VERITAS Observations of Supernova Remnants Reshmi Mukherjee 1 for the VERITAS Collaboration 1...
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VERITAS Observations of Supernova Remnants Reshmi Mukherjee 1 for the VERITAS Collaboration 1 Barnard College, Columbia University Chandra SNR Meeting,
VERITAS Observations of Supernova Remnants Reshmi Mukherjee 1
for the VERITAS Collaboration 1 Barnard College, Columbia
University Chandra SNR Meeting, Boston, Jul 8, 2009
Slide 2
Outline (Quick) introduction to VERITAS Scientific goals &
questions Observing program VERITAS -ray results
Slide 3
85 m 109 m 82 m 35 m T1 Fall 2006 April 2007 T4 T2 T3 Since
March 2006 Instrument design: Four 12-m telescopes 499-pixel
cameras (3.5 FoV) FLWO,Mt. Hopkins, Az (1268 m) Completed Spring,
2007 VERITAS at Whipple Observatory
Slide 4
VERITAS: The Atmospheric Cherenkov Technique ray camera
Cherenkov image Imaging ACTs use the shape and orientation of the
air shower image in the camera plane to distinguish between cosmic
& -rays. ns electronics Area = 10 4 10 5 m 2 ~60 optical
photons/m 2 /TeV
Slide 5
VERITAS Sensitivity Sensitive energy range: 100 GeV to > 30
TeV Spectral reconstruction begins at ~150GeV Energy resolution:
~15% - 20% Peak effective area: 100,000 m 2 Angular resolution: 0.1
o at 1 TeV, 0.14 o at 200 GeV (68% values) 1% Crab detection (5 )
in less than 50 h, 5% crab in ~2.5 h Observation time per year: 750
h non-moonlight, 100 h moonlight
Slide 6
Galactic Science Program VERITAS Key Science Project Supernova
remnants/PWNe Non-thermal shells Shell-molecular cloud interactions
TeV PWNe associated with high E/d 2 pulsars Goal of KSP:
Constraints on particle acceleration and diffusion. Cosmic ray
origin? Measurement of TeV emission from SNRs could resolve the
long-standing question of whether these are sites of hadronic
cosmic ray acceleration. Is there clear evidence of hadronic
emission? Is the TeV IC emission low? Can we demonstrate a robust
correlation of TeV emission with target matter? Combining the TeV
spectrum with the synchrotron spectra in the radio and X-ray bands
can possibly discriminate between IC and pion production/decay
models, and provide strong constraints on the acceleration
process.
Slide 7
VERITAS Observations of SNRs Supernova remnants are widely
considered to be the strongest candidate for the source of cosmic
rays below the knee at around 10 15 eV. Several SNRs have been
detected at TeV energies. Here we present results on: Cas A IC 443
W 44 TeVCat:://tevcat.uchicago.edu/
Slide 8
Results: Cas A Young (330 yr), shell-type SNR at a distance of
~3.4 kpc. Massive star progenitor 5 diameter (~TeV ang resolution).
Discovered in TeV by HEGRA (232 hrs, 5 ), confirmed by MAGIC (47
hrs, 5.3 Flux ~ 3.3 % Crab above 1 TeV Power-law 2.3 0.2 stat 0.2
sys Extensive modeling of cosmic-ray acceleration and ray
production exists. SNR & PWNe KSP: Deep Chandra image of Cas A
(7.3 by 6.4) Stage et al. 2006 credit: NASA/CXC/SAO/ D.Patnaude et
al.
Slide 9
Results: Cas A VERITAS: - wobble-mode observations, 0.5 offset,
during Oct/Nov 2007 with full 4 Tel. array Exposure: 22 hr: 8.3
detection Flux: ~ 3% Crab Consistent with a point source. Acciari
et al. (2009), in prep.
