![Pulsar-wind-nebel
Unbekannt
Binär-System
t = 10,000 yrs 20,000 yrs
log (
1
tivistic gas in three two-dimensional simulations with
varying resolutions. We also plot the e†ective value of
for these three simulations in Figure 6. Up until aR
p
/R
1
time of D35,000 yr, all three simulations are quite similar.
Once the Rayleigh-Taylor instability kicks in, however, the
resolution-dependent e†ects of mixing become quite
evident. Independent of the numerical resolution, it is clear
that the mixing of relativistic gas and thermal gas is very
efficient.
4.2. Evolution in Nonuniform Media
We have repeated our two-dimensional simulation with
the addition of a density gradient in the ambient medium
with the goal of understanding the displacement of the
pulsar bubble seen in the Vela SNR. Following Dohm-
FIG. 8.ÈEvolution of the pulsar nebula/supernova remnant for the mod
electronic edition of the Journal for a color version of this Ðgure.]
t=10,000yrs20,000yrs30,000yrs56,000yrs
log(ρ/ρc)
0 1
threetwo-dimensionalsimulationswith
ions.Wealsoplotthee†ectivevalueof
threesimulationsinFigure6.Upuntila
0yr,allthreesimulationsarequitesimilar.
igh-Taylorinstabilitykicksin,however,the
ndente†ectsofmixingbecomequite
ndentofthenumericalresolution,itisclear
ofrelativisticgasandthermalgasisvery
EvolutioninNonuniformMedia
eatedourtwo-dimensionalsimulationwith
adensitygradientintheambientmedium
ofunderstandingthedisplacementofthe
seenintheVelaSNR.FollowingDohm-
cx
suchthatthedensitycontrast,fromaminimumatlarge
positiveztoamaximumatlargenegativez,isgivenby
(x[1)~1,andHisthecharacteristiclengthscaleover
whichthedensitychanges.Thesimulationsshownhereuse
x1.2correspondingtoadensitycontrastof5.These
simulationsrequirethecomputationofthefulldomaininz
(i.e.,noassumptionofequatorialsymmetry).Asaresult,our
standardgridof2000zonesrepresentsonlyhalfthe
resolutionusedintheprevioustwo-dimensionalmodel.
InFigure8weshowtheevolutionofthePWN/SNR
systemforanambientmediumlengthscaleofH1]1019
cm,whichcorrespondstothesizeoftheSNRatanageof
D500yr.Earlyintheevolution,wecanestimatetheasym-
metryintheSNRbyassumingonlyradialmotion,such
ionofthepulsarnebula/supernovaremnantforthemodelwithascaleheightofH1]1019cmintheambientmedium.[Seethe
theJournalforacolorversionofthisÐgure.]
10,000 yrs
No. 2, 2001 PULSAR W
FIG. 5.ÈCrushing of the pulsar nebula in a two-dimen
is normalized to take out the expansion of the outer shock
that follows the outer shock front, so that the f
of the grid is always used.
The outer shock front remains very nearly
follows the time evolution of the one-dimensio
within 0.1%. The key di†erence is the instabil
shell of ejecta and the rapid mixing driven
bility. Even before the PWN/SNR interactio
bility of the SSDW (Chevalier et al. 1992) beg
out the shell of shocked ejecta. However, gi
time between the beginning of the simulation
of the reverse shock, there is not enough time
bility to grow to signiÐcant amplitude. F
PWN/SNR collision, the deceleration of the e
the shocked ambient medium (responsible fo
instability) increases in magnitude, thereby d
rapid Rayleigh-Taylor instability. The result is
shell of mixed ejecta and ambient medium a
Ðrst two frames of Figure 5.
Much more dramatic, however, is the Ra
instability working in the opposite direction w
pressure of the compressed pulsar bubble begi
ate the ejecta shell back outwards. Fro
dimensional simulation shown in Figure 2, we
drops below D0.5, the pressure in thR
p
/R
1PWN exceeds that in the SNR and the PW
decelerate the shell of shocked ejecta. This a
the dense ejecta gas by the low-density PWN
to the Rayleigh-Taylor instability. As a result
bility, much of the ejecta gas continues toward
the SNR almost unabated. In the absence o
spherical reverse shock would reach the c
remnant at an age of D35000 yr, and inde
Figure 5 that some has reached the center by
the same process some relativistic gas is displa
center.
