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AGN at ~1-100 Mev (Especially Non-Blazar AGN) (Also a Li[Le Bit

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AGN at ~1-100 Mev (Especially Non-Blazar AGN) (Also a Li[Le Bit AGN at ~1-100 MeV (Especially non-blazar AGN) (Also a li<le bit about polarizaon from blazars) Jus>n Finke (NRL) GSFC 24 March 2016 1 Compair AdEPT, COMPAIR, Fermi,LAT, Alex"Moiseev""""Future"Space4based" Gamma4ray"observa:ons"""Feb"6,"2015" 17" GSFC" 2 Instrument,Response,Func0ons,Instrument,Response,Func0ons,Compair PSF: 7o at 10 MeV 1o at 100 MeV Alex"Moiseev""""Future"Space4based" Gamma4ray"observa:ons"""Feb"6,"2015" 15" GSFC" 3 Alex"Moiseev""""Future"Space4based" Gamma4ray"observa:ons"""Feb"6,"2015" 15" GSFC" 1-100 MeV Telescope • Assume 10-12 erg cm-2 s-1 in ~1 Msec (11.5 days) and flux sensi>Vity goes as sqrt(me) • It will reach 10-13 erg cm-2 s-1 in ~3 years. • Will it be wide field of View instrument like Fermi? Mul>ply >mescales by 5 Compare with COMPTEL which AdEPT, COMPAIR, reached ~ 10-10 erg Fermi,LAT, cm-2 s-1 Alex"Moiseev""""Future"Space4based" Gamma4ray"observa:ons"""Feb"6,"2015" 17" GSFC" 4 Radio Quiet AGN Hot thermal corona “hot”, geometrically thick, op>cally thin (?) produces > 1 keV X-rays Czerny & Janiuk (2007), A&A, 464, 167 Thermal disk “cold”, geometrically thin, op>cally thick produces <1 keV X-rays Hot corona creates X-rays by inVerse Compton-scaering colder thermal disk emission. Radio Quiet AGN 176 JOHNSON ET AL. Vol. 482 of the high-energy emission from NGC 4151 and the impli- cations of the OSSE limits on nonthermal emission and nonthermal tail annihilation radiation. ) -1 s 0.10 3. PHYSICS OF THE SOURCE -2 Nonthermal tail in electron distribu>on can 3.1. Radiative Processes be created by: As discussed above, the OSSE spectra of NGC 4151 (E) (keV cm Φ taken during 1991È1996 are relatively similar to each other - pair produc>on 2 γγ in shape and di†er moderately (within a factor of D2) in the E (Svenson 1982, 1984; overall amplitude. Also, all broadband X-c spectra analyzed Guilbert et al. 1983; so far (from 1991 to 1993) are well Ðtted with the intrinsic Zdziarski 1985) X-ray power-law index, which is close to constant (ZJM96). 0.01 SpeciÐcally, the Ginga/OSSE spectrum of 1991 JuneÈJuly 100 1000 Energy (keV) - Reconnec>on (e.g. Liu et and the ASCA/OSSE spectra of 1993 May and December al. 2002, ApJ, 572, L173) can all be Ðtted with a thermal Comptonization spectrum FIG. 3.ÈAverage OSSE spectrum of NGC 4151. The solid curve is the with the low-energy photon index of ! ^ 1.8, the plasma Ðt by thermalOSSE spectrum of NGC 4151 Comptonization and Compton reÑection. The dotted curve temperature of D60 keV, and a Compton-reÑection com- gives theJohnson et al. (1997), best Ðt of the hybrid, thermal/nonthermalApJ, 482, 173 model, and the dotted ponent(ZJM96; Zdziarski et al. 1997). Changes in the X-ray curve gives that model with the maximum nonthermal fraction, 15%, 6 spectrum since 1991 appear to be caused mostly by variabil- allowed by the data. Error bars are 1 p statistical ] systematics. Upper limits are 2 . ity of absorption rather than that of the intrinsic spectrum p (Weaveret al. 1994; ZJM96). The above parameters of the thermal-Compton model correspond to the Thomson optical depth of a uniform spherical plasma cloud of q D 1.3 factor of 103, and Compton reÑection is Ðxed at )/2n \ 0.4 (ZJM96). (see above). The best Ðt of this model yields s2\32.8/49 Here we Ðt the average OSSE spectrum with the thermal- dof, which represents only slight statistical improvement Compton model and Compton reÑection. The energy range over the best-Ðt thermal model. It corresponds to 8% of the of OSSE, º50 keV, precludes an independent determi- source power channeled into nonthermal acceleration, and nation of the amplitude of the Compton-reÑection com- it is shown by the dashed curve inFigure 3. The 2È10 keV ponent. Therefore, we Ðx it at the solid angle of the reÑector spectral index of the intrinsic spectrum in this model is of 0.4 ] 2n and the viewing angle of 65¡(ZJM96). We use ! \ 1.82. The maximum allowed nonthermal fraction the most accurate currently available treatment of thermal (*s2\]2.7) equals 15%. This model is shown by the Comptonization, which is that ofPoutanen & Svensson dotted curve inFigure 3. Thus, the presence of nonthermal (1996). Their model assumes that the Comptonizing plasma processes at some level is allowed but not statistically is in the form of hemispheres irradiated from below, with q required. Note that