GALPROP Model for Galactic CR
propagation and diffuse γ-ray emission
Igor V. Moskalenko (Stanford)
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
LiBeB
He
CNO
+
e-
Flux
PSF
HESS
Preliminary
Chandra
20 GeV/n
BESS
PAMELA
Igor V. Moskalenko 2
AMS
helio-modulation
October 24, 2006
ACE
CR species:
 Only 1 location
 modulation
SCIPP/UCSC
Elemental Abundances: CR vs. Solar System
CR abundances: ACE
O
Si
Na
Fe
S
CNO
Al
Cl
LiBeB
CrMn
F
ScTiV
Solar system abundances
Long propagation history…
Igor V. Moskalenko 3
October 24, 2006
SCIPP/UCSC
Nuclear component in CR: What we can learn?
Stable secondaries:
Li, Be, B, Sc, Ti, V
Propagation parameters:
Radio (t1/2~1 Myr): Diffusion coeff., halo
size, Alfvén speed,
10Be, 26Al, 36Cl, 54Mn
convection velosity…
K-capture: 37Ar,49V,
51Cr, 55Fe, 57Co
Energy markers:
Reacceleration, solar
modulation
Short t1/2 radio 14C
& heavy Z>30
Heavy Z>30:
Cu, Zn, Ga, Ge, Rb
Igor V. Moskalenko 4
Local medium:
Local Bubble
Diffuse γ-rays
Galactic,
extragalactic:
blazars, relic
neutralino
Material & acceleration
sites, nucleosynthesis (rvs. s-processes)
October 24, 2006
SCIPP/UCSC
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 “Diffuse” emission from other normal galaxies (M31, LMC, SMC)
 Cosmic rays in other galaxies !
o Foreground in studies of the extragalactic diffuse emission
o 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 5
October 24, 2006
SCIPP/UCSC
A Model of CR Propagation in the Galaxy
 Gas distribution (energy losses, π0, brems)
 Interstellar radiation field (IC, e± energy losses)
 Nuclear & particle production cross sections
 Gamma-ray production: brems, IC, π0
 Energy losses: ionization, Coulomb, brems, IC, synch
 Solve transport equations for all CR species
 Fix propagation parameters
 “Precise” Astrophysics
Igor V. Moskalenko 6
October 24, 2006
SCIPP/UCSC
How It Works: Fixing Propagation Parameters
E2 Flux
B/C
Carbon
Radioactive isotopes:
Galactic halo size Zh
Ek, GeV/nucleon
Be10/Be9
Ek, MeV/nucleon
Using secondary/primary nuclei ratio & flux:
•Diffusion coefficient and its index
•Propagation mode and its parameters (e.g.,
reacceleration VA, convection Vz)
Zh increase
Ek, MeV/nucleon
Igor V. Moskalenko 7
October 24, 2006
SCIPP/UCSC
Wherever you look, the GeV -ray excess is there !
EGRET data
Excess: x2
4a-f
Igor V. Moskalenko 8
October 24, 2006
SCIPP/UCSC
Reacceleration Model vs. Plain Diffusion
Antiproton flux
B/C ratio
Plain Diffusion
(Dxx~β-3 R0.6)
B/C ratio
Antiproton flux
Diffusive
Reacceleration
Excess: x2
Igor V. Moskalenko 9
October 24, 2006
SCIPP/UCSC
Positron Excess ?
HEAT (Beatty et al. 2004)
e+/e
e+/e
E > 6 GeV
GALPROP
HEAT 2000
HEAT 1994-95
10
1
Excess: 20%
HEAT combined
1
E, GeV
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
Igor V. Moskalenko 10
October 24, 2006
SCIPP/UCSC
Diffuse emission models
Dark Matter
EGRET “GeV Excess”
Cosmic Ray
Spectral Variations
from Hunter et al. ApJ (1997)
from Strong et al. ApJ (2004)
from de Boer et al. A&A (2005)
>0.5 GeV
Igor V. Moskalenko 11
There are two possible BUT
fundamentally different
explanations of the excess, in
terms of exotic and traditional
physics:
 Dark Matter
 CR spectral variations
Both have their pros & cons.
October 24, 2006
0.5-1 GeV
SCIPP/UCSC
Electron Fluctuations/SNR stochastic events
GeV electrons
100 TeV electrons
E(dE/dt)-1,yr
GALPROP/Credit S.Swordy
107 yr
6
10 yr
Electron energy loss timescale:
1 TeV: ~300 kyr
100 TeV: ~3 kyr
Energy losses
Bremsstrahlung
Ionization
IC, synchrotron
Coulomb
1
GeV
1 TeV
Ekin, GeV
Igor V. Moskalenko 12
October 24, 2006
SCIPP/UCSC
GeV excess: Optimized/Reaccleration model
Uses all sky and antiprotons & gammas
to fix the nucleon and electron spectra



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)
antiprotons
 pbars
 e+ -flux
 γ-rays
Uses EGRET data up to 100 GeV
electrons
Ek, GeV
protons
x4
x1.8
Ek, GeV
Igor V. Moskalenko 13
Ek, GeV
October 24, 2006
SCIPP/UCSC
Secondary e± are seen in γ-rays !