We see two competing e†ects of this inst
PWN crushing phase. First, as relativistic ga
from the center, it escapes the full compressio
ling ejecta seen in one dimension. Second,
turbulence driven by this instability leads to ra
the thermal and relativistic gasses. To illustrate
we compare the e†ective value of inR
p
/R
1
10,000yrs30,000yrs50,000yrs
log(ρ/ρa)
0 −1
0
0.2
0.4
0.6
0.8
1
100010000100000
Rp/R1
time(yrs)
No.2,2001PULSARWINDNEBULAEINEVOLVEDSNRs811
FIG.5.ÈCrushingofthepulsarnebulainatwo-dimensionalsimulationusingtheparametersformodelAlistedinTable1.Thelengthscaleoftheimages
isnormalizedtotakeouttheexpansionoftheoutershockfront.[SeetheelectroniceditionoftheJournalforacolorversionofthisÐgure.]
thatfollowstheoutershockfront,sothatthefullresolution
ofthegridisalwaysused.
Theoutershockfrontremainsverynearlysphericaland
followsthetimeevolutionoftheone-dimensionalmodelto
within0.1%.Thekeydi†erenceistheinstabilityofthethin
shellofejectaandtherapidmixingdrivenbythisinsta-
bility.EvenbeforethePWN/SNRinteraction,theinsta-
bilityoftheSSDW(Chevalieretal.1992)beginstospread
outtheshellofshockedejecta.However,giventheshort
timebetweenthebeginningofthesimulationandthecrash
ofthereverseshock,thereisnotenoughtimeforthisinsta-
bilitytogrowtosigniÐcantamplitude.Followingthe
PWN/SNRcollision,thedecelerationoftheejectashellby
theshockedambientmedium(responsiblefortheSSDW
instability)increasesinmagnitude,therebydrivingamore
rapidRayleigh-Taylorinstability.Theresultisabroadened
shellofmixedejectaandambientmediumasseeninthe
ÐrsttwoframesofFigure5.
Muchmoredramatic,however,istheRayleigh-Taylor
instabilityworkingintheoppositedirectionwhenthehigh
pressureofthecompressedpulsarbubblebeginstoacceler-
atetheejectashellbackoutwards.Fromtheone-
dimensionalsimulationshowninFigure2,weseethatonce
dropsbelowD0.5,thepressureinthecompressed R
p
/R
1PWNexceedsthatintheSNRandthePWNbeginsto
deceleratetheshellofshockedejecta.Thisaccelerationof
thedenseejectagasbythelow-densityPWNgasissubject
totheRayleigh-Taylorinstability.Asaresultofthisinsta-
bility,muchoftheejectagascontinuestowardthecenterof
theSNRalmostunabated.IntheabsenceofaPWN,a
sphericalreverseshockwouldreachthecenterofthe
remnantatanageofD35000yr,andindeedweseein
Figure5thatsomehasreachedthecenterbythistime.In
thesameprocesssomerelativisticgasisdisplacedfromthe
center.
Weseetwocompetinge†ectsofthisinstabilityinthe
PWNcrushingphase.First,asrelativisticgasisdisplaced
fromthecenter,itescapesthefullcompressionoftheinfal-
lingejectaseeninonedimension.Second,thevigorous
turbulencedrivenbythisinstabilityleadstorapidmixingof
thethermalandrelativisticgasses.Toillustratethesee†ects,
wecomparethee†ectivevalueofintheone-and R
p
/R
1
two-dimensionalsimulationsinFigure6.Wecomputethe
radiusofthepulsarbubbleinthetwo-dimensionalsimula-
tionbysummingupthevolumeofgaswithc1.66(i.e.,
includingthepartiallymixedgas)andcalculateane†ective
radiusassumingasphericalvolume.Priortothebounce,
theone-andtwo-dimensionalsimulationsarenearlyidenti-
cal.However,atthemomentofbounce,thePWNinthe
two-dimensionalsimulationhasavolumetwicethatofthe
PWNintheone-dimensionalsimulation.Thecompressed
PWNquicklyreboundsintheone-dimensionalsimulation,
butintwo-dimensionsthevolumeofrelativisticgascon-
tinuestoshrinkbecauseofnumericalmixing.
ThisrapiddepletionofthevolumeofthePWNinthe
two-dimensionalsimulationisanartifactofnumericaldif-
fusion;whenonenumericalzonecontainsbothrelativistic
gas(c4/3)andejectagas(c5/3),themass-weighted
averagecisdominatedbythehighdensityoftheejecta.As
aresult,themixingÈandsubsequentlossofPWN
volumeÈisstronglydependentonthenumericalresolution
ofthesimulation.Higherspatialresolutionleadstoless
numericalmixingacrossthecontactinterfacebetweenthe
FIG.6.ÈEvolutionofthepulsarnebulathroughthecrashofthereverse
SNRshockinone(solidline)andtwo(dashedlines)dimensionswithdi†er-
entnumericalresolutions.
10,000 yrs
No. 2, 2001 PULSAR W
FIG. 5.ÈCrushing of the pulsar nebula in a two-dimen
is normalized to take out the expansion of the outer shock
that follows the outer shock front, so that the f
of the grid is always used.
