Fermi_PIC2009.ppt Gamma- Gamma -Ray Particle Ray Particle Astrophysics: Astrophysics: Astrophysics: Astrophysics: the first year of the the first year of the Fermi Gamma-ray Fermi Gamma Fermi Gamma-ray Fermi Gamma ray ray Space Telescope Space Telescope Tsunefumi Tsunefumi Mizuno Mizuno Hiroshima Univ. Hiroshima Univ. on behalf of the Fermi on behalf of the Fermi Collaboration Collaboration September 02, 2009, Kobe, Japan September 02, 2009, Kobe, Japan Tsunefumi Mizuno 1
Fermi_PIC2009.ppt Plan of the Talk Plan of the Talk • Review of the high energy gamma-ray missions • Highlights of the Fermi’s first year results: g g y � Gamma-ray bursts � implication on fundamental physics and UHECRs � properties of jets with highest Γ t Γ � ti f j t ith hi h � Galactic cosmic-rays and dark matter � Direct measurement of Galactic cosmic-rays � Direct measurement of Galactic cosmic rays � Galactic diffuse gamma-rays as an indirect probe of Galactic CRs � Selected Galactic/extragalactic gamma-ray objects � focus on the relation to Galactic CRs and UHECRs Tsunefumi Mizuno 2
Fermi_PIC2009.ppt R Review of High-Energy Gamma Review of High R i i f Hi h f Hi h E Energy Gamma- E G G -ray ray Astrophysics Missions Astrophysics Missions p y p y Tsunefumi Mizuno 3
GeV Gamma-ray Astrophysics Fermi_PIC2009.ppt (E γ = a few 10s MeV to ~100 GeV) • 1967 to 1968 -- OSO-3 : First detection of γ -rays from the Gal. plane • 1972 to 1973 -- SAS-2 : Crab, Vela, and Geminga • 1975 to 1982 -- COS-B : >=20 γ -ray sources EGRET: (on the Compton Gamma Ray Observatory) 271 (>5 σ ) γ ray sources + detailed map of the Galaxy 271 (>5 σ ) γ -ray sources + detailed map of the Galaxy 1991 -- 2000 • 2007 to present -- AGILE • 2008 to present -- Fermi A new gamma-ray satellite every 10 or 15 years Tsunefumi Mizuno 4
Fermi_PIC2009.ppt TeV γ -ray Astrophysics with Atmospheric Cherenkov Imager Arrays (E γ >= 100 GeV) HESS galactic survey Nearly 100 sources under study. CANGAROO III, Australia CTA (2013~) MAGIC II, Canary H.E.S.S., Namibia islands, Spain VERITAS, Arizona, USA Very important but not covered by this talk. See, e.g., talk by Schwanke in PIC 08 Tsunefumi Mizuno 5
Fermi_PIC2009.ppt Fermi Launch Fermi Launch • Launched from Cape Canaveral Air Station on June 11, 2008 • Science Operation on Aug 4, 2009 Science Operation on Aug 4 2009 • Orbit: 565 km, 26.5 o (low BG) Tsunefumi Mizuno 6
Fermi_PIC2009.ppt Large Area Telescope (LAT) on Fermi Large Area Telescope (LAT) on Fermi 20 MeV to >= 300 GeV FOV: 2.4 sr • Tracker: Si-strip detectors & W converters Identification and direction measurement of γ -rays • Calorimeter: hodoscopic CsI scintillators Energy measurement • ACD: segmented plastic scintillators BG rejection j Technology developed through HEP experiments See Atwood et al. (ApJ 697, 1071, 2009) for detail Tsunefumi Mizuno 7
Fermi_PIC2009.ppt Gamma Gamma- -ray Burst Monitor (GBM) on Fermi ray Burst Monitor (GBM) on Fermi Views entire unocculted sky with • 12 NaI detectors: 8 keV - 1 MeV • 2 BGO detectors: 150 keV - 40 MeV LAT+GBM=> more than 7 decades of energy OK, let’s start with GRBs Tsunefumi Mizuno 8
Fermi_PIC2009.ppt st year (1): Highlights from Fermi’s 1 Highlights from Fermi’s 1 st g g g g y y year (1): ( ) ( ) Gamma Gamma- -ray Bursts ray Bursts Tsunefumi Mizuno 9
Fermi_PIC2009.ppt Gamma- Gamma -Ray Bursts Overview (1) Ray Bursts Overview (1) • Discovered in 1967 • Cosmological origin (BeppoSAX, BATSE) � Large apparent energy release: E iso ~ 10 52 - 10 54 erg � Large Lorentz factor of jet: Γ >= 100 (a few for μ -QSO and ~10 for AGN) f j t Γ > � L L t f t 100 ( f f QSO d 10 f AGN) � Energetics may be consistent with origin of UHECRs • Peak in ~ MeV gamma-rays � Band function: smoothly joins two power-laws � Band function: smoothly joins two power laws � Synchrotron radiation of ultra-relativistic electrons in jet? 0.01 0.1 1 10 100 MeV Tsunefumi Mizuno 10
Fermi_PIC2009.ppt Gamma Gamma- -Ray Bursts Overview (2) Ray Bursts Overview (2) 2 s • Bimodal distribution of duration time � Short (<2 s) GRB: progenitor unknown � Merger of NSs or BHs? � Long (>2 s) GRB: association with supernova � Core collapse supernovae � Core-collapse supernovae T 90 (duration) in seconds • Gamma-ray emission mechanism not fully understood yet • Fermi observation of GRBs is expected to � constrain the emission mechanism � constrain the bulk Lorentz factor of jet � constrain the bulk Lorentz factor of jet � limit on Lorentz invariance violation � search for the clue of UHECRs � probe the extragalactic background light (star formation in early p g g g ( y universe) Tsunefumi Mizuno 11
