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transcript
Tsunefumi Mizuno 1
Fermi_Diffuse_ASJ_2010Mar.ppt
Fermi-LAT Study of Fermi-LAT Study of Galactic Cosmic-Ray Galactic Cosmic-Ray
DistributionDistribution-- CRs in the Outer Galaxy ---- CRs in the Outer Galaxy --
Tsunefumi MizunoTsunefumi MizunoHiroshima Univ.Hiroshima Univ.
on behalf of the Fermi-LAT on behalf of the Fermi-LAT CollaborationCollaboration
ASJ 2010 Spring MeetingASJ 2010 Spring MeetingMarch 25, 2010, Hiroshima, JapanMarch 25, 2010, Hiroshima, Japan
Tsunefumi Mizuno 2
Fermi_Diffuse_ASJ_2010Mar.pptIntroduction Introduction Cosmic-Rays and Galactic Diffuse Gamma-RaysCosmic-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
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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, 251101; Abdo et al. 2010, ApJ 710, 133)
LAT Study of the Galactic Diffuse EmissionLAT Study of the Galactic Diffuse Emission
Fermi-LAT all sky map (1yr)
Tsunefumi Mizuno 4
Fermi_Diffuse_ASJ_2010Mar.ppt
CR Distribution in Milky WayCR 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 (2nd and 3rd quadrant) will be discussed.• Study of the whole Galaxy is in progress
Gal.Center
Inner Galaxy
OuterGalaxy
Tsunefumi Mizuno 5
Fermi_Diffuse_ASJ_2010Mar.ppt
CR Distribution in the Outer GalaxyCR Distribution in the Outer Galaxy(2(2ndnd Quadrant) 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
OuterGalaxy
Inner Galaxy
Abdo et al. 2010 (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
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Fermi_Diffuse_ASJ_2010Mar.ppt
CR Distribution in 2CR Distribution in 2ndnd Quadrant 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 GalaxyCR Distribution in the Outer Galaxy (3 (3rdrd Quadrant) 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
OuterGalaxy
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 3CR Distribution in 3rdrd Quadrant Quadrant
Prelimina
Preliminaryry
• 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
Prelimina
Preliminaryry
GALPROP prediction using SNR distribution (Case & Bhattacharya 1998)
Fermi data
-ray emissivity (per H-atom)
-ray intensity profile
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Fermi_Diffuse_ASJ_2010Mar.ppt
Possible Scenario of CR Density Possible Scenario of CR Density DistributionDistribution
Preliminar
Preliminar
yy
• 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
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Fermi_Diffuse_ASJ_2010Mar.ppt
SummarySummary
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
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Fermi_Diffuse_ASJ_2010Mar.ppt
Backup SlidesBackup Slides
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Fermi_Diffuse_ASJ_2010Mar.ppt
CR Distribution in 3CR Distribution in 3rdrd Quadrant 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
Prelimina
Preliminaryry
Prelimina
Preliminaryry
Tsunefumi Mizuno 13
Fermi_Diffuse_ASJ_2010Mar.ppt
Fermi-LAT View of the 3rd QuadrantFermi-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
Preliminary
Vela
Crab
Geminga
Orion A/B
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Fermi_Diffuse_ASJ_2010Mar.ppt
Construction of the ModelConstruction of the ModelLocal arm
+2 HI maps(profile fitting technique;
arXiv:0907.0312)
+
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
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
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Fermi_Diffuse_ASJ_2010Mar.pptIntroduction Introduction Cosmic-Rays and Galactic Diffuse Gamma-RaysCosmic-Rays and Galactic Diffuse Gamma-Rays
e+-
X,γISM
diffusiondiffusion energy losses energy losses reaccelerationreacceleration convectionconvection etc.etc.
π0
synchrotron
bremssHESS
SNR SNR RX J1713-3946RX J1713-3946
B
Pulsar,-QSO
PPHeHeCNOCNO
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
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.