The outer shock front remains very nearly
follows the time evolution of the one-dimensio
within 0.1%. The key di†erence is the instabil
shell of ejecta and the rapid mixing driven
bility. Even before the PWN/SNR interactio
bility of the SSDW (Chevalier et al. 1992) beg
out the shell of shocked ejecta. However, gi
time between the beginning of the simulation
of the reverse shock, there is not enough time
bility to grow to signiÐcant amplitude. F
PWN/SNR collision, the deceleration of the e
the shocked ambient medium (responsible fo
10,000yrs30,000yrs50,000yrs
log(ρ/ρa)
0 −1
No.2,2001PULSARWINDNEBULAEINEVOLVEDSNRs811
FIG.5.ÈCrushingofthepulsarnebulainatwo-dimensionalsimulationusingtheparametersformodelAlistedinTable1.Thelengthscaleoftheimages
isnormalizedtotakeouttheexpansionoftheoutershockfront.[SeetheelectroniceditionoftheJournalforacolorversionofthisÐgure.]
thatfollowstheoutershockfront,sothatthefullresolution
ofthegridisalwaysused.
Theoutershockfrontremainsverynearlysphericaland
followsthetimeevolutionoftheone-dimensionalmodelto
within0.1%.Thekeydi†erenceistheinstabilityofthethin
shellofejectaandtherapidmixingdrivenbythisinsta-
bility.EvenbeforethePWN/SNRinteraction,theinsta-
bilityoftheSSDW(Chevalieretal.1992)beginstospread
outtheshellofshockedejecta.However,giventheshort
timebetweenthebeginningofthesimulationandthecrash
ofthereverseshock,thereisnotenoughtimeforthisinsta-
bilitytogrowtosigniÐcantamplitude.Followingthe
PWN/SNRcollision,thedecelerationoftheejectashellby
theshockedambientmedium(responsiblefortheSSDW
two-dimensionalsimulationsinFigure6.Wecomputethe
radiusofthepulsarbubbleinthetwo-dimensionalsimula-
tionbysummingupthevolumeofgaswithc1.66(i.e.,
includingthepartiallymixedgas)andcalculateane†ective
radiusassumingasphericalvolume.Priortothebounce,
theone-andtwo-dimensionalsimulationsarenearlyidenti-
cal.However,atthemomentofbounce,thePWNinthe
two-dimensionalsimulationhasavolumetwicethatofthe
PWNintheone-dimensionalsimulation.Thecompressed
PWNquicklyreboundsintheone-dimensionalsimulation,
butintwo-dimensionsthevolumeofrelativisticgascon-
tinuestoshrinkbecauseofnumericalmixing.
ThisrapiddepletionofthevolumeofthePWNinthe
two-dimensionalsimulationisanartifactofnumericaldif-
Pulsar-
Wind-Nebel
Stefan Klepser . Pulsar Wind Nebulae . ICRC . The Hague 2015
PWN Evolution in a Nutshell
Free expansion Reverse shock
interaction
Relic stage
SNR
PWN
▪ Easy & independent
▪ R ~ t6/5
▪ All the Crab wisdom, e.g.
▪ Kennel & Coroniti 1984
▪ Martín++, 2012
▪ ...
▪ Messy & depending on SNR
development
▪ Oscillative reverbations
▪ Analytically R ~ t0.3
▪ Only over-idealized and/or
numerical wisdom
▪ Swaluw++ 2001,2004
▪ ...
Pulsar
▪ More messy & more
depending on SNR dev. &
surroundings
▪ R ~ undefined
▪ Only case-by-case wisdom
2-6 kyr 20-100 kyr?
7
Die meisten Galaktischen TeV-Quellen sind PWN.
Elektronen und Positronen erzeugen die Emission.](https://image.slidesharecdn.com/gamma-astronomie-deil-170716163315/75/galaktische-gammaastronomie-73-2048.jpg?cb=1669056779)
Galaktische Gamma-Astronomie
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Ein (hoffentlich) allgemein-verständlicher Vortrag zu kosmischen Beschleunigern und Gammastrahlungs-Quellen in unserer Galaxie, der Milchstrasse. Vortrag gehalten im Haus der Astronomie, Heidelberg vom 10. März 2016. Videos sind leider nicht sichtbar im PDF. An introduction to Galactic gamma-ray astronomy for the general public.
