This is the presentation I gave when defending my Ph.D thesis at SLAC. The title of my defense was "Neutron Star Powered Nebulae: a New View on Pulsar Wind Nebulae with the Fermi Gamma-ray Space Telescope".
21. The Large Area Telescope
Tracker
Layers
Calorimeter Layers
Anti-Coincidence Detector (surrounding)
Large Area Telescope (LAT)
Fermi Gamma-ray Space
Telescope
photon
positron
electron
51. Crab Nebula
:26 (8pp), 2012 April 10 Buehler et al.
Pulsar phase
0.4 0.6 0.8
Pulsar phase
0.4 0.6 0.8 Figure 2. Spectral energy distribution for the Crab Nebula averaged over the
first 33 months of Fermi observations. The axis on the right side indicates the
1260 ABDO ET AL. Vol. 708
Figure 4. Counts maps (arbitrary units) presenting the pulsed (top row) and nebular (bottom row) emission, in three energy bands. Each panel spans 15◦ × 15◦ in
equatorial coordinates and is centered on the pulsar radio position. Left: 100 MeV < E < 300 MeV; middle: 300 MeV < E < 1 GeV; right: E > 1 GeV.
(A color version of this figure is available in the online journal.)
Abdo et al 2010 Abdo et al 2010
52. How do we know it is a PWN?
aharonian et al 2005
•PWN should have rising spectrum
•PWN can be extended
•Clear identification difficult:
•X-ray PWN often much smaller
•Pulsars can be offset
•other possible counterparts
•Pulsar energetics?
•PWN candidate vs clear detection?
•Energy dependent morphology
•Matching X-ray to Gamma-ray
mormorphology?
L26 F. A. Aharonian et al.: The association of HESS J1825–137 with G 18.0–0.7
1. Introduction
PSR B1823–13 (also known as PSR J1826–1334) is a 101 ms
evolved pulsar with a spin-down age of T = 2.1 × 104
years
(Clifton et al. 1992) and in these properties very similar to the
Vela pulsar. It is located at a distance of d = 3.9 ± 0.4 kpc
(Cordes & Lazio 2002) and ROSAT observations of this source
with limited photon statistics revealed a compact core, as well
as an extended diffuse nebula of size ∼5 south-west of the pul-
sar (Finley et al. 1998). High resolution XMM-Newton obser-
vations of the pulsar region confirmed this asymmetric shape
and size of the diffuse nebula, which was hence given the name
G 18.0–0.7 (Gaensler et al. 2003). For the compact core with
extent RCN ∼ 30 (CN: compact nebula) immediately sur-
rounding the pulsar, a photon index of ΓCN = 1.6+0.1
−0.2 was mea-
sured with a luminosity of LCN ∼ 9d2
4 × 1032
erg s−1
in the 0.5
to 10 keV range for a distance of 4d4 kpc. The corresponding
pulsar wind shock radius is Rs ≤ 15 = 0.3d4 pc. The com-
pact core is embedded in a region of extended diffuse emission
which is clearly one-sided, revealing a structure south of the
pulsar, with an extension of REN ∼ 5 , (EN: extended nebula)
whereas the ∼4 east-west extension is symmetric around the
north-south axis. The spectrum of this extended component is
-5
0
5
10
15
20
25
30
-14
-13.5
18h24m18h26m18h28m
PSR B1823-13
RA (hours)
)°Dec ( 3EG J1826-1302
PSF
HESS J1825-137
Fig. 1. Excess map of the region close to PSRB1823–13 (marked with
a triangle) with uncorrelated bins. The best fit centroid of the γ-ray
excess is shown with error bars. The black dotted circle shows the
LettertotheEditor
53. Many TeV Pulsar Wind Nebula
•Many PWN detected
at TeV energies
•Limited Background,
•Improved sensitivity
•No Pulsar signal
•32 TeV PWN
54. Harder at Gamma-ray
energies
•Limited Angular Resolution
•Large Galactic Background
•Non-linear Detector response
•Emission could be from the pulsar.
•Crowded gamma-ray sky
55. How do we search for new
gamma-ray emitting PWN?
Association
with LAT-
detected
Association
with TeV PWN
Spatial
Morphology
57. You can study extended LAT sources
using maximum-likelihood analysis
ering events). The likelihood function
d emission:
L =
Y
j
✓
kj
j e ✓j
kj!
.
tion and energy bins, kj are the counts
ts predicted in the same bin.
re computed by integrating the di↵ere
~⌦0
at a time t0
. The dispersion is written as P(E0
, t0
, ~⌦0
|E, t, ~⌦). It repre
probability and is therefore normalized such that
Z Z Z
dEd⌦dtP(E0
, t0
, ~⌦0
|E, t, ~⌦) = 1
Therefore, P(E0
, t0
, ~⌦0
|E, t, ~⌦) has units of 1/energy/SA/time
The convolution of the model a source with the IRFs produces the expec
ferential counts (counts per unit energy/time/SA) that are reconstructed to
energy E0
at a position ~⌦0
and at a time t0
:
⌧(E0
, ~⌦0
, t0
| ) =
Z Z Z
dE d⌦ dt F(E, t, ~⌦| )✏(E, t, ~⌦)P(E0
, t0
, ~⌦0
|E, t, ~⌦)
Here, this integral is performed over all energies, SAs, and times.
For LAT analysis, we conventionally make the simplifying assumption t
Here, j refers to a sum over position and energy bins, kj a
bin j, and ✓j are the model counts predicted in the same b
The model counts in bin j are computed by integrat
counts over the bin:
✓ij =
Z
j
dE d⌦ dt ⌧(E, ~⌦, t| i).
