1. Supernova Remnants @ HE Francesco Giordano University and INFN Bari Gamma 400 Workshop

2. Outline Why @ HE (Emission Processes) How Many @ HE (Towards the 1 st Catalog) How Good (Study of systematic errors) Different Families? Conclusions 3/5/20132F. Giordano @ Gamma 400

3. A “Typical” SNR SED 33/5/2013F. Giordano @ Gamma 400 Sync Fermi Range Brem IC on CMB 00 Scaling the environment density we pass from a p-p dominated SED to a IC dominated K ep =10 -1 E b =10TeV  1 =2  2 =4.5 B=100uG n H =100cm -3 n H =1cm -3

4. Populations F. Giordano @ Gamma 4003/5/20134

5. Synchrotron radiation F. Giordano @ Gamma 4003/5/20135 ω c = 1.5 Bp 2 /(mc) 3 Zirakashvili and Aharonian (2007) A&A 465

6. IC Scattering F. Giordano @ Gamma 4003/5/20136 U = 0.26 eV/cm 3 T = 2.73 K Stuner et al. (1997) ApJ 490

7. Cosmic Microwave Background We used the following expression for the number density of CMB photon as a function of energy (blackbody photon distribution): where: k is the Boltzmann constant and T = 2.73 K; The parameter U represents the energy density of CMB photons and it is equal to 0.26 eV cm -3. If we integrate over all values of energy we obtain the value of the number density: F. Giordano @ Gamma 4003/5/20137

8. F. Giordano @ Gamma 4003/5/20138 Bremsstrahlung yield Bethe-Heitler ultra-relativistic Cross Section Density of environment Baring et al. (2000) ApJ 528

9. F. Giordano @ Gamma 4003/5/20139 p-p interactions via  0 decay Parameterization proposed by Kamae et al 2006

10. Cygnus Loop Vela Jr Tycho CTB37A Fermi-Detected SNRs 13 identified SNRs: - 9 interacting - 4 young SNRs counts 3/5/2013F. Giordano @ Gamma 40010

11. Detection of the p 0 -decay bump in SNRs IC 443 and W44 are the two brightest SNRs in the Fermi-LAT range The low energy break is very significant (~19σ and ~21σ for 60 MeV  E  2 GeV); This gives unambiguous and robust detection of the pion decay bump and clear proof that these SNRs accelerate protons. M. Ackermann et al. 2013 3/5/201311F. Giordano @ Gamma 400

12. + 43 2FGL candidates, excluding spatial associations with PSRs, PWN, AGN counts Fermi-Detected SNRs 13 identified SNRs: - 9 interacting - 4 young SNRs 3/5/2013F. Giordano @ Gamma 40012

13. SNR Catalog: To better understand SNRs in a statistically significant manner within a MW context we: ● characterize the spatial and spectral morphology of all regions containing known SNRs. ● examine multi-wavelength (MW) correlation, including spectrum + morphology for radio, X-ray, and TeV and CO, maser, IR, … ● determine statistically significant SNR classification(s) and perform spectral modeling 3/5/201313F. Giordano @ Gamma 400

14. Data Set: 3 years of P7SOURCE_V6 LAT data E: 1-100 GeV Region Of Interest: 10° around each SNR Green’s Catalog (2009): 274+5 SNRs Starting Model: 2FGL Overlapping sources? = None: Add a new extended source = 1 source (not PSR): Replace w extended source > 1 source: Replace (non-PSR) source closest to radio centroid w extended source. Delete all other (non-PSR) sources. Localize source, fit extension Disk extension seed = radio size Spectral model: power law Normalization of Galactic diffuse and all sources w/in 5 o of candidate are free during minimization procedure. Output: Position, extension, significance Spectral energy distribution Region and residual maps Diagnostics Characterize GeV Emission: Analysis Procedure Identifying SNRs via extension: If a SNR’s spatial extension is larger than Fermi’s PSF, we can detect its size, helping to positively identify it. 3/5/2013F. Giordano @ Gamma 40014

15. SNR Catalog: ● Fermi-LAT has the ability to spatially resolve a large number of the 279 known SNRs assuming their GeV and radio sizes are similar. 3/5/201315F. Giordano @ Gamma 400

16. SNR Catalog: ● Fermi-LAT has the ability to spatially resolve a large number of the 279 known SNRs assuming their GeV and radio sizes are similar. ● Spatial extension measured for 15 SNRs, 6 of which are new candidates, permitting clear identification. 3/5/201316F. Giordano @ Gamma 400

