Summary Talk: AGN and Gamma Rays Martin Pohl Iowa State University XXXXth Rencontres de Moriond March 19, 2005

The Main Questions How are particles accelerated? What particles are accelerated, e- or p+ ? How are jets produced? Are jets matter-dominated outflows? Poynting-dominated beams transitioning between the two?

A Wealth Of Data A number of excellent observatories is available or forthcoming! HST Newton, Chandra, INTEGRAL GLAST, AGILE? HESS, MAGIC, CANGAROO, VERITAS Milagro AMANDA, ICECUBE

True TeV Astronomy

Jets Everywhere? SNR have small anisotropy! Red, blue: ejecta Green: non-thermal Cas A (Hwang et al. 2004)

RX J1713-3946 HESS spectrum

TeV / keV relation => Emission inside of the forward shock!

Hadronic emission? Leptonic emission? Little thermal X-ray emission => nH ~ ne < 0.1 /cc => Ecr > (1050 erg) Dkpc2 TeV electrons are not loss-limited! => power-law spectrum N(E) ~ E-3 unlikely

Profile and Energy Spectrum Milagro detects diffuse galactic emission at ~ 1 TeV Profile and Energy Spectrum Consistent with extrapolation from EGRET Any rapidly rising component to explain >1 GeV excess cannot continue to 1 TeV

Soft Gamma-ray Repeaters SGR 1806-20 Period: 7.56 s Giant flare Initial spike: Liso ~ 1046 erg/s

Magnetar Isolated neutron star B ~ (1014 – 1015) G

BUT Rotational energy ~ 10 M R2 / P2 ~ 1045 erg Magnetic energy ~ B2 R3 / 6 ~ B152 1047 erg Observed: L ~ 1046 erg, no period change observed (yet) Probably a jet, not an isotropic fireball!

The Galactic Center A supermassive black hole M ~ 3 106 Msolar Confirmed by stellar orbits Inefficient accretion  low luminosity Quasi-thermal relativistic plasma Nonthermal power-law tail during flares

DDo we understand AGN? Radio loud vs. Radio quiet Does not depend on type of host galaxy! Core dominance vs Lobe dominance Appears to depend on accretion rate

Marchesini, Celotti & Ferrarese 04 2 - MBH and Accretion rate Marchesini, Celotti & Ferrarese 04 FRII/HEG absorbed e = 1 m MBH • QSO 10-3 FRI Indication for bimodal accretion rate distribution FRII/LEG FRII/BLRG

Siemiginowska et al. 2002 - PKS 1127-145 at z=1.187 - offsets as possible indicators of acceleration in the wake of the shock (Hardcastle et al. 2003)

Jets I Poynting vs. matter Blob deceleration observed in microquasars Circular polarization => strong, ordered magnetic field no observational evidence for thermal matter in AGN jets low RM in large-scale structures => low ne in situ acceleration required in jets Jets I Plasma clouds in large-scale guiding magnetic field?

=> EBL studies possible Quiet state detectable

Counterparts and redshifts have been found for many long bursts No counterpart or redshift has been found for any short burst There are two morphological classes of GRBs, long bursts (~20 s duration) and short bursts (~0.2 s duration) Most of the long bursts display long-wavelength (radio and optical) “afterglows”; but some of them have no detectable optical or radio counterparts (“dark” bursts) There is good evidence which links some long bursts to the deaths of massive stars

The energy spectra of the long bursts form a continuum, from X-ray flashes (with few or no γ-rays), X-ray rich bursts, and GRBs There is no experimental evidence to suggest that any class of burst (long/short, X-ray rich, dark) has a different origin, or a different spatial distribution, from any other class – but there are many theories which do suggest different origins Attempts to unify GRB with SGR/XRF need more evidence!

Association of GRB with star-forming regions: X-ray lines Distribution of OT location in their host galaxies (Bloom et al) SN-GRB connection X-ray absorption column densities consistent with NH=1021-22 cm-2 in GMC Since the typical density in a GMC is n=102-104 cm-3 why the density derived from the standard fireball (e.g. Panaitescu, Kumar et al..) model is 3-4 orders of magnitude lower ? Wind ejection by progenitor. Wind environment is expected from progenitor (collapsar, in particular) but most afterglows are consistent with constant density profile ..

35% of the GRBs detected by BeppoSAX and the IPN had no detectable optical counterparts – why? Absorbed by dust within the host galaxy? Intrinsically faint and/or rapidly fading? High redshift? Only ~10% of the bursts detected by HETE are optically dark HETE gets positions out to the astronomers faster than BeppoSAX and the IPN did Swift is now doing the same, and carrying out optical observations within minutes Some Swift bursts do appear to be optically dark Confirmed by observation?  Not so far

Beaming angles range from ~1º to ~25º; average ~ 4º Isotropic energies, no beaming Beaming angles range from ~1º to ~25º; average ~ 4º Distribution of energy assumed uniform within the beam Energy ~ 1051 erg Corrected for beaming Frail et al. 2001

Theory of GRBs Old competitors: Semi-collimated fireballs  confined plasma balls How to explain the scalings and spectra? Photopair production on reflected emission of pairs Neutron decay in the upstream region Pair production in the upstream or shear region High compactness in the dense downstream plasma