DRAFTVERSIONJANUARY24,2017 PreprinttypesetusingLATEXstyleemulateapjv.5/2/11 MODELINGTHESPECTRALENERGYDISTRIBUTIONOFTHERADIOGALAXYIC310 N.FRAIJA1,A.MARINELLI2,A.GALVAŃ-GA´MEZ1ANDE.AGUILAR-RUIZ1 1InstitutodeAstronom´ıa,UniversidadNacionalAutońomadeMe´xico,CircuitoExterior,C.U.,A.Postal70-264,04510Me´xicoCity,Me´xico 2I.N.F.N.&PhysicsInstitutePoloFibonacciLargoB.Pontecorvo,3-56127Pisa,Italy DraftversionJanuary24,2017 ABSTRACT TheradiogalaxyIC310locatedinthePerseusClusterisoneofthebrightestobjectsintheradioandX-ray bands,andoneoftheclosestactivegalacticnucleiobservedinvery-highenergies.InGeV-TeVγ-rays,IC310 7 wasdetectedinlowandhighfluxstatesbytheMAGICtelescopesfromOctober2009toFebruary2010.Taking 1 intoaccountthatthespectralenergydistribution(SED)uptoafewGeVseemstoexhibitadouble-peakfeature 0 andthatasingle-zonesynchrotronself-Compton(SSC)modelcanexplainallofthemultiwavelengthemission 2 exceptforthenon-simultaneousMAGICemission,weinterpret,inthiswork,themultifrequencydatasetofthe n radiogalaxyIC310inthecontextofhomogeneoushadronicandleptonicmodels. Intheleptonicframework, a wepresentamulti-zoneSSCmodelwithtwoelectronpopulationstoexplainthewholeSEDwhereasforthe J hadronicmodel,weproposethatasingle-zoneSSCmodeldescribestheSEDuptoafewGeVsandneutralpion 2 decayproductsresultingfrompγ interactionscoulddescribetheTeV-GeVγ-rayspectra. Theseinteractions 2 occurwhenFermi-acceleratedprotonsinteractwiththeseedphotonsaroundtheSSCpeaks. Weshowthat,in the leptonic model the minimum Lorentz factor of second electron population is exceedingly high γ ∼ 105 e ] disfavoringthismodel,andinthehadronicmodeltherequiredprotonluminosityisnotextremelyhigh∼1044 E erg/s,providedthatchargeneutralitybetweenthenumberofelectronsandprotonsisgiven.CorrelatingtheTeV H γ-ray and neutrino spectra through photo-hadronic interactions, we find that the contribution of the emitting . regionofIC310totheobservedneutrinoandultra-high-energycosmicrayfluxesarenegligible. h p Subject headings: Galaxies: active – Galaxies: individual (IC310) – radiation mechanism: nonthermal – - gammarays: general o r t s 1. INTRODUCTION a [ Activegalacticnuclei(AGN)areoneofthemostextremeastrophysicalsourcesintheUniverse. Thesearecompact,extremely luminousandoftenmostvariableshortestobservedfrequencies.Perpendiculartotheplaneoftheaccretionmaterial,magnetically 1 drivenandcollimatedrelativisticplasmaoutflowsareejectedawayfromtheAGN(Lovelace&Kronberg2013;Lovelace1987; v Lovelaceetal.2002).They,extensivelystudiedfromradiowavelengthstovery-high-energy(VHE)γ-rays,areusuallyexplained 3 by the non-thermal synchrotron self-Compton (SSC) model (Abdo & et al. 2010; Fraija et al. 2012; Tavecchio et al. 1998), 7 although hadronic models in some cases have been required (Abdo et al. 2011; Aharonian 2002; Mu¨cke & Protheroe 2001; 1 Atoyan&Dermer2003). 6 Theradiogalaxies,atypeofAGN,areellipticalgalaxieswithtwogiantlobesandmisleading-bipolarjetsofgasextendingaway 0 fromacentralnucleus. Theradiogalaxiesaregenerallydescribedbythestandardnon-thermalSSCmodel(Abdo&etal.2010; . 