Lots of new effects !
electrons
Heliosphere:
e+/e~0.2
sec.
IC
positrons
brems
Improves an agreement at LE
Igor V. Moskalenko 14
October 24, 2006
SCIPP/UCSC
Diffuse Gammas at Different Sky Regions
Hunter et al. region:
l=300°-60°,|b|<10°
Inner Galaxy:
l=330°-30°,|b|<5°
Outer Galaxy:
l=90°-270°,|b|<10°
corrected
l=40°-100°,|b|<5°
Intermediate latitudes:
l=0°-360°,10°<|b|<20°
Intermediate latitudes:
l=0°-360°,20°<|b|<60°
Milagro
Igor V. Moskalenko 15
October 24, 2006
SCIPP/UCSC
Longitude Profiles |b|<5°
50-70 MeV
2-4 GeV
Igor V. Moskalenko 16
October 24, 2006
0.5-1 GeV
4-10 GeV
SCIPP/UCSC
Latitude Profiles: Inner Galaxy
50-70 MeV
0.5-1 GeV
4-10 GeV
Igor V. Moskalenko 17
October 24, 2006
2-4 GeV
20-50 GeV
SCIPP/UCSC
Latitude Profiles: Outer Galaxy
50-70 MeV
2-4 GeV
Igor V. Moskalenko 18
October 24, 2006
0.5-1 GeV
4-10 GeV
SCIPP/UCSC
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 19
e-
sun
October 24, 2006
SCIPP/UCSC
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 20
October 24, 2006
Intermediate latitudes
Galactic latitude, degrees
SCIPP/UCSC
Latitude profile of the outer Galaxy
anisotropic IC
0
Total
EG
isoIC
bremsstrahlung
• Agreement with
data impossible
without aniso IC
Latitude
Igor V. Moskalenko 21
• The aniso IC is
maximal (x2) in the
outer Galaxy around
b=20 -30
October 24, 2006
SCIPP/UCSC
Extragalactic Gamma-Ray Background
E2xF
Predicted vs. observed
EGRB in different
directions
Sreekumar et al. 1998
Elsaesser & Mannheim,
astro-ph/0405235
Strong et al. 2004
E, MeV
• Blazars
• Cosmological
neutralinos
Igor V. Moskalenko 22
October 24, 2006
SCIPP/UCSC
Inverse Compton scattering
e
QED
©UCAR
The heliosphere is filled with Galactic
CR electrons and solar photons
•electrons are isotropic
•photons have a radial angular distribution
IM, T.Porter, S.Digel: astro-ph/0607521
Igor V. Moskalenko 23
October 24, 2006
SCIPP/UCSC
The ecliptic
Averaged over one year,
the ecliptic will be seen
as a bright stripe on the
sky, but the emission
comes from all
directions
Galactic plane
AC
ecliptic
70°
>100 MeV
GC
Current EGRB
>1 GeV
IS spectrum
Modulated 500 MV
Modulated 1000 MV
Igor V. Moskalenko 24
October 24, 2006
SCIPP/UCSC
Matter, Dark Matter, Dark Energy…
Ω ≡ ρ/ρcrit
Ωtot
=1.02
ΩMatter =4.4%
ΩDM
=23%
ΩVacuum =73%
+/−0.02
+/−0.4%
+/−4%
+/−4%
SUSY DM candidate has also other reasons to exist -particle physics…
“Supersymmetry is a mathematically beautiful theory,
and would give rise to a very predictive scenario,
if it is not broken in an unknown way which unfortunately
introduces a large number of unknown parameters…”
Lars Bergström (2000)
Igor V. Moskalenko 25
October 24, 2006
SCIPP/UCSC
Where is the DM ?!





What (flavors):
Neutrinos ~ visible matter
Super-heavy relics: “wimpzillas”
Axions
Topological objects “Q-balls”
Neutralino-like, KK-like
Where (places):
 Galactic halo, Galactic center
 The sun and the Earth
How (tools):
 Direct searches
– low-background experiments
(DAMA, EDELWEISS)
– neutrino detectors
(AMANDA/IceCUBE)
– Accelerators (LHC)
 Indirect searches
– CR, γ’s (PAMELA,GLAST,BESS)
from E.Bloom presentation
Igor V. Moskalenko 26
October 24, 2006
SCIPP/UCSC
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GALPROP Web-site:
http://galprop.stanford.edu/na_home.html