Igor V. Moskalenko (Stanford) with S. Digel (SLAC) T. Porter (UCSC) O. Reimer (Stanford) O. Reimer...

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

withwith

S. Digel (SLAC)S. Digel (SLAC)

T. Porter (UCSC)T. Porter (UCSC)

O. Reimer (Stanford)O. Reimer (Stanford)

A. W. Strong (MPE)A. W. Strong (MPE)

Diffuse Galactic Diffuse Galactic -ray emission -ray emission

modelmodel

Igor V. Moskalenko 2 March 2, 2006 DC2/SLAC

GLAST LAT ProjectDiffuse 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 “Diffuse” emission from other normal galaxies (M31, LMC,

SMC) Cosmic rays in other galaxies !

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


GLAST LAT Project

Conventional model vs EGRET data

4a-f

Conventional model consistent with local p,e spectra exhibits the “GeV excess:” a factor ~2

0 ICBremssEG

We must

have at least

2 diffuse emiss

ion

models with

/with

out

the excess


GLAST LAT Project

galprop ID = 6002029RB

Based onStrong,Moskalenko,Reimer, 2004, ApJ 613,962

Strong,Moskalenko,Reimer,Digel,Diehl, 2004, A&A 422, L47

Optimized to fit EGRET data (GeV excess: CR spectra) Includes secondary electrons & positrons Pulsar/SNR source distribution Gradient in X-factor (H2/CO)

Improvements: new HI, CO data (Digel) new interstellar radiation field (Porter) fine adjustments to reflect these new inputs

Examples of model unconvolved and convolved with EGRET PSF

DC2 diffuse emission model


GLAST LAT ProjectGeV 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

pbarse+ -fluxγ-rays

Strong etal 2004


GLAST LAT Project

Secondary e± are seen in γ-rays !

Lots of new effects !

Improves an agreement at LE

brems

IC

Heliosphere: e+/e~0.2

electronselectrons

positronspositrons

sec.


GLAST LAT Project


GLAST LAT Project

Distribution of interstellar gas• Neutral interstellar medium – most of the interstellar gas mass

– 21-cm H I & 2.6-mm CO (standing for H2)

• Differential rotation of the Milky Way – plus random motions, streaming, and internal velocity dispersions – is largely responsible for the spectrum

• This is the best – but far from perfect – distance measure available

• Self-absorption of HI (21cm) and optical depth effects…

Dame et al.(1987)

Hartmann &Burton (1997)

(25°, 0°)

W. Keel

CO

H IG.C.

25°


GLAST LAT Project

New H2 maps (S.Digel)


GLAST LAT Project

New HI maps (S.Digel)


GLAST LAT Project

Interstellar Radiation Field

Systematic errors:Star distribution –star countsGrain properties –lab measurementsGas/dust proportion –extinction curve“Reasonable parameters”Compare with ISRF data only at R

• Target for CR leptons (IC)• Energy losses

Model components: Geometrical: disk, ring, halo, bar, triaxial

bulge, arms 87 stellar types (main sequence), AGB &

exotics Dust: silicate, graphite, PAH (5Å – few m) Absorbed light gives mid-IR (small grains

+PAH) and FIR (~0.1-1 m grains)

SMR00PS05

Old model Local ISRF (PS05)

R=0

Optical

Scatt.opt.

IR

PAH

4 kpc

12 kpc

16kpc


GLAST LAT ProjectDistribution 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


GLAST LAT Project

Inner Galaxy region

Comparison with EGRET & COMPTEL spectral data

Other regions demonstrate equally good agreement


GLAST LAT Project

Convolution with EGRET PSF: Important below 1 GeV A large effect at low energies especially in

latitude affecting the overall spectral

shape Convolution itself is model dependent -

depends on spectrum, not fully accounted

for

Model comparison with data


GLAST LAT Project

Unconvolved Convolved

Longitude profile |b|<5

Effect of Convolution: 70-100 MeV


GLAST LAT Project


Latitude profile |l|<30

Effect of Convolution: 70-100 MeV


GLAST LAT Project


Longitude profile |b|<5

Effect of Convolution: 0.5-1 GeV


GLAST LAT Project


Latitude profile |l|<30

Effect of Convolution: 0.5-1 GeV


GLAST LAT Project

1000 – 2000 MeV1-2 GeV

Convolution effect is negligible


GLAST LAT Project

NB here the spatial convolution correction is applied to the DATA based on the model. Hence the DATA changes, not the model (procedure appropriate for spectra)

“Convolved data” De-convolved

Effect of De-Convolution: Spectrum |l|<30 |b|<5

Igor V. Moskalenko (Stanford) with S. Digel (SLAC) T. Porter (UCSC) O. Reimer (Stanford) O. Reimer...

Documents

Transcript of Igor V. Moskalenko (Stanford) with S. Digel (SLAC) T. Porter (UCSC) O. Reimer (Stanford) O. Reimer...