Supernova Remnants:
dense gas and g-ray emission
Roger Chevalier
University of Virginia
M. Lorenzi
Vela
Evolution stages
(Spitzer 1968, Woltjer 1972,…)

Ejecta- dominated


Nonradiative Sedov blast wave


~104 years
0509-67.5 in LMC
Radiative shell


~103 years
~105 years
Return to interstellar medium
Complications: mass loss from progenitor, complex
interstellar medium, hydrodynamic instabilities, ejecta knots,
effects of magnetic fields and relativistic particles
S147
Radiative shock
Ha,…
(jump)
Recombination (to HI)
Compressed region:
Thermal gas
Relativistic particles
Magnetic field
Draine & McKee 1993
IC 443
D. Churchill
Radio
(Lee+ 2008)
Optical Ha
Duin & van der Laan (1975) showed detailed correspondence and
developed model of radio from compressed IS fields and particles
Application to g-ray emission: Chevalier (1977), Blandford & Cowie (1982)
Drew + 2005
S147 Ha
Radio 11 cm
Optical Ha
Xiao et al. 2008
S147
Optical (Ha)
Fermi – LAT
Katsuta + 2012
Models for S147

Non-radiative blast wave,
radiative filaments (Katsuta +)
 Distance – 1.3 kpc
 Age – 30,000 yr
 E=(1-3)×1051 erg
 n0=2-6 cm-3 (fil.)
 vsh ~ 100 km/s
 f=0.001-0.008 (filling
factor of filaments)
 Blast wave: n0=0.03-0.1
cm-3, vb=500 km/s
S147 in radiative phase?

Pro
Morphology
 Diffuse optical emission is radiative shock emission
 Filaments have comparable velocities to diffuse
emission (Kirshner, Arnold 1979); filaments – edge on
shocks plus intersecting shock regions
 Non-detection of X-rays (Sauvageot + 1990)


Con
Need age ≥ 60,000 yr
 Distance ~0.8 kpc

PSR J0538+2817 now
40,000 years old
60,000 years old
Ng et al. 2007
Models for S147

Non-radiative blast wave,
radiative filaments (Katsuta +)
 Distance – 1.3 kpc
 Age – 30,000 yr
 E=(1-3)×1051 erg
 n0=2-6 cm-3 (fil.)
 vsh ~ 100 km/s
 f=0.001-0.008 (filling
factor of filaments)
 Blast wave: n0=0.03-0.1
cm-3, vb=500 km/s

Radiative shell
…
 0.8 kpc
 60,000 yr
 ~1×1051 erg
 1-2 cm-3
 ~ 100 km/s
 f~1
S147 g-ray emission


Fermi ~1×1034 erg/s (Katsuta + 2012)
With standard assumptions (shock acceleration
of IS cosmic rays, compression to cool shell),
radiative shell model overpredicts luminosity by
≥10 (Tang & RAC)
Escape from dense shell?
IC 443 – a molecular cloud interactor
Pulsar
21 cm continuum emission
Lee et al. 2008
All molecular
emission
Radio continuum
Shocked CO contours
Lee et al. 2012
Radiative shock
emission
21 cm continuum emission
Lee et al. 2008

Shocked HI contours on optical image
Lee et al. 2008
Column density of HI is
about as expected for
radiative shell in 10 cm-3
gas
Radiative shell/clump interaction
model (Chevalier 1999)
High pressure
Applied to IC 443,
W44, 3C 391
Competing model:
nonradiative blast
wave in intercloud
region (Reach + 2005,
Uchiyama + 2010)
IC 443 g-ray emission
Molecular clumps
EGRET
Fermi - GeV
VERITAS - TeV
MAGIC
Abdo + 2010
IC 443 – AGILE
Tavani et al. 2010
IC 443


Observe ~1035 ergs/s in g-rays, which is close to
prediction in radiative shell model
But, unlike radio, g-rays are primarily from region of
molecular interaction
J (jump) and C (continuous) shocks are present
 Possible shell interaction with clumps
 Crucial aspect may be mass


g-rays from radiative shell are expected (as in S147)
Early interaction with dense
mass loss
Shocked region:
X-ray and
radio emission,
expect g-rays
Optical light curves
powered by cs interaction
1044 erg/s
Stoll
et al.
2011

SN 2006gy faint in X-rays near maximum light,
≤1040 erg/s. Reasons:
Inverse Compton cooling by photospheric photons
more important than bremsstrahlung
 Comptonization in the cool wind reduces energy of
the highest energy X-ray photons
 Photoelectric absorption in the cool wind

SN 2006gy
SN 2010jl
D*=1
0.1 M/yr at 100 km/s
RAC + Irwin 2012
SN 2010jl X-ray
Chandra
Dec 2010,
t ~ 2 months
T>12 keV
NH ~ 1e24 cm-2
L~1042 ergs/s
Chandra
Oct 2011,
t ~ 1 year
T>8 keV
NH ~ 3e23 cm-2
L~1042 ergs/s
P. Chandra, RAC,…. 2012
Fermi
CTA
Model A – like SN 2006gy
Emission
Allowing for pair production in
matter and g-g pair production
Model B – like SN 2010jl
Assumes d= 10 Mpc
from Murase + 2011
also Katz + 2011
Final remarks



Interpretation of g-ray emission can depend on
model for the remnant (S147)
Interaction with molecular clouds is complex
and multiple emission components are likely
Detecting a very young SNR will take fortunate
nearby event with strong interaction