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Page 1: Supernova Remnants and Pulsar Wind Nebulae observed in TeV …now/now2014/web-content/TALKS/aMon/Par2/... · 2014-09-09 · Kathrin Valerius Erlangen Centre for Astroparticle Physics

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

Page 2: Supernova Remnants and Pulsar Wind Nebulae observed in TeV …now/now2014/web-content/TALKS/aMon/Par2/... · 2014-09-09 · Kathrin Valerius Erlangen Centre for Astroparticle Physics

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

Page 3: Supernova Remnants and Pulsar Wind Nebulae observed in TeV …now/now2014/web-content/TALKS/aMon/Par2/... · 2014-09-09 · Kathrin Valerius Erlangen Centre for Astroparticle Physics

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?

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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)

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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

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“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±

Rwind ~ 0.1 pc

non-thermalnebula

RPWN ~ several pc

Synchrotron Inv. Compton

Pulsar wind nebulae: synopsis

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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

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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

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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

Page 10: Supernova Remnants and Pulsar Wind Nebulae observed in TeV …now/now2014/web-content/TALKS/aMon/Par2/... · 2014-09-09 · Kathrin Valerius Erlangen Centre for Astroparticle Physics

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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

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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

Page 12: Supernova Remnants and Pulsar Wind Nebulae observed in TeV …now/now2014/web-content/TALKS/aMon/Par2/... · 2014-09-09 · Kathrin Valerius Erlangen Centre for Astroparticle Physics

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

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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

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Preliminary

Selection of PWN candidates

S. Klepser et al., arXiv:1307:7905

● Most PWNe likely in reverseshock interaction phase

● Candidates: more evolved

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● 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

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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

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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

Page 18: Supernova Remnants and Pulsar Wind Nebulae observed in TeV …now/now2014/web-content/TALKS/aMon/Par2/... · 2014-09-09 · Kathrin Valerius Erlangen Centre for Astroparticle Physics

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● 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

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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

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Supplementary slides

Page 21: Supernova Remnants and Pulsar Wind Nebulae observed in TeV …now/now2014/web-content/TALKS/aMon/Par2/... · 2014-09-09 · Kathrin Valerius Erlangen Centre for Astroparticle Physics

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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

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The TeV gamma-ray sky today

Http://tevcat.uchicago.edu

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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

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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

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● 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

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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)

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Aharonian, Bogovalov & Khangulyan (2012)http://www.nature.com/nature/journal/v482/n7386/images/nature10793-f2.2.jpg

What is a Pulsar Wind Nebula?

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Pulsar Wind Nebulae: Overview

Hydrodynamical simulations, Van der Swaluw, Downes & Keegan (2004)

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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

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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

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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

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