1 Fraijaetal.2012;Tavecchioetal.1998),low-energyemission(fromradiotooptical)fromsynchrotronradiationandHEphotons 0 (from X-rays to γ-rays) from inverse Compton scattering emission. This model with only one electron population, predicts a 7 spectral energy distribution (SED) that can be hardly extended up to higher energies than a few GeVs (Georganopoulos et al. 1 2005; Lenain et al. 2008). Therefore, some authors have claimed that the emission in the GeV - TeV energy range may have : v originindifferentphysicalprocesses(Brown&Adams2011;Georganopoulosetal.2005). TheradiogalaxyIC310,alsocalled i B0313+411andJ0316+4119,locatedinthePerseusClusterataredshiftofz=0.00189(Bernardietal.2002)isoneofbrightest X objectsofthePerseusclusterofgalaxiesintheradioandX-raybands. Duetoitskiloparsec-scaleradiomorphology,ithasbeen r classifiedasahead-tailor,morespecifically,narrow-angletailradiogalaxy(Ferettietal.1998;Sijbring&deBruyn1998). This a radio galaxy being one of the fourth closest AGN observed in VHE γ-rays (after Cen A, M87 and NGC1275) is an excellent sourceforstudyingthephysicsofrelativisticoutflows.Ithasbeendetectedabove30GeVbyLargeAreaTelescope(LAT)-Fermi (Neronov et al. 2010). They reported the flux in two energy bands, F = 2.3+2.3 ×10−11 erg cm−2 s−1 between 30 30−100 −1.2 and 100 GeV, and F = 1.4+1.1 ×10−11 erg cm−2 s−1 from 100 to 300 GeV. In addition, this source was detected by 100−300 −0.6 MAGICtelescopesatahighstatisticalsignificanceof7.6σin20.6hrofstereodata. TheTeVγ-rayfluxof(3.1±0.5)×10−12 cm−2 s−1 (between2009Octoberand2010February)wasflatwith adifferentialspectralindexof2.00±0.14(Aleksic´ 2010). The indications for flux variability on times scales of months and years were reported. The variability time scales of years was confirmed by the non-detection of the source reported in 2010 August - 2011 February (Aleksic´ & et al. 2012). A re- analysisoftheMAGICstereo-observationtakenduringthesameperiodwasperformed(Aleksic´ etal.2014b). Afterfittingthe spectraathighandlowstatebetween0.12and8.1TeVwithasimplepowerlaw,theobservedfluxesreportedbyauthorswere (4.28±0.21±0.73)×10−12 TeV−1 cm−2 s−1 and(0.608±0.037±0.11)×10−12 TeV−1 cm−2 s−1,respectively(Aleksic´ etal.2014b). nifraija@astro.unam.mx,antonio.marinelli@pi.infn.it,agalvan@astro.unam.mxandeaguilar@astro.unam.mx 2 Fraijaetal. Located at the South Pole, the IceCube telescope was designed to detect the interactions of neutrinos. With a volume of one cubickilometeroficeandalmostfouryearsofdatataking,theIceCubetelescopereportedwiththeHigh-EnergyStartingEvents (HESE)1catalogasampleof54extraterrestrialneutrinoeventsintheTeV-PeVenergyrange. Arrivaldirectionsoftheseevents are compatible with an isotropic distribution and possible extragalactic origin (Ahlers & Murase 2014; Gaggero et al. 2015). HadronicprocessesproducingafractionoftheobservedneutrinoeventsrevealedbytheIceCubeviatheaccelerationofcomic rays in radio galaxies have been explored (Reynoso et al. 2011; Khiali & de Gouveia Dal Pino 2016; Sahu et al. 2012; Fraija 2014a,b;Marinellietal.2014). InthisworkweintroduceleptonicandhadronicmodelstodescribethebroadbandSEDobservedintheradiogalaxyIC310.Inthe leptonicframework,wepresentamulti-zoneSSCmodelwithtwoelectronpopulationstoexplainthewholeSEDwhereasforthe hadronicmodel,weproposethatasingle-zoneSSCmodeldescribestheSEDuptoafewGeVsandneutralpiondecayproducts theproton-photon(pγ)interactionscouldmodeltheγ-rayspectra(highandlowstate)attheGeV-TeVenergyrange.Correlating theTeVγ-rayandneutrinospectrathroughphoto-hadronicinteractions,weestimatetheneutrinoandultra-high-energycosmic ray(UHECR)fluxes. 