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Towards the first fermi SNR Catalog

Towards the first fermi SNR Catalog. F. Giordano 1 , T. Brandt 2 & F. Acero 2 , F. de Palma 1 , J. Hewitt 2 for the Fermi Collaboration. 1 University and INFN Bari 2 NASA Goddard Space Flight Center. Why a dedicated pipeline?.

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Towards the first fermi SNR Catalog

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  1. Towards the first fermi SNR Catalog F. Giordano1, T. Brandt2 & F. Acero2, F. de Palma1, J. Hewitt2 for the Fermi Collaboration 1University and INFN Bari 2NASA Goddard Space Flight Center

  2. Why a dedicated pipeline? Of the 78 SNRs with GeV associations detected in the 2-year Fermi-LAT catalog (2FGL) roughly 45% are expected to be chance coincidences. With this project we intend to: - Characterize GeV emission in regions containing known SNRs - Evaluate systematics, including diffuse models and variability - Examine multiwavelength correlation, including spectrum and morphology for radio, X-ray, and TeV and CO, maser, IR, … - Determine statistically significant SNR classification(s) and perform spectral modeling

  3. Where we started from… We survey 278 known Galatic SNRs, identified mainly in radio compiled in Green’s (2009) SNR Catalog

  4. Some preliminary numbers • SNR catalog results: • 52 of 278 Radio SNRs Detected Sources • 12 previously identified SNRs • 7 are identified as NOT SNRs (PSR, PWN, HMB or AGN) • 6 New significantly Extended SNR Candidates • 27 Pointlike Candidates • 14 more SNR-like • 17 more PSR-like

  5. We have run our extended search tool We have a powerful and reliable tool to search for spatially extended source and determine the significance of the extension (Lande+ 2012) This pipeline resulted in 6 new significantly extended new SNR candidate GeV Extension Fermi LAT best PSF

  6. And Collected MW data MW data are being used to confirm or discard the associations/identification W49B Case Green Circle: radio SNR Cyan Circle: Fermi error circle

  7. And studied Systematics from the Diffuse • A grid of 8 models, varying the CR source distribution (SNR and Lorimer), the halo size (4 kpc and 10 kpc), and the HI spin temperature (150K and optically thin) • free independent normalization coefficients for the inverse Compton component and for the components associated to HI and CO divided in 4 Galactocentric annuli L=-30° L=30° L=-60° L=60° 4 1 2 3 PuppisA Case More plots: poster by T.J.Brandt+

  8. Preliminary results I SNRs Radio vsGeV Flux Remnants known to be interacting with large molecular clouds show a good correlation Young seems to be more out-liers PSRs contamination is under investigation (MW data) New Candidates

  9. Preliminary results II Effect of Environment? • Diameter traces SNR evolution (in Sedov stage R  t2/5) • Interacting SNRs generally show higher L(GeV) than young SNRs

  10. Preliminary results IIIEffect of Age? • Young SNRs have generally harder GeV indices, but no clear trends for interacting SNRs • We also observe softening of the GeV index with increasing age • due to changing emission mechanism? • due to different environments?

  11. Concluding… • Procedure: We have set-up a dedicated procedure to characterize GeV Emission (MW data, extension, diffuse systematics…) • Numbers: We now have 52 detected: 12 previously identified SNRs, 6 new extended, 27 point-like • Classes: • Interacting SNRs • Soft index (possible indication of a break @ GeV) • Higher density clouds act as target for high LGeV • Young SNRs • Seem to have Harder index • No GeV spectral break • Lower density ISM/CSM • “Collective” behavior • Radio-gamma correlation apparent, but not universal (SNR upper limits are interesting constraint) • Luminosity and Index show correlation with age/environment For more details see poster by T.J.Brandt’s

  12. Preliminary results IVRadio vsGeV Index • Young SNRs (i.e. RX J1713, VelaJr) show harder GeV index than inferred from radio ( Γ = 2+1 ), possibly suggesting an IC origin • Many SNRs show soft GeV index suggesting a ~ GeV break. PRELIMINARY

  13. Some results: PuppisA Hewitt+ 2012 see M.Lemoine-Goumard talk

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