Tsunefumi Mizuno 1 Fermi_Diffuse_ASJ_2009Sep.ppt Fermi-LAT Study of Galactic Cosmic-Rays by Observing Diffuse Gamma-rays (Fermi 衛星による拡散 γ 線放射の観測と銀河 系宇宙線 ) Tsunefumi Mizuno Hiroshima Univ. on behalf of the Fermi-LAT Collaboration ASJ 2009 Autumn Meeting September 15, 2009, Yamaguchi, Japan

Tsunefumi Mizuno 2 Fermi_Diffuse_ASJ_2009Sep.ppt Introduction 銀河宇宙線と拡散 γ 線放射 e + - X,γ ISM diffusion energy losses energy losses reacceleration reacceleration convection convection etc. etc. π 0 synchrotron bremss HESS SNR RX J B Pulsar,  -QSO PHeCNO Chandra, Suzaku, Radio telescopes A powerful probe to study CRs in distant locations HE  -rays are produced via interactions between Galactic cosmic-rays (CRs) and the interstellar medium (or interstellar radiation field) IC ACTs and Fermi (see K. Hayashi’s talk) gas ISRF e + - π + - (CR accelerator) (Interstellar space) (Observer) (GMC is one of the best target matter) Pioneering theoretical works by Hayakawa (1952), Morrison (1958), etc. 拡散 γ 線は宇宙線を探るプローブ

Tsunefumi Mizuno 3 Fermi_Diffuse_ASJ_2009Sep.ppt Fermi 衛星による拡散 γ 線放射の観測 (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: [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

Tsunefumi Mizuno 4 Fermi_Diffuse_ASJ_2009Sep.ppt Fermi 衛星による拡散 γ 線放射の観測 (2) electron- bremsstrahlung nucleon-nucleon LAT data model for the LIS GeV EGRET LAT Preliminary Orion MC (M~10 5 M sun ) Cham MC (M~10 4 M sun ) Preliminary [1]:GMCs 物質分布 [2]: non-GeV-excess GeV-excess の否定 [3]: local CRs 近傍の宇宙線は LIS に酷似

Tsunefumi Mizuno 5 Fermi_Diffuse_ASJ_2009Sep.ppt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) Gal. Center Inner Galaxy Outer Galaxy Fermi-LAT is able to map out CR distributions in the Galaxy with unprecedented accuracy Large scale analysis in progress. (arXiv: ) We will focus on the preliminary analysis of the 3 rd quadrant (outer Galaxy). See also the relevant study of the 2 nd quadrant (arXiv: ) local arm Perseus arm 宇宙線の空間分布は、起源・伝播を探る鍵 銀河系の外側の領域の結果の紹介

Tsunefumi Mizuno 6 Fermi_Diffuse_ASJ_2009Sep.ppt Fermi-LAT のカウントマップ One of the best studied regions in  -rays  Vela, Geminga, Crab and Orion A/B Galactic plane between Vela and Geminga (green square) is ideal to study diffuse  -rays and CRs.  small point source contamination, kinematically well-separated arms (local arm and Perseus arm) Count Map (E>100 MeV) Preliminary Vela Crab Geminga Orion A/B 宇宙線分布の研究に適した領域

Tsunefumi Mizuno 7 Fermi_Diffuse_ASJ_2009Sep.ppt  線 = 星間物質からの放射 + 点源 Local arm +2 HI maps (profile fitting technique; arXiv: ) + Local arm + 1 CO map + excess E(B-V) map (Grenier et al. 2005) + IC map (galprop model) + point sources (11 month list) I(E, l, b) =  A(E)*HI(l,b) +  B(E)*Wco(l,b) +  others+  point_sources Preliminary Perseus arm Fit  -ray data with 8 maps + 15 point sources (11 month source list) CR spectrum (  -ray emissivity) is assumed to be uniform in each Galactocentric ring 詳細は林の講演参照 (Q28a)