Here, j represents the integral over the jth position/energ
source, i refers to the parameters defining the ith source, a
1 0
plicated hypothesis and H0 th
mpare the likelihood when ass
ended spatial model:
TSext = 2 log(Lext/Lps).
n be written as:
L = L( ).
ysis, one typically fits parameters of a model
ction of the parameters of the model.
max = arg maxL( )
60. IC 443
Puppis A
W44
MSH 15−52
W51C
W28
SMC
Gamma Cygni
Vela X
Cygnus Loop
Vela Jr.
LMC
RX J1713.7−3946
HESS J1825−127
W30
Centarus A
New Extended Sources
68. Is it a pulsar or a PWN?Grondin et al.
Energy [MeV]
3
10 4
10
5
10
6
10 7
10
]-1s-2
dN/dE[ergcm2
E
-12
10
-11
10
-10
10
pectral energy distribution of HESS J1825−137 in gamma-rays. The LAT spectral points (in red) are obtained using the maximum likelihood
described in section 4.2 in 6 logarithmically-spaced energy bins. The statistical errors are shown in red, while the black lines take into account both
nd systematic errors as discussed in section 4.2. The red solid line presents the result obtained by fitting a power-law to the data in the 1 – 100 GeV
using a maximum likelihood fit. A 95 % C.L. upper limit is computed when the statistical significance is lower than 3 σ. The H.E.S.S. results are
blue (Aharonian et al. 2006).
pulsar, we fix the initial spin period at 10 ms and
ex at 2.5, yielding an age of 26 kyr for the sys-
simple injection spectrum slightly underestimates
ata but the overall fit is still reasonable. For the
of 26 kyr, we require a power-law index of 1.9,
57 TeV and a magnetic field of 4 µG. The corre-
sult is presented in Figure 4 (Top).
option to fit the multi-wavelength data is adopting
tic Maxwellian plus power-law tail electron spec-
sed by Spitkovsky (2008). For this injection spec-
sume a bulk gamma-factor (γ0) for the PWN wind
f the termination shock. At the termination shock
t pressure balances the wind pressure, fully ther-
e wind; in this case the downstream post-shock
= (γ0 − 1)/2. One could also interpret this as
e temperature kT of mec2
(γ0 − 1)/2. Per the
of Spitkovsky (2008), a power-law tail begins at
mec2
γ0, and suffers an exponential cutoff at some
The Fermi LAT Collaboration acknowledges generous ongoing support
from a number of agencies and institutes that have supported both the de-
velopment and the operation of the LAT as well as scientific data analysis.
These include the National Aeronautics and Space Administration and the
Department of Energy in the United States, the Commissariat `a l’Energie
Atomique and the Centre National de la Recherche Scientifique / Institut Na-
tional de Physique Nucl´eaire et de Physique des Particules in France, the
Agenzia Spaziale Italiana, the Istituto Nazionale di Fisica Nucleare, and the
Istituto Nazionale di Astrofisica in Italy, the Ministry of Education, Culture,
Sports, Science and Technology (MEXT), High Energy Accelerator Research
Organization (KEK) and Japan Aerospace Exploration Agency (JAXA) in
Japan, and the K. A. Wallenberg Foundation and the Swedish National Space
Board in Sweden. Additional support for science analysis during the opera-
tions phase from the following agencies is also gratefully acknowledged: the
Instituto Nazionale di Astrofisica in Italy and the Centre National d’´Etudes
Spatiales in France.
The Nanc¸ay Radio Observatory is operated by the Paris Observatory, associ-
ated with the French Centre National de la Recherche Scientifique (CNRS).
The Lovell Telescope is owned and operated by the University of Manchester
as part of the Jodrell Bank Centre for Astrophysics with support from the
Science and Technology Facilities Council of the United Kingdom.
The Parkes radio telescope is part of the Australia Telescope which is funded
– 37 –
Energy (MeV)
2
10
3
10
4
10
]-1
s-2
dN/dE[ergcm2
E
-11
10
-10
10
1
]-1
s-2
dN/dE[ergcm2
E
-12
10
-11
10
Energy (MeV)
2
10
3
10 10
]-1
s-2
dN/dE[ergcm2
E
-12
10
-11
10
4 Grondin et al.
HESS J1825-137
(Grondin et al 2011)
PSR J2021+4026
Ackermann et al 2010
HESS J1825-137
(Grondin et al 2011)
Spectral Shape:
• Pulsars are cutoff
• PWN rising spectrum
Morphology
• Pulsars are point sources
• PWN could be extended
69. 10 13
10 12
10 11
10 10
10 9
10 13
10 12
10 11
10 10
E2
dN/dE(ergcm2
s1
)
10 13
10 12
10 11
10 10
10 9
10 1
100
101
102
Energy (GeV)
10 1
100
101
102
Energy (GeV)
We
performed
a spectral
and spatial
analysis of
each off-
peak region
70. Off-peak Sources
•116 pulsars tested
•34 significant sources
•9 are clearly pulsar emission
•4 are pulsar wind nebula
•1 new pulsar wind nebula
71. 3C 58 is
associated and
PSR J0205+6449
Coincident with
SNR 3C 58 and
SN 1181
75. PWN Detected by LAT
•Before Fermi, 1 PWN Detected (Crab)
•Now, 17 PWN candidates
•5 clearly associated with PWN
•12 have less certain identification.
81. The lifetime of gamma-ray emitting
electrons is longer than of X-ray
emitting electrons.EVOLUTION OF THE γ - AND X-RAY LUMINOSITIES OF PWNe
102
103
104
105
Time (yr)
0.01
0.10
1.00
Normalizednumberofparticles
nγnX
tcγtcX 10-1
100
101
102
103
104
Rationγ/nX
nγ /nX
Mattana et al 2009