Prospect of Gamma-ray Astrophysics by Fermi Gamma-ray Space - - PowerPoint PPT Presentation

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Prospect of Gamma-ray Astrophysics by Fermi Gamma-ray Space - - PowerPoint PPT Presentation

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Prospect of Gamma-ray Astrophysics by Fermi Gamma-ray Space Telescope Hiroyasu Tajima on behalf of Fermi LAT and GBM Collaborations KIPAC SLAC National Accelerator Laboratory (Stanford Linear Accelerator Center) September 12, 2009 Japan

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September 12, 2009 Japan Physical Society Meeting Konan University, Japan

Hiroyasu Tajima

  • n behalf of Fermi LAT and GBM Collaborations

KIPAC SLAC National Accelerator Laboratory (Stanford Linear Accelerator Center)

Prospect of Gamma-ray Astrophysics by Fermi Gamma-ray Space Telescope

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Fermi Prospect Japan Physical Society Meeting, SEP 12, 2009, Konan Univ. Japan

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Outline

✤ Introduction

❖ LAT bright source list ❖ LAT bright AGN sample

✤ Cosmic ray origins

❖ Gamma-ray bursts ❖ Supernova remnants

✤ Dark matter search

❖ Cosmic-ray electrons ❖ Extragalactic diffuse gamma-ray emission

✤ Extragalactic background light (EBL) ✤ This is not a comprehensive list of prospects for astrophysics

explored by Fermi

Note: All results in this talk are preliminary unless published

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Fermi Prospect Japan Physical Society Meeting, SEP 12, 2009, Konan Univ. Japan

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Fermi/LAT Collaboration

Stanford University & SLAC NASA Goddard Space Flight Center Naval Research Laboratory University of California at Santa Cruz Sonoma State University University of Washington Purdue Univeristy-Calumet Ohio State University University of Denver Commissariat a lʼEnergie Atomique, Saclay CNRS/IN2P3 (CENBG-Bordeaux, LLR-Ecole polytechnique, LPTA-Montpellier) Hiroshima University Institute of Space and Astronautical Science Tokyo Institute of Technology RIKEN Instituto Nazionale di Fisica Nucleare Agenzia Spaziale Italiana Istituto di Astrofisica Spaziale e Fisica Cosmica Royal Institute of Technology, Stockholm Stockholms Universitet

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✤ EGRET: 1991–2000

❖ 271 gamma-ray sources (Hartman et al. 1999)

  • Only 38% (101 sources) have clear “identifications”

Fermi Prospect Japan Physical Society Meeting, SEP 12, 2009, Konan Univ. Japan

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Predecessor, EGRET

EGRET all-sky (galactic coordinates) E>100 MeV

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✤ Fermi LAT 3-month bright gamma-ray source list ≠ catalog

❖ 207 sources above TS=100 (444 sources above TS=25) ❖ Large number of citation (~60)

✤ LAT one-year catalog (based on 11-month data) soon

❖ ~1000s of sources expected

Fermi Prospect Japan Physical Society Meeting, SEP 12, 2009, Konan Univ. Japan

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The LAT 3 Month All-Sky Map

3 month arXiv:0902.1340 LAT all-sky E>200 MeV

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✤ 125 non-pulsar sources at |b|>10° ✤ 106 high-confidence (P>90%) associations with AGNs

❖ 11 lower-confidence (40%<P<90%) associations ❖ 9 unidentified (3EG: 96/181 at |b|>10°)

Fermi Prospect Japan Physical Society Meeting, SEP 12, 2009, Konan Univ. Japan

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LAT Bright AGN Sample (LBAS)

57 FSRQ 42 BL Lac 6 of Uncertain class 2 Radio Galaxies 6

FSRQ BLLac Uncertain Radio galaxies

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Fermi Prospect Japan Physical Society Meeting, SEP 12, 2009, Konan Univ. Japan

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Source Associations

Θ95% ~0.14° (EGRET ~0.62°)

90 2 7 1 8 180

+90 90 Unassociated AGN Pulsar Xray binary Globular cluster

Class Number FSRQ 62 BL Lac 46 Radio galaxy 11 Other blazar 2 Radio/X-ray pulsar 15 LAT γ-ray pulsar 14 HMXB 2 Globular cluster 1 LMC 1 Special cases 13 Unidentified 38

✤ >80% of sources have “associations”:

121 AGN class, 29 pulsars

✤ Thanks to better angular resolution

⇒ better localization and S/B

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Fermi Prospect Japan Physical Society Meeting, SEP 12, 2009, Konan Univ. Japan

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Source Associations

Θ95% ~0.14° (EGRET ~0.62°)

90 2 7 1 8 180

+90 90 Unassociated AGN Pulsar Xray binary Globular cluster

Class Number FSRQ 62 BL Lac 46 Radio galaxy 11 Other blazar 2 Radio/X-ray pulsar 15 LAT γ-ray pulsar 14 HMXB 2 Globular cluster 1 LMC 1 Special cases 13 Unidentified 38

270 285 300 315 330 345 15 30 45 60 75 90 30 15 15 30 Galactic Longitude [deg] Galactic Latitude [deg]

✤ >80% of sources have “associations”:

121 AGN class, 29 pulsars

✤ Thanks to better angular resolution

⇒ better localization and S/B

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✤ Origin of cosmic ray protons?

