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

2. 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?

3. 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

4. True TeV Astronomy

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

6. RX J
HESS spectrum

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

8. 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

9. 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

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

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

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

13. 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

16. 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

17. 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

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

19. 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?

21. => EBL studies possible Quiet state detectable

22. 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

23. 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!

24. 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= cm-2 in GMC
Since the typical density in a GMC is n= 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 ..

25. 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

26. 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

27. 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