Constraints on galactic magnetic
field from radio synchrotron
emission of SN1006
F. Bocchino, S. Orlando
INAF - Osservatorio Astronomico di Palermo, Italy
M. Miceli
Università di Palermo, Italy
O. Petruk
National University, Lviv, Ukraine
G. Dubner, G. Castelletti
Istituto de Astronomia y Fisica del Espacio, Buenos Aires, Argentina
F. Bocchino: synchrotron emission from SN1006
SNRs and PWNe in the Chandra Era, July 8-10, 2009, Boston
The magnetic field around SN1006

Two configurations have been discussed for the bright limbs of
SN1006
Equatorial belts
Polar caps
v
v
B

B
The two scenarios give very different obliquity dependance of
injection efficiency (quasi-perpendicular vs. quasi-parallel)
F. Bocchino: synchrotron emission from SN1006
SNRs and PWNe in the Chandra Era, July 8-10, 2009, Boston
Quasi-par or quasi-perp?

Rothenflug+ 2004 shown that X-ray emission is too “dark” at
the center of SN1006 for it to be equatorial belt


Quasi-parallel scenario is strongly suggested
Petruk+ 2009 compared model and observations of syncrothron
radio emission of SN1006 assuming expansion in a uniform B.
quasi-par
Quasi-parallel scenario for SN1006 is ok for X-ray but NOT for radio
F. Bocchino: synchrotron emission from SN1006
SNRs and PWNe in the Chandra Era, July 8-10, 2009, Boston
Asymmetries in BSNRs (Orlando+ 07)
G296.5+10.0
SN1006
Converging limbs,
due to |B| (or r)
along the limb axis
G327.4+1.0
G356.3-1.5
Different limb brigthness,
due to |B| (or r)
across the limbs
F. Bocchino: synchrotron emission from SN1006
SNRs and PWNe in the Chandra Era, July 8-10, 2009, Boston
The idea of this work

MHD simulations of SNR evolution up to 1 kyr
gradient of B (a factor 1.3 variation over 10 pc scale)
 g = 5/3, 4/3, see S. Orlando talk


Synthesize synchrotron radio emission
Consider different dependences from obliquity angle
 Consider two aspect angles (fB and f|B|)


Compare with SN1006 radio data

we want to be quantitative
F. Bocchino: synchrotron emission from SN1006
SNRs and PWNe in the Chandra Era, July 8-10, 2009, Boston
Aspect angles
f|B| is the angle
between the plane of
the sky and |B|
Plane of the sky
fB is the angle
between the plane
of the sky and B
TOP VIEW
FB
Plane of the sky
SN1006
SIDE VIEW
To the Earth
SN1006
B
F|B|
grad B
To the Earth
F. Bocchino: synchrotron emission from SN1006
SNRs and PWNe in the Chandra Era, July 8-10, 2009, Boston
Aspect angles
f|B|=0o
F. Bocchino: synchrotron emission from SN1006
SNRs and PWNe in the Chandra Era, July 8-10, 2009, Boston
Synthesized radio emission at 1 GHz
Polar-caps scenario
Aspect angles
fB=0o
F. Bocchino: synchrotron emission from SN1006
SNRs and PWNe in the Chandra Era, July 8-10, 2009, Boston
Quantifying the asymmetries

A = max/min




C = center /max1


May be sensitive to bkg and beamsize
Rmax = max1/max2



Introduced by Fullbright & Reynolds (1990)
Sensitive to bkg and beamsize
It is a measure of bilaterality
Less sensitive to bkg and beamsize
It is a measure of brightness asymmetries
min
max
center
max1
max2
max1
q = angular separation between max1 and max2


Insensitive to bkg and beamsize (almost)
It is a measure of shape asymmetries
max1 q
max2
F. Bocchino: synchrotron emission from SN1006
SNRs and PWNe in the Chandra Era, July 8-10, 2009, Boston
fB=0o
fB=90o
F. Bocchino: synchrotron emission from SN1006
Quasi-parallel scenario
SN1006
Gradient of B
A solution can be found in
the quasi-parallel scenario !
Best-fit:
fB ~ 50o
fB ~ 15o
fB values is < 90° !!
Consistent with Rbw/Rcd findings
of Miceli (yesterday talk)
SNRs and PWNe in the Chandra Era, July 8-10, 2009, Boston
Best-fit model image
Synthesized radio emission
Best-fit fB ~ 50o fB ~ 15o
SN1006 smoothed radio map
1.5 GHz, Petruk+ 09
We conclude that a small gradient of B (B varies 1.3 times in 10
pc) and the quasi-parallel scenario consistently explain BOTH
X-ray and radio morphology
F. Bocchino: synchrotron emission from SN1006
SNRs and PWNe in the Chandra Era, July 8-10, 2009, Boston
Galactic center
SN1006 in the Galaxy
SN1006
Sun
F. Bocchino: synchrotron emission from SN1006
SNRs and PWNe in the Chandra Era, July 8-10, 2009, Boston
SN1006 in the Galaxy
F. Bocchino: synchrotron emission from SN1006
SNRs and PWNe in the Chandra Era, July 8-10, 2009, Boston
Conclusions



Uniform B models cannot reproduce the radio morphology in
quasi-parallel scenario, while they can reproduce the X-ray
morphology
We built a set of MHD models to be used for interpretation
of SN1006 radio images, using a small gradient of B to try
reconciling the radio-Xray discrepancy
A good fit to radio morphology is obtained with fB ~ 50
and fB ~ 15°, in the quasi-parallel scenario


Quasi-par and B now are consistent with BOTH radio and X-ray
morphologies
The magnetic field is aligned with the Sagittarius arm of the
Galaxy and B point down in the plane toward the same arm,
a very reasonable configuration !!
F. Bocchino: synchrotron emission from SN1006
SNRs and PWNe in the Chandra Era, July 8-10, 2009, Boston
Thank you LOC, we had
great time in Boston!!!!!
Uniform magnetic field
min
max
A solution cannot be found in
the quasi-parallel scenario
(Petruk+ 2009)
F. Bocchino: synchrotron emission from SN1006
center
max1
SNRs and PWNe in the Chandra Era, July 8-10, 2009, Boston
F. Bocchino: synchrotron emission from SN1006
SNRs and PWNe in the Chandra Era, July 8-10, 2009, Boston