Slide 10
VERITAS Spectrum = 2.61 +/- 0.24 stat +/- 0.20 sys Acciari et
al. (2009), in prep. Results: Cas A Well-fit by power law spectrum:
dN/dE = N 0 (E/TeV) - Flux (E > 1 TeV): ~ 3.5% Crab (7.76 +/-
1.10 stat +/- 1.55 sys ) X 10 -13 cm -2 s -1 No sign of energy
cut-off at high energy Solid: VERITAS Dashed: HEGRA Dotted:
MAGIC
Slide 11
Results: IC 443 Stage et al. 2006 Distance ~ 1.5 kpc Age ~
30,000 years Diameter 45 Distinct shell in radio, optical 3-10 keV
X-rays Bocchino & Bykov 2001 Black optical White EGRET Color -
CO + MAGIC Shell interacting with molecular cloud -> potential
target material EGRET emission centered on remnant, overlaps cloud
MAGIC emission centered on cloud PWN at southern edge of shell
Compelling reasons to search for TeV emission from IC 443: s from
cosmic rays, or from the PWN?
Slide 12
Results: IC 443 Stage et al. 2006 Discovered in TeV in 2007 by
VERITAS (7.1/6.0 pre/post-trials in 15.9 hrs) by MAGIC (5.7 in 29
hrs) Wobble-mode observations, 0.5 offset Observed during two
epochs: Feb / Mar 2007 with 3 telescopes PWN location, CXOU
J061705.3+222127 Oct / Nov 2007 with 4 telescopes Center of Feb/Mar
hot spot: 06 16.9 +22 33 Total livetime: 37.1 hrs. Flux ~3% Crab
8.2 peak significance pre-trials 2-D Gaussian profile fit:
Centroid: 06 16.9 +22 32.4 0.03(stat) 0.07(syst) Extension: ~ 0.17
0.02(stat) 0.04(syst) Acciari et al. ApJL 698 L133 (2009)
Slide 13
Results: IC 443 Stage et al. 2006 Overlap with CO indicating
molecular cloud along line of sight Maser emission suggests SNR
shock interacting with cloud TeV emission could be CR-induced pion
production in cloud associated with the pulsar wind nebula to the
south GeV and TeV emission spatially separated? Multiwavelength
Picture Acciari et al. ApJL 698 L133 (2009)
Slide 14
Results: IC 443 Stage et al. 2006 Power-law fit 0.3 2 TeV: =
2.99 0.38 stat 0.30 sys Threshold of energy spectrum - 300 GeV The
integral ux above 300 GeV is (4.63 0.90 stat 0.93 sys ) X10 12 cm 2
s 1 (3.2% Crab), in good agreement with the spectrum reported by
MAGIC Acciari et al. ApJL 698 L133 (2009)
Slide 15
Observations of Other SNRs CTB 109 (G109.1-1.0): Shell-type
SNR, interacting with a molecular cloud on its eastern rim.
Observed briefly for 4.3 hrs (live time). No emission detected.
Flux UL (E > 400 GeV) < 2.5X10 -12 cm -2 s -1 FVW 190.2+1.1:
Forbidden Velocity Wings may be the vestiges of very old SNRs. FVW
190.2+1.1 shows a clear shell-like morphology in the HI maps.
Motivated by the possible association of HESS J1503-582 with an
FVW. VERITAS observed for 18.4 hrs (live time) No emission
detected. Flux UL (E> 500 GeV) < 0.26X10 -12 cm -2 s -1 (<
1% Crab nebula flux) W 44: SNR promising source of 0 induced -rays.
13 hr live time around W44. No emission detected around SNR. Flux
UL (E > 300 GeV) < 2% Crab nebula flux.
Slide 16
Observations of Other SNRs Fig. from Wolsczcan et al. 1991
Contours: Radio emission Shaded area: X-rays W44 is an SNR with
large angular extent. W44 is a bright radio source. X-ray emission
centrally peaked, predominantly thermal X- ray emission A plerion
is visible in radio and X-rays associated with PSR 1853+01 (Harrus
1997). 0FGL J1855.9+0126, marginally coincident with PSR 1853+01,
has ux 2.5% of Crab in the energy range (1 100)GeV.
Slide 17
The field of W 44 9.2 hrs livetime on W44 position. 6.4 hrs on
UIDs J1857+026 possibly associated with PWN AX J185651+0245 powered
by newly discovered radio pulsar PSR J1856+0245 W44: UL ~2 % Crab
J1857+026: 5.6 J1858+020: not detected Agreement with HESS:
HESSJ1857+026 is detected in the position reported by HESS.
