The γ -ray sky above 10 GeV seen by the Fermi satellite

1. The γ-ray skyabove 10 GeV seen by theFermi satellite Jean Ballet (AIM, CEA Saclay, France) Grenoble, December 5, 2011

2. Above 1 GeV 2FGL: 1873 sources(ArXiv1108.1435)

3. Above 10 GeV Many fewer events (2 years data) Galactic diffuse emission not dominant, except in the Ridge Fermi bubbles

4. Spatial resolution PSF improves considerably with energy up to 10 GeV R68 approximately constant at 0.2° above 10 GeV (in flight) Not as good as simulation. Could still be improved.

5. Fermi sources > 100 GeV 0.6° 1 – 10 GeV 10 – 100 GeV 100 – 300 GeV Neronov et al 2010 (A&A 519, L6) have found 8 Fermi sources above 100 GeV, among which one was not a previously known TeV source IC 310 in Perseus cluster: 3 events within 0.1° over 18 months

6. Fermi sources > 10 GeV > 300 sources over 2 years Integral flux above 50 GeV estimated from power-law fit above 10 GeV Even though AGN are variable, flux above 50 GeV is a good indicator of TeV detectability Several Fermi-based TeV detections already Paneque et al 2011, Fermi Symposium (2 years)

7. Fermi sources > 10 GeV Paneque et al 2011, Fermi Symposium (2 years) Mostly AGN Tail of bright pulsars Hard Galactic sources (SNR, PWN) Individuals Preliminary LMXB PSR LBV PWN AGN SNR LMC

8. Crab pulsar McCann 2011, ICRC Crab pulsar has been detected by MAGIC then VERITAS over 100 GeV Clearly incompatible with exponential decay Not obvious this can happen in older less energetic pulsars, but worth looking

9. Pulsar Wind Nebulae Fermi HESS HESS J1825-137 Grondin et al 2011, ApJ 738, 42 TS > 10 GeV+ HESS contours Special case when the pulsar itself was not detected by Fermi PWN normally much harder to detect on top of bright pulsar, but possible with phase selection PWN will remain much easier to detect at TeV than GeV energies Main help from Fermi in pulsar itself for interpretation (power input)

10. Supernova remnants RX J1713.7-3946 Hadronic Brightest TeV SNR Very faint, hard Fermi source in a complicated region of the Galactic plane, not detected below 5 GeV Extended, compatible with HESS image Clearly below the extrapolation of hadronic models, in line with leptonicmodels Does not mean that protons are absent, but that density is low (as indicated by absence of thermal X-rays). Abdo et al 2011, ApJ734, 28 Fermi HESS Leptonic model 10 TeV 1 GeV

11. Old SNRs: IC 443 Older SNR, between 3 and 30 kyr Extended, emission where molecular clouds interact with the SNR, does not follow radio contours Break frequency at ~ 3 GeV, corresponding to 20 GeVon proton spectrum. Probably reflects the maximum energy reached by freshly accelerated particles Clearly hadronic, but soft (Γ = 2.9 at TeV) TeV Fermi Abdo et al 2010, ApJ 712, 459 Albert et al 2007, ApJ 664, L87 Acciari et al 2009, ApJ 698, L133 1 GeV 1 TeV Very large diversityin SNR spectra, depending on age (shock speed) and surroundings (density) Global emission very slowly variable: no need for coincidence GeV and TeV observations are very complementary

12. FSRQs BL Lacs otherAGNs AGN – 2LAC 886 high-confidence AGN Nearly flux-limited sample in terms of energy flux over full band Follows nicely blazar sequence 395 BL Lacsin 2LAC (291 in 1LAC) Longer exposure time favors hard sources 100 MeV to 100 GeV B. Lott at Fermi meets Jansky 2011 Abdo, A. A. et al., accepted by ApJ, arXiv:1108.1420  

13. AGN: GeV - TeV connection Abdo et al. 2009, ApJ 707, 1310 Fermi spectra of known TeV AGN Fermi: average flux Comparison difficult due to intrinsic variability Fermi is not well suited to MW studies of correlated variability

14. AGN: GeV - TeV connection Compare spectral index rather than flux 39/45 TeV AGNs are in the 2LAC (34 in clean sample) 26 AGN are well fitted with simple power law in the LAT band 17 HSP, 2 ISP, 2LSP, 5 unknown Deficit of distant sources with small values ofΔΓ EBL: softening of the VHE spectrum dependent on z B. Lott at Fermi meets Jansky 2011 Updatedfrom Abdo et al. 2009, ApJ 707, 1310

15. AGN: variability When variability is detected, large relative variations Fermi can characterize variability on long time scales, but short time scales not reachable for most sources TeV instruments can characterize short term(but not long term) variability GeV and TeV observations are very complementary for statistical studies 1FGL: Abdo et al 2010, ApJS 188, 405

16. Flaring sources • Automated search for flaring sources on 6 hour, 1 day and 1 week timescales. • LAT scientists perform follow-up analyses, produce ATels, and propose ToOs • >100 Astronomers telegrams • Discovery of new gamma-ray blazars • Flares from known gamma-ray blazars Fermi is an excellent all-sky monitor Detects flaring sources at low energy, but TeV behavior can be guessed from average spectrum This one is very soft, no good for TeV

17. Gamma-ray Bursts GRB 080916C Abdo et al 2009, Science 323, 1688 Fermi has shown that GeV emission can extend up to 10 minutes in some GRBs Alpha = -1.02 ± 0.02 Beta = -2.21 ± 0.03 Epeak = 1170 ± 142 keV • Consistent with Band function from 10 keV to 10 GeV • No evidence for rolloff or γγ absorption  Γ ≥ 900 • No evidence for Compton component

18. Power-law detection threshold P7Source_V6 Rocking angle 50° |Latitude| > 10° • Softsources • limited by: • Knowledge of diffuse background(5% precision) • Source density(extrapolated from measured logNlogS) E-1.5 E-2.5 Hard sourceslimited by source count rate Detection threshold improves faster than 1 / √t

19. Fermi at high energy • Spatial resolution 0.2° limiting in Galactic plane • Detects 100s of sources above 10 GeV • All-sky survey: reservoir of TeV targets • Excellent GeV – TeVcomplementarity for SNRs • PWN: can detect pulsar inside and measure power • AGN: blazar sequence, variability over long time scales • GRBs await detection at TeV energies. Need to be fast. • Good prospects for hard sources with increasing exposure It costs NASA money to operate Fermi 5-year operations are guaranteed (up to mid 2013) Good prospects to extend it for two more years, hopefully five But not indefinitely, and no other GeV instrument in sight