supernova remnants and pulsar wind nebulae observed in tev...
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Kathrin ValeriusErlangen Centre for Astroparticle PhysicsUniv. Erlangen-Nürnberg
KCETAKarlsruhe Institute of Technology
Supernova Remnants and Pulsar Wind Nebulaeobserved in TeV γ rays
NOW 2014Conca Specchiulla, Sept 7-14, 2014
K. Valerius . NOW 2014 . Supernova Remnants and Pulsar Wind Nebulae 2
Particle acceleration by stellar remnants
Gamma-ray astronomy at energies ~100 MeV to ~10 TeV:rich evidence of particle acceleration in ...
… supernova remnants … pulsar wind nebulae … young and “rejuvenated” pulsars
Crab Nebula→ talk by F. Calore
SN 1006
Powered by
Acceleration at
Time scale after death of star
explosion energy pulsar rotation strong EM fields; accretion
shock front shocked wind polar cap, slot gap?
few kyr few 10 kyr few 100 kyr – Myr
Adapted from F. Acero
K. Valerius . NOW 2014 . Supernova Remnants and Pulsar Wind Nebulae 3
Particle acceleration by stellar remnants
Gamma-ray astronomy at energies ~100 MeV to ~10 TeV:rich evidence of particle acceleration in ...
… supernova remnants … pulsar wind nebulae … young and “rejuvenated” pulsars
Crab Nebula → talk by F. CaloreSN 1006
Major Galactic TeV γ-ray source classes:
5 shell-type, 9 interacting SNRs, 33 PWNe
● Flux and composition (hadr./e± ?)● Max. energy (~1 PeV ?)
of accelerated particles ?
Important Fermi source class
● Release & acceleration?● Contribution to
diffuse γ flux?
K. Valerius . NOW 2014 . Supernova Remnants and Pulsar Wind Nebulae 4
Supernova remnants W2835-150 kyr
Young SNRs Older SNRs
● Hadronic scenariofavoured
● Electronaccelerationless efficient
● π0 → 2γenhanced bymol. clouds:
- interactionw/ shellor - illuminationby escapingCR flux
H.E.S.S. coll.,Acero et al. (2010)
● Efficient particle acceleration in the shell
● Spectral features well reproduced bymixed hadr./lept. models
SN 10061 kyr
Multi-band X-ray image(Chandra; F. Winkler 2013)
K. Valerius . NOW 2014 . Supernova Remnants and Pulsar Wind Nebulae 5
Pulsar wind nebulae: synopsis
“A bubble of shockedrelativistic particles,produced when apulsar's relativistic wind interacts withits environment“
(Gaensler & Slane, 2006)
Crab Nebula
(infrared, optical, X-rays) radio vis X γ VHE γIR
K. Valerius . NOW 2014 . Supernova Remnants and Pulsar Wind Nebulae 6
“A bubble of shockedrelativistic particles,produced when apulsar's relativistic wind interacts withits environment“
(Gaensler & Slane, 2006)
Crab Nebula
(infrared, optical, X-rays)
RL ~ 106 m pulsar windmagnetized outflow
wind termination shock
e±e±
e±
e±
e±
e±
Rwind ~ 0.1 pc
non-thermalnebula
RPWN ~ several pc
Synchrotron Inv. Compton
Pulsar wind nebulae: synopsis
K. Valerius . NOW 2014 . Supernova Remnants and Pulsar Wind Nebulae 7
Pulsar wind nebulae: evolution
2-6 kyr 20-100 kyr?
I. Free expansion II. Reverse shock interaction III. Relic phase
pulsar
PWN
SNR
● Simplest phase● R ~ t6/5
● Well studied, e.g. via CrabKennel & Coroniti 1964,Martín++ 2012, ...
● Even more influenced by SNR evolution, surroundings
● R ~ ??● Only case-by-case studies
● Depends on SNR development● Oscillatory reverberations● Analytically: R ~ t0.3
● Only over-idealized and/ornumerical modelse.g. Swaluw++ 2001, 2004, ...