2. THEORETICALMODEL Injected electrons and protons are accelerated in the emitting region which moves at relativistic velocities. These particles confined at the emitting region by magnetic fields are expected to cool down by synchrotron radiation, Compton scattering emission and photo-hadronic processes. We hereafter use primes (unprimes) to define the quantities in a comoving (observer) frame, the universal constants c=(cid:126)=1 in natural units and the values of cosmological parameters H = 71 km s−1 Mpc−1, 0 Ω =0.27,Ω =0.73(Spergeletal.2003). m Λ 2.1. Synchrotronradiation Kardashevet al.(1962) showedthat ifthe spectrumof injectedelectrons is ∝ γ−αe, then thespectrum varieswith timeas a e result of losses due to emission in the magnetic field. This variation differs for different energy intervals: N (γ ) = N γ−αe e e 0,e e for γ < γ < γ and N γ γ−(αe+1) for γ ≤ γ < γ , where N is the proportionality electron constant, α e,min e e,c 0,e e,c e e,c e e,max 0,e e is the power index of the electron distribution and γ are the electron Lorentz factors. The index i is min, c or max for e,i minimum,coolingandmaximum,respectively. Assumingthatafractionoftotalenergydensityisgiventoaccelerateelectrons (cid:82) U = m γ N (γ )dγ (m istheelectronmass),theelectronluminosityandtheminimumelectronLorentzfactorareL = e e e e e e e e 4πδD2 rd2Ue and γe,min = m(eα(eα−e−2)1) NUee, respectively. Here r√d is the size of the emitting region and δD is Doppler factor. The electron distribution submerged in a magnetic field B = 8πU cools down following the cooling synchrotron time scale B t(cid:48)c = 34mσTe UB−1γe−1, with σT = 6.65×10−25cm2 the Thomson cross-section. Comparing the synchrotron time scale with thedynamicscalet(cid:48)d (cid:39) rd/δD, wegetthatthecoolingLorentzfactorisγe,c = 34mσTe (1+Y)−1δDUB−1rd−1. HeretheCompton (cid:16) (cid:17)1/2 parameterisY = ηUe for ηUe (cid:28) 1and ηUe for ηUe (cid:29) 1,withη = (γ /γ )2−αe givenforslowcoolingandη = 1forfast UB UB UB UB e,c e,min cooling(Sari&Esin2001). Byconsideringthataccelerationt(cid:48) (cid:39)(cid:112)πm /q U−1/2γ andcoolingtimescalesaresimilar,itispossibleto acc 2 e e B e writethemaximumelectronLorentzfactorasγ =(cid:16) 9qe2 (cid:17)1/4 U−1/4whereq istheelectriccharge.Itisworthnotingthatthedirection e,max 8πσ2 B e T oftheaveragemagneticfieldattheshockisshowntohavealargeeffect. Iftheperpendiculardiffusioncoefficientismuchsmallerthanthe parallelcoefficient,particlescangainmuchmoreenergyiftheshockisquasi-perpendicularthanquasi-parallel. Inthiscase,theacceleration (cid:113) timescalecouldbeevenshorter(Jokipii1987). Takingintoaccountthesynchrotronemission(cid:15) (γ )= 8πqe2 δ U1/2γ2 andfromthe γ e,i m2e D B e,i electronLorentzfactors,thesynchrotronbreakenergiesare √ 8πq (cid:15)syn = e δ U1/2γ2 , γ,m √me D B e,min 9 2πq m (cid:15)syn= e e (1+Y)−2δ3 U−3/2r−2, γ,c 8σ2 D B d T 3q2 (cid:15)syn = e δ . (1) γ,max m σ D e T