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PoS(ICRC2017)659 http://pos.sissa.it/ ) and thus shed a new on the formation of supermassive [email protected]

, M 9 10 > BH –LAT Collaboration M * Fermi [email protected] [email protected] [email protected] Speaker. holes in theblazars early beyond . z=3.1 using Here theto sensitive we host Pass extremely report 8 massive the black dataset holes of first atmodelling Fermi-LAT. their detection These with centers, objects of as a are confirmed gamma-ray standard from found emitting bothoptical IR-UV spectroscopy. disk continuum Further and details also of the withdisk-jet results connection the will in emission be powerful presented jetted line within AGNs. measurements the using framework of the detected high- blazarsus about (z>3) the are evolution intrinsically of gamma-ray interestingblazars in since the and they Universe. are, It inform by has definition, beenmassive found black some in holes of many ( the studies that more such luminous high z blazars host extremely * © Copyright owned by the author(s)Attribution-NonCommercial-NoDerivatives 4.0 under International the License terms (CC of BY-NC-ND the 4.0). Creative Commons 35th International Cosmic Ray Conference —10–20 ICRC2017 July, 2017 Bexco, Busan, Korea Roopesh Ojha NASA Goddard Space Flight Center, Greenbelt, MDE-mail: 20771, USA on behalf of the Vaidehi S. Paliya and Marco Ajello Department of Physics and , Clemson29634-0978, University, Kinard USA Lab of Physics, Clemson,E-mail: SC Dario Gasparrini Space Science Data Center - AgenziaIstituto Spaziale Nazionale Italiana, di I-00133 Fisica Roma, Nucleare, Sezione Italy E-mail: di Perugia, I-06123 Perugia, Italy Gamma-Ray Beacons at the Dawn of the Universe PoS(ICRC2017)659 - γ . The Pass 8 1 satellite Fermi Fermi Dario Gasparrini ) and host pow- 1 − blazars can constrain z erg s band flux These 48 is the bulk Lorentz factor) B blazars. Moreover, Pass 8 10 Γ z > . bol 600, L 1.4 million included in the − ∼ 400 ∼ -ray sources, i.e., blazars whose high-energy (i.e., γ 2 blazars. Because the energy resolution becomes 2 Γ 1 sources and retain only radio-loud (RL) quasars ; 5]. Since blazars are highly beamed, the detec- z .