Morphology of HESS J1857+026 is well reproduced. Unidentified
Sources: HESS J1857+026 and HESS J1858+020 Acciari et al. in
prep
Slide 18
Summary IC 443: Extended and complicated Extended emission;
soft spectrum Origin: PWN or SNR/MC interaction? Strong Fermi
source: broadband spectral, morphological evolution will be
illuminating Cas A: Detection with 8.3 significance in 22hrs
Consistent with a point source Power-law spectrum up to ~5 TeV; no
sign of a cut-off Well-measured spectrum. Boon to modelers Other
SNRs: Lack of strong (>5% Crab) sources
Slide 19
Future Directions Upgrade New platform for T1 Disassembly of T1
Relocating T1 will improve the sensitivity of VERITAS by ~15%
equivalent of gaining an annual 300 hr extra in obs. time. Impacts
all physics goals.
Slide 20
Extra Slides
Slide 21
VERITAS Concept VERITAS Concept
Slide 22
Observations of Other SNRs
Slide 23
Results: Cas A The non-thermal X-ray emission predominantly
originates from laments and knots in the reverse-shock region of
Cas A (Helder & Vink 2008). The presence of a large ux of
high-energy electrons in the reverse-shock region, responsible for
the non-thermal radio to X-ray emission, will also produce
high-energy -ray emission through non-thermal bremsstrahlung and IC
scattering (Atoyan 2006). Based on that leptonic emission, Cas A
would appear in VERITAS data as a disk or ring-like source with
outer radius 2.5 (Uchiyama & Aharonian 2000). If, on the other
hand, the VHE -ray emission from Cas A were dominated by 0 decay
produced in inelastic collisions of relativistic protons, the
location of the particle- acceleration site is less constrained by
data in other wavebands. The question of whether or not there is a
sufficiently high flux of Galactic nuclear CRs resulting in a
steady flux of VHE rays, remains one of the most stimulating
scientific questions of ground-based ray astronomy. (Berezhko et
al. 2003)
Slide 24
VERITAS Observations of SNRs Stage et al. 2006 Cosmic rays
accelerated at expanding shock front electrons and/or nuclei
synchrotron radiation observed in radio through X-rays TeV
observations constrain Nature of particles Acceleration process
Role of SNRs in production of Galactic cosmic rays Growing class:
~8 known or likely SNR associations IC 443 Cas A CTB 109 FVW
190.2+1.1 W44
Slide 25
B. Humensky, U. of Chicago31 st ICRC, Lodz, PolandObservations
of SNRs with VERITAS IC 443 Stage et al. 2006 Distance ~ 1.5 kpc
Age ~ 30,000 years Diameter 45 Distinct shell in radio, optical
Shell interacting with molecular cloud potential target material
EGRET emission centered on remnant, overlaps cloud MAGIC emission
centered on cloud PWN at southern edge of shell Compelling reasons
to study TeV emission from IC 443: s from cosmic rays, or from the
PWN? Green Radio Red Optical Blue X-rays
Slide 26
VERITAS Galactic Science TeV observations of X-ray binaries: Is
the compact object BH emitting jet ? Is it a pulsar with pulsar
wind? Are these systems accreting binaries (microquasars?) Emission
mechanisms? J. Paredes Unidentified Galactic sources EGRET
unidentified sources TeV unidentified sources Fermi unidentified
sources & transients In addition Cygnus region sky survey (key
science) Compact sources in the Milky Way
Slide 27
VERITAS: Astrophysics at the highest energies Gamma-Ray Bursts.
Active galaxies: Relativistic jets. - shock acceleration? -
particle type? Fundamental Physics/ Dark Matter Studies (Neutralino
Annihilation). Search for Dark matter in Galactic Center.
Minihaloes? Supernova remnants, plerions, unidentified sources: -
cosmic ray origin? Constraints on particle acceleration and
diffusion. Diffuse extragalactic background light VERITAS will
explore astrophysical situations in which physics operates under
extreme conditions (e.g. intense gravitational or magnetic fields.)
Study particle acceleration in extreme astrophysical environments
(AGN, GRBs). Use -rays to probe intergalactic space -- Diffuse
radiation fields. Probe novel astrophysical phenomena which could
arise as a result of new physics beyond the standard model of
particle interactions.