Fermi_2011Mar.ppt Fermi- Fermi -LAT Study of LAT Study of Cosmic Cosmic- -rays/Diffuse Gamma rays/Diffuse Gamma- y -rays and rays and y Implications on Particle Physics Implications on Particle Physics Mar. 7, 2011 @ Kyoto Univ. Tsunefumi Mizuno (Hiroshima Univ ) Tsunefumi Mizuno (Hiroshima Univ.) On behalf of the Fermi-LAT collaboration T. Mizuno et al. 1
Fermi_2011Mar.ppt Fermi Fermi 衛星による広がったガンマ線・ 衛星による広がったガンマ線・ 宇宙線電子の観測と基礎物理への制限 宇宙線電子の観測と基礎物理への制限 2011 年 3 月 7 日 @ 京都大学基礎物理研究所 水野 恒史 ( 広島大学理学部 ) 水野 恒史 ( 広島大学理学部 ) On behalf of the Fermi-LAT collaboration T. Mizuno et al. 2
Fermi_2011Mar.ppt Outline Outline Outline Outline Introduction Fermi LAT instrumentation Galactic Diffuse Gamma-rays Behind the diffuse γ s: EGB and DM search B hi d h diff EGB d DM h Cosmic-ray Electrons T. Mizuno et al. 3
Fermi_2011Mar.ppt Gamma Gamma- -ray Sky ray Sky • GeV gamma-ray sky = Point sources + Diffuse Gamma-rays >=80% of γ -rays Geminga Vela Crab 3c454.3 Fermi-LAT 1 year all-sky map T. Mizuno et al. 4
Fermi_2011Mar.ppt What makes Diffuse γ -rays? What makes Diffuse rays? InterStellar Medium • Diffuse Gamma-rays InterStellar Radiation Field = Cosmic-rays x (ISM, ISRF) Galactic pl n plane nearby gas in nearby gas in Pl Planck microwave map k mi m high latitude = ISM gas T. Mizuno et al. 5
Fermi_2011Mar.ppt Gamma Gamma- -ray Sky ray Sky phys. processes are • GeV gamma-ray sky well understood ~ Diffuse Gamma-rays = CRs x (ISM, ISRF) Fermi-LAT 1 year all-sky map T. Mizuno et al. 6
Fermi_2011Mar.ppt Why are they important? Why are they important? • Diffuse Gamma-rays are – “probe” to study Galactic CRs and ISM “probe” to study Galactic CRs and ISM – “foreground” to study exotic physics, e.g., • signal from dark matter (DM) signal from dark matter (DM) annihilation or decay annihilation or decay • extragalactic γ -ray background (EGB) new source classes or DM signal F Fermi-LAT 1 year all-sky map i LAT 1 ll k T. Mizuno et al. 7
Fermi_2011Mar.ppt Example: GeV Example: GeV Excess (EGRET Era) Excess (EGRET Era) • EGRET (1991-2000) reported excess emission when compared with a standard diffuse γ -ray model compared with a standard diffuse γ ray model – variety of explanations including DM signal ux E 2 x Flu excess Γ ~ 2.7 (CR protons ) (CR protons ) 0 1 0.1 1 10 GeV 1 10 GeV Hunter+97 T. Mizuno et al. 8
Fermi_2011Mar.ppt Example: Example: GeV GeV Excess (Fermi Era) Excess (Fermi Era) • EGRET GeV excess not confirmed. • However, Fermi data allow us investigating H F i d t ll i ti ti more subtle “anomalies” (and detailed study of CRs/ISM) of CRs/ISM) E 2 x Flux EGRET E Fermi-LAT Abdo+09 Γ ~ 2.7 PRL 103 251101 PRL 103, 251101 0.1 1 10 GeV T. Mizuno et al. 9
Fermi_2011Mar.ppt Fermi Fermi- -LAT as Electron Detector LAT as Electron Detector • Fermi-LAT reported a harder CR e - + e + spectrum compared with a conventional model compared with a conventional model highest statistics: 4.5 M events (6 months) E 3 x Flux x Fermi Data (2009) Abdo+09 PRL 102, 181101 10 100 1000 GeV T. Mizuno et al. 10
Fermi_2011Mar.ppt Fermi Fermi- -LAT as Electron Detector LAT as Electron Detector • Fermi-LAT reported a harder CR e - + e + spectrum compared with a conventional model compared with a conventional model – Lots of interpretations (astrophysical and exotic) Fermi e - + e + PAMELA e + ratio Fermi e e PAMELA e ratio + = DM? DM? Nearby objects? T. Mizuno et al. 11
Fermi_2011Mar.ppt Fermi Fermi- -LAT as Electron Detector LAT as Electron Detector • Fermi-LAT reported a harder CR e - + e + spectrum compared with a conventional model compared with a conventional model – Lots of interpretations (astrophysical and exotic) … and the paper is highly cited 2009 Jan. – 2010 Sep. T. Mizuno et al. 12
Fermi_2011Mar.ppt Fermi Fermi LAT Fermi Fermi-LAT LAT LAT Instruments Instruments Instruments Instruments T. Mizuno et al. 13
Fermi_2011Mar.ppt Fermi Launch Fermi Launch • Launched on June 11, 2008 • Science Operation on Aug 4, 2008 • Orbit: 565 km, 26.5 o (low BG) 5-yr mission (10-yr goal) y g F rmi LAT GBM Fermi=LAT+GBM Cape Canaveral Air Station @ Florida T. Mizuno et al. 14
