMBH andM˙,aKerrblackholewouldproduce
mostpowerfuldisc.TheradioandtheX–raydata,ontheotherhand,have moreoptical–UVflux(withrespecttoanonspinningblackhole),
luminositysimilartotheotherblazars.Thefigureshowsalsotheinterpo- thenexceedingtheobserveddatapointsatthepeakoftheoptical–
latingmodels,whoseparametersarelistedinTab.1. UVSED.OnemustlowerM˙,butthisleadstounder–representthe
IR–opticalpoint,thatcanberecoveredbyincreasingthemass(i.e.
increasingthediscsurface,implyingasmallertemperature).
for theeaseof thereader, theparameters weused tofittheother
3 known blazars1 at z > 5. The parameters are all very similar, Howcansuchalargemassbeproducedatz = 5.18?Atthis
andarealsointhebulkofthedistributionofparametersaccount- redshift the Universe is 1.1 Gyr old. Fig. 4 shows the change of
ingformuchlargersampleofblazarsshowingbroademissionlines the black hole mass in time, assuming different efficiencies η. If
(Ghisellinietal.2010;2014b,Ghisellini&Tavecchio2015). the black hole is not spinning, and η < 0.1, then it is possible
Fig.3showshowtheSEDofSDSS0131–0321compareswith togrowablackholeupto11billionsolarmassesstartingfroma
theSED(inνLν vsrestframeν)ofthethreeotherblazarknown 100M⊙seediftheaccretionproceedsattheEddingtonrateallthe
atz > 5. The4non–thermal jetSEDsarerathersimilar,butthe time. But if η = 0.3, appropriate for a maximally spinning and
accretiondisccomponentofSDSS0131–0321standsout,beinga accretingblackhole(Thorne1974),thenthegrowthisslower,and
factor∼4moreluminous. an Eddington limited accretion cannot produce a 1.1×1010M⊙
blackholeatz=5,unlesstheseedis108M⊙atz=20.
Thisposestheproblem:jettedsourcesarebelievedtobeasso-
1 Forthejetpowers,wehereconsiderthesumofpowerofeachofthetwo ciatedwithfastlyspinningblackholes,thereforewithhighlyeffi-
jets,whileintheoriginalpapersdiscussingthesesources,thepowerofonly cientaccretors.IftheaccretionisEddingtonlimited,jettedsources
onejetwasreported. shouldhaveblackholeslighterthanradio–quietquasarswithnot–
(cid:13)c 2012RAS,MNRAS000,1–6
SDSSJ0131–0321:11billionsolarmassblackholeat z=5.18 5
spinningblackholes.Thesolutiontothispuzzlecanbethat,when
ajetispresent,thennotallthegravitationalenergyoftheinfalling
matteristransformedintoheatandthenradiation,assuggestedby
Jolley&Kunzic(2008)andGhisellinietal.(2010).Inthiscasethe
totalaccretionefficiencycanbeη = 0.3,butonlyafractionofit
(ηd)goestoheatthedisc,whiletherest(η−ηd)goestoamplifythe
magneticfieldnecessarytolaunchthejet(bytappingtherotational
energyoftheblackhole).ThediscluminositybecomesEddington
limitedforagreateraccretionrate(makingtheblackholegrowing
faster).ThisisshowninFig.4asthecaseη =0.3,ηd =0.1,that
requires a seed of 104M⊙ at z = 20; and by the case η = 0.3,
ηd = 0.06,thatcanreach11billionM⊙ startingfroma100M⊙
seedatz∼11.
Inthisscenario,thejetisrequiredifverylargemassesmust
bereachedatlargeredshifts,togetherwithavastreservoirofmass
that can be accreted. In this respect, the recent finding of Punsly
(2014),namelythatradio–loudobjectshaveadeficitofUVemis-
sionwithrespecttoradio–quietquasarofsimilardiscluminosity,
isveryintriguing,pointingtothepossibilitythattheinnerpartof
theaccretiondiscaroundaKerrblackholeisproducingmuchless
luminosity than expected, because the produced energy does not
gointoheatingthedisc,butinotherforms,suchasamplifyingthe Figure 4. The black hole mass as a function of time in system charac-
magnetic field of the inner disc, a necessary ingredient to let the terisedbyanEddingtonlimitedaccretion rate,andbydifferentvalues of
Blandford&Znajekprocessworkefficiently. the efficiency η (see also Fig. 3 in Trakhtenbrot et al. 2011) Values of
η = 0.06 and η = 0.3 correspond to no spinning Schwarzschild and
maximallyspinningKerrblackholes,respectively. Allcasescorresponds
toMBH = 1.1×1010M⊙atz = 5.18,themassofSDSS0131–0321.
