Dr. Charles D. Dermer Naval Research Lab, Code 7653 Washington, DC USA

Transcription

1 Origin and Impact of Radiation Backgrounds Chuck Dermer High-Energy Messengers: Connecting the Non-Thermal Extragalactic Backgrounds KICP Workshop, June 9-11, 2014, Chicago, IL Dr. Charles D. Dermer Naval Research Lab, Code 7653 Washington, DC USA Dermer KICP Workshop on High Energy Messengers June 11,

2 Outline The cause of the catastrophic cutoff is the intense isotropic radiation first detected by Penzias and Wilson at 4080 Mc/sec. K. Greisen, End to the Cosmic Ray Spectrum? PRL, EBL Modeling 2. Measurement of IGMF 3. BL Lac objects as Sources of UHECRs 4. FSRQs as Sources of PeV Neutrinos -ray perspective Fermi 5 year > 1 GeV -ray sky

3 Extragalactic Background Light (EBL) Modeling Infrared/optical/UV EBL difficult to measure Provides a source of opacity through ' e + + e (Gould & Schreder 1967) in IGM; target photons for photodisintegration of ions Stellar emissivity at redshift z: j stars z max 2 dt* ( ; z) fesc( ) dm( m) dz1 ( z1) N *( ; m, t* ( z, z1)) dz Photon Escape Fraction (using ~10 5 galaxies in Millennium Galaxy Catalog; Driver 2008) Initial Mass Function ( m -2.2 at m > 0.5, ~Salpeter; m -0.5 at 0.1 < m < 0.5: Baldry & Glazebrook 2003) 1. Empirical Models using IR/optical galaxy data Malkan & Stecker 1998, 2001; Stecker et al. 2006; ~~~Franceschini et al. 2008; Dominguez et al Semi-analytic merger-tree models of galaxy formation Primack et al. 2001, 2005, 2008 Gilmore et al. 2009, 2009, Inoue et al Star formation and dust re-radiation Kneiske et al. 2004, 2010 Finke, Razzaque, Dermer 2010 z Star Formation Rate per comoving volume (Hopkins & Beacom 2006 using Cole et al parametrization) 1 Stellar photon production rate using stellar radii and luminosities, and time on various parts of HR diagram (Eggleton et al corrections) 3

4 4 EBL from Stars and Dust )), (, ; ( ) ( ) ( ) ( ) ; ( 1 * * 1 1 * 1 2 max z z m t N z dz dt dz m dm f z j z z esc stars ) ; ( ] ) ( ) ( 1 [ 1] ) / [exp( 15 ) ; ( z j f f d f z j stars esc esc n n n n dust Comparison with stellar population synthesis model (Bruzal & Charlot 2003) for stars all born at the same time with Salpeter IMF

5 -ray Constraints on EBL Models 1. Deabsorbed VHE ( > ~ 100 GeV) spectrum softer than, e.g., Deabsorbed VHE spectrum bounded by Fermi spectrum extrapolated into VHE range 3. Use Fermi measurements to constrain UV EBL; look for Ly edge in the IGRB (cf. Oh 2001) Finke, Razzaque, Dermer

6 Highest Energy Photons and the Stecker-Scully Relation Highest energy photons compared to E (z; = 1) curves E (z; = 1) ~ 100 GeV/z (red line) GeV TeV spectral index difference Stecker & Scully 2006, 2010; Essey & Kusenko 2012 (cf. Sanchez et al. 2013) Mrk 421 GeV TeV Mrk 421 Update with recent Fermi/IACT data

7 Deabsorbed Blazar Spectra Deabsorbed spectrum shows spectral hardening Finke et al Hard spectrum arises for a wide range of EBL models Values consistent with int > 1.5 (except for Stecker s models) Origin of hard spectral component? 7