3 M > 100 MeV by up to 75 %, with respect to Pass 7, which 9 z < 10 10 MeV) as typical for high- − ∼ 1 ∼ BH blazars, we start from the M z for a given accretion efficiency; e.g., 4]. In general, they harbor 92 months (from 2008 August 5 to 2016 April 1) of 2 ∼ blazars will test the hypotheses of evolution, since these high ˙ Mc z & is the ratio of the rest-frame 5 GHz to optical j catalogs, possibly due to the shift of the IC peak to lower frequencies in 200 MeV). This increases the capability of the LAT to detect spectrally soft, P R < -ray sky [2]. Nonetheless, high-redshift blazars above a redshift of 3.1 are γ blazars. z Fermi ; 9]. σ 10, where > R http://fermi.gsfc.nasa.gov/ssc/data/analysis/documentation/ Blazars are the most powerful Active Galactic Nuclei (AGN) with relativistic jets oriented These objects typically have large bolometric luminosities ( For each object we use Since we are dealing with faint sources, we modify the standard data reduction procedure as In order to search for high- 1 -Ray Beacons at the Dawn of the Universe which LAT is less sensitive. The newlylevel released Pass analysis, 8 substantially photon enhances data set the [3], sensitivitylower with energies of an (i.e., the improved event- LAT at allpotentially energies high- and in particular at close to the line of sight. The jet radiation dominates their broadband emission, especially at γ 1. Introduction rays where the inverse Compton (IC)around hump tens of the or blazar hundreds spectral[1] of energy has distribution MeV. (SED) The already peaks Large detectedpopulation Area thousands in Telescope of (LAT) blazars, the onboard thus the missing confirming in that the they are the most numerous erful relativistic jets [ extremely massive black holes [ follows. We expand thethe energy analysis range to considered be more so sensitive it to spans spectrally 60 soft MeV to 300 GeV. This allows 1103 objects represent our parent samplefollowing and procedure. we analyze LAT data for all of them according to the source class photons anddetails analyze about them the region following of theconsider interest a standard source (ROI) to data size, be significantly background reduction detectedthan models procedure if 25 used the [4.2 maximum can likelihood be test statistic found (TS) in is greater [8]. We peak is shifted to lowerprovides an energies increase ( in the acceptancetranslates at into an improved sensitivity for high- tion of a single blazar implies the existence of 2 with increasingly worse at low energies we enablesources the except energy the dispersion empirical correction diffuse in models. the analysis A for novelty all introduced by Pass 8 is the characterization misaligned blazars with similar properties. Therefore, the detection of high- Million Catalog [7]. We select all models of supermassive formation inthe the detection early of Universe [see, new e.g., high- 6]. This constrain suggests the that time available for such extreme objects to grow. 2. Sample selection and Analysis PoS(ICRC2017)659 5), . 2 > γ Γ Dario Gasparrini -ray band [e.g., 13], γ -ray spectra to become . γ 2 ). This suggests their IC peak lie 1 -LAT band. Indeed, all the blazars -ray emitting blazar. ) and soft photon indices ( γ 1 − Fermi 25 are optimized and inserted into the sky erg s compares the redshift distributions of these ≥ 1 47 5, see Table 80%). By repeating the LAT analysis adopting . 10 2 > 3 > -ray luminous quasars. According to our analysis, > γ γ γ L Γ -ray emitters among a large sample of RL quasars has γ ) is now the farthest known where we also show the results of the LAT data analysis. As can 31 -ray spectra ( . γ 1 4 -ray sources are spurious is negligible. The basic information for these = -ray luminosities ( γ γ blazars with that of the 3LAC blazars. Though the population of distant z -LAT detected AGN [3LAC; 2]. As can be seen in the left panel, these sources , we compare these newly detected distant objects with the blazars included in the Fermi 1 -ray sources and their radio counterparts [from NRAO VLA Sky Survey or NVSS; γ http://fermi.gsfc.nasa.gov/ssc/data/analysis/software/ In Figure In general, high-redshift blazars are brighter at hard X-rays than in the Our systematic search for significant As in the case of our target sources, there could be faint gamma-ray emitters present in the data 2 -Ray Beacons at the Dawn of the Universe newly discovered high- steeper and to move slightly outside,discovered or here at exhibit the steep limit, of the at MeV energies. third catalog of occupy the region of high be seen, all the objectsNVSS are J151002+570243 extremely (z RL and 1000 random positions drawn from a randomizedany NVSS of catalog, the we newly found detected thatobjects the probability is that presented in Table probably due to the shift ofshift the of blazar the SED high-energy to peak lower to frequencies.