ACKNOWLEDGEMENTS Thisfigureshowsthatonlyiftheaccretiondiscefficiencyηd issmallwe
cangrowalargemassblackholeintherequiredtimestartingfromarea-
Thispublication makes useof data products fromtheWide–field
sonableseed.Ontheotherhand,thismaynotimplyanonrotatingblack
Infrared Survey Explorer, which is a joint project of the Univer- hole.
sity of California, Los Angeles, and the Jet Propulsion Labora-
tory/Caltech,fundedbyNASA.Italsomakesuseofdataproducts
JolleyE.J.D&KuncicZ.,2008,MNRAS,386,989
fromtheTwo Micron AllSkySurvey, which isajoint project of
KalberlaP.M.W.,BurtonW.B.,HartmannD.,ArnalE.M.,BajajaE.,Morras
the University of Massachusetts and the Infrared Processing and
R.&Po¨ppelW.G.,2005,A&A,440,775
Analysis Center/Caltech, funded by NASA and the National Sci-
KellermannK.I.,SramekR.,SchmidtM.etal.,1989,AJ,98,1195
ence Foundation. Part of this work is based on archival data and
McGreerI.D.,HelfandD.J.&WhiteR.L.,2009,AJ,138,1925
on–lineserviceprovidedbytheASIScienceDataCenter(ASDC). PetersonB.M.,1997,AnIntroductiontoActiveGalacticNucleiPublisher:
Cambridge,NewYork,CambridgeUniv.Press
PetersonB.M.,FerrareseL.,GilbertK.M.etal.,2004,ApJ,613,682
PunslyB.,2014,ApJ,797,L33
REFERENCES
RichardsG.T.,LacyM.,Storrie–LombardiL.J.etal.,2006,ApJS,166,470
RomaniR.W.,Sowards–EmmerdD.,Greenhill L.&Michelson P.,2004,
BaldwinJ.A.&NetzerH.,1978,ApJ,226,1
ApJ,610,L9
BeckerR.H.,WhiteR.L.&HelfandD.J.,1995,ApJ,450,559
RomingP.,KennedyT.,MasonK.etal.,2005,SpaceSci.Rev.120,95
BlandfordR.D&ZnajekR.L.,1977,MNRAS,179,433
SbarratoT.,GhiselliniG.,NardiniM.,etal.,2012,MNRAS,426,L91
CalderoneG.,SbarratoT.&GhiselliniG.,2013,MNRAS,431,210
SbarratoT.,TagliaferriG.,GhiselliniG.etal.,2013,ApJ,777,147
Calderone G.,Ghisellini G.,ColpiM.&Dotti, M.,2013,MNRAS,425,
SbarratoT.,GhiselliniG.,TagliaferriG.,FoschiniL.,NardiniM.,Tavecchio
L41
F.&GehrelsN.,2015,MNRAS,446,2483
CashW.,1979,ApJ,228,939
ShakuraN.I.&SunjaevR.A.,1973,A&A,24,337
CohenM.,WheatonWm.A.&MegeathS.T.,2003,AJ,126,1090
SkrutskieM.F.,CutriR.M.,StieningR.etal.,2006,AJ,131,1163
DermerC.D.,1995,ApJ,446,L63
SmithM.G.,CarswellR.F.,WhelanJ.A.Jetal.,1981,MNRAS,195,437
FrancisP.J.,HewettP.C.,FoltzC.B.,ChaffeeF.H.,WeymannR.J.&Morris
ThorneK.S.,1974,ApJ,191,507
S.L.,1991,ApJ,373,465
TrakhtenbrotB.,NetzerH.,LiraP.&ShemmerO.,2011,ApJ,730,7
GehrelsN.,ChincariniG.,GiommiP.etal.,2004,ApJ,611,1005
VandenBerkD.E.,RichardsG.T.,BauerA.etal.,2001,AJ,122,549
GhiselliniG.&TavecchioF.,2009,MNRAS,397,985
Volonteri M.,Haardt F.,Ghisellini G. &Della Ceca R.,2011, MNRAS,
Ghisellini G., Tavecchio F., Foschini L., Ghirlanda G., Maraschi L. &
416,216
CelottiA.,2010,MNRAS,402,497
YiW.–M.,WangF.,WuX.–B.etal.,2014,ApJ,795,L29(Yi14)
GhiselliniG.,HaardtF.,DellaCecaR.,VolonteriM.&SbarratoT.,2013,
WandelA.,1997,ApJ,490,L131
MNRAS,428,1449
WuJ.,BrandtW.N.,MillerB.P.,GarmireG.P.,SchneiderD.P.&Vignali
Ghisellini G., Sbarrato T., Tagliaferri G., Foschini L., Tavecchio F.,
C.,2013,ApJ,763,109
GhirlandaG.,BraitoV.&GehrelsN.,2014a,MNRAS,440,L111
WuX.–B.,HaoG.,JiaZ.etal.,2012,AJ,144,49
GhiselliniG.,TavecchioF.,MaraschiL.,CelottiA.&SbarratoT.,2014b,
Nature,515,376
GhiselliniG.&TavecchioF.,2015,MNRAS,448,1060
HarrisonF.A.,CraigW.W.,ChristensenF.E.etal.,2013,ApJ,770,103
(cid:13)c 2012RAS,MNRAS000,1–6