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Galaktische Gamma-Astronomie
- 1. Galaktische Gamma-Astronomie Vortragsreihe “Faszination Astronomie” Haus der Astronomie, Heidelberg 10. März 2016 Christoph Deil
- 2. Übersicht 1. Was ist Gamma-Strahlung? 2. Wie entsteht kosmische Gamma-Strahlung? 3. Wie misst man kosmische Gamma-Strahlung? Teleskope für Gamma-Strahlung. Fokus auf Fermi-LAT und H.E.S.S. 4. Was haben wir entdeckt? Galaktische Quellen kosmischer Gamma-Strahlung 5. Wie geht’s weiter? Die Zukunft — Cherenkov Telescope Array (CTA)
- 5. Sichtbares Spektrum ist ca. eine Oktave (Faktor 2 in Frequenz) kurze Wellenlänge hohe Frequenz hohe Energie lange Wellenlänge tiefe Frequenz niedrige Energie Sichtbares Licht Licht aus dem Kosmos: ein 15 meter langes Klavier!
- 6. SN 1006
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- 9. Photon-Energie in Einheit “Elektron-Volt” = eV Optisch 1 eV Röntgen 1 keV = 1000 eV Gamma 1 MeV — 1 GeV — 1 TeV • 1 GeV = 10^9 eV = 1,000,000,000 eV • 1 TeV = 10^12 eV = 1,000,000,000,000 eV
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- 15. Teilchen-Spektrum Fluss Radio Optisch Röntgen EnergieGamma ? T ~ 10^3 K E ~ 1 eV T ~ 10^6 K E ~ 1 keV T ~ 10^12 K E ~ 1 GeV
- 16. Teilchen-Spektrum Fluss Radio Optisch Röntgen EnergieGamma T ~ 10^3 K E ~ 1 eV T ~ 10^6 K E ~ 1 keV Es gibt keine Objekte im die viel heißer sind als ein paar Millionen Grad! Gamma-Strahlung ist nicht-thermisch!
- 18. Teilchen-Spektrum Fluss Radio Optisch Röntgen EnergieGamma T ~ 10^3 K E ~ 1 eV T ~ 10^6 K E ~ 1 keV Thermisch Nicht-thermisch
- 19. Wie entstehen aus den geladenen Teilchen Gammas? Atome Licht 2. “Target” 1. energetisches geladenes Teilchen Atomkerne (z.B. Proton, Helium, Eisen) Elektron (oder Positron) +
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- 22. Photon-Spektrum von Protonen Fluss Radio Optisch Röntgen EnergieGamma Thermisch Nicht-thermisch Pion-Zerfall
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- 27. Supernova-Überreste als Galaktische kosmische Teilchen-Beschleuniger Fritz Zwicky 1933 “Genug Energie” Tycho's SNR 1572 Enrico Fermi 1949 “Shock-Beschleunigung”
- 29. Fermi Schock Beschleunigung Wie Tennis-Spielen mit einem Laster…
- 30. Der Himmel der kosmischen Strahlung ist gleichförmig auf dem 0.1%-Niveau
- 31. = Gamma-Strahlung fliegt gerade und zeigt uns die kosmischen Teilchen-Beschleuniger Geladene kosmische Strahlung verliert Richtungs-Info
- 32. Wie misst man kosmische Gamma-Strahlung? Teleskope für Gamma-Strahlung. Fokus auf Fermi-LAT und H.E.S.S.
- 33. Gamma-Spiegel?
- 36. Fermi-LAT — Start 2008
- 37. Fermi-LAT (LAT = Large Area Telescope)
- 40. Fermi-LAT • Fermi-LAT ist super im Energie- Bereich 100 MeV — 1 TeV • Bei Energien > 1 TeV ist es zu klein um Photonen zu sammeln. • Vom hellste TeV-Gamma-Quelle, der Krebs-Nebel, hat es seit 2008 nur ein paar Photonen detektiert. • Für > TeV Astronomie brauchen wir eine andere Methode! 1 m x 1 m
- 42. 4 Detektions- Prinzip Gamma Elektromagnetischer Schauer (viele Elektronen und Positronen) Tscherenkov-Licht Teleskope am Boden 10 nano-Sekunden Bild 1 km^2 1 m^2
- 43. Teleskop-Arrays Stereoskopie! Viele Schauer-Bilder -> viele Photonen -> gute Richtungs-Bestimmung -> gute Energie-Bestimmung
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- 45. H.E.S.S. — High Energy Stereoscopic System
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- 47. 14.13 m 33.68 m 14.13 m 14.13 m 14.13 m H.E.S.S. 1 12 m 100 m^2 H.E.S.S. 2 30m x 20m 600 m^2
- 49. Wie schwer ist H.E.S.S. 2 ? 10 – 50 –100 ?
- 50. Wie schwer ist H.E.S.S. 2 ? 100 Elefanten x 6 Tonnen = 600 Tonnen
- 51. Ein Tag beim Bau von H.E.S.S. 2
- 52. Eine Nacht — Beobachtungen mit den H.E.S.S. Teleskopen
- 53. Was haben wir entdeckt? Galaktische Quellen kosmischer Gamma-Strahlung
- 54. Fermi-LAT macht das erste gute Bild vom Gamma-Himmel!