Theobservedsynchrotronspectrumcanbewrittenas(Longair1994;Rybicki&Lightman1986) (cid:2)(cid:15)2γN((cid:15)γ)(cid:3)γ,syn =Aγ,syn((((cid:15)(cid:15)(cid:15)(cid:15)sγsγsγ(cid:15)(cid:15)sγyyyyγγ,,,,nnnmmmnc )))−−43ααee22−−33((cid:15)(cid:15)γγ,c)−αe2−2, (cid:15)(cid:15)(cid:15)γsγsγyy,,mcnn<<<(cid:15)sγ(cid:15)y,(cid:15)γmnγ,<<(cid:15)(cid:15)sγsγy,y,mncna,x, (2) where 4σ A = T d2δ3 U r3N γ2 , (3) γ,syn 9 z D B d e e,min istheproportionalityconstantofsynchrotronandd isthedistancebetweenIC310andEarth. z 1http://icecube.wisc.edu/science/data/HE-nu-2010-2014 TheradiogalaxyIC310 3 2.2. Comptonscatteringemission Fermi-acceleratedelectronsintheemittingregioncanupscattersynchrotronphotonsuptohigherenergiesas(cid:15)ssc (cid:39)γ2 (cid:15)syn . γ,(m,c,max) e,(min,c,max) γ,(m,c,max) FromtheelectronLorentzfactorsandthesynchrotronbreakenergies(eq. 1),wegetthattheComptonscatteringbreakenergiesaregivenin theform √ 8πq (cid:15)ssc = e δ U1/2γ4 , γ,m m√e D B e,min 81 2πq m3 (cid:15)ssc= e e (1+Y)−4δ5 U−7/2r−4, γ,c 128σ4 D B d T 9q3 (cid:15)ssc = √ e δ U−1/2. (4) γ,max 2 2πm σ2 D B e T TheComptonscatteringspectrumobtainedasafunctionofthesynchrotronspectrum(eq.2)is (cid:2)(cid:15)2γN((cid:15)γ)(cid:3)γ,ssc =Aγ,ssc((((cid:15)(cid:15)(cid:15)(cid:15)sγsγsγ(cid:15)(cid:15)sγsssγγ,,,scc,mmmccc)))−−43ααee22−−33((cid:15)(cid:15)sγγs,cc)−αe2−2 (cid:15)(cid:15)(cid:15)γsγsγss,,ccmc<<<(cid:15)sγ(cid:15)s,(cid:15)γmcγ<,<(cid:15)(cid:15)sγsγs,scm,cca,x, (5) whereA =Y [(cid:15)2N ((cid:15) )]syn istheproportionalityconstantofinverseComptonscatteringspectrum. γ,ssc γ γ γ max 2.3. Photo-hadronicInteractions RadiogalaxieshavebeenproposedaspowerfulacceleratorsofchargedparticlesthroughtheFermiaccelerationmechanism(Dermeretal. 2009), magnetic reconnection (Khiali et al. 2015; Lovelace et al. 2005) and the magnetized accretion disk working as an electric dynamo (Lovelace1976;Lovelaceetal.1987,1994).Weconsideraprotonpopulationdescribedasasimplepowerlawgivenby (cid:18) (cid:19) dN =A E−αp, (6) dE p p p withA theproportionalityconstantandα thespectralpowerindexoftheprotonpopulation.Fromeq.(6),theprotondensitycanbewritten p p as U = Lp with the proton luminosity given by L = 4πd2A (cid:82) E E−αpdE . Fermi-accelerated protons lose their energies by p 4πδ2 r2 p z p p p p D d electromagneticchannelsandhadronicinteractions. ElectromagneticchannelssuchasprotonsynchrotronradiationandinverseComptonwill notbeconsideredhere,wewillonlyassumethatprotonscooldownbypγinteractionsattheemittingregionoftheinnerjet.Charged(π+)and neutral(π0)pionsareobtainedfrompγinteractionwithafractionof2/3and1/3forpπ0andnπ+,respectively.Afterthatneutralpiondecays intophotons,π0 → γγ,carrying20%(ξ = 0.2)oftheproton’senergyE . Theefficiencyofthephoto-pionproductionis(Stecker1968; π0 p Waxman&Bahcall1997) t r (cid:90) (cid:90) dn f (cid:39) dyn = d d(cid:15) σ ((cid:15) )ξ (cid:15) dxx−2 γ((cid:15) =x), (7) π0 t 2γ2 γ π γ π0 γ d(cid:15) γ π0 p γ wheredn /d(cid:15) isthespectrumofseedphotons,σ ((cid:15) )isthecrosssectionofpionproductionandγ istheprotonLorentzfactor. Solving γ γ π γ p theintegralsweobtain σ ∆(cid:15) ξ L (cid:18)(cid:15)πγ,0c(cid:19)−1(cid:18)(cid:15)πγ0(cid:19) (cid:15) <(cid:15)π0 fπ0 (cid:39) 4pπγδ2 rres(cid:15)π0 (cid:15)γ,IC (cid:15)0 (cid:15)0 γ γ,c (8) D d pk,ic res 1 (cid:15)π0 <(cid:15) , γ,c γ where ∆(cid:15) =0.2 GeV, (cid:15) (cid:39) 0.3 GeV, (cid:15) is the energy of the second SSC peak, (cid:15) is the normalization energy and (cid:15)π0 is the break res res pk,ic 0 γ,c photon-pionenergyis(cid:15)π0 (cid:39) 31.87GeVδ2 (cid:0)(cid:15)pk,ic(cid:1)−1. Itisworthnotingthatthetargetphotondensityisn (cid:39) Lγ,IC andtheoptical γ,c D MeV γ 4πrd2(cid:15)pk,ic depthisτ (cid:39) Lγ,ICσT . Takingintoaccountthatphotonsreleasedintherange(cid:15) to(cid:15) +d(cid:15) byprotonsintherangeE andE +dE γ 4πrdδD(cid:15)pk,ic γ γ γ p p p aref E (dN/dE) dE =(cid:15) (dN/d(cid:15)) d(cid:15) ,thenphoto-pionspectrumisgivenby π0 p p p π0,γ π0,γ π0,γ (cid:2)(cid:15)2N((cid:15) )(cid:3) =A (cid:18)(cid:15)(cid:15)πγ0,0c(cid:19)−1(cid:16)(cid:15)(cid:15)γ0(cid:17)−αp+3 (cid:15)γ <(cid:15)πγ,0c (9) γ γ γ,π0 pγ(cid:16)(cid:15)(cid:15)γ0(cid:17)−αp+2 (cid:15)πγ,0c <(cid:15)γ, wheretheproportionalityconstantA isintheform pγ L σ ∆(cid:15) (cid:15)2 (cid:16) 2 (cid:17)1−αp A = γ,IC pγ res 0 ξπ0 A . (10) pγ 4πδ2 r (cid:15) (cid:15) p D d pk,ic res ThepreviousequationsindicatethatthevalueofA isnormalizedusingtheTeVγ-rayflux. p 4 Fraijaetal. 3. HIGHENERGYNEUTRINOEXPECTATION Photo-hadronic interactions in the emitting region (see subsection 3.2) also generate neutrinos through the charged pion decay products (π± → µ±+ν /ν¯ → e±+ν /ν¯ +ν¯ /ν +ν /ν¯ ). TakingintoaccountthedistanceofIC310,theneutrinofluxratiocreatedonthe µ µ µ µ µ µ e e source(1: 2: 0)willarriveonthestandardratio(1: 1: 1;e.g. seeBecker2008). Theneutrinospectrumproducedbythephoto-hadronic interactionsis (cid:16) (cid:17)2 (cid:2)E2N((cid:15) )(cid:3) =A (cid:15)2 E(cid:15)0ν Eν (cid:39) 15◦. In T addition,Dasetal.(2008)foundthatforobserverssituatedwithingroupsofgalaxieslikeours,about70%(35%)ofUHECRswithenergies above60EeVemergeinside∼15◦(5◦),oftheastrophysicalobjectposition. WecanseethatnumberofUHECRscalculatedwithourmodel isconsistentwiththosereportedbytheTAand/orPAOcollaborations. ItisworthnotingthatthelatterresultsreportedbyPAOsuggestedthat UHECRsareheavynucleiinsteadofprotons(Abrahametal.2010).IfUHECRshaveaheavycomposition,thenasignificantfractionofnuclei mustsurvivephotodisintegrationsintheirsources. Inthiscase,ultra-relativisticprotonscanbeconfinedbytheemittingregionssothatthese particlescanachievemaximumenergiesof(cid:38)54EeVforZ(cid:38)2. InterpretingtheTeVγ-rayfluxesfromIC310asπ0decayproductsfromthepγinteractions,thenthenumberofneutrinoeventsare0.16and 0.02whenthesefluxesinhighandlowstatesareconsidered,respectively. Asneutrinofluxeswereobtainedfromthepγinteractionsbetween acceleratedprotonsandtheseedphotonsattheSSCpeaks,thenfluctuationsinthemagneticfield,Dopplerfactorand/oremittingradiuswould change the seed photon density and finally the neutrino fluxes. These fluxes for IC310, Cen A and M87 were computed from relativistic protonsinteractingwiththeseedphotonsaroundtheSSCpeaks,asshowninFigure5. Inthisfigurecanbeseentheneutrinospectrapeaking aroundafewEeV,asexpectedfromtheinteractionswithseedphotonsaroundthesynchrotronpeak(thefirstSSCpeak)(Cuoco&Hannestad 2008). NeutrinofluxesatTeVenergiesareobtainedfromtheinteractionswithseedphotonsaroundtheinverseComptonscatteringpeak(the secondSSCpeak). ConsideringtheneutrinoIceCubedata(Aartsenetal.2014)andtheupperlimitsatUHEssetbyIceCube(IC40;Abbasi etal.