Igor V. Moskalenko (Stanford U.) with A.Strong (MPE), S.Digel (SLAC), T.Porter (USCS), O.Reimer (SU)...

Igor V. Moskalenko Igor V. Moskalenko (Stanford U.)(Stanford U.)

with

A.Strong (MPE), S.Digel (SLAC), T.Porter (USCS), O.Reimer (SU)

Modeling of the Galactic diffuseModeling of the Galactic diffuse

continuum continuum γγ-ray emission-ray emission

Igor V. Moskalenko 2 July 4, 2006 6th INTEGRAL Workshop/Moscow

GLAST Large Area Telescope (LAT)

EGRET(>100 MeV)

Simulated LAT (>1 GeV, 1 yr)

This is an animation that steps from 1. EGRET (>100 MeV), to 2. LAT (>100 MeV), to 3. LAT (>1 GeV)

Seth Digel


Diffuse Galactic Gamma-ray Diffuse Galactic Gamma-ray EmissionEmission

~80% of total Milky Way luminosity at HE !!!

Tracer of CR (p, e−) interactions in the ISM (π0,IC,bremss):o Study of CR species in distant locations (spectra & intensities)

CR acceleration (SNRs, pulsars etc.) and propagationo Emission from local clouds → local CR spectra

CR variations, Solar modulationo May contain signatures of exotic physics (dark matter etc.)

Cosmology, SUSY, hints for accelerator experimentso Background for point sources (positions, low latitude sources…)

Besides:o Foreground in studies of the extragalactic diffuse emissiono 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


CR Interactions in the Interstellar Medium

e+-

PPHeHe

CNOCNO

X,γ

gas

gas

ISRF

e+-

π+-

PP__

LiBeBLiBeB

ISM

diffusiondiffusion energy losses energy losses reaccelerationreacceleration convectionconvection etc.etc.

π0

synchrotron

IC

bremss

Chandra

GLAST

ACEhelio-modulation

pp

42 sigma (2003+2004 data)

HESS Preliminary

SNR RX J1713-3946SNR RX J1713-3946

PSF

B

HeHeCNOCNO Fl

ux

20 GeV/n

CR species: Only 1 location modulation

e+-

π+-

PAMELABESS

AMS


A Model of CR Propagation in the Galaxy

Gas distribution (Leiden-Argentina-Bonn HI, CfA CO surv.)Gas distribution (Leiden-Argentina-Bonn HI, CfA CO surv.)

Interstellar radiation field (87 stellar classes, gas, dust, Interstellar radiation field (87 stellar classes, gas, dust,

including heating and re-emission)including heating and re-emission)

Source distribution (SNR, pulsars)Source distribution (SNR, pulsars)

Nuclear & particle production cross sections (LANL, Nuclear & particle production cross sections (LANL,

Webber)Webber)

Gamma-ray production: brems, IC, Gamma-ray production: brems, IC, ππ00

Energy losses: ionization, Coulomb, brems, IC, synchEnergy losses: ionization, Coulomb, brems, IC, synch

Solve transport equations for all CR species (~90!)Solve transport equations for all CR species (~90!)

Fix propagation parametersFix propagation parameters


Wherever you look, the GeV -ray excess is there !

4a-f

EGRET data


Reacceleration Model vs. Plain Reacceleration Model vs. Plain DiffusionDiffusion

Plain Diffusion

(Dxx~β-3 R0.6)

DiffusiveReacceleration

B/C ratio

Antiproton flux

Antiproton flux

B/C ratio


More excesses: Positron Excess ?

HEAT (Beatty et al. 2004)

GALPROP

GALPROP

1E, GeV

10

e+/e e+/e

HEAT 2000 HEAT 1994-95

HEAT combined

1E, GeV

10

Q: Are all the excesses connected?Q: Are all the excesses connected?

A: “Yes” and “No”A: “Yes” and “No”

Same progenitor (CR p or DM) for pbars, e+’s, γ’s… or a local positron source?

Systematic errors of different detectors

E > 6 GeV


GeV excess: Optimized/Reaccleration model

Uses Uses all skyall sky and antiprotons & gammas and antiprotons & gammas to fix the nucleon and electron spectrato fix the nucleon and electron spectra

Uses Uses antiprotonsantiprotons to fix to fix the the intensityintensity of CR nucleons @ HE of CR nucleons @ HE

Uses Uses gammasgammas to adjust to adjust the nucleon spectrum at LEthe nucleon spectrum at LE the the intensity intensity of the CR electrons of the CR electrons (uses also synchrotron index)(uses also synchrotron index)

Uses EGRET data Uses EGRET data up to 100 GeVup to 100 GeV

protonsprotonselectronselectrons

x4x4

x1.8

antiprotonsantiprotons

EEkk, GeV, GeV

EEkk, GeV, GeV

EEkk, GeV, GeV


Secondary e± are seen in γ-rays !

Improves an agreement in MeV range

brems

IC

In the heliosphere: In the heliosphere: ee++/e~0.2/e~0.2

In the Galaxy: eIn the Galaxy: e++/e~1 <1 /e~1 <1 GeVGeV

electronselectrons

positronspositrons

sec.


Distribution of CR Sources & Gradient in the CO/H2

CR distribution from diffuse gammas (Strong & Mattox 1996)

SNR distribution (Case &Bhattacharya 1998)

sun

XXCOCO=N(H=N(H22)/W)/WCOCO::

Histo –This work, Strong et al.’04----- -Sodroski et al.’95,’971.9x1020 -Strong & Mattox’96~Z-1 –Boselli et al.’02~Z-2.5 -Israel’97,’00, [O/H]=0.04,0.07 dex/kpc

Pulsar distribution Lorimer 2004


Seth Digel’05

Gas Rings: HI (Our Neighborhood)

Longitude

Lati

tud

e


Interstellar radiation field

R= 0 kpc4 kpc8 kpc

12 kpc 16 kpc

Local ISRF

stars

IR CMB

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 !)

scattered


Anisotropic Inverse Compton Scattering

Electrons in the halo see anisotropic radiation Observer sees mostly head-on collisions

e-

e-

head-on:large boost &more collisions

γγ

small boost &less collisions

γ

sun

Energy density

Z, kpc

R=4 kpc

Important @ high

latitudes !


Effect of anisotropic ICS

Galactic latitude, degrees

Ratio anisoIC/isoIC

Intermediate latitudesGC

anti-GCpole

• The anisotropic IC scattering plays important role in modeling the Galactic diffuse emission

• Affects estimates of isotropic extragalactic background


Latitude profile of the outer Galaxy

anisotropic IC

• The aniso IC is maximal (x2) in the outer Galaxy around b=20 -30

• Agreement with data impossible without aniso IC

Latitude

isoIC

bremsstrahlung

0

TotalEG


Diffuse emission from the inner Galaxy

• 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

Extragalactic

EGRETASCAHEAO A2HEAO A4

COMPTEL

G+EG EGRET

G COMPTEL(Strong’99)

EG COMPTEL(Weidenspointner’00)

EG EGRET(Strong’04)

INTEGRAL(Strong’05)

isoICanisoIC

Tota

l Gala

ctic

Tota

l Gala

ctic

G+EG

G+EG COMPTEL

Positronium+ sources??


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 MeV-GeV 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


Diffuse emission from the outer Galaxy

anisotropic IC

isoIC

bremss

Igor V. Moskalenko (Stanford U.) with A.Strong (MPE), S.Digel (SLAC), T.Porter (USCS), O.Reimer (SU)...

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