- 55. Fermi-LAT Diffuse Galaktische Emission Diffuse extra-galaktische emission Fermi Bubbles 3000 Quellen!
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- 58. Blazare sind sehr variabel
- 59. ~150 PulsarePulsare sind schnell rotierende Neutronen-Sterne, mit extrem hohen magnetischen und elektrischen Feldern in ihrer “Magnetosphäre”. Vela-Pulsar Die hellste Quelle am Fermi-Himmel.
- 60. Pulsar
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- 63. Fermi-Bubbles
- 64. Fermi-Bubbles
- 65. Illustrations by Ron Miller GIANT BUBBLES OF THE MILKY WAY By Douglas Finkbeiner, Meng Su and Dmitry Malyshev
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- 69. Stars: Galactic TeV sources outside HGPS region Triangles: Galactic GeV sources (1FHL) Image: Planck CO map 250 o 65 0 o R. Hurt NASA H.E.S.S. Survey
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- 73. Pulsar-wind-nebel Unbekannt Binär-System t = 10,000 yrs 20,000 yrs log ( 1 tivistic gas in three two-dimensional simulations with varying resolutions. We also plot the e†ective value of for these three simulations in Figure 6. Up until aR p /R 1 time of D35,000 yr, all three simulations are quite similar. Once the Rayleigh-Taylor instability kicks in, however, the resolution-dependent e†ects of mixing become quite evident. Independent of the numerical resolution, it is clear that the mixing of relativistic gas and thermal gas is very efficient. 4.2. Evolution in Nonuniform Media We have repeated our two-dimensional simulation with the addition of a density gradient in the ambient medium with the goal of understanding the displacement of the pulsar bubble seen in the Vela SNR. Following Dohm- FIG. 8.ÈEvolution of the pulsar nebula/supernova remnant for the mod electronic edition of the Journal for a color version of this Ðgure.] t=10,000yrs20,000yrs30,000yrs56,000yrs log(ρ/ρc) 0 1 threetwo-dimensionalsimulationswith ions.Wealsoplotthee†ectivevalueof threesimulationsinFigure6.Upuntila 0yr,allthreesimulationsarequitesimilar. igh-Taylorinstabilitykicksin,however,the ndente†ectsofmixingbecomequite ndentofthenumericalresolution,itisclear ofrelativisticgasandthermalgasisvery EvolutioninNonuniformMedia eatedourtwo-dimensionalsimulationwith adensitygradientintheambientmedium ofunderstandingthedisplacementofthe seenintheVelaSNR.FollowingDohm- cx suchthatthedensitycontrast,fromaminimumatlarge positiveztoamaximumatlargenegativez,isgivenby (x[1)~1,andHisthecharacteristiclengthscaleover whichthedensitychanges.Thesimulationsshownhereuse x1.2correspondingtoadensitycontrastof5.These simulationsrequirethecomputationofthefulldomaininz (i.e.,noassumptionofequatorialsymmetry).Asaresult,our standardgridof2000zonesrepresentsonlyhalfthe resolutionusedintheprevioustwo-dimensionalmodel. InFigure8weshowtheevolutionofthePWN/SNR systemforanambientmediumlengthscaleofH1]1019 cm,whichcorrespondstothesizeoftheSNRatanageof D500yr.Earlyintheevolution,wecanestimatetheasym- metryintheSNRbyassumingonlyradialmotion,such ionofthepulsarnebula/supernovaremnantforthemodelwithascaleheightofH1]1019cmintheambientmedium.[Seethe theJournalforacolorversionofthisÐgure.] 10,000 yrs No. 2, 2001 PULSAR W FIG. 5.ÈCrushing of the pulsar nebula in a two-dimen is normalized to take out the expansion of the outer shock that follows the outer shock front, so that the f of the grid is always used. The outer shock front remains very nearly follows the time evolution of the one-dimensio within 0.1%. The key di†erence is the instabil shell of ejecta and the rapid mixing driven bility. Even before the PWN/SNR interactio bility of the SSDW (Chevalier et al. 1992) beg out the shell of shocked ejecta. However, gi time between the beginning of the simulation of the reverse shock, there is not enough time bility to grow to signiÐcant amplitude. F PWN/SNR collision, the deceleration of the e the shocked ambient medium (responsible fo instability) increases in magnitude, thereby d rapid Rayleigh-Taylor instability. The result is shell of mixed ejecta and ambient medium a Ðrst two frames of Figure 5. Much more dramatic, however, is the Ra instability working in the opposite