[14]. lower energies This Another as could possible the be reason bolometric due for non-thermal tohigh-redshift the luminosity the blazars shift increases intrinsic is could powered be via the ICline fact scattering region that off (BLR), photons the which from high-energy also the emission contributes torusAlternatively, of to the rather such SED the than peaks lowering the can of broad- also the shift frequencythe to of lower dense their energies BLR provided SED photon the peak emission field. [15]. regionthe is In lowering within this of case, the an SED efficient peaks cooling [16]. of the The emitting electrons shift will of cause the SED causes their 12] with high confidence (association probability model with power-law spectra. This procedureremains in is the iterated ROI. until no significant unmodeled emission 3. Results led to the detection of fivethe sources. detected A likelihood ratio (LR) method [see 11, for details] associates but not in the 3FGL cataloginsert [10]. such Thus, sources we into rely the on skyThe an model. iterative spatial This procedure is positions to done of discover, by localize, unmodeled generating and excesses a residual with TS TS map for each ROI. γ of the photons in PSFquartiles (point-spread by function) quality type of events, angular which reconstruction,(PSF3) sub-classify with having the the the events lowest into worst quartile four and (PSF0)advantage and the of highest best, this quartile respectively, improvement, direction we reconstruction.type by perform In considering a the order component-wise product to of data takeevent the analysis types, full likelihood using function for the (sum each SUMMED of PSF likelihood the method logarithms) event of for the the four Science PSF Tools typical of powerful blazars. The right panel of Figure PoS(ICRC2017)659 ) 2 Dario Gasparrini blazars [e.g., 5]. state of the blazar z 020603 is included − . Both methods predict 2 typical blazars we look into the liter- blazars and may have a major -ray detected quasars. In Table z z γ and the modeled SEDs are shown 2 153841 is a hard X-ray spectrum lu- − -ray photon statistics are not good enough to -Burst Alert Telescope catalog [20]. NVSS γ -LAT detection and the available data confirm ), a characteristic feature exhibited by powerful 2 4 Swift Fermi ). The X-ray spectra, on the other hand, are hard and 1 − 20, Table erg s > 46 10 RL quasars. -ray emitter by [18], whereas NVSS J135406 z > γ disk L -ray band of the SED can be explained by the IC scattering off the photons γ -ray emitting region to be inside the BLR. However, it should be noted that with γ . 2 Powerful blazars are generally found to host massive black holes at their centers. It is, there- In order to understand the broadband behavior of these high- In each of the three objects, the IR-UV emission is found to be dominated by an extremely We generate broadband SEDs of the three objects that have archival X-ray observations and , we report the black hole for each of the five sources using information that we could -Ray Beacons at the Dawn of the Universe rather than any period of specific activity. Also, the with a standard [24] and the results are presented in Table fore, of great interest to determine the black hole of these search for temporal variability.the Overall, blazar the of the 5 high- 4. Discussion find/derive from the optical spectroscopic information availablewe in also the derive literature the [23]. masses Furthermore, by modeling the observed IR-UV emission for three objects (Figure blazars. Other SED parameters areThough similar the to data used those here generally are observed mostly in non-simultaneous, high- they indicate a 1 the sparse available observations, it isregion. not possible to The tightly Compton constrainthe the dominance location three (ratio of sources of the is emission the also very IC large to ( synchrotron peak luminosities) of each of originating from the BLR.surrounding A the strong jet, accretion which disk incording turn to radiation our is implies SED observable modeling a in analysis,the dense the a high-energy large form BLR emission BLR originates of photon radiative from broad energy the field density opticalThis interaction indicates of emission suggests that the lines. that most BLR of photons the Ac- with coolingemission the of will jet electrons. peak the at electrons low will frequencies,the be location which of efficient, is the supported and by accordingly the the modeling synchrotron results. This indicates impact on constraining the various physicale.g., parameters 17, associated for with a the relevant blazar discussion]. population [see, ature for multi-frequency information.noteworthy observations Though that there support is the awas blazar predicted paucity nature as of of a such these candidate objects.in data, the we NVSS ROMA-BZCAT found J064632+445116 [19]. a few The quasar NVSS J212912 in Figure luminous accretion disk ( the entire X-ray to γ blazars is small, this work opens a window for the study of high- minous blazar and included in the 70 month model them using a simpledetails one on zone synchrotron-IC the emission modelling approach andcalculated prescribed the jet in powers different [22]. and contributions More SED to parameters the are IC given peak in can Table be found in [8]. The J151002+570243 is one of thehard X-ray best spectrum studied [e.g., among 21]. all of the objects and exhibits an intense and PoS(ICRC2017)659 -rays, for hosted in -ray lumi- γ are derived γ