Tsunefumi Mizuno 8 Fermi_Diffuse_ASJ_2009Sep.ppt  線スペクトル (~ 宇宙線スペクト ル ) Preliminary HI Emissivity Spectrum of each ring Point sources with Ts>=100 are included in the fitting (local arm) (interarm) (Perseus arm) Emissivity (CR) spectrum of local arm (R= 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 Similar CR spectral shape up to R=16 kpc Can constrain the CR source distribution and propagation parameters  study in progress 宇宙線陽子で 1-100GeV に対応 ( 主成分 ) 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

Tsunefumi Mizuno 9 Fermi_Diffuse_ASJ_2009Sep.pptSummary Thank you for your attention! 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 progress  individual GMCs  non-GeV-excess  Mid/high-latitude region (local CRs)  large scale analysis (CR distribution throughout the Galaxy) Preliminary analysis of the 3 rd quadrant is disucssed  See also the relevant study of the 2 nd quadrant  Similar CR spectral shape up to R=16 kpc  CR density gradient toward the outer Galaxy is obtained Comparison with the CR source/propagation model prediction is in progress 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 ) 銀河系、とくに外側の領域で宇宙線分布 があきらかになりつつある

Tsunefumi Mizuno 10 Fermi_Diffuse_ASJ_2009Sep.ppt Backup Slides

Tsunefumi Mizuno 11 Fermi_Diffuse_ASJ_2009Sep.ppt LAT vs pre-Fermi Model Preliminary Compare with a CR propagation model prediction based on pre- Fermi CR data (Strong et al. 2004, Porter et al. 2008) π 0- decay, e-Brems, Inverse Compton Source and isotropic (w/ residual BG) component come from fitting the data to the sky above 30 deg latitude with model fixed Although there is a uniform excess above the model, data is reasonably reproduced by the model The model is successful considering it is a priori pre-Fermi model LAT model total  0- decay IC e-Brems

Tsunefumi Mizuno 12 Fermi_Diffuse_ASJ_2009Sep.ppt Probing CRs using Gamma-rays 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  Sensitivity significantly improved ISM (e.g., LAB HI survey) ( Gamma-ray intensity (Fermi LAT data) Mid/high latitude region & Galactic plane: Study of the local CRs and CR gradient in the outer Galaxy GCsun (From Wikipedia)

Tsunefumi Mizuno 13 Fermi_Diffuse_ASJ_2009Sep.ppt Accurate Measurements of Local CRs (1) Mid-high lat. region in 3 rd quadrant: small contamination of IC and molecular gas correlate  -ray intensity and HI gas column density Abdo et al. 2009, accepeted by ApJ (arXiv: ) contact author: TM MeV HI column density (10 20 cm -2 ) (error bars are statistical only) E 2 x  -ray Intensity HI column density (10 20 cm -2 ) GeV MeV

Tsunefumi Mizuno 14 Fermi_Diffuse_ASJ_2009Sep.ppt Accurate Measurement of Local CRs (2) Best quality  -ray emissivity spectrum in 100 MeV-10 GeV (Tp = GeV) Agree with the model prediction from the local interstellar spectrum (LIS) Prove that local CR nuclei spectra are close to those directly measured at the Earth E  <100 MeV constrain the e- spectrum MeV 10 4 EGRET (Digel et al. 2001) electron- bremsstrahlung nucleon-nucleon LAT data model from the LIS

Tsunefumi Mizuno 15 Fermi_Diffuse_ASJ_2009Sep.ppt CR Flux Distribution 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 halo size, etc. Comparison with the model prediction is in progress. Preliminary LAT “measured” CR density SNR distribution by radio survey or traced by pulsar

Tsunefumi Mizuno 16 Fermi_Diffuse_ASJ_2009Sep.ppt HI Maps R<=10 kpc R<= kpc R<= kpc R>=16 kpc

Tsunefumi Mizuno 17 Fermi_Diffuse_ASJ_2009Sep.ppt Wco Maps R<=10 kpc R<= kpc