8 Measurement of the Intergalactic Magnetic Field Pair halos, echoes, spectral features TeV rays absorbed by EBL make e + e - pairs that Compton scatter CMB photons to GeV energies To satisfy Fermi-LAT data, require B IGMF large enough to deflect pairs away from jet direction For persistent jet, B IGMF > G ~ (Neronov & Vovk 2010; Tavecchio et al. 2011) For jet active during observing period, B IGMF > ~ G (Dermer et al. 2011; Dolag et al. 2011) Cascade GeV rays will be nonvariable; no reason for TeV rays to be nonvariable Dermer et al

9 Strongly Variable Class of BL Lac Objects Strongly variable class Mrk 421, z = 0.03 Aharonian et al PKS July 2006 flare Mrk 501, z= PKS , z = t var < R S /c, L > L EDD Extreme sources Feb 2010 VERITAS OBS of MRK 421 Furniss 2011, Fortson 2012 R S /c = 10 4 M 9 s t var ~ 5 min = 300 s (?) M << 10 8 M 0 9

10 Weakly Variable Class of TeV BL Lac Objects Weak Fermi LAT fluxes 1ES z = ES z = ES z = ES z = RGB J z = ES Tavecchio et al Cerruti et al Compton-scattered CMBR from extended jet/lobe produces weakly variable TeV rays Böttcher, CD, Finke 2008

11 The Synchrotron Puzzle and Equipartition Blazar Modeling In first-order Fermi scenarios, acceleration rate < 1/Larmor timescale tacc tl / B t syn = t L maximum synchrotron energy ~ 100 MeV (de Jager & Harding 1992) Orders of magnitude > peak or maximum synchrotron frequency of blazars! Second-order Fermi Acceleration q t II 2 A 2 q is index of turbulence spectrum. Describe curved particle distribution by log-parabola function 2 N e K 2 pk ) ( ) ( ) Equipartition modeling L pk syn pk blog( / pk,, t B,, R var syn Dermer, Cerruti, Lott, Boisson, Zech 2014 Require extremely out-of-equipartition blazar to make inferred extra spectral component 11

12 BL Lac Objects as the Sources of the UHECRs Gamma-ray and Cosmicray Induced VHE Radiation Mechanism for making Weakly variable TeV cascade radiation Hard VHE component UHECR-induced cascade in IGM Photon-induced cascade in IGM e + e - p,e + p e +,e - e - ~100 Mpc ~ Gpc UHECR protons with energies ~10 19 ev make ~10 16 ev e that cascade in transit and Compton-scatter CMBR to GeV -- TeV energies Essey, Kalashev, Kusenko, Beacom (2010, 2011) Undermines B IGMF measurements and -ray EBL inferences from BL Lac objects with nonvariable TeV emission Limits for variable, moderate redshift (z~ ) TeV blazars; blazar spectral component 12

13 Luminosity Density of UHECR Candidates from Fermi Data UHECR requirements GRB observations CD & Razzaque (2010) GRBs have adequate energy production rate only if baryon loading large Fermi data favors ion acceleration by BL Lacs/FR1 radio galaxies Redo both source rate density and energy emissivity with latest Fermi data 13

14 Maximum UHECR energies in blazars and GRBs Standard one-zone synchrotron/ssc model for BL Lac objects and GRBs Parameters: B,, Rc t var Hillas condition: GRBs can accelerate UHECR protons to > ev Transition predicted from proton composition to heavy ion composition at ~10 19 ev in BL Lac objects Provided ions can escape the acceleration zone Murase, CD, Takami, Migliori (2012) 14

15 Electromagnetic Signatures of UHECRs Photon-induced cascade in IGM UHECR-induced cascade in IGM Polisensky & Ricotti 2011 Murase et al

