TeV Observations of Extragalactic Sources

Transcription

1 TeV Observations of Extragalactic Sources Henric Krawczynski (Washington University in St. Louis), Oct. 2, 2009 Plan of Talk: Status of Experiments Key-Results: Radio Galaxies Blazars Starburst Galaxies Summary

2 Status of Experiments New config.: 09/09 VERITAS 1% Crab (2x10-13 erg cm-2 1 TeV) in 28 hrs MAGIC Start of routine stereo operation in 1-2 months. H.E.S.S. 28 m telescope under construction.

3 TeV-Bright Radio Galaxies M87 (R/O/X): Cen A (R+O+X): 3ʼ Marshall et al X-ray: NASA/CXC/CfA/R.Kraft et al.; Submillimeter: MPIfR/ESO/APEX/A.Weiss et al.; Optical: ESO/WF TeV Observations: HEGRA (2003), HESS (2006),VERITAS (2008), MAGIC (2008) TeV Detection: Aharonian et al. 2009, ApJ, 695, L40

4 M87: Chandra Images of HST-1 X-ray Flare HST-1 VLBA 0.86, 60 pc D. Harris et al Cheung et al X-ray flare coincides with brightening of knot HST-1c and emergence of fast knot.

5 M87 Observations: TeV γ-rays

6 M87 Observations: TeV γ-rays Acciari et al. 2008, ApJ,679, 397

7 M87 Observations: TeV γ-rays Acciari et al. 2008, ApJ,679, 397 HST-1: no X/TeV 2007 and 2008 data break correlation

8 M87 Observations: TeV γ-rays VERITAS Aharonian et al Acciari et al. 2008, ApJ,679, day flares: c tfl = 3 Rg

9 50 light days, 76 Rg C. Walker et al.

10 ] -1 s -2 cm Φ radio [10 [Jy] -12 VHE Φ X-ra Φ VHE instruments VLBA VERITAS (43 GHz) MAGIC nucleus (r = 1.2 mas) H.E.S.S. peak flux density 10 jet w/o nucleus ( mas) ] -1 s -2 cm -12 Φ VHE [ Jan 05 Feb 12 Feb Time A C Acciari et al. 2009, Sci, 325, 444 Brightest monitored TeV γ-ray flare 4 02 Apr Jul Oct Jan Apr 2008 Time B

11 0 [kev/s] -1 s ] -2 cm -12 Φ X-ray [10 VHE Φ VHE instruments VERITAS MAGIC H.E.S.S. Chandra (2-10 kev) knot HST-1 nucleus ] -1 s -2 cm -12 Φ VHE [ VLBA (43 GHz) nucleus (r = 1.2 mas) peak flux density jet w/o nucleus ( mas) 0 29 Jan 05 Feb 12 Feb Time A B C Acciari et al. 2009, Sci, 325, 444 Brightest monitored TeV γ-ray flare 1.5 [kev/s] Φ radio [Jy] Φ X-ray Chandra (2-10 kev) knot HST-1 nucleus B Brightest flare from core detected by Chandra 02 Apr Jul Oct Jan Apr 2008 Time

12 ] -1 s 20 VHE instruments VERITAS MAGIC H.E.S.S. ] -1 s -2 cm A Acciari et al. 2009, Sci, 325, cm -12 [10 VHE Φ 10 0 Φ VHE [ Jan 05 Feb 12 Feb Time Brightest monitored TeV γ-ray flare [kev/s] Φ X-ray Chandra (2-10 kev) knot HST-1 nucleus B Brightest flare from core detected by Chandra VLBA (43 GHz) nucleus (r = 1.2 mas) peak flux density jet w/o nucleus ( mas) C Φ radio [Jy] Apr Jul Oct Jan Apr 2008 Time Brightest radio flare from core detected with VLBA Evidence for correlated radio/x-ray/γray flare.

13 Acciari et al. 2009, Sci, 325, light days, 76 Rg Flare comes from central resolution element 50 Rg/sin θ!

14 Modeled 43 GHz emission Acciari et al. 2009, Sci, 325, 444 Use γ-ray light curve as source function to inject electron population. Electron population cools adiabatically as plasma moves down hollow cone. Account for differences in δ and in light travel time. Acceptable model fits for α=5, θ=20, Γ = 1.01, βjet = 0.14, B = 0.5G.

15 Magnetically Driven Jet Formation Magnetic acceleration and confinement: Spruit, arxiv: log ρ Analytic calculations: Bisnovatyi-Kogan and Ruzmaikin 1976, Blandford- Znajek 1977, Blandford & Payne 1982, Li, Chiueh, Begelman 1992) GR-MHD simulations: McKinney 2006, Kommissarov 2007, Krolik, Hawley, Hirose, 2007, and others. McKinney & Gammie 2004, ApJ, 611, 977. Jet accelerates within 50R g sinθ ~ 150R g

16 1e+44 1e+43 E f(e) (erg/sec) 1e+42 1e+41 1e+40 1e+39 1e+38 typical nuclear emission External soft photons Synchrotron EIC SSC Total inverse Compton Giannios, Uzdensky, Begelman, 2009, MNRAS, 395, L29, arxiv g e+06 1e+08 1e+10 1e+12 1e+14 1e+16 E (ev) Relativistic generalization of Petschek-type reconnection (Lyubarsky, 2005): Lorentz factor of minijets: Γ co = σ Magnetic energy density in mini-jets: σ em ~ 1 3 Energy per particle before (after) reconnection: σ m p c 2 ( σ m p c 2 ) Model explains fast time variability and γ-transparency of jets even though δ 1 Reconnection: kink instabilities or B-field reversals in BH magnetosphere.