Fermi_PIC2009.ppt Fermi GRB Skymap Fermi GRB Skymap (as of Jun. 29, 2009) (as of Jun. 29, 2009) • 7 long + 2 short GRB by GBM+LAT, from 8 keV to tens of GeV • Short & long GRBs: similar phenomenology at high energy? Abdo et al. Sci.323, 1688 (2009) 241 GBM GRBs 9 LAT GRBs 9 LAT GRB 129 In Field-of-view of LAT Abdo et al., submitted to Nature (arXiv:0908.1832) Tsunefumi Mizuno 12
Fermi_PIC2009.ppt GRB080916C Prompt Emission (<=100s) GRB080916C Prompt Emission (<=100s) • z=4.35 +/- 0.15 (GROND; GCN8257) 8-260 keV • More than 3000 LAT photons, 145 above 100 MeV and 14 260 keV-5 MeV above 1 GeV • Delayed HE onset (1 st peak not seen > 100 MeV) LAT (all) Opacity effect ( γγ ->e + e - )? But no evidence of spectral cutoff • Single Band-function >100 MeV dominant for 6 decades of dominant for 6 decades of energy Lack of prominent SSC >1 GeV component implies high magnetic field or high γ e 0 20 40 60 80s Tsunefumi Mizuno 13
Fermi_PIC2009.ppt Long Long- -Lived HE Emission Lived HE Emission • HE (>100 MeV) emission shows different temporal behavior � Temporal break in LE emission while no break in HE emission � Cascades induced by ultra-relativistic ions? Cascades induced by ultra relativistic ions? � Angle-dependent scattering effects? Flux in LAT/GBM bands Flux in LAT/GBM bands • E>100 MeV index = -1.2 +/- 0.2 • E= 50 -300 keV i d index: ~-0.6 => ~-3.3 0 6 > 3 3 (at ~T0+55s) Photon Index (LAT only) no significant evolution no significant evolution (E peak gradually decreases) Tsunefumi Mizuno 14
Fermi_PIC2009.ppt Constraints on Bulk Lorentz Factor Constraints on Bulk Lorentz Factor • Large luminosity and short variability time imply large optical depth due to γγ -> e + e - (compactness problem) � Small emission region: R ~ c Δ t � τ γγ ( E ) ~ (11/180) σ T N >1/E /4 π R 2 � τ γγ (1 GeV) ~ 7x10 11 for a typical GRB of fluence=10 -6 erg/cm 2 , z =1, Δ t =1 s • Relativistic motion ( Γ >> 1) can reduce optical depth • Relativistic motion ( Γ >> 1) can reduce optical depth � Lager emission region: R ~ Γ 2 c Δ t � Reduced photon # densities: N >1/E � Γ 2 β +2 (note: β ~ -2.2) β ( ) � Blue shift of energy threshold: E th � Γ � Blue shift of spectrum: N ( E ) = ( Γ E ) β +1 N ( E ) = ( Γ E ) β +1 � Overall reduction of optical depth: Γ 2 β +2 / Γ 4= Γ 2 β -2 ∼Γ -6.4 (<=10 -12 for Γ =100) • Limit from GRB 080916C: Γ � 890 ± 21 ( Largest ever observed as of May 2009) Tsunefumi Mizuno 15
Fermi_PIC2009.ppt Limits on Lorentz Invariance Violation (LIV) Limits on Lorentz Invariance Violation (LIV) 16 5 16.5 s • Some QG models violate Lorentz invariance. A high-energy photon would arrive after a low-energy one would arrive after a low energy one emitted simultaneously. (Jacob & Piran 2008. n=1 for linear LIV) GRB080916C: G 0809 6C � 13.2 GeV @ T 0 +16.5 s � M QG, 1 > (1.5 ± 0.2) x 10 18 GeV/c 2, 1/10 of the Plank mass and the 1/10 of the Plank mass and the highest as of May 9, 2009. GRB080916C Planck mass Pulsar Pulsar GRB GRB AGN AGN GRB GRB AGN AGN min M QG i M (Kaaret 99) (Ellis 06) (Biller 98) (Boggs 04) (Aharonian 08) (GeV) 10 15 10 16 10 17 10 18 10 19 Tsunefumi Mizuno 16
Fermi_PIC2009.ppt GRB090510 (1) GRB090510 (1) Abdo et al. 2009 Submitted to Nature (arXiv:0908.1832) Tsunefumi Mizuno 17
Fermi_PIC2009.ppt GRB095010 (2) GRB095010 (2) • Time vs. photon energy 10 LAT all events E>100 MeV 1GeV • Short GRB with > 150 photons above Short GRB with > 150 photons above 100 MeV 0.1 • 31 GeV @ ~T0+0.83s 0.01 • Solid and dotted line are LIV for n=1 S lid d d tt d li LIV f 1 and 2, respectively • Several assumptions of t start indicated by different colors by different colors • Even the conservative case (black line) implies M QG, 1 > 1.19 M Planck • Other important findings � deviation from Band function � highest Epeak: 5.1 MeV (Band+PL model fit) model fit) � delayed onset of LAT emission by 0.1- 0.2 s � highest Γ min (~1200) Tsunefumi Mizuno 18 0 0.5 1 1.5 2 (s)
Fermi_PIC2009.ppt st year (2): Highlights from Fermi’s 1 Highlights from Fermi’s 1 st year (2): Direct Measurements of Galactic Direct Measurements of Galactic Direct Measurements of Galactic Direct Measurements of Galactic CR Electrons CR Electrons Tsunefumi Mizuno 19
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