Pulsar-Wind Nebulae in gamma-rays · Aharonian et al. (2007) • Modest size, diameter~20’ (excluding the faint tail) HESS J1809-193 • The region is very rich in sources emitting

Pulsar-Wind Nebulae in gamma-rays

Oleg Kargaltsev (University of Florida)George Pavlov (Penn State University)Zdenka Misanovic (Monash University)

Wednesday, June 2, 2010

Pulsar Wind Nebulae.

• All active pulsars emit relativistic winds • c > cs shock forms• Shocked matter: subrelativistic flow of relativistic particles in magnetic field and radiation field (e.g. CMBR) synchrotron (radio through X-rays) and IC radiation (GeV and TeV) PWN

The above cartoon assumes symmetricwind expansion which may not be the case if the SNR shock becomes asymmetric (due tothe interaction with the environment). In this case the propagating back reverse shock will also be asymmetric and can ``crush’’ a PWN pushing it to the side from the pulsar.


Galactic Plane Survey with H.E.S.S.

Extended TeV sources resolved:

Aharonian et al. (2006)

So far extended TeV sources are either PWNe or SNRs.

Galactic Survey of Cygnus region - VERITAS.

Weinstein et al. (2009)


Relic PWNe: B1823-13

• Extremely large size, diameter exceeds 1°

HESS J1825-137

• Bright IR/Radio sources within the extent of the TeV source

• No clear sign of a host SNR (at any wavelength) • No evidence for highly non-uniform ISM, e.g. of a “wall” that could have reflected the SNR shock making it asymmetric wrt. to the explosion center (but see Lemiere et al. 2005).

• The pulsar is moving at 440 km/s but its proper motion does not correlate with the asymmetry of the TeV emission wrt the PSR• Correlation between TeV and extended X-ray emission, bothshow softening with the distance from the pulsar

IR flux ~10-8 c.g.s.

Pavlov, Kargaltsev & Brisken (2007)


Relic PWNe: J1809-1917HESS - TeV


• Modest size, diameter~20’ (excluding the faint tail)

HESS J1809-193


Relic PWNe: J1809-1917

Kargaltsev & Pavlov (2007)

ACIS

HESS - TeV



HESS J1809-193

• Pulsar proper motion does not correlate with the asymmetry of the TeV emission wrt the pulsar

• Correlation between TeV and extended X-ray emission


Relic PWNe: J1809-1917

Kargaltsev & Pavlov (2007)

ACIS

HESS - TeV



HESS J1809-193

• The region is very rich in sources emitting in Radio/IR, some correlatewith the asymmetry wrt the pulsar

• No clear sign of a host SNR (at any wavelength) . There are some background SNRs

• No evidence for highly non-uniform ISM, e.g. of a “wall” that could have reflected the SNR shock making it asymmetric wrt the explosion center.

• Pulsar proper motion does not correlate with the asymmetry of the TeV emission wrt the pulsar

• Correlation between TeV and extended X-ray emission

IR flux ~10-7 c.g.s.

PSR J1809-1917


HESS J1616-508: Not a relic PWN? Then what?

Kargaltsev, Pavlov & Wong 2007


ACIS

ACIS

HESS - TeV


• Large size, diameter~1°, rather symmetric

HESS J1616-508


HESS J1616-508: Not a relic PWN? Then what?



ACIS

ACIS

HESS - TeV


• Large size, diameter~1°, rather symmetric

HESS J1616-508

• The region is very rich in sources emitting in Radio/IR/X-rays, some correlation with the TeV is seen in the radio/IR

• Possibly a hint of an unidentified SNR in radio . There also are two background SNRs and a large number of compact diffuse sources in the Radio/IR.

• NO correlation between TeV and extended X-ray emission from the J1617-5055 PWN


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33 TeV PWNe or PWN candidates, although someare questionable

Distribution of X-ray (red) and TeV (blue) PWNeon the sky. Sizes of the circles are proportional to the source luminosities.