(2011)), PAO(Abreuetal.2011), RICE(Kravchenkoetal.2012)andANITA(Gorhametal.2010)weconfirm, withourmodel, the impossibilitytoobservenorTeVneitherEeVneutrinoeventsfromIC310. Itisworthnotingthatifheavynucleiwouldhavebeenconsidered insteadofprotons,HEneutrinosfromUHEnucleiaresignificantlowerthantheneutrinofluxobtainedbyprotons. IC310 CenA M87 Highstate Lowstate δd 1.9 1.8 1.0 2.8 B(G) 1.3 1.2 3.6 1.61 rd(cm) 4.5×1015 5.0×1015 5.2×1015 2.1×1015 αp 3.05 3.07 2.81 2.80 γp,min 5.0×104 8.0×103 1.0×105 7.0×106 γp,max 2.8×1010 2.8×1010 6.73×1010 6.76×1010 (cid:15)peak (MeV) 0.2 0.2 0.1 0.5 (cid:15)π0,γ,c (TeV) 0.52 0.52 0.32 0.54 UB (erg/cm3) 5.7×10−2 5.7×10−2 0.52 0.10 Up (erg/cm3) 17.1 27.58 2.55 2.69 Lp (erg/s) 3.65×1044 4.3×1044 3.74×1043 4.89×1043 Ep,max (EeV) 24.1 24.2 40.1 6.55 NUHECRs 0.28 0.09 1.52 0.41 Table3.ComparisonofthevaluesfoundwiththehadronicmodelusedtodescribetheradiogalaxiesIC310,CenAandM87. Inordertocomparetheparametersderivedwithourlepto-hadronicmodelforIC310,CenAandM87(Fraija&Marinelli2016),wesummarize thesevaluesinTable3.Inthistablecanbenoticedseveralfeatures:i)althoughprotonluminositiesobtainedinIC310presentthelargestvalues, thenumbersexpectedofUHECRsarethesmallest.ItisduetoIC310exhibitsthesoftestspectralindexes,ii)asexpected,thevaluesofDoppler factors of IC 310 are in the range of Cen A and M87, which classify to IC310 as radio galaxy in stead of blazar and iii) the values of the maximumenergiesthatprotonscanachieveintheaccelerationregionindicatethatonlyheavyionscanbeexpectedfromtheseradiogalaxies. 6. SUMMARYANDCONCLUSIONS WehaveproposedleptonicandhadronicmodelstoexplainthebroadbandSEDobservedinIC310. Takingintoaccountthatoneelectron populationthroughtheone-zoneSSCmodelcanexplainthemultiwavelengthemissionexceptforthenon-simultaneousMAGICemission,we haverequiredadditionalelectronandprotonpopulations.Intheleptonicframework,theadditionalelectronpopulationisconfinedinadifferent emittingregion,requiringaminimumLorentzfactorexceedinglyhighγ ∼105whichdisfavorsthismodel.Inthehadronicmodel,relativistic e protons co-accelerated with the electrons that explain the SED up to a few GeV interact with seed photons at the second SSC peak. The requiredprotonluminositiesarenotextremelyhigh1044erg/s,providedthatthechargeneutralityconditionbetweenthenumberofelectrons andprotonsisgiven. CorrelatingtheTeVγ-rayandneutrinospectrathroughphoto-hadronicinteractions,wehaveestimatedthefluxesandnumberofeventsexpected inIceCubetelescope,respectively. Wefoundthattheneutrinofluxproducedbypγ interactionscannotexplaintheastrophysicalfluxandthe expectedν eventsintheIceCubetelescopeareconsistentwiththenonneutrinotrack-likeassociatedwiththelocationofIC310(Aartsenetal. µ 8 Fraijaetal. 