direction w pressure of the compressed pulsar bubble begi ate the ejecta shell back outwards. Fro dimensional simulation shown in Figure 2, we drops below D0.5, the pressure in thR p /R 1PWN exceeds that in the SNR and the PW decelerate the shell of shocked ejecta. This a the dense ejecta gas by the low-density PWN to the Rayleigh-Taylor instability. As a result bility, much of the ejecta gas continues toward the SNR almost unabated. In the absence o spherical reverse shock would reach the c remnant at an age of D35000 yr, and inde Figure 5 that some has reached the center by the same process some relativistic gas is displa center. We see two competing e†ects of this inst PWN crushing phase. First, as relativistic ga from the center, it escapes the full compressio ling ejecta seen in one dimension. Second, turbulence driven by this instability leads to ra the thermal and relativistic gasses. To illustrate we compare the e†ective value of inR p /R 1 10,000yrs30,000yrs50,000yrs log(ρ/ρa) 0 −1 0 0.2 0.4 0.6 0.8 1 100010000100000 Rp/R1 time(yrs) No.2,2001PULSARWINDNEBULAEINEVOLVEDSNRs811 FIG.5.ÈCrushingofthepulsarnebulainatwo-dimensionalsimulationusingtheparametersformodelAlistedinTable1.Thelengthscaleoftheimages isnormalizedtotakeouttheexpansionoftheoutershockfront.[SeetheelectroniceditionoftheJournalforacolorversionofthisÐgure.] thatfollowstheoutershockfront,sothatthefullresolution ofthegridisalwaysused. Theoutershockfrontremainsverynearlysphericaland followsthetimeevolutionoftheone-dimensionalmodelto within0.1%.Thekeydi†erenceistheinstabilityofthethin shellofejectaandtherapidmixingdrivenbythisinsta- bility.EvenbeforethePWN/SNRinteraction,theinsta- bilityoftheSSDW(Chevalieretal.1992)beginstospread outtheshellofshockedejecta.However,giventheshort timebetweenthebeginningofthesimulationandthecrash ofthereverseshock,thereisnotenoughtimeforthisinsta- bilitytogrowtosigniÐcantamplitude.Followingthe PWN/SNRcollision,thedecelerationoftheejectashellby theshockedambientmedium(responsiblefortheSSDW instability)increasesinmagnitude,therebydrivingamore rapidRayleigh-Taylorinstability.Theresultisabroadened shellofmixedejectaandambientmediumasseeninthe ÐrsttwoframesofFigure5. Muchmoredramatic,however,istheRayleigh-Taylor instabilityworkingintheoppositedirectionwhenthehigh pressureofthecompressedpulsarbubblebeginstoacceler- atetheejectashellbackoutwards.Fromtheone- dimensionalsimulationshowninFigure2,weseethatonce dropsbelowD0.5,thepressureinthecompressed R p /R 1PWNexceedsthatintheSNRandthePWNbeginsto deceleratetheshellofshockedejecta.Thisaccelerationof thedenseejectagasbythelow-densityPWNgasissubject totheRayleigh-Taylorinstability.Asaresultofthisinsta- bility,muchoftheejectagascontinuestowardthecenterof theSNRalmostunabated.IntheabsenceofaPWN,a sphericalreverseshockwouldreachthecenterofthe remnantatanageofD35000yr,andindeedweseein Figure5thatsomehasreachedthecenterbythistime.In thesameprocesssomerelativisticgasisdisplacedfromthe center. Weseetwocompetinge†ectsofthisinstabilityinthe PWNcrushingphase.First,asrelativisticgasisdisplaced fromthecenter,itescapesthefullcompressionoftheinfal- lingejectaseeninonedimension.Second,thevigorous turbulencedrivenbythisinstabilityleadstorapidmixingof thethermalandrelativisticgasses.Toillustratethesee†ects, wecomparethee†ectivevalueofintheone-and R p /R 1 two-dimensionalsimulationsinFigure6.Wecomputethe radiusofthepulsarbubbleinthetwo-dimensionalsimula- tionbysummingupthevolumeofgaswithc1.66(i.e., includingthepartiallymixedgas)andcalculateane†ective radiusassumingasphericalvolume.Priortothebounce, theone-andtwo-dimensionalsimulationsarenearlyidenti- cal.However,atthemomentofbounce,thePWNinthe two-dimensionalsimulationhasavolumetwicethatofthe PWNintheone-dimensionalsimulation.Thecompressed PWNquicklyreboundsintheone-dimensionalsimulation, butintwo-dimensionsthevolumeofrelativisticgascon- tinuestoshrinkbecauseofnumericalmixing. ThisrapiddepletionofthevolumeofthePWNinthe two-dimensionalsimulationisanartifactofnumericaldif- fusion;whenonenumericalzonecontainsbothrelativistic gas(c4/3)andejectagas(c5/3),themass-weighted averagecisdominatedbythehighdensityoftheejecta.As aresult,themixingÈandsubsequentlossofPWN volumeÈisstronglydependentonthenumericalresolution ofthesimulation.Higherspatialresolutionleadstoless numericalmixingacrossthecontactinterfacebetweenthe FIG.6.