❖ Galactic SNRs (Supernova Remnants) are considered as the best

candidates for cosmic-rays below “Knee”

  • Only circumstantial evidence
  • Diffusive shock acceleration

(Blanford&Eichler 1977)

  • CR energy sum consistent

with SNR kinetic energy (Ginzburg&Syrovatskii 1964)

  • No observational evidence

for hadronic acceleration

  • Spectral index (~2.7) is difficult to explain

❖ Cosmic-rays above “Knee” are

considered extragalactic

  • Gamma-ray bursts (GRB)
  • Active Galactic Nuclei (blazar)
  • Merging galaxy clusters

Fermi Prospect Japan Physical Society Meeting, SEP 12, 2009, Konan Univ. Japan

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Cosmic Particle Accelerators

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Fermi Prospect Japan Physical Society Meeting, SEP 12, 2009, Konan Univ. Japan

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High-Energy Emissions from GRB (Past)

✤ EGRET observations of delayed

HE gamma-ray emissions

❖ It is not straightforward to explain by

conventional electron synchrotron models

❖ Proton acceleration?

Origin of UHECR?

  • 18 – 14s

14 – 47s 47 – 80s 80 – 113s 113 – 211s Gonzalez, Nature 2003 424, 749

EGRET/TASC BATSE

Two γ >GeV @~T0 Hurley et al. 1994 18 GeV γ @ ~T0+75 min

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Fermi Prospect Japan Physical Society Meeting, SEP 12, 2009, Konan Univ. Japan

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EGRET High-Energy GRB Spectra

✤ 5 EGRET bursts with >50 MeV observations in 7 years

❖ No evidence of cutoff or extra HE component in the summed

spectrum

Composite spectrum of 5 EGRET Bursts Dingus et al. 1997

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Fermi Prospect Japan Physical Society Meeting, SEP 12, 2009, Konan Univ. Japan

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Common Feature of LAT GRBs

GRB duration # of events > 100 MeV # of events > 1 GeV delayed HE onset Long-lived HE emission Extra HE component Redshift 080825C long ~10 ✔ ✔ — 080916C long >200 >10 ✔ ✔ hint 4.35 081024B short ~10 2 ✔ ✔ — 081215A long — — — — — 90217 long — — — — — 90323 long >10 >0 — ✔ — 3.57 90328 long >10 — — ✔ — 0.736 90510 short >150 >20 ✔ ✔ ✔ 0.903 90626 long — — — ✔ — 090902B long >200 >20 — — ✔ 1.82

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Fermi Prospect Japan Physical Society Meeting, SEP 12, 2009, Konan Univ. Japan

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LAT Localization

✤ Precise LAT localization is critical for successful follow-up

  • bservations of afterglow

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GRB inclination angle LAT stat. error measured error Redshift 080916C 52 0.09 0.05 4.35 90323 55 0.09 0.03 3.57 90328 65 0.11 0.17 0.736 90510 12 0.11 0.23 0.903 090902B 51 0.04 0.05 1.82

GRB 080916C

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Fermi Prospect Japan Physical Society Meeting, SEP 12, 2009, Konan Univ. Japan

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GRB Summary and Prospect

✤ The delayed onset of the LAT emission suggests a separate

region from initial GBM emission

✤ Different behaviors of HE emission from LE emission may indicate

separate emission mechanisms

✤ Extra HE component! ✤ Stimulated significant interest (# of citation for 080916C: ~50) ✤ In GRB 090510 (@ z~0.95):

❖ Highest bulk Lorentz factor measured (≳ 1200) ❖ Most stringent constraint on violation of Lorentz invariance

  • Simple linear dispersion relation disfavored: mass scale > Planck mass
  • Constraints on other dispersion relation is far below Planck mass

✤ More GRBs (~2 bright GRB/year) with better inclination angle

❖ Further constraints on HE gamma-ray emission process

  • Origin of UHE cosmic ray?