2013;IceCubeCollaboration2013;Aartsenetal.2014). ByconsideringthattheprotonspectrumgivenbyasimplepowerlawcanbeextendeduptoUHEs,wehaveshownthatintheradiogalaxy IC310neitherfromtheemittingregionnorotherregions(inflaringintervals)UHECRscouldbeexpected,whichisinagreementwiththeTA andPAOobservations. Consideringtheflaringactivities,cosmicrayswouldneedaprotonluminosityhigherthantheEddingtonluminosity whichisimplausible. Ontheotherhand,IfUHECRshaveaheavycompositionassuggestedbyPAO(Abrahametal.2010),UHEheavynucleiinIC310couldbe acceleratedatenergiesbelow∼57EeV,althoughthenumberofeventexpectedwouldbelessthanone.Itisworthnotingthatifradiogalaxies arethesourcesofUHECRs,theiron-axiscounterparts(i.e. blazars,andflat-spectrumradioquasars)shouldbeconsideredamorepowerful neutrinoemitters(Atoyan&Dermer2001;Dermeretal.2014). Infact,aPeVneutrinoshower-likewasrecentlyassociatedwiththeflaring activityoftheblazarPKSB1424-418(Kadleretal.2016). Severalluminousblazarswhicharerelatedwithquasar-typeAGNexhibitadouble-humpedshapecharacterizedbyalargeluminosityratio betweenlowandhighenergyhumps. Sikoraetal.(2009)studiedthoseblazarswithluminosityratiobetween10-100whichposechallenges tothestandardSSCandhadronicmodels. TheseauthorsconcludedthathadronicmodelscannotaccountfortheveryhardX-rayspectraand alsorequireextremelyefficientaccelerationofrelativisticprotonstothehighestenergies,surpassingtheEddingtonluminosity. Bo¨ttcheretal.(2013)proposedleptonicandhadronicmodelstodescribesomeofFermi-LAT-detectedblazars.Theyfoundthateitherleptonic orhadronicmodelsprovideacceptablefittotheSEDsofmostoftheblazars, althoughinthehadroniccasetheprotonluminositydemands valuesintherangeL ∼ 1047 −1049 erg/s. Recently, Zdziarski&Bo¨ttcher(2015)reviewedthehadronicmodelinradio-loudAGN,and p theimplicationsfortheaccretioninthosesources. Authorsfoundthatthemajorprobleminthehadronicmodelsisrelatedwithhighlysuper- EddingtonjetpowerrequiredtointerprettheSEDspresentedinAGNs.Thisproblem,inturnwoulddemandhighlysuper-Eddingtonaccretion ratesandthen,highluminositieswhichhavenotbeenobserved. Inourmodel,theprotonluminosityislowerthantheEddingtonluminosity, similar to other hadronicmodels whichhave beensuccessful inexplaining, a PeVneutrino shower-like recently associated with theflaring activity of the blazar PKS B1424-418 (Kadler et al. 2016), the SED of BL Lac Mrk421 in low state activity (Abdo et al. 2011) and radio galaxiessuchasCenAandM87(Fraija2014a,b;Khialietal.2015;Fraija&Marinelli2016;Petropoulouetal.2014). The basic discrepancy between our model and those shown in Sikora et al. (2009) and Bo¨ttcher et al. (2013) lies in the distinct radiative processesusedtodescribethehigh-energyγ-raypeakintheSED.WhereasBo¨ttcheretal.(2013)fittedthehigh-energyγ-raypeakwitha substantial contribution of proton synchrotron radiation, we have used SSC emission, which is a more efficient process than that generated by proton synchrotron. As pointed out by Sikora et al. (2009), given the characteristic proton- and electron-related synchrotron energies (cid:15)syn (γ = γ ) = m /m (cid:15)syn andtherelationbetweenthecorrespondingcoolingrates| γ˙ | (γ = γ ) = (m /m ) | γ˙ | ,the γ,c,p p e e p γ,c,e p syn p e e p e syn resultingefficiencyofsynchrotronprotonemissionbecomesverylowincomparisonwithsynchrotronelectron,althoughthisefficiencycanbe increasedbyconsideringalargestrengthofmagneticfieldintheemittingregion(Aharonian2000). Bymeansofeq. 