FermiFermi--LAT Study of LAT Study of Galactic ......Gamma-rays (Fermi 衛星による拡散γ 線放射の観測と銀河系宇宙線) Ts nef miTsunefumi Mi noMizuno Hiroshima Univ

Fermi_Diffuse_ASJ_2009Sep.ppt

FermiFermi--LAT Study of LAT Study of Galactic CosmicGalactic Cosmic--Rays Rays yyby Observing Diffuse by Observing Diffuse

GammaGamma--raysraysGammaGamma raysrays(Fermi(Fermi衛星による拡散衛星による拡散γγ線放射の観測と銀河系線放射の観測と銀河系線放射の観測と銀河系線放射の観測と銀河系

宇宙線宇宙線))Ts nef miTs nef mi Mi noMi noTsunefumiTsunefumi MizunoMizuno

Hiroshima Univ.Hiroshima Univ.on behalf of the Fermion behalf of the Fermi--LAT LAT

Tsunefumi Mizuno 1

CollaborationCollaborationASJ 2009 Autumn MeetingASJ 2009 Autumn Meeting

September 15, 2009, Yamaguchi, JapanSeptember 15, 2009, Yamaguchi, Japan

Fermi_Diffuse_ASJ_2009Sep.pptIntroduction Introduction 銀河宇宙線と拡散銀河宇宙線と拡散γγ線放射線放射

HE γ-rays are produced via interactions between Galactic cosmic-rays (CRs) and the interstellar medium (or interstellar radiation field)

(CR accelerator) (Interstellar space) (Observer)

X,γISMSNR SNR

RX J1713RX J1713--39463946Chandra Suzaku

(CR accelerator) (Interstellar space) (Observer)

e+-

diffusiondiffusionHESS

B

PP

Chandra, Suzaku, Radio telescopes

ICISRFdiffusiondiffusionenergy losses energy losses

reaccelerationreaccelerationconvectionconvection

etcetcπ0Pulsar,

μ-QSO

HeHeCNOCNO

ACT d Fermi

gase +-

π+-etc.etc. ACTs and Fermi(see K. Hayashi’s talk)gas

π(GMC is one of the best

target matter)

Pioneering theoretical works by Hayakawa (1952), Morrison (1958), etc.

Tsunefumi Mizuno 2

A powerful probe to study CRs in distant locationsPioneering theoretical works by Hayakawa (1952), Morrison (1958), etc.

拡散γ線は宇宙線を探るプローブ


FermiFermi衛星による拡散衛星による拡散γγ線放射の観測線放射の観測 (1)(1)

[1]: GMCs (e.g., Orion, Cham): matter distribution, correlation with mol. gas tracer[2]: Mid/low-latitude region (EGRET GeV excess). submitted to PRL.See also ArXiv:0907.0294

[3]: Mid/high latitude region to study local CRs (Abdo et al 2009; contact: T Mizuno)

Tsunefumi Mizuno 3

[3]: Mid/high-latitude region to study local CRs. (Abdo et al. 2009; contact: T. Mizuno)[4]: Galactic plane (CR distribution in the MW)

[1]~[3]について、これまでの結果を簡単に紹介(次項)[4]について若干詳しく


FermiFermi衛星による拡散衛星による拡散γγ線放射の観測線放射の観測 (2)(2)

[2]: non-GeV-excessGeV-excessの否定

EGRETLATOrion MC

(M~105M )

0.1 1 10 GeV

(M 10 Msun)[1]:GMCs物質分布

[3]: local CRs

LAT datamodel for the LIS

[3]: local CRs近傍の宇宙線はLISに酷似

nucleon-nucleonCham MC(M~104Msun)

Tsunefumi Mizuno 4

electron-bremsstrahlung


銀河系内の宇宙線分布銀河系内の宇宙線分布• CR distribution in our Galaxy is a key to understand their origin and propagation• Distribution of SNRs not well measured• Previous Gamma-ray data suggests a flatter distribution than SNR/pulsar distributions (e.g., Strong et al. 2004)

宇宙線の空間分布は、起源・伝播を探る鍵

G l

• Fermi-LAT is able to map out CR distributions in the Galaxy with unprecedented accuracy• Large scale analysis in progress.Gal.

