Are TeV blazars heating the IGM?

Transcription

1 Are TeV blazars heating the IGM? Ewald Puchwein! collaborators: Christoph Pfrommer, Avery Broderick, Phil Chang, Volker Springel

2 TeV blazars unified AGN model:

3 Photon-photon pair production e + e TeV blazar extragalactic backgroud light (infrared, ev) Pfrommer

4 Photon-photon pair production e + e TeV blazar extragalactic backgroud light (infrared, ev) -> the universe is not transparent to TeV γ-rays Pfrommer

5 Inverse Compton cascade? cosmic microwave background, 10 3 ev TeV blazar GeV e e+ extragalactic backgroud light (infrared, ev) Pfrommer

6 Inverse Compton cascade? cosmic microwave background, 10 3 ev TeV blazar GeV e e+ extragalactic backgroud light (infrared, ev) -> every TeV source should also be seen in GeV γ-rays Pfrommer

7 TeV blazars observed in the GeV range expected cascade emission TeV detections intrinsic spectra Neronov & Vovk (2010)

8 TeV blazars observed in the GeV range expected cascade emission TeV detections intrinsic spectra Fermi Fermi constraints exclusion region Neronov & Vovk (2010)

9 Extragalactic magnetic fields? pair deflection in intergalactic magnetic field GeV e e + TeV blazar extragalactic backgroud light (infrared, ev) Pfrommer

10 Extragalactic magnetic fields? pair deflection in intergalactic magnetic field GeV e e + TeV blazar extragalactic backgroud light (infrared, ev) -> point source diluted to faint pair halo -> need volume-filling magnetic field B Pfrommer G (difficult from outflows, primordial origin?)

11 Extragalactic magnetic fields? pair deflection in intergalactic magnetic field GeV e e + TeV blazar extragalactic backgroud light (infrared, ev) -> no increase in co-moving number density with redshift allowed (as observed for other AGN) Pfrommer -> otherwise extragalactic GeV background would be overproduced

12 Other processes? intergalactic medium e e + TeV blazar pair plasma beam propagating through the intergalactic medium -> pair beam propagating through the plasma of the IGM Pfrommer

13 Plasma instabilities pair beam IGM one frequency (timescale) and one length in the problem: s -> such a configuration can be unstable to plasma instabilities

14 Plasma instabilities f(v) thermal IGM slower s beam plasma (Langmuir) wave i v v v ph 0 Φ p p + e e v ph

15 Plasma instabilities f(v) thermal IGM slower gain energy from wave loose energy to wave s beam plasma (Langmuir) wave i v v v ph 0 Φ p p + e e v ph

16 Plasma instabilities f(v) thermal IGM slower gain energy from wave -> growth of the wave by inverse Landau damping loose energy to wave s beam plasma (Langmuir) wave i v v v ph 0 Φ p p + e e v ph

17 Oblique instability Plasma instabilities - in -> oblique modes grow fastest k oblique to v k oblique to vp perturbatio beam : real word alignment = alignment = all orientations PIC simulations oblique grow oblique grows faster than two-stream: E ultra-relativis (Nakar, Bret & Milosa ultra-relativistic particles than change th (Nakar, Bret & Milosavljevic 2011)! -> grows close to linear rate up to saturation Bret (2009), Bret+ (2010) Bret (2009), Bret+ (2010) Christoph Pfrommer The Physics

18 Plasma instabilities vs. inverse Compton cooling assuming growth close to the linear rate up to saturation oblique instability inverse Compton Broderick et al. 2012

19 Plasma instabilities vs. inverse Compton cooling assuming growth close to the linear rate up to saturation oblique instability -> plasma instabilities beat inverse Compton cooling of the pair beam inverse Compton Broderick et al. 2012

20 Summary of the two scenarios requires (primordial?) extragalactic magnetic fields & a redshift evolution of TeV blazers quite different from other AGN TeV + ev! e + + e! 8 < : inv. Compton cascades! GeV plasma instabilities! IGM heating (?) assumes growth close to linear rate! -> invalidates lower limits on extragalactic B-fields -> different thermal properties of the IGM

21 TeV blazar heating rate -> assume: redshift evolution of the TeV blazar luminosity density traces the redshift evolution of the quasar luminosity density! -> large mean free path -> roughly homogeneous EBL roughly constant volumetric heating rate φ B (0.1,L TeV ) φq (0.1,1.8L TeV ) Broderick et al. 2012

22 Extragalactic γ-ray background -> assuming:! redshift evolution of the TeV blazar luminosity density traces the redshift evolution of the quasar luminosity density unabsorbed EBL absorption removing resolved sources φ B (0.1,L TeV ) φq (0.1,1.8L TeV ) φ B (z,l TeV,Γ l ) = φ B (z,l TeV ) e (Γ l Γ l ) 2 /2σ 2 l 2πσl. Broderick, Pfrommer, EP, Chang 2013

23 Cosmological hydrodynamical simulations -> include predicted volumetric heating rate in cosmological hydrodynamical simulations! -> study: thermal properties of IGM! Lyman-α forest: PDF power spectrum line-width distribution

24 Thermal properties of the IGM Puchwein et al z=3 inverted density-temperature relation in low-density IGM standard relation at higher density

25 Thermal properties of the IGM -> boosted temperatures at mean density boost due to blazar heating Puchwein et al. 2012

26 Thermal properties of the IGM -> boosted temperatures at the overdensity to which Lyman-α forest measurement are sensitive Puchwein et al. 2012

27 The Lyman-α forest flux PDF -> effects of blazar heating on the flux PDF PDF of transmitted flux fraction tuned UV background no blazar heating weak blazar heating intermediate blazar heating strong blazar heating Kim et al z = 2.52 z = Puchwein et al transmitted flux fraction

28 The Lyman-α forest power spectrum -> effects of blazar heating on the power spectrum Puchwein et al. 2012

29 The Lyman-α forest line width distribution -> increased thermal broadening due to blazer heating Puchwein et al. 2012

30 Figure A1. Scatter plot of the distribution of Lyman-α lines in column density, N HI,andlinewidth,b, Puchwein forsimulationswithout(left et al panels) andwithintermediate blazar heating (middle panels) atredshiftz = 3.Intheright panels, datafromkirkman&tytler(1997) are shown for comparison. All Lyman-α lines with redshifts 2.75 <z<3.05 listed in their Table 1 were included. The lengths of the (stitched) simulated lines-of-sight were chosen so as to yield the same number of significant (N HI > cm 2 )Lyman-α absorption lines as in the observed sample. The blue-dashed lines indicate fits to the lower b-envelope found by Kirkman & Tytler (1997, given The Lyman-α forest lower line-width cutoff z=3

31 Summary & Conclusions TeV blazars produce a beam of e+/e- plasma instabilities may drain the beam energy invalidates extragalactic B-field lower limits allows different redshift evolution of TeV blazers & explains high-energy EGRB beam energy is then likely dissipated in the IGM inverted density-temperature relation in the low-density IGM & standard relation at higher density improved agreement of Lyman-α forest flux PDFs, line widths & power spectra with the data