Fermi_2011Mar.ppt Fermi Fermi- -LAT Collaboration LAT Collaboration France Italy • Hiroshima Univ. • Tokyo Tech Tokyo Tech • ISAS/JAXA Japan • Waseda Univ. • Tokyo Univ. • Nagoya Univ. N U i Sweden • Aoyama Gakuin Univ. US US ~400 members T. Mizuno et al. 15
Fermi_2011Mar.ppt Large Area Telescope Large Area Telescope • Pair-conversion type γ -ray telescope 20 MeV- 300 GeV • Tracker: Si-strip detectors direction measurement ~200 um pitch => high precision tracking • ACD: plastic scintillators BG rejection BG j ti segmented tiles => prevent self-veto • Calorimeter: CsI scintillators Energy measurement Energy measurement hodoscopic crystals => shower profile T. Mizuno et al. 16
Fermi_2011Mar.ppt Large Area Telescope Large Area Telescope • Pair-conversion type γ -ray telescope • Tracker: Si-strip detectors direction measurement Key element of LAT developed by Key-element of LAT, developed by HPK and Hiroshima Univ. Low-noise (~2.5nA/cm2) High-quality (dead strip: <0.01%) g q y ( p ) SSD SSD ~10 6 channels in total T. Mizuno et al. 17
Fermi_2011Mar.ppt Performance of the LAT Performance of the LAT • Large FOV (2.4 sr) • Large Aeff (>=8000 cm2 in 1-100 GeV) L A ff (> 8000 2 i 1 100 G V) • Good PSF (0.6 deg@ 1GeV) sensitivity to point sources EGRET 3 rd Catalog 271 sources Fermi-LAT 1 st year catalog 1451 sources Atwood+09 T. Mizuno et al. 18
Fermi_2011Mar.ppt Science Breakthroughs of 2009 Science Breakthroughs of 2009 • Fermi is recognized as one of the top science breakthroughs science breakthroughs Science , December 2009 Discovery of 16 new pulsars T. Mizuno et al. 19
Fermi_2011Mar.ppt GeV GeV Gamma Gamma- -ray Sky by LAT ray Sky by LAT • and provides us with high-quality data! – γ -ray sources, diffuse γ -rays and more diff d >100 publications as of Feb. 2011 Fermi-LAT 1 year all-sky map T. Mizuno et al. 20
Fermi_2011Mar.ppt Diffuse γ rays as Diffuse γ -rays as Diffuse Diffuse rays as rays as probe of CRs and probe of CRs and probe of CRs and probe of CRs and ISM ISM ISM ISM T. Mizuno et al. 21
Fermi_2011Mar.ppt GeV “Non” Excess GeV “Non” Excess • Fermi does not confirm EGRET GeV excess l local (<= 1 kpc from the sun) l (< 1 k f th ) Diffuse Gamma-rays x Flux EGRET Fermi-LAT Fermi LAT E 2 Abdo+09, PRL 103, 251101 (CA: Johannesson, P Porter, Strong) t St ) 0.1 1 10 GeV T. Mizuno et al. 22
Fermi_2011Mar.ppt GeV “Non” Excess GeV “Non” Excess • Fermi does not confirm EGRET GeV excess Instead, data is compatible with a standard model Gamma = CR x (ISM, ISRF) x Flux EGRET Fermi LAT Fermi-LAT E 2 Γ ~ 2.7 Abdo+09 (CA: Johannesson, P Porter, Strong) t St ) 0.1 1 10 GeV T. Mizuno et al. 23
Fermi_2011Mar.ppt Diffuse γ s in the Outer Galaxy Diffuse s in the Outer Galaxy • Any unexpected in diffuse γ s? – Yes. New information on CRs and ISM Yes New information on CRs and ISM The outer Galaxy (from outside) sun L=90deg L=270deg II quad II quad III quad III quad L=180deg T. Mizuno et al. 24
Fermi_2011Mar.ppt Diffuse γ s in the Outer Galaxy Diffuse s in the Outer Galaxy • Any unexpected in diffuse γ s? – Yes. New information on CRs and ISM Yes New information on CRs and ISM The outer Galaxy (from the Fermi-LAT) Abdo+10 ApJ 710 133 Abdo+10, ApJ 710, 133 Ackermann+11, ApJ 726, 81 GC anticenter T. Mizuno et al. 25
Fermi_2011Mar.ppt ISM not visible by Standard Tracers ISM not visible by Standard Tracers • Fermi revealed ISM gas not traced by radio surveys Residual when fitted by N(H I )+CO excess gammas = residual gas = residual gas Ackermann+11, ApJ 726, 81 (CA: Grenier, Mizuno, Tibaldo) T. Mizuno et al. 26
Fermi_2011Mar.ppt ISM not visible by Standard Tracers ISM not visible by Standard Tracers • Fermi revealed ISM gas not traced by radio surveys – confirming an earlier claim based on EGRET study confirming an earlier claim based on EGRET study (Grenier+05) Residual when fitted by N(H I )+CO Residual gas inferred by dust Ackermann+11, ApJ 726, 81 (CA: Grenier, Mizuno, Tibaldo) T. Mizuno et al. 27
Fermi_2011Mar.ppt More CRs than Expected More CRs than Expected • Fermi detected more γ s (more CRs) than a prediction based on SNR distribution and standard CR halo based on SNR distribution and standard CR halo nsity -ray inte Gamma Sun Ackermann+11 ApJ 726, 81 (CA: Grenier, Mizuno, Tibaldo) Distance from GC (kpc) T. Mizuno et al. 28
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