High Resolution Radio Imaging of thePulsar Wind Nebula MSH 15-52
Ryan, Wai Yan Leung1

Stephen C.-Y. Ng 1

EAYAM 2017 - November 15, 20171

The University of Hong Kong

Department of Physics
The University of Hong Kong

0

Outlines▶

Pulsar Wind Nebula (PWN)?

▶

Why PWN is a fascinating object to study?

▶

What special about MSH 15−52?

▶

New observations of young PWN MSH 15−52.

1X-ray/radio composite of the Pulsar Wind Nebula MSH 15−52

2

The energetic pulsar : PSR B1509-58▶

Young, t = 1700 yr.

▶

High surface magnetic ﬁeld,B = 3.1 × 1013 G.

▶

High spin down luminosity,Ė = 2 × 1037 erg s−1 .
10−8Radio Pulsars
Millisecond pulsars
Associated with SNRMagnetars
PSR B1509-58

10−10

Artist’s impression of a pulsar (NASA).

▶

▶

▶

Strong magnetic ﬁeld.
Spinning rapidly (spinningmagnetic dipole).
Energetic emission (from spindown).
Up to ∼ 4 × 1038 erg s−1 .

r10 y
210−14

10 13
G10−16r

10 y610−1810 11G

Surface B-field▶

Neutron star (Size ∼ 10 km).

Period derivative Ṗ

▶

10 15G

10−1210−20010 y

10−22 110−3r
10−2

10−1
Period P100

101

10 9G

PSR B1509-58 on the P − Ṗ diagram using PSRCAT data, Manchesteret al.(2005)

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Pulsar Wind : Highly energetic charged particles from pulsars.

Pulsar’s magnetosphere (Credit: Davy Page)

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Pulsar Wind Nebulae (PWNe)▶

“Bubble” of magnetic ﬁeld andrelativistic winds.

▶

Broadband synchrotron radiations
from radio to X-ray : highlypolarised.

▶

Even from gamma-ray to TeV, butwith IC radiations.

▶

Morphology depends onevolutionary stage.

▶

Complex morphology with jets +torus structure in young PWNe.

▶

A ﬂat radio spectrum:0 ≲ α ≲ −0.3 where Sν ∼ ν αSchematic diagram of PWN shocks.

5Young PWNe in Chandra X-rays : Torus/jet features

The Crab Neubla.

G54.1+0.3
MSH 15-52

Low/medium/high-energy X-rays of 3C 58 are red, green, and blue respectively (also for MSH 15-52).
▶
▶

X-ray jet : Collimated outﬂows, related to the pulsars spin axis.
Torus : Toroidal magnetic ﬁeld.

Image Credits: G54.1+0.3: NASA/CXC/SAO/T.Temim et al.; MSH 15-52: NASA/CXC/SAO/P.Slane, et al. Others: NASA/CXC/SAO;

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Young PWNe in X-ray and radio

Chandra X-ray▶

Synchrotron cooling time: tcool ≈1.2 × 103 (B/10µG)−1.5 (E/1keV)−0.5▶

Fast cooling time.

▶

Reﬂect most recent PWN
condition.

(Image Credit: NASA, ESA, NRAO/AUI/NSF and G. Dubner)

VLA Radio▶

Synchrotron cooling time: tcool ≈2 × 107 (B/10µG)−1.5 (ν/1GHz)−0.5▶

Much longer coolong time →Preserved history of injection.

▶

B-ﬁeld is crucial → Radio
polarisation study.

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MSH 15-52 (G320.4−1.2) : A complex SNR/PWN system

Left: ATCA 20-cm Radio continuum of MSH 15−52 with resolution ∼ 20′′ , darker is brighter(Gaensler et al., 1999; Dubner et al., 2002). Right: Chandra images with red, green, and blue as
Low/medium/high-energy X-rays, brighter is brighter (NASA/CXC/SAO/P.Slane, et al.).
8MSH 15−52 : Is it really “crab-like”?

9Why we study PWNe and what is special about MSH 15-52?

PWN
Shock physics.

▶

Intense magnetic ﬁeld.

▶

Ultarelativistic particles outﬂows.

MSH 15-52▶

Nature of one-sided jet, ﬁlaments,
the “thumb” and other ﬁlamentary
structures.

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Injected particles energy
distribution? Radio observations!

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The intrinsic magnetic ﬁeldorientation? Radio polarimetary!

−58◦480b=540

Dec (J2000)

▶

−1 ◦

−59◦000060

120l = 320.32◦
18016m00s

15m00s
14m00sRA (J2000)

100
15h13m00s

Radio/X-rays Composite of MSH 15−52 from ATCA
data and Chandra X-ray data; Gaensler etal.(1999); NASA/CXC/SAO/P.Slane, et al.

10Observations with Radio interferometary▶

6 cm (5.5 GHz) and 3 cm (9GHz) bands.

