Transcript Propagation of Cosmic Rays & Diffuse Galactic Gamma Rays

Modeling of the Galactic diffuse
continuum γ-ray emission
Igor V. Moskalenko (Stanford U.)
with
A.Strong (MPE), S.Digel (SLAC), T.Porter (USCS), O.Reimer (SU)
GLAST Large Area Telescope (LAT)
This is an animation that steps from 1.
EGRET (>100 MeV), to 2. LAT (>100 MeV),
to 3. LAT (>1 GeV)
EGRET
Simulated LAT
(>1 GeV, 1 yr)
(>100 MeV)
Seth Digel
Igor V. Moskalenko 2
July 4, 2006
6th INTEGRAL Workshop/Moscow
Diffuse Galactic Gamma-ray Emission
~80% of total Milky Way luminosity at HE !!!
Tracer of CR (p, e−) interactions in the ISM (π0,IC,bremss):
o
o
o
o
Study of CR species in distant locations (spectra & intensities)
 CR acceleration (SNRs, pulsars etc.) and propagation
Emission from local clouds → local CR spectra
 CR variations, Solar modulation
May contain signatures of exotic physics (dark matter etc.)
 Cosmology, SUSY, hints for accelerator experiments
Background for point sources (positions, low latitude sources…)
Besides:
o
o
Foreground in studies of the extragalactic diffuse emission
Extragalactic diffuse emission (blazars ?) may contain signatures
of exotic physics (dark matter, BH evaporation etc.)
Calculation requires knowledge of CR (p,e) spectra in the entire Galaxy
Igor V. Moskalenko 3
July 4, 2006
6th INTEGRAL Workshop/Moscow
CR Interactions in the Interstellar Medium
SNR RX J1713-3946
42 sigma (2003+2004 data)
ISM
X,γ
+
e-
B
P diffusion
He energy losses
CNO
reacceleration
+
convection e etc. π +-
IC
ISRF
gas
π0
GLAST
gas
_
P
+
π- p
+
e-
LiBeB
He
CNO
Flux
PSF
HESS
Preliminary
Chandra
20 GeV/n
BESS
PAMELA
Igor V. Moskalenko 4
AMS
July 4, 2006
helio-modulation
ACE
CR species:
 Only 1 location
 modulation
6th INTEGRAL Workshop/Moscow
A Model of CR Propagation in the Galaxy
 Gas distribution (Leiden-Argentina-Bonn HI, CfA CO surv.)
 Interstellar radiation field (87 stellar classes, gas, dust,
including heating and re-emission)
 Source distribution (SNR, pulsars)
 Nuclear & particle production cross sections (LANL, Webber)
 Gamma-ray production: brems, IC, π0
 Energy losses: ionization, Coulomb, brems, IC, synch
 Solve transport equations for all CR species (~90!)
 Fix propagation parameters
Igor V. Moskalenko 5
July 4, 2006
6th INTEGRAL Workshop/Moscow
Wherever you look, the GeV -ray excess is there !
EGRET data
4a-f
Igor V. Moskalenko 6
July 4, 2006
6th INTEGRAL Workshop/Moscow
Reacceleration Model vs. Plain Diffusion
Antiproton flux
B/C ratio
Plain Diffusion
(Dxx~β-3 R0.6)
B/C ratio
Antiproton flux
Diffusive
Reacceleration
Igor V. Moskalenko 7
July 4, 2006
6th INTEGRAL Workshop/Moscow
More excesses: Positron Excess ?
HEAT (Beatty et al. 2004)
e+/e
e+/e
E > 6 GeV
GALPROP
HEAT 2000
HEAT 1994-95
10
1
E, GeV
HEAT combined
1
GALPROP
10
E, GeV
Q: Are all the excesses connected?
A: “Yes” and “No”
Systematic errors of different detectors
Same progenitor (CR p or DM) for pbars, e+’s, γ’s… or a local positron source?
Igor V. Moskalenko 8
July 4, 2006
6th INTEGRAL Workshop/Moscow
GeV excess: Optimized/Reaccleration model
Uses all sky and antiprotons & gammas
to fix the nucleon and electron spectra



antiprotons
Uses antiprotons to fix
the intensity of CR nucleons @ HE
Uses gammas to adjust
 the nucleon spectrum at LE
 the intensity of the CR electrons
(uses also synchrotron index)
Uses EGRET data up to 100 GeV
electrons
Ek, GeV
protons
x4
x1.8
Ek, GeV
Igor V. Moskalenko 9
Ek, GeV
July 4, 2006
6th INTEGRAL Workshop/Moscow
Secondary e± are seen in γ-rays !