Adapted from S. Klepser
K. Valerius . NOW 2014 . Supernova Remnants and Pulsar Wind Nebulae 8
Pulsar wind nebulae in TeV γ rays
H.E.S.S. coll.,Aharonian et al. (2006)
Funk et al. (2008)
pulsar
● Middle-aged (τc~21 kyr, r~35 pc)
● “Crushed” shape(asymmetry, displacement)
● Synchr. burn-off of high-E particles
~25 pc
3C 58
MAGIC coll.,Aleksić et al. (2014)
● Weakest TeV PWN ever detected:
L >1TeV ~0.65% Crab, ~10-5 Ė
● Probably young (τc~5 kyr)
● TeV source coincides with pulsar,size not resolved (r < 4 pc)
NEW !
exce
ss/b
ackg
rd
K. Valerius . NOW 2014 . Supernova Remnants and Pulsar Wind Nebulae 9
PWN population study: aims
● Link between properties of pulsarand TeV PWN?
● Benchmark common perceptionsof PWN evolution
● Uniform analysis of TeV sources,selection and evaluation of candidates
● Upper limits for non-detections
Observational data Interpretation
K. Valerius . NOW 2014 . Supernova Remnants and Pulsar Wind Nebulae 10
PWN population study: ingredients
(1) H.E.S.S. Galactic Plane Survey~2800 h obs. of the inner Galaxy (2004-13)better than 2% Crab sensitivitydiscovery of ~60 new sources
→ Position, size, F(1-10 TeV)
(2)
> 2000 pulsars (radio, X, γ)
→ Position, P, Pdot, Edot, τc, d
K. Valerius . NOW 2014 . Supernova Remnants and Pulsar Wind Nebulae 11
PWN population study: methods
HGPS+ ATNFcatalogs
(w/o SNR, GCBinaries, AGN)
TeVCat
online catalogof ~150 VHEγ-ray sources
Previouslyassociated
New candidates
Externals
known PWNe
not in HGPS, from TeVCat
Pulsars for limits
Association & selection of candidates
no TeV detection
HGPS source + matching PSR
● Uniform analysis of TeV sources,selection and evaluation of candidates
● Upper limits for non-detections
● Link between properties of pulsarand TeV PWN?
● Benchmark common perceptionsof PWN evolution
K. Valerius . NOW 2014 . Supernova Remnants and Pulsar Wind Nebulae 12
HGPS+ ATNFcatalogs
(w/o SNR, GCBinaries, AGN)
TeVCat
online catalogof ~150 VHEγ-ray sources
Previouslyassociated
New candidates
Externals
known PWNe
not in HGPS, from TeVCat
Pulsars for limits
Association & selection of candidates
no TeV detection
HGPS source + matching PSR
Population plotsrelating PSR to TeV properties
● Common trends?● Theory expectations?
Simple leptonic modeling● Plausibility of candidates
PWN population study: methods
● Uniform analysis of TeV sources,selection and evaluation of candidates
● Upper limits for non-detections
● Link between properties of pulsarand TeV PWN?
● Benchmark common perceptionsof PWN evolution
K. Valerius . NOW 2014 . Supernova Remnants and Pulsar Wind Nebulae 13
Correlation of TeV sources and pulsars
(b) angular separation criterion(a) energy-dep. detection fraction
Klepser et al., arXiv:1307.7905Carrigan et al., arXiv:0709.4094
High-Edot pulsars:TeV signal within ~0.5°
candidate selection
log10 (Ė)
Nde
tect
ed/
Nal
l
can
did
ate
sel
ect
ion
No correlation beyond chancecoincidences below ~1035 erg/s
K. Valerius . NOW 2014 . Supernova Remnants and Pulsar Wind Nebulae 14
Preliminary
Selection of PWN candidates
S. Klepser et al., arXiv:1307:7905
● Most PWNe likely in reverseshock interaction phase
● Candidates: more evolved
K. Valerius . NOW 2014 . Supernova Remnants and Pulsar Wind Nebulae 15
● PWNe trace close-byspiral arms
● Average distance: ~5 kpc● Exposure covers ~1/4 of
the Milky Way
How far can we reach out?