Population Properties (I):


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TeV PWNe and PWN candidates

Population Properties (II):X-ray PWNe with known pulsars

A more common P-Pdot diagram (TeV PWNe are shown as blue stars, X-ray PWNe are black rectangles).

Sizes proportional to luminosities

Sizes “proportional” (in nonlinear way) to radiative efficiencies L/Edot


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Red error bars are X-ray PWNe with TeV counterparts

Blue error bars TeV objects without X-ray counterparts

Thick error barsare firm assoc.

Population Properties (III):TeV luminosity vs. Edot X-ray luminosity vs. Edot

Lines in the top two panels correspond to constant radiative efficiency L/Edot => Notice, large spread in both panels.


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Population Properties (V):

Mattana et al. (2009)

No correlation

May be some dependenceon age similar to





Flattening?Could be the one that follows from toy model


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Sample TeV PWN spectra (arranged by increasing age):

Crab

Vela X

B1509–58

J1809-1917

J1913+1011

Γγ = 2.63 ± 0.20

Γγ=2.27 ± 0.2

Γγ=2.3 ± 0.3

Γγ=1.45 ± 0.22curves

Γγ=2.26 ± 0.2

Γγ=2.20 ± 0.22

Γγ= 2.7 ± 0.2

log τ=3.09

log τ=5.23


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Fermi view of the Galactic Plane 0.5-100 GeV

Region around l=150o shown as example.

Different high-energy sources are marked.


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Fermi view of the Galactic Plane: Geminga region.

CO map 5-100 GeV

5-100 GeV0.5-100 GeV

Good (but not one to one!) correlation between CO and GeV maps. Some UNID horspots

most of which are 1FGLc sources (sometimes offset) but not all.

1FGL sources shown

Known HE sources shown


~200 other pulsars should be detectable eventually

Pulsars should also accompanied by γ-ray bright PWNe, but most of them cannot be resolved with Fermi


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So far only few PWNe are detected at GeV energies with Fermi LAT:

Vela XCrab

PSR J1509-5850

(Slane et al. 2010)

(Abdo et al. 2010)

(Abdo et al. 2010)

(Abdo et al. 2010)


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PWNe detected at GeV and TeV: Spectra

Crab (Abdo et al. 2010)

Vela X (Abdo et al. 2010)

(Slane et al. 2010)

MSH 15-52 (Abdo et al. 2010)Attention! GeV and TeV photons apparently come from different regions!


• Pulsar winds inject electrons/positrons with energies of up to 10-100 TeV

• Relic pulsar-winds fill much larger volumes than we can see in X-rays.

Reasons: Weak magnetic field? Efficient cooling of X-ray emitting electrons? Possibly both... • TeV PWNe are not standard candles but spread in luminosities is noticeably smaller than for X-ray luminosities. TeV PWNe exhibit significant diversity (sizes, efficiencies, spectra) which is likely to be due to the intrinsically different pulsar winds and environmental effects.

Short Summary :


Question and problems:

• Why radiative efficiencies of TeV plerions are quite different? Different environments, evolutionary stages?

• Why don’t we see SNRs associated with some TeV plerions?ISM absorption in X-rays? No radio either ...

• What causes the displacement of the TeV emission wrt to the pulsar? Is the “crushed PWM’’ scenario the only explanation?Alternatives: Intrinsically anisotropic winds,e.g. jets? Strongly non-uniform photon background, IR ``flashlights’’ ?

• Are the X-ray (synchrotron) and TeV (IC) emission producedby the same population of electrons (similar photon indices in X-rays and TeV, e.g. in the B1823 PWN)? If yes, why TeV brightness is lower near the pulsar (Klein-Nishina effect)? Are there hadrons in the wind? Why no TeV from pulsar tails is seen so far?


Documents

Pulsar-Wind Nebulae in gamma-rays · Aharonian et al. (2007) • Modest size, diameter~20’ (excluding the faint tail) HESS J1809-193 • The region is very rich in sources emitting