towards the first fermi snr catalog

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

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:

Where we started from…Where we started from…

We survey 278 known Galatic SNRs, identified mainly in radio compiled inGreen’s (2009) SNR Catalog

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

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

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

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.

Some results: PuppisASome results: PuppisA

see M.Lemoine-Goumard talk

Hewitt+ 2012