3,wecanestimatethe contributionofprotonsynchrotronradiationtotheSEDandalsocompareitwiththeelectronsynchrotronradiation. Inthiscase,therelation ofproton-andelectron-synchrotronproportionalityconstantsis Aγ,syn,p (cid:39) σT,pUB,pNp , whereσ = m2e σ andU isthemagnetic Aγ,syn σTUBNe T,p m2p T B,p fieldenergydensityassociatedwiththeproton-synchrotronradiationusedtofitthebroadbandSED.Here,thevaluesofDopplerandminimum Lorentzfactorshavebeenconsideredofthesameorder(Abdoetal.2011). TakingintoaccountthechargeneutralityconditionN =N ,the p e contributionofprotonsynchrotronemissionisanalyzedintwocases: 1. Inourmodel,relativisticprotonswillradiatebysynchrotronemissionproportionaltothemagneticfieldobtainedafterfittingtheSED up to GeV energies. In this case, U = U and then the contribution of proton synchrotron emission in our model is very low B,p B Aγ,syn,p ∼ 10−6. Since the SED has been described successfully up to a few GeV with one-zone SSC model, proton synchrotron Aγ,syn emission is not taken into account and then the proton luminosity normalized by photo-hadronic interactions does not increase. As reportedinthiswork,moderateprotonluminositiesarerequired(∼1044erg/s)andweaklyaccretingdisksareexpectedforIC310. 2. Inothermodels,someauthorshavereportedthatthetypicalvaluesofmagneticfieldfoundafterfittingthehigh-energyγ-raypeakof theSEDwithprotonsynchrotronemissionliesintherangeofB =(10-100)B(e.g. seeBo¨ttcheretal.2013;Sikoraetal.2009),with p BthemagneticfieldobtainedwhenaleptonicmodelisusedtodescribetheSED.Inotherwords,themagneticfieldobtainedforproton synchrotronradiationis10-100timeslargerthanthatobtainedforelectronsynchrotronradiation.Inthiscase,theprotonandelectron- relatedsynchrotroncontributionbecomes Aγ,syn,p ∼(10−5−10−3).Normalizingtheprotonluminositiesthroughproton-synchrotron Aγ,syn emission,theprotonluminositiesisincreased∼(103-105)timesmorethantheelectronluminosity,achievingvaluesof∼1047−1049 erg/s.Inthiscase,ahighlysuper-EddingtonjetpowerisrequiredtointerpretthebroadbandSEDs,asdiscussedbyZdziarski&Bo¨ttcher (2015). Basedonthepreviousanalysis, wecanconcludethatamixedmodel, withahigh-energyγ-raypeakbeingleptonicismorerealisticthana hadronicmodelwithasubstantialcontributionofprotonsynchrotronemissiontothehigh-energypeak.Itisworthnotingthatthismodelcould besuccessfullyusedforthegeneralpopulationofblazarsandradiogalaxies. Wethanktheanonymousrefereeforacriticalreadingofthepaperandvaluablesuggestionsthathelpedtoimprovethequalityofthiswork. WealsothankMariaPetropoulou,WilliamLeeandFabiodeColleforusefuldiscussions. ThisworkwassupportedbyUNAMPAPIITgrant IA102917. 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Theelectronpopulationisrequiredtofitthe SEDuptoafewGeVandneutralpiondecayproductsresultingfrompγinteractionsisusedtointerprettheTeV-GeVγ-rayspectra. 90 UHECRs (PAO) 75 75 UHECR's (TA) Neutrinos 60 60 45 45 30 30 15 15 180 150 120 90 0 60 30 0 330 300 0270 240 210 180 -15 -15 -30 -30 -45 -45 -60 -60 -75 -75 -90 FIG.3.—SkymapinequatorialcoordinatesofUHECRs,neutrinoeventsandIC310.BlueandredpointsaretheUHECRsreportedbyTAandPAOcollabora- tions,respectively.IngreenaretheneutrinoeventsreportedbyIceCubeCollaboration.

Modeling the Spectral Energy Distribution of the radio galaxy IC310

Similar Modeling the Spectral Energy Distribution of the radio galaxy IC310