γ M Γ 9 Dario Gasparrini blazars becomes 10 z and This work > γ L BH Redshift M 3LAC redshift sample ) similar systems, but with jets 13, derived from our SED mod- 2 Γ = 2 Γ blazars newly detected in 153841 hosts one of the most mas- × z − . Already at redshift 4, this implies that 3 − . 4

2.0 2.4 2.8 3.2 3.6 4.0 4.4 9 6 3 0 Gpc

18 15 12 ubro sources of Number blazars with 3LAC objects in, left: ) and match reasonably well within a factor of 37 25

z 675 (i.e., 2 + − 5 -ray emitting blazars, confirmed both from optical M ∼ γ 49 0.4 dex) associated with the virial BH mass estimation methods 10 10 ∼ − 8 10 48 10 ∼ ) in the same redshift range, considering black hole masses ) 1

− . However, the optimal instrument would be a sensitive all-sky 47 M 10 9 , ever found in , erg s -ray detected high- γ

10 γ L 46 M 10 > NuSTAR [26]. This estimate is based on the luminosity function reported in [27], 9 BH 3 45 10 − M 10 × 7 44 ∼ -ray Luminosity ( 10 γ blazars z 300 GeV energy band, both for 3LAC and high- 43 − 3LAC BL Lacs 3LAC FSRQ High- 10 , except for NVSS J151002+570243, for which the modeling approach predicts a higher 3 42 https://pcos.gsfc.nasa.gov/physpag/probe/AMEGO_probe.pdf One should keep in mind the large uncertainties ( At redshifts between 3 and 4, the space density of black holes with 10