Graphic: C. Deil, S. Klepser
1% 10%of Crab luminosity > 1 TeVPreliminary
K. Valerius . NOW 2014 . Supernova Remnants and Pulsar Wind Nebulae 16
Evolutionary trends
● RPWN ~t0.3 as a rough guideline, butlarge scatter due to surrounding mediumor SNR interaction
● Good for evaluating candidates
● Compares accumulated e± populationwith momentary energy output of pulsar
● Time-dependent one-zone model basedon M. Mayer et al., arXiv:1202:1455 (added free expansion phase)
Size RPWN EfficiencyL1-10TeV/Ė
S. Klepser et al., arXiv:1307:7905
K. Valerius . NOW 2014 . Supernova Remnants and Pulsar Wind Nebulae 17
Evolutionary trends
● RPWN ~t0.3 as a rough guideline, butlarge scatter due to surrounding mediumor SNR interaction
● Good for evaluating candidates
● Compares accumulated e± populationwith momentary energy output of pulsar
● Time-dependent one-zone model basedon M. Mayer et al., arXiv:1202:1455 (added free expansion phase)
Size RPWN EfficiencyL1-10TeV/Ė
S. Klepser et al., arXiv:1307:7905
Upperlimits
K. Valerius . NOW 2014 . Supernova Remnants and Pulsar Wind Nebulae 18
● VHE γ-rays allow to study mostpowerful particle acceleratorsin the Galaxy
● Data quality & quantity supportscumulative studies: SNRs, PWNe
● PWN population: biggest(& rather diverse) Galacticsource class
● Many UNID sourcesmight be ageing PWNe
● Modeling: need betterunderstanding of evolvedPWNe …
Summary & outlook
… in particular for the leap ahead with CTA
UNID
PWN SNR (shell)
SNR (int.)
binarycluster
Composition of Gal. TeV sourcestevcat.uchicago.edu
K. Valerius . NOW 2014 . Supernova Remnants and Pulsar Wind Nebulae 19
References
Selection of recent reports on progress of Galactic TeV survey & source census:
● H.E.S.S. Galactic Plane Survey● Carrigan et al., Charting the TeV Milky Way, arXiv:1307.4868
● Carrigan et al., The H.E.S.S. Galactic Plane Survey, arXiv:1307.4690
● PWN population study● Klepser et al., A population of Teraelectronvolt Pulsar Wind Nebulae in the H.E.S.S. Galactic Plane Survey,
arXiv:1307.7905
● SNR population study● Fernandez et al., Study of the Very High Energy emission from Supernova Remnants with H.E.S.S.,
arXiv:1307.6347
● Future perspectives: 'CTA special edition', Astrop. Phys. 43 (2013)● Aharonian, Gamma rays from supernova remnants, p. 71
● Acero et al., Gamma-ray signatures of cosmic-ray acceleration, propagation, and confinement in the era ofCTA, p. 276
● de Ona Wilhelmi et al., Prospects for observations of pulsars and pulsar wind nebulae with CTA, p. 287
K. Valerius . NOW 2014 . Supernova Remnants and Pulsar Wind Nebulae 20
Supplementary slides
K. Valerius . NOW 2014 . Supernova Remnants and Pulsar Wind Nebulae 21
Galactic Sources of VHE γ rays
~90 sources of VHE γ rays (E > 100 GeV) in the Milky Way known today*:
*) tevcat.uchicago.edu, Aug. 2014
335 5
11
926
Dominantsource class
How manyare ancientPWNe?
Differentorigin ofγ-ray emission
K. Valerius . NOW 2014 . Supernova Remnants and Pulsar Wind Nebulae 22
The TeV gamma-ray sky today
Http://tevcat.uchicago.edu
K. Valerius . NOW 2014 . Supernova Remnants and Pulsar Wind Nebulae 23
Mattana et al. (2009)
Old PWNe as unidentified VHE γ-ray sources?
