Observations of Supernova Remnants with VERITAS

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1 Observations of Supernova Remnants with VERITAS Presented by Nahee Park

2 What do we want to learn? Are SNRs the main accelerators of the Galactic cosmic rays? Efficiency of cosmic-ray acceleration? Maximum energy that can be accelerated in SNRs? Tycho Morlino & Caprioli (2012) Ackerman et al (2013) Compiled data up to Jan from CR database ( A.W.Strong et al, 2009 ICRC)

3 What do we want to learn? (2) Study of the gamma-ray emissions from SNRs Evolution of the SNRs as CR accelerators? Difference depending on the environments & SNR types? Resolving different components in SED? Properties of escaping CRs CRs with higher energy escape first. Possible high energy gamma-ray emissions from nearby MC? (e.g. W44 & W28) Gamma-ray observations of SNRs provide a unique window - to study the acceleration & propagation of CRs - to study the environments & properties of SNRs

4 TeV SNRs in Northern sky Tycho IC 443 W51C W49B VER J VER J MGRO J Cas A

5 VERITAS SNR Program Deep observation of TeV SNRs Cassiopeia A Tycho IC 443 Study of unidentified TeV sources with nearby SNRs VER J (γCygni) MGRO J VER J (SNR G ) Search for the discoveries Fermi SNR searching : W44, CTB109, etc SNRs located nearby MC : VRO , HB3, etc Strong radio SNRs : W63, etc

6 Deep Observations Estimated results (calculated by Igor Telezhinsky) Cassiopeia A Tycho

7 Deep Observations Estimated results (calculated by Igor Telezhinsky) Cassiopeia A Tycho

8 IC 443 MC interacting, nearby SNR Two shells expanding to different density regions OH masers Distance ~ 1.5 kpc PWN in the southern part CXOU J With TeV gamma-ray observations, Study CR diffusion Morphology studies with deeper exposure Estimate the flux from PWN Acciari et al (2009) Ackerman et al (2013)

9 A historic, core-collapse SNR Cassiopeia A Age : ~ 350 years, distance : ~ 3.4 kpc Non-thermal X-ray emissions from both forward & reverse shocks With TeV gamma-ray observations, Study the origin of gamma-ray emissions Leptonic vs. hadronic Contributions from reverse shock Estimate the maximum energy of CRs Abdo et al (2010) Yuan et al (2013)

10 Tycho A historical, Type Ia SNR Age : ~440 yr, distance : 2~5 kpc Exploded in relatively clean environment Nearby MC in NE side Hint of density gradient of ISM Complicated structures in X-ray Thin filaments, bright strips With TeV gamma-ray observations, Determine the origin of the emission : MC vs. shell Estimate the maximum energy of CRs Study the acceleration theory in detail e.g. Understanding a softer spectral index measured by Fermi-VERITAS Acciari et al (2011) Morlino & Caprioli (2012)

11 Tycho (2) Provide a laboratory to test various theoretical models

12 Tycho (2) Provide a laboratory to test various theoretical models

13 Observational Status VERITAS accumulated 2~3 times larger data for TeV SNRs since the first reports of detections Tycho ~ 140 hours ( from 67 hours ) Cassiopeia A ~ 100 hours ( from 22 hours ) Large zenith angle observation : increase of effective area for higher energy IC 443 ~ 90 hours ( from 37 hours )

14 Study of unidentified TeV sources VER J Coincide with NW shell of γcygni, Located within the Fermi cocoon c.f. Fermi : extended emission from the entire remnant MGRO J Partially coincide with SNR G Interaction of the pulsar wind with nearby molecular clouds or the SNR shock? PWNe of PSR J & undetected pulsar? VER J Coincide with SNR G & Milagro C4 PWN(PSR J )/SNR(G ) complex?

15 Search for other TeV SNRs Fermi-bright SNR search W44 Search for SNRs nearby MC (w/ potential Fermi source) HB3/W3 complex VRO CTB 109 Search for emissions from other FoVs 3C396, 3C397, Kes79, HC40...

16 Long term plan Future plan What is the best way for VERITAS to contribute to SNR studies in next 3~5 years? Collaboration with other gamma-ray experiments Fermi HAWC