ÈEvolutionofthepulsarnebulathroughthecrashofthereverse SNRshockinone(solidline)andtwo(dashedlines)dimensionswithdi†er- entnumericalresolutions. 10,000 yrs No. 2, 2001 PULSAR W FIG. 5.ÈCrushing of the pulsar nebula in a two-dimen is normalized to take out the expansion of the outer shock that follows the outer shock front, so that the f of the grid is always used. The outer shock front remains very nearly follows the time evolution of the one-dimensio within 0.1%. The key di†erence is the instabil shell of ejecta and the rapid mixing driven bility. Even before the PWN/SNR interactio bility of the SSDW (Chevalier et al. 1992) beg out the shell of shocked ejecta. However, gi time between the beginning of the simulation of the reverse shock, there is not enough time bility to grow to signiÐcant amplitude. F PWN/SNR collision, the deceleration of the e the shocked ambient medium (responsible fo 10,000yrs30,000yrs50,000yrs log(ρ/ρa) 0 −1 No.2,2001PULSARWINDNEBULAEINEVOLVEDSNRs811 FIG.5.ÈCrushingofthepulsarnebulainatwo-dimensionalsimulationusingtheparametersformodelAlistedinTable1.Thelengthscaleoftheimages isnormalizedtotakeouttheexpansionoftheoutershockfront.[SeetheelectroniceditionoftheJournalforacolorversionofthisÐgure.] thatfollowstheoutershockfront,sothatthefullresolution ofthegridisalwaysused. Theoutershockfrontremainsverynearlysphericaland followsthetimeevolutionoftheone-dimensionalmodelto within0.1%.Thekeydi†erenceistheinstabilityofthethin shellofejectaandtherapidmixingdrivenbythisinsta- bility.EvenbeforethePWN/SNRinteraction,theinsta- bilityoftheSSDW(Chevalieretal.1992)beginstospread outtheshellofshockedejecta.However,giventheshort timebetweenthebeginningofthesimulationandthecrash ofthereverseshock,thereisnotenoughtimeforthisinsta- bilitytogrowtosigniÐcantamplitude.Followingthe PWN/SNRcollision,thedecelerationoftheejectashellby theshockedambientmedium(responsiblefortheSSDW two-dimensionalsimulationsinFigure6.Wecomputethe radiusofthepulsarbubbleinthetwo-dimensionalsimula- tionbysummingupthevolumeofgaswithc1.66(i.e., includingthepartiallymixedgas)andcalculateane†ective radiusassumingasphericalvolume.Priortothebounce, theone-andtwo-dimensionalsimulationsarenearlyidenti- cal.However,atthemomentofbounce,thePWNinthe two-dimensionalsimulationhasavolumetwicethatofthe PWNintheone-dimensionalsimulation.Thecompressed PWNquicklyreboundsintheone-dimensionalsimulation, butintwo-dimensionsthevolumeofrelativisticgascon- tinuestoshrinkbecauseofnumericalmixing. ThisrapiddepletionofthevolumeofthePWNinthe two-dimensionalsimulationisanartifactofnumericaldif- Pulsar- Wind-Nebel Stefan Klepser . Pulsar Wind Nebulae . ICRC . The Hague 2015 PWN Evolution in a Nutshell Free expansion Reverse shock interaction Relic stage SNR PWN ▪ Easy & independent ▪ R ~ t6/5 ▪ All the Crab wisdom, e.g. ▪ Kennel & Coroniti 1984 ▪ Martín++, 2012 ▪ ... ▪ Messy & depending on SNR development ▪ Oscillative reverbations ▪ Analytically R ~ t0.3 ▪ Only over-idealized and/or numerical wisdom ▪ Swaluw++ 2001,2004 ▪ ... Pulsar ▪ More messy & more depending on SNR dev. & surroundings ▪ R ~ undefined ▪ Only case-by-case wisdom 2-6 kyr 20-100 kyr? 7 Die meisten Galaktischen TeV-Quellen sind PWN. Elektronen und Positronen erzeugen die Emission.
- 74. SNR RX J1713-3949 Peter Eger . H.E.S.S. precision measurements of RX J1713.7-3946 . August 201 The new high-resolution H.E.S.S. map ■ exposure: 170 h ■ angular resolution: 0.05º ■ energy threshold: 250 GeV ■ Analysis: Model w/ HiRes cuts (de Naurois & Rolland, 2007) 5 Peter Eger . H.E.S.S. precision measurements of RX J1713.7-3946 . August 2015 Mapping the magnetic field 15 Peter, March 18th , 2014, HESS coll. meeting, Potsdam The X-ray hotspots B-field map X-rays: XMM-Newton H.E.S.S.-PSF-convolved TeV: H.E.S.S. War in 2004 das erste aufgelöste Gamma-Bild von einem astronomischen Objekt. Jetzt in 2016 haben wir genug Photonen um ein Bild des Magnetfeldes zu machen.
