Fuentes de radiación gamma

1. Fuentes de radiación gamma Gustavo E. Romero Instituto Argentino de Radioastronomía, (CONICET) romero@irma.iar.unlp.edu.ar

2. The Third Egret Catalog E >100 MeV • EGRET cycles 1-4: 416 gamma-ray excesses above 3 sigma. • 271 of them included in the 3EG catalog. • The significance of sources close to the Galactic plane is 5 sigma. Sources off the the plane have 4 sigma.

3. Positional distribution of low latitude sources

4. Correlation with our Galaxy: Spiral arms Correlation studies with giant HII regions, considered as tracers of the spiral arms of the Galaxy, show that a significant number of the low latitude sources should be located in the arms (Romero 2001). There is a significant number of Population I objects in the parent population of low latitude gamma-ray sources.

5. Log N – log S plot for low latitude sources

6. The observed Log N – Log S slope suggests a concentration of sources towards the Carina arm, at typical distances of 5 kpc from the Galactic center. Bhattacharya et al. A&A 404, 163 (2003)

7. Gamma-ray sources off the galactic plane • At latitudes |b|>5 deg there seem to exist 3 different populations (Grenier 2001): • A group of ~ 45 relatively hard and stable sources associated with the Gould Belt. • A group of ~ 45 softer and more variable sources mostly within 60 degrees from the galactic center. • An isotropic component with ~35 potentially extragalactic sources (AGNs?)

8. Luminosity and spectrum • Sources along the Galactic plane: L ~ 5 10^34 – 5 10^35 erg/s <p> ~ 2.18 (N(E)~K E^-p) • Halo sources: L ~ 10^35 – 10^37 erg/s <p> ~ 2.52 • Gould belt sources: L ~ 10^32 – 10^33 erg/s <p> ~ 2.25 • Isotropic sources: Extragalactic See Romero et al. (1999), Geherels et al. (2000) and Grenier (2001)

9. Variable gamma-ray sources

10. d index Based on a likelihood analysis of the full EGRET data set Nolan et al., ApJ 597, 615 (2003)

11. Non-variable low-latitude EGRET sources Variable low-latitude EGRET sources From Bosch-Ramon, Romero & Paredes, A&A 429, 267, 2005

12. What are these variable galactic sources? Some possibilities: * Microquasars * Colliding wind binaries * Isolated black holes * Pulsar wind nebulae * Interacting neutron stars * Be/X-ray binaries

13. Pulsars: • Condensed cold matter • 1018 kg/m3 • Superfluid interior • High magnetic fields • 108 T • High temperature • 106 K • Strong gravitational fields

15. The Seven Highest-Confidence Gamma-ray Pulsars Once identified, the important next step is to learn what sources tell us about the Universe. Multiwavelength light curves of pulsars provide information about the physics and geometry of the emission regions near the neutron stars.

16. Pulsars – Multiwavelength Spectra Very different from blazar spectra. Multiple emission components are visible.

17. Colliding wind binaries Gamma rays from IC cooling of relativistic electrons locally accelerated at the collinding wind shock (Eichler & Usov 1993). Highest energies E<1 TeV

18. An interesting case: Cygnus OB2 #5 VLA radio maps of Cygnus OB2 No.5 (Contreras et al. 1997) The system is well within the 95% CL contour of 3EG J2033+4118 The primary is an O7 Ia + Ofpe (WN9) contact binary. The secondary is a B0 V star located at 1700 AU.

20. SNR RXJ 1713.7-3946 Butt et al. 2001, ApJ Lett. 562, L167

23. High-mass micrcoquasars: leptonic models The jet must traverse different external photon fields generated by the hot corona, the accretion disk and the companion star. IC interactions between relativistic leptons in the jet and the external photons may produce a significant gamma-ray flux. If a magnetic field is present, SSC interactions will also contribute to the high-energy emission.

24. Accretion disc + corona/jet Jet Companion star (OB) ‘Non-thermal’ Broadband spectral changes in ‘jet on’ + ‘jet off’ states Cygnus X-1 Apart from the companion star, the spectrum is comparable to LMXBS in same state (Tigelaar, Fender 2004)

25. High-mass microquasars: leptonic models External photon fields Let us consider an inhomogeneous jet with bulk Lorentz factor G and magnetic field B interacting with these fields. Particles in the jet are assumed to be distributed with a power-law of index p=2 in the comoving frame. The high-energy cut-off for electrons is at some gemax (z), where z is the propagation axis.The jet power is a fraction q of the accreting power. From Romero, Kaufman, & Mirabel, 2002, A&A Lett, 393, L61

26. SED of high-mass microquasars q=10^-3 B=200 G Gjet=1.1 gemax=10^4 q=10 deg q=10^-4 B=10 G Gjet=10 gemax=10^6 Q=1 deg q=10^-4 B=10 G Gjet=2.5 gemax=10^4 q=10 deg From Bosch-Ramon, Romero & Paredes (astro-ph/0405017)

27. Microquasares as TeV gamma-ray sources? Details in : Romero et al. astro-ph/042285

28. Hadronic gamma-ray emission from high-mass microquasars? Romero et al., A&A 410, L1, 2003

29. SMBH model & unification • blazar • Sy 1 • BLRG • QSO • Sy 2 • NLRG • IR QSO?

30. Núcleos galácticos activos

31. 1.2 mag (~3 times in flux units) brightening in ~24 hs AO 0235+164 (BL Lac object z = 0.94) 2.8 < C < 14.3 Romero, Cellone, Combi (2000, A&A 360, L47)

33. thermal(disk) Synchrotron(jet) inverse Compton(jet) Spectrum of a gamma-ray blazar Lichti et al. (1994)

34. Cygnus A VLA, 21-cm radio emission RADIO GALAXIES lobe hot spot nucleus

35. CYGNUS A - VLA, 6cm

36. CYGNUS A - VLA, 6cm undisturbed intergalactic gas “cocoon” (shocked jet gas) splash point backflow bow shock