M. J. Mayer, J. Brucker, I. Jung, KV, C. Stegmann, arXiv:1202.1455
Comparison of X-ray and VHE γ-rayluminosities for several identified PWNe
Time-dependent leptonic model of broad-band emission for a generic PWN
K. Valerius . NOW 2014 . Supernova Remnants and Pulsar Wind Nebulae 24
PWN population study: potential selection bias
S. Klepser et al., ICRC'13
Closer objects tend to have larger lower efficiencies and smaller extensions
● Far away sources need to be more efficient in order to get detected
● Clipping of large, nearby sources due to limited field of view ?
● Far, small sources cannot be resolved → upper limits on extension
K. Valerius . NOW 2014 . Supernova Remnants and Pulsar Wind Nebulae 25
● We can learn something about …
– the pulsar: spin-down characteristics/history, proper motion, …
– the pulsar wind: composition, energetics, geometry, termination shock, …
– the ambient medium: local density/homogeneity, magnetic field, …
● Increasing sample of detected PWNe allows to
– identify general properties
– investigate various evolutionary stages
Why study (multi-wavelength) properties of PWNe?
Multi-wavelengthobservational data
+Detailed modeling
K. Valerius . NOW 2014 . Supernova Remnants and Pulsar Wind Nebulae 26
Imaging Atmospheric Cherenkov Technique
~ 10 kmParticle shower
~ 10 km
Photon
Che
renk
ov li
ght
Air shower observed simultaneously by multiple telescopes
~ 120 m
Shower image:
Intensity → energyOrientation → directionShape → primary particle
for ground-based gamma-ray detection (Eγ ~ 100 GeV … 10 TeV)
K. Valerius . NOW 2014 . Supernova Remnants and Pulsar Wind Nebulae 27
Aharonian, Bogovalov & Khangulyan (2012)http://www.nature.com/nature/journal/v482/n7386/images/nature10793-f2.2.jpg
What is a Pulsar Wind Nebula?
K. Valerius . NOW 2014 . Supernova Remnants and Pulsar Wind Nebulae 28
Pulsar Wind Nebulae: Overview
Hydrodynamical simulations, Van der Swaluw, Downes & Keegan (2004)
K. Valerius . NOW 2014 . Supernova Remnants and Pulsar Wind Nebulae 29
Time-dependent leptonic modelof non-thermal emission from PWNe
Cooling processes (see Zhang et al., 2008):
PWN evolution (Gaensler & Slane, 2006):
Time evolution of energy output and magn. field (see Zhang et al., 2008):
Characteristic age and spin-down timescale
free expansion
after RS interaction
K. Valerius . NOW 2014 . Supernova Remnants and Pulsar Wind Nebulae 30
Dissecting the broad-band SED into contributions from different epochs
Generic middle-aged PWN:
P0 = 30 ms, P = 100 msB0 = 50 µGĖ = 2.8·1036 erg/s
Mayer, Brucker, Holler, Jung, KV, Stegmann: Predicting the X-ray flux of evolved pulsarwind nebulae based on VHE gamma-ray observations, arXiv:1202:1455
K. Valerius . NOW 2014 . Supernova Remnants and Pulsar Wind Nebulae 31
Supernova Remnants
● Paradigm of galactic cosmic rays (E ≤ 1015 eV):young SNRs as acceleration sites ('PeVatrons' ?)
● Both high-energy hadrons (p, nuclei) and leptons (e±)can be present → VHE γ-ray production via
π0 decay or inverse Compton scattering
pγ
Multi-band X-ray image(Chandra; F. Winkler 2013)
SN 1006
H.E.S.S. coll.,Acero et al. (2010)
● TeV γ-rays coincidentwith non-thermal X-raysfrom the shell
● Spectral energydistribution wellreproduced by mixedhadronic-leptonic model
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