Tsunefumi Mizuno 1 Fermi_Diffuse_ASJ_2010Mar.ppt Fermi-LAT Study of Galactic Cosmic-Ray Distribution -- CRs in the Outer Galaxy -- Tsunefumi Mizuno Hiroshima Univ. on behalf of the Fermi-LAT Collaboration ASJ 2010 Spring Meeting March 25, 2010, Hiroshima, Japan

Tsunefumi Mizuno 2 Fermi_Diffuse_ASJ_2010Mar.ppt Introduction Cosmic-Rays and Galactic Diffuse Gamma-Rays A powerful probe to study CRs and ISM in distant locations HE  -rays are produced via interactions between cosmic-rays (CRs) and the interstellar medium (or the interstellar radiation field) ISM distribution => CRs those “measured” CRs => ISM Fermi-LAT (2008-present) 2.4  sr, 30 MeV-300 GeV

Tsunefumi Mizuno 3 Fermi_Diffuse_ASJ_2010Mar.ppt [1]: CR sources: SNRs, HESS unIDs (Katagiri et al., Hanabata et al.) [2]: ISM and possible CR sources: molecular clouds (Okumura et al., Sada et al.) [3]: Galactic CRs: This talk (cf. Abdo et al. 2009, ApJ 703, 1249; Abdo et al. 2009, PL 103, ; Abdo et al. 2010, ApJ 710, 133) LAT Study of the Galactic Diffuse Emission Fermi-LAT all sky map (1yr)

Tsunefumi Mizuno 4 Fermi_Diffuse_ASJ_2010Mar.ppt CR Distribution in Milky Way CR distribution is a key to understand the CR origin and propagation ISM gas distribution is traced by radio surveys + Galactic rotation Then, Fermi-LAT is able to map out CR distributions in Milky Way with unprecedented accuracy Detailed study of the outer Galaxy (2 nd and 3 rd quadrant) will be discussed. Study of the whole Galaxy is in progress Gal. Center Inner Galaxy Outer Galaxy

Tsunefumi Mizuno 5 Fermi_Diffuse_ASJ_2010Mar.ppt CR Distribution in the Outer Galaxy (2 nd Quadrant) CR distribution is a key to understand the CR origin and propagation ISM gas distribution is traced by radio surveys + Galactic rotation Then, Fermi-LAT is able to map out CR distributions in Milky Way with unprecedented accuracy Gal. Center Outer Galaxy Inner Galaxy Abdo et al (ApJ 710, 133) Contact: L. Tibaldo, I. Grenier R=8.8 kpc R=10 kpc R=14 kpc Gould Belt local arm Perseus arm outer arm

Tsunefumi Mizuno 6 Fermi_Diffuse_ASJ_2010Mar.ppt CR Distribution in 2 nd Quadrant GALPROP prediction using PSR distribution as input sources The shape of CR spectrum in Gould Belt (d<=300 pc) is close to those measured at the Earth Fermi data Decrease of CR densities with gradient flatter than expectations for SNR sources as traced by PSR Property of molecular clouds is also discussed in paper pion-dacay Bremsstrahlung model (scaled) 200 MeV  -ray emissivity (per H-atom)  -ray intensity profile

Tsunefumi Mizuno 7 Fermi_Diffuse_ASJ_2010Mar.ppt CR Distribution in the Outer Galaxy (3 rd Quadrant) CR distribution is a key to understand the CR origin and propagation ISM gas distribution is traced by radio surveys + Galactic rotation Then, Fermi-LAT is able to map out CR distributions in Milky Way with unprecedented accuracy Gal. Center Outer Galaxy Inner Galaxy R=16 kpc R=12.5 kpc R=10 kpc outer arm Perseus arm inter arm local arm

Tsunefumi Mizuno 8 Fermi_Diffuse_ASJ_2010Mar.ppt CR Distribution in 3 rd Quadrant Preliminary Spectral shape agrees well with the model for the LIS, and no significant spectral shape variation is observed. CR spectrum in Tp~1-100 GeV does not vary significantly in the region studied Consistent view of CR density gradient: Decrease of CR densities with gradient flatter than expectations by a conventional model Preliminary GALPROP prediction using SNR distribution (Case & Bhattacharya 1998) Fermi data  -ray emissivity (per H-atom)  -ray intensity profile

Tsunefumi Mizuno 9 Fermi_Diffuse_ASJ_2010Mar.ppt Possible Scenario of CR Density Distribution Preliminary We ran GALPROP to search a possible scenario to explain the flat CR density distribution obtained by the LAT  Large halo size is required to reproduce the LAT data  Or, a flat source distribution in the outer Galaxy is required A larger halo size and/or a flatter CR source distribution than those by a conventional models are required Other scenarios may also explain the observed profile (e.g., Evoli et al. 2008) test of several halo sizes test of a flat CR source distribution in R>Rbk Zh = 1, 2, 4, 10, 15, 20 kpc Rbk = 10, 11, 12, 13, 14, 15 kpc

Tsunefumi Mizuno 10 Fermi_Diffuse_ASJ_2010Mar.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  CR sources (Katagiri et al., Hanabata et al.)  individual GMCs (Okumura et al., Sada et al.)  non-GeV-excess, mid/high-latitude region (local CRs)  large scale analysis (CR distribution throughout the Galaxy) Detailed study of the outer Galaxy is discussed  Flatter CR density gradient than a conventional model toward the outer Galaxy Flat CR source distribution and/or a large CR halo is a possible scenario

Tsunefumi Mizuno 11 Fermi_Diffuse_ASJ_2010Mar.ppt Backup Slides

Tsunefumi Mizuno 12 Fermi_Diffuse_ASJ_2010Mar.ppt CR Distribution in 3 rd Quadrant Spectral shape agrees well with the model for the LIS, and no significant spectral shape variation is observed. CR spectrum in Tp~1-100 GeV does not vary significantly in the region studied Preliminary Preliminary

Tsunefumi Mizuno 13 Fermi_Diffuse_ASJ_2010Mar.ppt Fermi-LAT View of the 3rd Quadrant 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

Tsunefumi Mizuno 14 Fermi_Diffuse_ASJ_2010Mar.ppt Construction of the Model 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

Tsunefumi Mizuno 15 Fermi_Diffuse_ASJ_2010Mar.ppt Introduction Cosmic-Rays and Galactic Diffuse Gamma-Rays 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 and ISM 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.