4 3

3.5 3.0 2.5 2.0 1.5 1.0

γ ) three (Γ Index Photon -Ray Beacons at the Dawn of the Universe [see, e.g., 25]. Figure 1 Comparison of new nosity vs. photon index plane, andfor right: the 0.1 the redshift histogram. The plotted γ the existence of massive black holes ( jetted AGN is 50 Gpc which, at those redshifts,massive relies black only holes on ( fivederived blazars. from the This optical spectroscopic work information. finds Adopting two more blazars hosting an equal comparison. ∼ black hole mass. In particular, the object NVSS J212912 sive black holes, spectroscopic and disk modeling approaches. eling, these two objects imply the presence of pointing in all directions, in themassive black same holes redshift hosted bin. in jetted This systems brings to the 70 estimate of the space density of there is a similar number ofthat, massive given black their holes strong hosted evolution, above inradio-loud that radio-loud systems redshift and [28]. most radio-quiet This massive systems clearly black and quick shows holes black that might hole the be growth radio-loud hosted in phase the in very early may Universe. important. be To a this Currently, key end, the ingredient the mostof for detection of promising the high- approaches LAT, and are, (2) (1) using MeV lowering telescope, the e.g., energy e-ASTROGAM [29] threshold and AMEGO

PoS(ICRC2017)659

ν − ) s (erg L ν 1 48 47 46 45 44 10 10 10 10 10 Dario Gasparrini 24 LAT 10 20 corona

EC

10

ν − ) s (erg L ν 1 31) . 44 45 46 47 48 49 (Hz) 16 SSC ν = 4 10 10 10 10 10 10 10 z ( 24 disk LAT Syn 12 10 NVSS J151002+570243 torus 10 EC 20 corona 153841 8 10 − 10 12 13 14 15 11 28) . − − − − −

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10 10 10 10 10

ν − −

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10 1 2

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ν − ) s (erg L

ν disk 1 12 Syn NVSS J212912 10 48 47 46 45 44 torus 10 10 10 10 10 8 24 10 14 15 10 11 12 13 10 LAT − − − − − −

10 10 10 10 10 10

ν − − ) s cm (erg F ν

1 20 2 EC corona 10 41) . SSC (Hz) = 3 16 ν z 10 ( disk -LAT Collaboration acknowledges support for LAT development, operation and Syn 12 NVSS J064632+445116 10 torus Fermi 8 10 11 12 13 14 15 -LAT data points and bow-tie plots are in black. The dotted black line represents thermal − − − − − The

10 10 10 10 10

ν − − ) s cm (erg F ν

1 -Ray Beacons at the Dawn of the Universe 2 data analysis from NASAand and DOE INFN (United (Italy), States), MEXT,Swedish CEA/Irfu KEK, Research and and Council IN2P3/CNRS JAXA and (France), (Japan), thethe ASI National operations and Space phase the from Board INAF K.A. (Sweden). (Italy)work Wallenberg and performed Science Foundation, CNES in analysis (France) the part support is under in also DOEarchival gratefully data, Contract acknowledged. software, DE-AC02-76SF00515. or This Part online of services this provided work by is the ASI based Science on Data Center (ASDC). radiations from the IR-torus, thegreen accretion long disk, dashed, and and the orangeSSC, and long-dash-dash-dot X-ray EC lines corona, emissions, respectively. correspond whereas, The blue to pinkfrom thick all non-thermal thin solid the line synchrotron, solid, radiative denotes components. the sum of the contributions Acknowledgments Figure 2 The broadband SEDsmodel. of three Lime quasars reproduced greenFermi using data the points one zone are leptonic the emission archival observations (http://tools.asdc.asi.it/SED/) and γ PoS(ICRC2017)659 , 515 (Mar., TS 1538 697 − ) 1 , Nature − , ApJ 0.4 66 0.40.80.5 62 0.2 44 34 151 γ ± ± ± ± ± erg s L -ray flux and apparent 48 Dario Gasparrini γ ArXiv e-prints , 0.140.160.14 2.5 0.10 1.1 7.0 1.9 0.10 1.4 γ ± ± ± ± ± Γ ) (10 1 − s 2 − 0.520.300.960.43 2.88 2.55 3.15 2.82 0.40 2.68 300 GeV ± ± ± ± ± is the logarithmic central black hole mass, in units of solar 46.15 45.38 46.58 − s ph cm , 06 . 2.32 0.86 5.31 2.65 2.03 8 0 BH -LAT data analysis − F M (10 Fermi ) 1.8 1.8 2.2 ) 0.5 0.5 0.5 p ) 0.1 0.1 0.1 -LAT data analysis of high-redshift blazars. ) 4.4 4.1 4.5 IR f q for all of them. is the 95% error radius derived from the analysis. The s , ) 9.60 9.48 9.85 † † † $ $

