World Cup of VHE Gamma Rays

J-Dog, for the SNR/PWN Pack

SNR Types/Evolution• Type Ia: result from accretion in a binary; explosion typically into

~uniform medium.• Type II: core collapse of a ~8-15 M star; explosion into slow

(~10 km/s) wind; neutron star left behind.• Type Ib: core collapse of a >~15 M star; explosion into fast

(~1000 km/s) wind; black hole left behind.• All yield ~0.5 – 2.0 · 1051 erg initial ejecta kinetic energy.

– Rate of ~3/century need ~16% energy converted to CRs to maintain galactic CR flux.

• Sedov phase begins – mass of swept-up material = ejecta energy.– Usually takes few 100 – few 1000 years to reach.– SN energy now split roughly evenly between bulk kinetic, thermal, and

relativistic particles.– Beginning of Sedov phase is when gamma-ray emission from CR-proton

interactions (pion decay) is expected to peak.– SNR expands adiabatically for ~100 kyr until gas cools enough to radiate

efficiently, starting a phase of rapid cooling.

PWN OverviewEvolution of a PWN•Expansion Phase

•nebula expands into cold gas medium

•Interaction with reverse shock•compression and transition to hot gas medium•possible distortion of nebula by asymmetric reverse shock arrival

•Sedov Phase•pulsar exits the original relic nebula and generates a new smaller nebula. •At ~2/3 distance to the forward shock becomes supersonic and generates a bow shock

•Interstellar Gas Phase – “the pulsar has left the building”

Gaensler & Slane, 2006

SNR/PWN Science: Morphology• Resolve locations of maximum

particle acceleration in nearby

remnants•in SNR shells (RXJ 1713, Vela Jr) •to distinguish nebula emission

from shell (e.g. G0.9-0.1)•to resolve jets in jet-dominated

PWN (MSH 15-52)

• PWN evolution indicators•pulsar/X-ray/TeV nebula offsets inhomogeneous interaction with

reverse shock (Vela X, G18.0-0.9,

Kookaburra, Rabbit)•TeV vs X-ray size differing

synchrotron lifetimes (G18.0-0.9)

RXJ 1713.7-3946

MSH 15-52

Vela X

G0.9-0.1(contours VLA)

Utility of MWL Information

(from Aharonian, etal., arXiv:astro-ph/0606311)

Radio + X-ray + TeV: Constrain species of emitting particlesX-ray + TeV: Constrain history of nebula’s magnetic field

Constrain shell magnetic fieldMorphology effect of reverse shock, medium homogeniety

X-ray + GeV + TeV: Study nebula’s synchrotron coolingGeV + TeV: Study effect of CRs on shell dynamics

Key Project Justification IScience Motivation:• Understand the role of SNRs in cosmic-ray acceleration. • Study particle acceleration (ion and electron) mechanisms.

– Maximum energy achievable in shock acceleration.– Resolution of jet structure, pulsar and X-ray nebula offsets, Doppler boosting.

• Use the spectral shape, morphology, and MWL information to discriminate between acceleration models. – Even upper limits can place important constraints on models.– What are the conditions that lead to efficient cosmic-ray acceleration?– Extending spectrum to GeV with GLAST, study modification of shock dynamics by

cosmic rays.• Study shell/nebula structure and evolution.

– Constrain shell, nebula magnetic fields.– Reverse shock compression/asymmetries in surrounding medium.– Measure synch. cooling break, particularly in combination with GLAST.– TeV provides integrated history of injected electron population while X-ray

indicates recent history.– Expansion rate and age of nebula.

• Probe interstellar medium.– Indirect measure of local photon densities.

Key Project Justification II

Discovery Potential:• The largest class of objects that HESS has detected is SNRs/PWNe.

• Most of the HESS sources are in a region of the galactic plane at a distance of ~4-10 kpc, whereas the region of the plane visible to VERITAS (~30o < l < ~220o) contains spiral arms at ~2-4 kpc.

• SNRs and PWNe are steady sources and have fairly hard spectra (index ~2.0-2.5), making them more readily detectable with a new instrument.

Why VERITAS?• Cas A, Tycho, 3C 58, and J2021 are unobservable by HESS/CANGAROO.

• VERITAS has better sensitivity than MAGIC for extended sources and at higher energies.

Why a Key Project?• These objects form a set of the best known candidates of different classes of

SNRs/PWNe; synergy between them maximizes their science reach.

Proposal IYear I: Observe a number of SNRs/PWNe with sensitivity

to detect or set limits at few % Crab level.

Year II: We anticipate a request of ~100-150 hours.– Follow up of sources detected in the first year.

– Follow up of Sky Survey and GLAST detections.

Month Primary Targets Secondary

Oct J2021 Cas A 3C 58

Nov Cas A Tycho J2021

Dec Cas A Tycho 3C 58

Jan IC 443 Monoceros

Feb IC 443 Monoceros

Proposal II

Object J2021 Cas A Tycho 3C 58 IC 443 Mono

Shell PWN Progenitor Type CC CC Ia CC CC ?

Cloud Interaction Months Oct-

NovOct-Dec

Nov-Dec

Oct-Dec

Jan-Feb

Jan-Feb

Hours 10 25 25 25 25 25*CC: Core collapse

SNR/PWN Observability ( > 55 deg)Hours perYear (Jul, Aug,Septexcluded)

~ Sky survey region

Midi

W49B

Mono

IC443

Crab

J1930

Cygnus

Loop

W44

CTB80

CTB87Cygni

J2021

Tycho

Cas A

3C58

R5

DA530

J2229

Summary

• Is that the end?

Additional Info

3C 58 (G130+3.1)

• Powered by 3rd most energetic pulsar in the galaxy, J0205+6449 (after Crab and G21.5-0.9).

• Relatively nearby at 3.2 kpc.• Possible association with SN 1181 but observations

imply an older object.– age important for X-ray constraints on neutron star cooling.

• Crab-like morphology (jet/torus).

• Low magnetic field e- producing TeV emit synchrotron in the UV band.– TeV probes otherwise unobservable section of e- spectrum.

– Similar nebula of PSR B1509-58 detected in TeV.

IC 443

J2021+3651