17 TeV-Bright AGN Entries 26 blazars Cen-A M C 66A? 3C redshift RG, FSRQ, LBL, IBL, HBL,

18 Whipple/VERITAS Observations of Mrk 421 in 2007 & s -1 ] -2 [cm! 2-10keV s -1 ] -2 [cm! keV [cm -2 s -1 ] " 10-9 " 10 Swift (XRT) RXTE (PCA) RXTE (ASM) Swift (BAT) -9 " 10 VERITAS Whipple 10m Soft X-Ray Hard X-Ray 2 min bins! E>300GeV Time [MJD] Rich data set, 1. The Mrk 421 light curves measured by different experiments (see Sec. 2) in Shown the radio band (upper panel), the optical band (second panel), the X-ray band (third & fourth panel) the TeV band (bottom). Evidence Somefor of thex/tev RXTE/ASM correlation. and Swift/BAT flux points have been rebinned for VHE Beilicke, H.K., et al. 2009

19 Whipple/VERITAS Observations of Mrk 421 in 2007 & 2008 ] -1 TeV -1 s -2 dn/de [cm very-low-state low-state mid-state high-state A high-state B high-state C very-high-state VERITAS (2008) 1 10 Energy [TeV] Fig. 4. Time-averaged VERITAS energy spectra for different flux levels. Only data taken in 2008 is used. A power-law with exponential cutoff is fit to each spectrum (curves), the fit parameters are summariyed in Table 2. The high-flux spectra were taken at zenith angles z>35 deg with a correspondingly higher energy threshold. are observed on longer time scales on the order of months. No significant flux variations can be observed at radio energies. The flux correlations between the different energy bands are discussed # photon index Energy spectra. The RXTE PCA spectra were fit in an energy range of 3 20 kev, where the Swift XRT spectra were fit between kev. Two models were tested to best fit the data: a power VERITAS E cut = 4 TeV (fixed) [cm s! 1TeV run-by-run [r = -0.55] flux states [r = -0.86] Whipple ( ) -1-1 TeV ] -9 "10 Fig. 5. Photon index Γ vs. flux normalization I 0 obtained from a power-law fit with exponential cutoff (fixed to E cut = 4 TeV). Each grey data point corresponds to a data run with a duration of 10 to 20 min. The black points correspond to the values obtained from the fits to the spectra grouped according to their flux states (compare with Fig. 4 and Tab. 2). Results Beilicke, H.K., et al obtained from earlier Whipple 10m observations (Krennrich et al. 2002) are shown for reference. Spectrum hardens with increasing flux but the trend saturates.

20 Suzaku Observations of Mrk 421 in May, 2008 f(2-10 kev)/f(0.5-2 kev) 3.8 days Garson, H.K., 2009

21 Suzaku Observations of Mrk 421 in May, 2008 Garson, H.K., 2009

22 Suzaku Observations of Mrk 421 in May, 2008 Different behavior in different flares... Garson, H.K., 2009

23 PKS in July 2006 July 29/30, 2006 Aharonian et al Problems fitting with 1-zone SSC models EC models, or 2-zone models.

24 PKS in August/ September 2008 s cm HESS ( TeV ) -7 cm -2 s Fermi ( GeV) Index! s erg cm -2 s -1 erg cm B V R RXTE, SWIFT (2-10 kev) ATOM Time (MJD ) Index! γ1 = , γ2 = γmax = , B= 18mG L. Gerard for the Fermi LAT team, and the H.E.S.S. Collaboration (2009)

25 R-Band 3C 66A (Fermi-VERITAS) SSC - - EC - Fermi L. Reyes for the Fermi LAT team, and the VERITAS Collaboration (2009)

26 γ-rays from Starburst Galaxies High star formation rate: ~10x Milky Way High supernova rate: ~0.1 to ~0.3 / year High CR density: ~100x Milky Way Inferred from intense radio-synchrotron emission High gas density: ~150 particles / cm3 CR hadrons + gas => pions => γ-rays CR electrons + ambient photons => γ-rays HEGRA & Whipple: VHE flux <10% Crab Theoretical predictions: Akyüz 1991, Völk et al. 1996, Pohl 1996, Paglione 1996, Völk 2003, Torres et al. 2004, Zirakashvili & Völk 2005.

27 γ-rays from Starburst Galaxies VERITAS ( ): ~137 hrs of M82 observations, Standard VERITAS analysis + hard cuts : Eth ~ 700 GeV; NB: Sensitivity less at θ ~ 39º The results are embargoed by the Nature news embargo policy.

28 γ-rays from Starburst Galaxies! Acero et al. 2009, science

29 Summary - TeV γ-ray Observations of Extragalactic Objects M87: - Excellent laboratory: proximity and MBH= M (Cen A: 5.5 ± M ) - Evidence that γ-ray emission comes from jet collimation region, < 50 Rg / sin θ from the supermassive Black Hole. Blazars: - 24 sources, FSRQs, LBLs, IBLs, HBLs. - Broadband observations: Simple 1-zone SSC models do not work (Mrk 421, 1ES , PKS ) Flare to flare variations make it difficult to break model degeneracies. More exciting Fermi/TeV results soon. Starburst galaxies are a new class of VHE γ-ray emitters.