Center

Large scale analysis in progress. (arXiv:0907.0304)

• We will focus on the preliminary l i f th 3rd d t ( t

Inner Galaxy

Outer

analysis of the 3rd quadrant (outer Galaxy). See also the relevant study of the 2nd quadrant (arXiv:0907.0312)

local arm

Tsunefumi Mizuno 5

GalaxyPerseus arm

銀河系の外側の領域の結果の紹介


FermiFermi--LATLATのカウントマップのカウントマップ• One of the best studied regions in γ-rays

Vela, Geminga, Crab and Orion A/B• Galactic plane between Vela and Geminga (green square) is ideal to study diffuse γ-rays and CRs.

small point source contamination, kinematically well-separated arms (local arm and Perseus arm) 宇宙線分布の研究に適した領域

VelaGeminga

Vela

Crab

Orion A/B

Tsunefumi Mizuno 6Count Map (E>100 MeV)

Orion A/B


ΓΓ線線 = = 星間物質からの放射星間物質からの放射++点源点源Local arm

+2 HI maps(profile fitting technique;+

Perseus arm

(profile fitting technique;arXiv:0907.0312)

詳細は林の講演参照(Q28a)• Fit γ-ray data with 8 maps + 15 point sources (11 month source list)

詳細は林の講演参照(Q28a)

L l

)• CR spectrum (γ-ray emissivity) is assumed to be uniform in each Galactocentric ringLocal arm

+ 1 CO map + excess E(B-V) map (Grenier et al. 2005)+ IC map (galprop model) + point sources (11 month list)

Galactocentric ring

Tsunefumi Mizuno 7

+ IC map (galprop model) + point sources (11 month list)

I(E, l, b) = ΣA(E)*HI(l,b) + ΣB(E)*Wco(l,b) +Σothers+Σpoint_sources


ΓΓ線スペクトル線スペクトル (~(~宇宙線スペクトル宇宙線スペクトル))HI Emissivity Spectrum of each ring

(local arm)(interarm)(P )(Perseus arm)

Point sources with Ts>=100 are included in the fitting宇宙線陽子で1-100GeVに対応(主成分)

• Emissivity (CR) spectrum of local arm (R=8.5-10 kpc) is slightly smaller than the model for LIS• Decreasing emissivity (local arm => interarm => Perseus arm) are consistent with decreasing CR density across the Galaxy 宇宙線の強度分布・スペクトルが得られた

Tsunefumi Mizuno 8

decreasing CR density across the Galaxy• Similar CR spectral shape up to R=16 kpc• Can constrain the CR source distribution and propagation parameters

study in progress

宇宙線の強度分布・スペクトルが得られたモデルとの比較で宇宙線源や伝播に制限


SummarySummary• Diffuse gamma-ray emission is a powerful probe to study the CR (and matter) distribution in distant locations in our Galaxy• Extensive analysis by Fermi-LAT is in progressExtensive analysis by Fermi-LAT is in progress

individual GMCsnon-GeV-excessMid/high-latitude region (local CRs)

拡散γ線放射は宇宙線を探るプローブ様々な成果(分子雲,non-GeV-excess,近傍の宇宙線)

Mid/high-latitude region (local CRs)large scale analysis (CR distribution throughout the

Galaxy)• Preliminary analysis of the 3rd quadrant is disucssed• Preliminary analysis of the 3rd quadrant is disucssed

See also the relevant study of the 2nd quadrantSimilar CR spectral shape up to R=16 kpcCR d it di t t d th t G l i bt i dCR density gradient toward the outer Galaxy is obtained

Comparison with the CR source/propagation model prediction is in progress 銀河系、とくに外側の領域で宇宙線分布が