◦ BLR m BH f ) 0.26 0.12 0.68 M , 95% M R 7 Fermi BH Edd band flux density. ) 47.11 46.65 47.78 L M B [23]. ]. 1 1 † / ]. − − RL disk [30], $ L ) 44.88 44.94 45.14 1 ) 47.38 47.45 47.89 z , erg s 1 ) 45.89 45.70 46.31 − ) 0.025 0.017 0.059 ), erg s 1 − B − disk P blob ) 0.009 0.029 0.002 L 0 e R , erg s U e ( , erg s ) 0.25 0.17 0.59 P p , erg s 3 r P P − diss ) 0.37 0.22 0.79 ]. 15 38 41.0 3.3 263 9.8 02 06 03.2 3.7 3741 8.9 R ) 2e3 3e3 2e3 ) 1 1 1 − − arXiv:1501.0605 300 GeV. BLR arXiv:0902.1089 Basic information 0 max 0 − min R ) 2.1 1.4 1.3 γ γ B ) 72 82 51 The Third Catalog of Active Galactic Nuclei Detected by the Fermi Large Area Telescope 0 b The Large Area Telescope on the Fermi Gamma-Ray Space Telescope Mission ) 12 11 14 γ The power of relativistic jets is larger than the luminosity of their accretion disks Γ Pass 8: Toward the Full Realization of the Fermi-LAT Scientific Potential . The viewing angle is taken as 3 2 (Sept., 2015) 14, [ arXiv:1303.3514 020603 13 54 06.90 153841 21 29 12.13 − − 810 Name Radio position (J2000) (NVSS) hh mm ss.ss dd mm ss.s (June, 2009) 1071–1102, [ ApJ 2013) [ J135406 J151002+570243J163547+362930 15 10J212912 02.92 16 35 47.24 +57 02 43.4 +36 29 30.0 4.3 3.6 1850 2842 8.5 8.7 Note. — Name, radio positions have been adopted from the NVSS catalog. Redshifts are taken from MQC. Radio-loudness (RL) is the ratio of the rest-frame 5 J064632+445116 06 46 32.00 +44 51 17.0 3.4 1253 9.1 Jet power in protons in log scale ( Black hole mass in log scale, in units of solar mass ( Fraction of the disk luminosity reprocessedFraction by of the the BLR disk ( luminosity reprocessed by the IR-torus ( Radiative jet power in log scale ( Size of the emission region inDissipation distance ( in parsec ( Size of the BLR in parsec ( Maximum Lorentz factor ( Accretion disk luminosity in log scaleAccretion ( disk luminosity in Eddington units ( Jet power in magnetic field in log scale ( Break Lorentz factor ( Compton dominance (CD)Jet power in electrons in log scale ( 25 47 99 Slope of the electron energy distribution after break energy ( Bulk Lorentz factor ( Minimum Lorentz factor ( Particle energy density in erg cm ParameterSlope of the electron energy distribution before break energy ( Magnetic field in Gauss ( J0646+4451 J1510+5702 J2129 GHz (extrapolated from 1.4 GHzmass, assuming derived/taken from a available flat optical spectroscopic radio information: spectrum) to optical luminosity are in the energy range of 0.06 -Ray Beacons at the Dawn of the Universe [3] W. Atwood et al., [4] G. Ghisellini et al., [1] W. B. Atwood et al., [2] M. Ackermann et al., Table 1. Basic information and results of the References γ Table 2 Summary of theshown in parameters Figure used/derived from the modeling of the SED of the objects PoS(ICRC2017)659 , ]. ]. (June, ]. (1973) ]. (July, 2009) 194 24 . (June, 2010) 699 Dario Gasparrini (Dec., 1998) (Mar., 2008) 405 (Sept., 1998) , ApJS , A&A , ApJ 301 175 arXiv:1502.0630 (May, 2015) 75, 299 (Nov., 2013) 147, arXiv:1103.5565 (Aug., 2013) 19, (Jan., 2015) 2483–2489, 357 777 (Mar., 2017) L5, , MNRAS 207 , ApJS 446 , Rev. Mexicana Astron. Astrofis. , MNRAS 837 arXiv:1301.0012 astro-ph/0205527 (July, 2016) 74, , ApJ , MNRAS (June, 2015) 23, (Aug., 2009) 985–1002, arXiv:1608.0373 , ApJS , Ap&SS 825 , ApJ 218 397 , MNRAS ]. (Apr., 1996) 396. (Mar., 2015) e010, [ Space Telescopes and Instrumentation 2016: , ApJ 32 , ApJS 461 , in (Sept., 2011) 216–224, [ , MNRAS (Feb., 2013) 109, [ ]. , ApJ 416 , PASA (Sept., 2002) 78–84, [ 763 (May, 1998) 1693–1716. 8 577 115 , ApJ ]. , MNRAS arXiv:1304.1152 , ApJ ]. , AJ ]. arXiv:1501.0096 ]. ]. Black holes in binary systems. Observational appearance. ]. ]. ]. ]. Canonical high-power blazars arXiv:1108.1420 , vol. 9905 of Proc. SPIE, p. 99052N, July, 2016. arXiv:1411.5368 ]. ]. ]. ]. ]. ]. ]. ]. The 70 Month Swift-BAT All-sky Hard X-Ray Survey arXiv:1107.3416 (July, 2013) 2818–2823, [ The Second Catalog of Active Galactic Nuclei Detected by the Fermi Large Area Telescope Gamma-ray Blazars Within the First 2 Billion Years (July, 2015) 12, [ Chasing the heaviest black holes of jetted active galactic nuclei The role of relativistic jets in the heaviest and most active supermassive black holes at high A theoretical unifying scheme for gamma-ray bright blazars Blazars in the early Universe The e-ASTROGAM gamma-ray space mission CGRaBS: An All-Sky Survey of Gamma-Ray Blazar Candidates The NRAO VLA Sky Survey The Likelihood Analysis of EGRET Data Optical Spectroscopic Atlas of the MOJAVE/2cm AGN Sample Broadband Observations of High Redshift Blazars 432 The 5th edition of the Roma-BZCAT. A short presentation Blazar candidates beyond redshift 4 observed by Swift NuSTAR Detection of the Blazar B2 1023+25 at Redshift 5.3 A unifying view of the spectral energy distributions of blazars On the Nature of MeV Blazars The Evolution of Swift/BAT Blazars and the Origin of the MeV Background 219 Fermi Large Area Telescope Third Source Catalog The Eleventh and Twelfth Data Releases of the Sloan Digital Sky Survey: Final Data from A Catalog of Quasar Properties from Sloan Digital Sky Survey Data Release 7 The Half Million Quasars (HMQ) Catalogue An X-Ray and Multiwavelength Survey of Highly Radio-loud Quasars at z > 4: Jet-linked Emission in arXiv:1006.5178 arXiv:0905.0472 astro-ph/9804103 astro-ph/9807317 arXiv:0912.0001 arXiv:0709.1735 (Dec., 2011) 171, [ , ApJS , MNRAS 743 (Apr., 2012) 9–40, [ arXiv:1410.0364 arXiv:0902.0793 arXiv:1502.0775 arXiv:1212.3336 arXiv:1604.0856 arXiv:1309.3280 arXiv:1702.0400 arXiv:1501.0200 337–355. 48 [ Ultraviolet to Gamma Ray SDSS-III the Brightest Radio Beacons of the Early Universe ApJ [ 2011) 45, [ 603–625, [ [ 97–104, [ [ (Nov., 2014) 376–378, [ redshift 387–400, [ [ [ 433–448, [ 451–468, [ [ [ -Ray Beacons at the Dawn of the Universe [7] E. W. Flesch, [9] J. R. Mattox et al., [5] G. Ghisellini et al., [6] G. Ghisellini et al., [8] M. Ackermann et al., [25] Y. Shen et al., [30] J. Torrealba et al., [27] M. Ajello et al., [24] N. I. Shakura and R. A. Sunyaev, [28] M. Volonteri et al., [29] V. Tatischeff et al., [21] J. Wu et al., [23] S. Alam et al., [26] T. Sbarrato et al., [14] G. Fossati et al., [18] S. E. Healey et al., [20] W. Baumgartner et al., [12] J. J. Condon et al., [15] M. Sikora et al., [17] V. S. Paliya et al., [19] E. Massaro et al., [22] G. Ghisellini and F. Tavecchio, [11] M. Ackermann et al., γ [10] F. Acero, et al., [13] T. Sbarrato et al., [16] G. Ghisellini et al.,