17. Systematic Error Study To explore systematic uncertainties related to the choice of the Interstellar Emission Model (IEM), we localized and fit 8 representative candidate SNRs using alternative IEMs. The eight remnants are a combination of hard and soft and point-like (x) and extended (o) sources and they are located in regions with different intensities of the IEM. 3/5/201317F. Giordano @ Gamma 400

18. Alternative IEMs They are build using GALPROP with input parameters set as: HI spin temperature =[150K and optically thin], CR source distribution =[SNR and Lorimer], Halo height = [4 kpc and 10 kpc], and then fit to the data. The HI and CO emission split into 4 Galactocentric rings and the inverse Compton emission are fit simultaneously with the source of interest. Warning: these 8 models do not span the complete uncertainty of the systematics. the method for creating this model differs from that used to create the official Fermi-LAT interstellar emission model, so these 8 models do not bracket the official model. 3/5/201318F. Giordano @ Gamma 400

19. Systematic Error Study Our automated analysis finds a softer index and a much larger flux for SNR347.3-0.5 (RX J1713) than that obtained in a dedicated analysis. [Abdo et al. 2010] Since the best fit radius (0.8 o ) is larger than the dedicated analysis’ (0.55 o ), the disk encompasses nearby sources that are not in the model. This make it softer than the more accurate analysis. SNR candidates' flux and index averaged over the alternative IEMs' solutions, compared to the standard (STD) model result. PRELIMINARY Flux:Index: SNRs: 3/5/201319F. Giordano @ Gamma 400

20. End of slide show Radio synchrotron emission indicates the presence of relativistic leptons. LAT-detected SNRs tend to be radio-bright: ● Interacting SNRs: general correlation suggests a physical link ● Young SNRs show more scatter Radio-GeV Correlation? upper limits (i=2.5, 99%) 3/5/201320F. Giordano @ Gamma 400

21.  p 0 decay or e +/- brem.  inverse Compton ● Young SNRs: seem consistent ● Others, including interacting SNRs: softer than expected Data now challenge model assumptions! ● Underlying particle populations may have different indices. ● Emitting particle populations may not follow a power law: breaks? ● Multiple emission zones? Radio-GeV Index If radio and GeV emission arise from the same particle population(s), under simple assumptions, the GeV and radio indices should be correlated:  =2a+1  =a+1 213/5/2013F. Giordano @ Gamma 400

22. Break region FermiIACT E E 2 dN/dE IC 443 IC 443 SED 1 TeV1 GeV GeV-TeV Index Indication of break at TeV energies Caveat: TeV sources are not uniformly surveyed. 3/5/201322F. Giordano @ Gamma 400

23. E RX J1713-3946 RX J1713-3946 SED 1 TeV1 GeV FermiIACT GeV-TeV Index E 2 dN/dE Break region Indication of break at TeV energies Caveat: TeV sources are not uniformly surveyed. 3/5/201323F. Giordano @ Gamma 400

24. Interacting SNRs tend to be more luminous than young SNRs. Young SNRs: Low L g  evolving into low density medium? Interacting SNRs: Higher L g  encountering higher densities? Environment? 3/5/201324F. Giordano @ Gamma 400

25. Young SNRs tend to be harder than older, interacting SNRs. Or Evolution? Due to decreasing shock speed allowing greater particle escape? decreasing maximum acceleration energy as SNRs age? 3/5/201325F. Giordano @ Gamma 400

26. May a simple simulation help??? F. Giordano @ Gamma 4003/5/201326 =4.5 Particle injection

27. F. Giordano @ Gamma 4003/5/201327 =4.5 Particle injection

28.  0 ->  SEDs F. Giordano @ Gamma 4003/5/201328 =4.5 Particle injection 11 

29. Conclusions Our systematic study has identified a statistically significant population of Galactic SNRs, including: – 6 new extended and >25 pointlike SNR candidates, – evidence for at least 2 SNRs’ classes: young and interacting. Combining GeV and MW observations suggests that: – some SNRs' emitting particle populations may be linked, – simple model assumptions are no longer sufficient, allowing more complex models to be tested. Improved observations and modeling will give us greater insight into SNRs, their acceleration mechanisms and their accelerated particles. Accurately estimating SNRs’ aggregate particle acceleration mechanisms will also allow us to better quantify SNRs’ capability to produce the observed CRs. 3/5/201329F. Giordano @ Gamma 400