あきらかなりある

Tsunefumi Mizuno 9Thank you for your attention!あきらかになりつつある


Backup SlidesBackup SlidesBackup SlidesBackup Slides

Tsunefumi Mizuno 10


LAT LAT vsvs prepre--Fermi ModelFermi Model• Compare with a CR propagation model prediction based on pre-F i CR d t (St t l 2004 LATFermi CR data (Strong et al. 2004, Porter et al. 2008)π0-decay, e-Brems, Inverse Compton

LATmodel total

π0-decay

• Source and isotropic (w/ residual BG) component come from fitting the data to the sky above 30 deg

ICe-Bremsthe data to the sky above 30 deg latitude with model fixed • Although there is a uniform

b th d l d t iexcess above the model, data is reasonably reproduced by the model

Th d l i f l id i i i i i

Tsunefumi Mizuno 11

The model is successful considering it is a priori pre-Fermi model


Probing CRs using GammaProbing CRs using Gamma--rays from ISMrays from ISM• Correlation with gas column density reveals the CR spectrum• Fermi-LAT’s high performance + CR propagation model (e.g. GALPROP) to predict IC

S iti it i ifi tl i dSensitivity significantly improvedISM

(e.g., LAB HI survey)(http://www.astro.uni-bonn.de/~webaiub/english/tools_labsurvey.php)

Gamma-ray intensity(Fermi LAT data)

Mid/high latitude region & Galactic plane:Study of the local CRs and CR gradient in the outer Galaxy

Tsunefumi Mizuno 12GCsun

(From Wikipedia)


Accurate Measurements of Local CRs (1)Accurate Measurements of Local CRs (1)Mid-high lat. region in 3rd quadrant:

• small contamination of IC and molecular gas• correlate γ-ray intensity and HI• correlate γ-ray intensity and HI gas column densityAbdo et al. 2009, accepeted by ApJ(arXiv:0908.1171) contact author: TM

(error bars are statistical only)

ity 1 6 2 3 G V400-560 MeV

400-566 MeV

HI column density (1020 cm-2)

y In

tens

i 1.6-2.3 GeV400-560 MeV

E2x γ-

ray

Tsunefumi Mizuno 13HI column density (1020 cm-2)


Accurate Measurement of Local CRs (2)Accurate Measurement of Local CRs (2)• Best quality γ-ray emissivity spectrum in 100 MeV-10 GeV (Tp = 1-100 GeV)• Agree with the model prediction from the local interstellar spectrum (LIS)

EGRET (Digel et al. 2001)

LAT datamodel from the LIS ( g )

nucleon-nucleon

electron-bremsstrahlung

• Prove that local CR nuclei spectra are close to those directly

102 103 MeV 104

Tsunefumi Mizuno 14

measured at the Earth• Eγ<100 MeV constrain the e- spectrum


CR Flux DistributionCR Flux Distribution

LAT “measured” CR density

SNR distribution by radio survey or traced by pulsar

• Emissivity gradient traces the CR density. Robust against the thresholds for point sources included. • Significantly flatter than the SNR distributions

may indicate more CR sources than previously thought in the outer Galaxy large

Tsunefumi Mizuno 15

may indicate more CR sources than previously thought in the outer Galaxy, large halo size, etc.

• Comparison with the model prediction is in progress.


HI MapsHI MapsR<=10 kpc R<=10-12.5 kpc

R<=12.5-16 kpc R>=16 kpc

Tsunefumi Mizuno 16


WcoWco MapsMapsR<=10 kpc R<=10-12.5 kpc

Tsunefumi Mizuno 17

Documents

FermiFermi--LAT Study of LAT Study of Galactic ......Gamma-rays (Fermi 衛星による拡散γ 線放射の観測と銀河系 宇宙線) Ts nef miTsunefumi Mi noMizuno Hiroshima Univ

FermiFermi--LAT Study of LAT Study of Galactic ......Gamma-rays (Fermi 衛星による拡散γ 線放射の観測と銀河系宇宙線) Ts nef miTsunefumi Mi noMizuno Hiroshima Univ