16 >10 GeV Sources Explained by Cascade Emission GeV TeV sources EBL effects greater on more distant blazars Model >10 GeV Fermi LAT emission by cascades /Compton cascade Kneiske et al. (2004) EBL models Assume no suppression from IGMF (B IGMF < G) Intrinsic spectrum F(E ) E 1.76, 5.6 GeV < E < 100 TeV UHECR induced cascade Bethe Heitler pair production Assume no suppression from IGMF (B IGMF < G) UHECR proton spectrum: F(E p ) E 2.6 p exp( E p /10 19 ev) KUV (z = 0.61) Takami et al Normalization imposed to fit > 10 GeV Fermi- LAT spectrum from cascade emission Definitive test of UHECR Hypothesis with CTA

17 FSRQs as the Sources of PeV Neutrinos Broad-line region (Ly radiation Accretion-disk: disk spectrum with 20 ev maximum temperature IR torus radiation: 1200K thermal with u = 10-3 erg/cm 3 Threshold p >~ 400, so most neutrinos are made with energy E ~ 0.05 m p c 2 p >~ 0.05 x 10 9 ev 400 / 0 ~ ev for 0 ~ 2 x 10-5 (Ly ) (Murase, Inoue, CD 2014; CD, Murase, Inoue 2014) 1041 TeV High-energy cutoff in GeV radiation from KN effects in Ly scattering (Cerruti et al. 2013) PeV Neutrinos from FSRQs IceCube Collaboration, Science, 342, 2013

18 GeV-TeV Radiation in 4C from Hadronic Processes Ultra-relativistic leptons from UHECRs: B e n B e n 2 0 Make synchrotron -rays Dermer, Murase, Takami (2012) Detailed GeV and VHE studies with Fermi/CTA 18

19 Origin and Impact of Radiation Backgrounds Straightforward calculation of IR/optical EBL Deabsorbed spectra of distant (z > 0.1) TeV blazars show unexplained hard emission component Hard Component not easily explained in equipartition modeling GeV TeV relation violated Detect photons from blazars with z ~ with >>1 Weakly variable class of TeV blazars Allows measurements of IGMF if emission from TeV photons at source Negates measurements of IGMF if TeV emission is from UHECRs BL Lac objects best candidate source class of UHECRs? Misaligned BL Lacs within GZK radius (Cen A!) More than adequate emissivity (~10 46 erg Mpc 3 yr) Simple acceleration predicts maximum proton energy between ev Neutrinos from FSRQs Hardening/gap below 1 PeV Second source class for TeV neutrinos (if not from atmospheric background) VHE from UHECR acceleration in FSRQs Dermer KICP Workshop on High Energy Messengers 11 June

20 Detailed Outline EBL Model (Finke, Razzaque, Dermer 2010) gamma-ray optical depth Deabsorb blazars: extra component Measurement of IGMF Persistent vs. Impulsive Blazars Special class of blazars Extra component? Blazar spectral modeling (Equipartition) BL Lac objects as Sources of UHECRs Maximum Particle Energy Emissivity Diagram: CTA test for UHECR Origin FSRQs as Sources of PeV Neutrino Escape from the Black Hole PeV Neutrinos Prediction for Diffuse Neutrinos Comparison with FSRQ Fluence

21 Blazars and the Extragalactic Background Light Ajello/Fermi Collaboration 2012

22 Pair halo radiation Blazars are demonstrably sources of multi-tev photons: Attenuation by the EBL: what happens to the generated pairs? Lepton secondaries of e + e - e + e - Pair halos (Aharonian, Coppi, & Völk 1994; Roustazadeh & Böttcher 2011) Temporal delay and Intergalactic Magnetic Field (IGMF) (Plaga 1995) Temporal delay/echoes from bursting sources (Razzaque et al. 2004; Murase et al. 2008) Angular extent of halos around blazars (Elyiv et al. 2009, Aharonian et al. 2009) Halo extent at GeV energies measurement of IGMF Spectral TeV/GeV constraints on IGMF (d Avezac et al. 2007; Neronov & Vovk 2010; Tavecchio et al. 2010) Nondetection by Fermi of TeV blazar sources B IGMF >~ G for assumed persistent blazar engine and B IGMF >~ G for variable engine 22