- 75. Galaktisches Zentrum TeV-Strahlung mit H.E.S.S. 2 deg, 1000 Lichtjahre
- 76. Galaktisches Zentrum VLA Radio Bild TeV-Strahlung mit H.E.S.S. Komplexe Emission. Vieles ist noch unklar, z.B. “Ist Teil der Halo-Emission von dunkler Materie” “Welche Quellen erzeugen die Emission auf der rechten Seite?” “Ist die zentrale Quelle ein SNR oder das supermassive schwarze Loch?” “Wie hängt das Galaktische Zentrum mit den Fermi Bubbles zusammen?”
- 77. Wie geht’s weiter? Die Zukunft - Cherenkov Telescope Array
- 79. Super Fermi-LAT ? • Geht nicht gut … • Wäre extrem teuer, ein Fermi-LAT kostet 500 Millionen Euro. • Aber ein Cherenkov- Teleskop nur ~ 2 Million Euro … 1 Meter
- 80. Cherenkov Telescope Array (CTA)
- 81. CTA Konsortium ~ 100 Teleskope ~ 200 Millionen Euro ~ 1000 Astronomen ~ 30 Länder
- 82. 82 CTA Zeitplan
- 83. CTA Standorte 20 Teleskope auf La Palma 100 Teleskope in Chile
- 84. Teleskop- und Array-Optimierung • Die letzten Jahre: lange wissenschaftliche Diskussionen und detaillierte Simulationen um das beste Cherenkov Teleskope Array zu machbaren Kosten zu bauen. • 3 Teleskop-Typen: • LST = Large size telescopes • MST = Mid size telescopes • SST = Small size telescopes
- 85. ~ 8 LSTs kleiner als H.E.S.S. 2, ähnlich wie MAGIC-Teleskope CTA LST MAGIC
- 86. ~ 40 MSTs ähnlich wie VERITAS oder H.E.S.S. Teleskope PrototypinBerlinAdlershof MSTKamerasteilweisevonMPIKHeidelberg
- 87. ~ 70 SSTs SST Prototyp Einweihung (Dezember 2015 in Meudon. Kamera von MPIK Heidelberg.)
- 88. CTA Survey Größeres Gesichtsfeld + Bessere Sensitivität = Survey-Geschwindigkeit 300 x schneller als H.E.S.S. Simulation LMCLMC jetzt
- 89. Galachic Plane Survey 1000 Stunden ~ 1 Jahr Beobachtung 5°8°
- 90. HESS SNR G0.9+0.1 Sgr B2 Sgr A* NRAO: 20cm, 1.1mm, 5 µm CTA PSF HESS PSF 90 Auflösung
- 91. (Fast am) Ende
- 92. Zusammenfassung • Gamma-Strahlung ist hoch-energetisches Licht. Es ist nicht-thermische Emission. • Man kann Gamma-Strahlung mit Satelliten (z.B. Fermi- LAT) oder von der Erde (z.B. H.E.S.S. oder CTA) messen. • Gamma-Astronomie ist ein sehr junger Zweig der Astronomie, vor 10 Jahren gab es noch kein gutes Bild der Milchstraße in Gamma-Licht. • Die Milchstrasse ist voll von kosmischen Teilchen- Beschleunigern (z.B. Pulsare und Supernova-Überreste), die geladene kosmische Strahlung und Gamma- Strahlung erzeugen.
- 93. Danke schön • Carolin Liefke, für die Einladung und Organisation für der Reihe “Faszination Astronomie”. • Kollegen, die Bild-Material und Feedback zu dem Vortrag gegeben haben: Werner Hofmann, Axel Donath, Johannes King, Christopher van Eldik, Mathieu de Naurois, Rolf Bühler, Heinz Völk, Stefan Funk, Karl Kosack, Bernhold Feuerstein
- 94. Vielen Dank für Ihre Aufmerksamkeit. Fragen?
- 95. Backup Folien
- 96. HAWC
- 98. 30-Nov-2015 F. Salesa Greus - HAWC 14 HAWC SkyMap 150 days (Pass 3)
- 99. 30-Nov-2015 F. Salesa Greus - HAWC 15 HAWC SkyMap 150 days (Pass 3) Geminga* - 6σ Mrk 501 - 13σ Galactic Plane Mrk 421 - 17σ Crab Nebula - 38σ