Towards the first fermi SNR Catalog
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Transcript of Towards the first fermi SNR Catalog
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TOWARDS THE FIRST TOWARDS THE FIRST FERMI SNR CATALOGFERMI SNR CATALOG
F. Giordano1, T. Brandt2
&F. Acero2, F. de Palma1, J. Hewitt2
for the Fermi Collaboration
1University and INFN Bari2NASA Goddard Space Flight Center
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F. Giordano 2
Of the 78 SNRs with GeV associations detected in the 2-year Fermi-LAT catalog (2FGL) roughly 45% are expected to be chance coincidences.
Why a dedicated pipeline?Why a dedicated pipeline?
- 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
With this project we intend to:
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Where we started from…Where we started from…
We survey 278 known Galatic SNRs, identified mainly in radio compiled inGreen’s (2009) SNR Catalog
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Some preliminary numbersSome 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
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We have run our extended search tool 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
Fermi LAT best PSFGeV Extension
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And Collected MW dataAnd Collected MW data
Green Circle: radio SNRCyan Circle: Fermi error circle
MW data are being used to confirm or discard the associations/identification
W49B Case
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And studied Systematics from the And studied Systematics from the DiffuseDiffuse
- 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
More plots: poster by T.J.Brandt+
PuppisA Case
1 2 3 4
L=30°
L=60°L=-60°
L=-30°
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Preliminary results IPreliminary results I SNRs Radio vs GeV Flux SNRs Radio vs GeV 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
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• Diameter traces SNR evolution (in Sedov stage R t2/5)• Interacting SNRs generally show higher L(GeV) than young SNRs
Preliminary results IIEffect of Environment?
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Preliminary results IIIPreliminary results IIIEffect of Age?Effect of Age?
We also observe softening of the GeV index with increasing age due to changing emission mechanism? due to different environments?
• Young SNRs have generally harder GeV indices, but no clear trends for interacting SNRs
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Concluding…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
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Preliminary results IVPreliminary results IVRadio vs GeV IndexRadio vs GeV Index
PRELIMINARY
• 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.
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Some results: PuppisASome results: PuppisA
see M.Lemoine-Goumard talk
Hewitt+ 2012