In the heliosphere: e+/e~0.2
In the Galaxy: e+/e~1 <1 GeV
electrons
sec.
IC
positrons
brems
Improves an agreement in
MeV range
Igor V. Moskalenko 10
July 4, 2006
6th INTEGRAL Workshop/Moscow
Distribution of CR Sources & Gradient in the CO/H2
Pulsar distribution
Lorimer 2004
CR distribution from diffuse gammas
(Strong & Mattox 1996)
SNR distribution (Case &
Bhattacharya 1998)
sun
XCO=N(H2)/WCO:
Histo –This work, Strong et al.’04
-----Sodroski et al.’95,’97
1.9x1020 -Strong & Mattox’96
–Boselli et al.’02
~Z-1
~Z-2.5 -Israel’97,’00, [O/H]=0.04,0.07 dex/kpc
Igor V. Moskalenko 11
July 4, 2006
6th INTEGRAL Workshop/Moscow
Latitude
Gas Rings: HI (Our Neighborhood)
Seth Digel’05
Longitude
Igor V. Moskalenko 12
July 4, 2006
6th INTEGRAL Workshop/Moscow
Interstellar radiation field
R= 0 kpc
4 kpc
8 kpc
12 kpc
16 kpc
Local ISRF
stars
IR
CMB
scattered
The ISRF plays an important role:
•Generation of Galactic diffuse -ray emission (IC)
•IC energy losses of electrons and positrons
It is very intense in the Galactic center
•Attenuation of TeV -ray sources (see Poster 18C !)
Igor V. Moskalenko 13
July 4, 2006
6th INTEGRAL Workshop/Moscow
Anisotropic Inverse Compton Scattering
 Electrons in the halo see anisotropic radiation
 Observer sees mostly head-on collisions
Energy density
e-
R=4 kpc
small boost &
less collisions
head-on:
large boost &
more collisions
γ
γ
Z, kpc
γ
Important @
high latitudes !
Igor V. Moskalenko 14
e-
sun
July 4, 2006
6th INTEGRAL Workshop/Moscow
Effect of anisotropic ICS
Ratio anisoIC/isoIC
pole
anti-GC
GC
• The anisotropic IC scattering
plays important role in
modeling the Galactic diffuse
emission
• Affects estimates of isotropic
extragalactic background
Igor V. Moskalenko 15
July 4, 2006
Intermediate latitudes
Galactic latitude, degrees
6th INTEGRAL Workshop/Moscow
Latitude profile of the outer Galaxy
anisotropic IC
0
Total
EG
isoIC
bremsstrahlung
• Agreement with
data impossible
without aniso IC
Latitude
Igor V. Moskalenko 16
• The aniso IC is
maximal (x2) in the
outer Galaxy around
b=20 -30
July 4, 2006
6th INTEGRAL Workshop/Moscow
Diffuse emission from the inner Galaxy
Extragalactic
INTEGRAL
(Strong’05)
G+EG COMPTEL
G COMPTEL
ASCA
HEAO A2
HEAO A4
G+EG EGRET
EGRET
COMPTEL
(Strong’99)
G+EG
isoIC
Positronium
+ sources??
EG COMPTEL
(Weidenspointner’00)
EG EGRET
(Strong’04)
anisoIC
• The “optimized” model
describes the spectrum of the
diffuse emission from MeV to
TeV energies
• Predictions down to keV’s
(note, INTEGRAL data include
positronium continnum)
• MeV region appears to be
transitional between Galactic
and EG emission dominance
Igor V. Moskalenko 17
July 4, 2006
6th INTEGRAL Workshop/Moscow
Conclusions
• We are building a model of the diffuse emission
preparing for the GLAST mission
• The diffuse emission model becomes more realistic
now with more prediction capability outside the MeVGeV region
• MeV region is transitional (Galactic vs. extragalactic
dominance)
• On the other hand, GLAST will resolve 1000’s of
unresolved sources putting stricter constraints on the
diffuse emission model
• Prepare to see unexpected !
• This will have an impact on CR studies, derivation and
interpretation of the extragalactic background, and
will possibly affect the dark matter studies
Igor V. Moskalenko 18
July 4, 2006
6th INTEGRAL Workshop/Moscow
Diffuse emission from the outer Galaxy
anisotropic IC
isoIC
bremss
Igor V. Moskalenko 19
July 4, 2006
6th INTEGRAL Workshop/Moscow