acceleration is expected in scenarios corresponding to the optical depth along the hemisphere involving magnetic Ðelds (e.g.,Haardt, Maraschi, & Ghisel- radius. We also assume that only 10% of the Compton lini1994); however, purely nonthermal models (e.g., reÑection component undergoes further Compton scat- Zdziarskiet al. 1993) are ruled out for NGC 4151. tering in the hot plasma (seeZJM96). We obtain parameters similar to those obtained byZJM96 for the 1991 JuneÈJuly 3.2. Pair Production and 1993 May observations, viz.,kT \ 62`13 keV and q \ The hot Comptonizing plasma may contain some eB ~11 2.0`0.9 at s2\34.7/50 dof. Note that the di†erence of the pairs. The pairs are produced in photon-photon collisions present~0.5 q from q \ 1.3 obtained byZJM96 is mostly due to by photons emitted by the plasma and are destroyed by pair the di†erent source geometries assumed in the two models. annihilation. In equilibrium, the rates of the two processes The 2È10 keV spectral index of the best-Ðt Comptonization are equal. The relative fraction of pairs in the source turns spectrum is ! \ 1.89. This model is shown by the solid out to depend on the ratio of the X-c luminosity,L , of an curve inFigure 3. We have also checked that the plasma active region to its size,r . It is convenient to use insteadXc a c parameters obtained are rather insensitive to the assumed dimensionless quantity,X the compactness parameter, l 4 amount of reÑection (which is relatively uncertain). L p /(r mec3). (Svensson 1984). Below, we will compute l We also use the spectrum shown inFigure 3 to study the requiredXc T X forc the X-c source in NGC 4151 to consist entirely presence of nonthermal processes in the X-c source in NGC of eB pairs. There will be no pairs in the source in the limit 4151. We consider a model in which a fraction of the avail- of l much less than that value. able power is used to accelerate selected electrons (or eB In the purely thermal case, there are very few photons pairs) to relativistic energies, and the rest is distributed above the threshold for pair production, 511 keV, as shown approximately equally among the remaining electrons, i.e., by the solid curve inFigure 3. Therefore, a very large com- it heats the plasma. Such a hybrid model for NGC 4151 was pactness parameter is required for pair domination. We proposed byZdziarski et al. (1993) and was Ðtted to the obtain the value of l D 104, which agrees with the result of 1991 JuneÈJuly ROSAT /Ginga/OSSE spectrum by ZJM96. ZJM96 for the 1991 JuneÈJuly spectrum. This l corresponds The presence of nonthermal acceleration gives rise to a tail to a rather small source size,r ^ 2 ] 1011/N cm, where N on top of the thermal spectrum. This tail is a result of both is the number of active regionsXc in the nucleus. Thisr is Compton scattering by the relativistic electrons and of anni- much less than 3 Schwarzschild radii for either the dynamicXc hilation of eB pairs from the resulting pair cascade estimates of the black hole mass(Clavel et al. 1987) or for (Svensson 1987; Lightman& Zdziarski 1987). We assume Eddington-limited accretion. Furthermore, the Eddington that the relativistic electrons are accelerated to a Lorentz limit is reduced for pair-dominated sources (Lightman, Radio Quiet AGN Nonthermal tail can be created by γγ pair produc>on in hot corona. It has been proposed that pairs can regulate temperature in corona (Fabian et al. 2015). Poten>ally testable with MeV obserVaons of nonthermal tail. NuSTAR Fabian et al. (2015), MNRAS, 451, 4375 7 AGN populaon No. ] 7 0.3-1 MeV 1-3 MeV 3-10 MeV 104 103 str] π 102 101 N(>z) [4 100 10-1 30-100 MeV 0.01 0.1 1 10 4 10-30 MeV 10 Redshift z 3 -12 2 10 Flim = 10 erg/cm /s str] π 102 U03 Seyfert I08 Seyfert 101 A09 FSRQ N(>z) [4 A12 FSRQ 100 10-1 0.01 0.1 1 10 0.01 0.1 1 10 Redshift z Redshift z Inoue et al. (2015), PASJ, 67, 76 8 Fig. 5. The same as Figure. 4, but for the limiting sensitivity of 10−12 [erg cm−2 s−1]. < For the Seyfert models, the detectable Seyferts will Seyfert is faint, we can detect only nearby (z ∼ 1)Seyfertseven be only local Seyferts. Even if the sensitivity limit of with the sensitivity limit of 10−12 erg cm−2 s−1. 10−12 erg cm−2 s−1 is achieved, the most distant Seyfert If FSRQs make up the whole MeV background (A09), the will be at z ∼ 1.Ontheotherhand,fortheFSRQmod- sensitivity of ∼ 4 × 10−12 erg cm−2 s−1 is needed to de- els, we can expect z ∼ 3–4 FSRQs with the sensitivity tect several hundreds of FSRQs at the MeV gamma-ray band.
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