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5 full-track observations (CABBupgraded).

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From 2011 to 2013.

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Polarization data recorded:
Stokes I,Q,U,V.

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Data reduction: MIRIAD

u-v coverage of the ﬁve observations

Obs. DateArray Conﬁg.

Max. baseline

Time (hr)2011 Nov 14
2011 Dec 03
2012 Feb 23
2013 Feb 16
2013 Mar 01

750D
EW367
1.5D
6A
6B

4469 m4408 m4439 m5939 m5969 m

9.2
8.5
9.1
11.1
9.4

Parameters for the new ATCA observations ofMSH 15−52 with central frequency at 5500 and9000 GHz with 2048 MHz bandwidths.

Australia Telescope Compact Array (ATCA) inNarrabri, Australia

11New High Resolution radio intensity map of 6 cm and 3 cm
0.3

0.5

1.0

1.5

2.0

2.5

3.0

0.3

6cm

−59◦ 000−59◦ 000

030

030

060

090

120

0.5

1.0

1.5

−58◦ 570

Dec (J2000)

Dec (J2000)−58◦ 570

2.0

2.5

3.0

3cm

060

090

120

5020s

14m 00s40s

20s

15h 13m 00s

RA (J2000)

MSH 15−52 at 6 cm. Darker is brighter. Restoring
beam: ∼ 4′′ (Leung et al., in prep.)

5020s

14m 00s40s

20s

15h 13m 00s

RA (J2000)

MSH 15−52 at 3 cm. Darker is brighter. Restoring
beam: Same as 6 cm (Leung et al., in prep.)

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The inner PWN▶

Filamentary structures ofthe inner PWN : “sheath”▶

“sheath” extents andcurve like the X-ray jet.

▶

East: Filament withlengths ∼ 100′′ .

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West: Relatively uniform
emission and no obvious
ﬁlament.

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Filaments have no X-rayemission.

(a)

Filaments

Hollow jet(b)arcpartial
arc

(c)

(d)

Close-up view of the inner PWN at 6 cm and 3 cm shown in(a) and (b). The (c) and (d) images show the interesting
features and X-ray countour comparision (Leung et al., inprep.).
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Faint features of MSH 15−52

X-rayempty cavity

RCWed 89gehelixlittleﬁnger

6 cm

inner PWN

thumb

Faint features of MSH 15−52 comparision in X-ray and 6 cm radio. Close-up view between the RCW 89 and the inner PWN (Leung et al., inprep.).

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MSH 15−52 is highly polarised

Polarisation fraction of MSH 15−52 at 6 cm and 3 cm (Leung et al., in prep.). The average fractional polarisaions are 38, 30, 27 % for Inner
PWN, thumb and little ﬁnger, repectively for 6cm.

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Inner PWN : Intrinsic Magnetic Field Orientation▶

Highly ordered magneticﬁeld!

▶

B-ﬁelds aligns with the“sheath”▶

Wraps around the X-rayjet! → Opened at the jetdirection!

▶

Not a torodial ﬁeld? Orsome outﬂows blown
away the ﬁelds?

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B-ﬁeld at the narrow
ﬁllament →? Not likely aradio jet.

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Part of the little ﬁnger isaligned with B-ﬁeld →magnetic driven!

6cm

10Intrinsic magnetic ﬁeld structure of the inner PWN ofMSH 15−52 overlaid on the 6 cm intensity map (Leung et al.,in prep.). Faraday rotation using the RM of the pulsar
RM = 216. Orientation of the magnetic ﬁeld is shown.

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Discussion : Nature of MSH 15−52?

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Polarised synchrontron nebula. Even the Hii region RCW 89 is polarised
synchrontron in nature.

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The inner PWN is hard to explain → jet + torus not explaining well in
MSH 15−52.

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Lobed ﬁlaments: Possibly kink instabilities similiar to 3C 58.

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No radio jets → Probably looking at different distribution of particles.

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“Thumb” and “little ﬁnger” → also synchronton-natured → large-scaleB-ﬁeld!

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Summary and take-home message

What we know?
▶

The radio inner PWN is highlypolarised.

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Appearance of inner PWN matches
the X-ray jets.

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No sign of radio jet / radio
counterpart of X-ray jet.

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Several polarised ﬁlaments areobserved.

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Polarised features like “Thumb”
and “little ﬁnger” → large-scale
B-ﬁeld.
Radio/X-ray Composite of MSH 15−52. Credits:
NASA/CXC/SAO, Leung et al.

18Summary and take-home message

What is still unclear?
▶

Nature of the ﬁlaments.

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Jet + Torus structure.

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Opened magnetic structure in
inner PWN.

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Different paricle populations in
the jet / RCW 89?

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How magnetic ﬁeld shapes thePWN? MHD is required!

Radio/X-ray Composite of MSH 15−52. Credits:
NASA/CXC/SAO, Leung et al.

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Questions?

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