❖ EBL (Extragalactic background light) implications

  • τγγ ~ 3.6 for 13 GeV @ z=4.35, τγγ ~ 5.7 for 33 GeV @ z=1.82

with Stecker model

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✤ Potential associations in LAT 3-month bright source list ✤ It is very hard to distinguish SNRs, PWNe and pulsars

❖ Source confusions due to SNR/PWN/pulsar in close vicinity ❖ One of useful tool is morphological identification

Fermi Prospect Japan Physical Society Meeting, SEP 12, 2009, Konan Univ. Japan

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SNR/PWN Associations with LAT

0FGL Name l b Associations Age (x103 y) Molecular clouds J0617.4+2234 189.08 3.07 SNR G189.1+3.0 (IC 443) 3~30 ✔ J1018.2-5858 284.30 -1.76 SNR G284.3-1.8 (MSH 10-53), PSR J1013-5915 ~10 ✔ J1196.4-6055 290.52 -0.60 SNR G290.1-0.8 (MSH 11-61A), PSR J1105-6107 10~20

✔

J1615.6-5049 332.35 -0.01 SNR G332.4+0.1 (MSH 16-51), PWN G332.5-0.28, PSR B1610-50 ~5

?

J1648.1-4606 339.47 -0.71 PSR J1648-4611 J1714.7-3827 348.52 0.10 SNR G348.5+0.1 (CTB37A) ?

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J1801.6-2327 6.54 -0.31 SNR G6.4-0.1 (W28) 35~150

✔

J1814.3-1739 13.05 -0.09 PWN G12.82-0.02 J1834.4-0841 23.27 -0.22 SNR G23.3-0.3 (W41) 148?

✔

J1855.9+0126 34.72 -0.35 SNR G34.7-0.4 (W44) ~20

✔

J1911.0+0905 43.25 -0.18 SNR G43.3-0.2 (W49B) 1~4

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J1923.0+1411 49.13 -0.40 SNR G49.2-0.7 (W51C) ~20

✔

J1954.4+2838 65.30 0.38 SNR G65.1+0.6 40~140

X

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Fermi Prospect Japan Physical Society Meeting, SEP 12, 2009, Konan Univ. Japan

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Fermi Observations of SNR

✤ Common feature of potential SNRs observed by Fermi

❖ Middle aged SNRs (~104 years) ❖ Interacting with molecular clouds ❖ Spectrum steepening between GeV and TeV?

  • Faint in TeV band (compared with GeV)

✤ SNR observed by Fermi may give new clues on

❖ Evolution of cosmic ray acceleration with aging SNR ❖ Effect on cosmic ray acceleration

from interacting molecular clouds

✤ Ensemble of SNRs with different cutoff

may explain cosmic ray spectral index of ~2.7

❖ Shock acceleration @ ~2.0 ❖ Propagation effect is not sufficient

to describe the difference

❖ Note: #(middle aged SNRs) >> #(young SNR)

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Fermi Prospect Japan Physical Society Meeting, SEP 12, 2009, Konan Univ. Japan

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LAT Dark Matter Search

✤ Detection of dark matter signal from Space is complementary

❖ Direct detection and accelerator production

✤ Mutil-pronged approaches

❖ Line emission, Continuum ❖ Galactic center, Milky Way halo, Satellites ❖ CR electrons, Diffuse gamma-ray background

16 Galactic center: Good Statistics but source confusion/diffuse background Satellites: Low background and good source id, but low statistics, astrophysical background Good Statistics but source confusion/diffuse background Milky Way halo: Large statistics but diffuse background

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❖ Modeling of galactic diffuse is critical

for studies of galactic sources including DM sources

Fermi Prospect Japan Physical Society Meeting, SEP 12, 2009, Konan Univ. Japan

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LAT Observation Galactic Diffuse

Preliminary Preliminary π0 decay Inverse Compton Brems Sources isotropic π0 decay (HI) Inverse Compton Brems π0 decay (H2) isotropic

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Fermi Prospect Japan Physical Society Meeting, SEP 12, 2009, Konan Univ. Japan

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LAT DM Search Prospects

✤ GC: Current ULs without BG subtraction

❖ Proper removal of sources to lower ULs (or find signal)

  • Image deconvolution to resolve source confusions

✤ Subhalo

❖ Search for extended sources in high galactic latitude

  • New tool developed to evaluate source extension quantitatively
  • 1~3 detection/year at 5σ significance
  • NFW consistent, no molecular cloud, spectral feature, stable

❖ Known dwarf spheroidal galaxies (dSph)

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Fermi Prospect Japan Physical Society Meeting, SEP 12, 2009, Konan Univ. Japan

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Cosmic-ray Electron

✤ Recent report by ATIC indicates high energy excess

❖ Could be interpreted as evidence of dark matter

✤ LAT can measure CR electron spectrum with high statistics

❖ All events above ~20 GeV are sent to ground ❖ Hadron rejection > 103, large effective area, long observation

✤ # of citations: ~130 ✤ Next step

❖ Extend lower-end

to ~ 5 GeV

  • Low energy region using

minimum bias events

❖ Extend higher-end

to ~2 TeV

  • Confirm a feature
  • bserved by H.E.S.S.

❖ Anisotropy measurement

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Fermi Prospect Japan Physical Society Meeting, SEP 12, 2009, Konan Univ. Japan

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Cosmic-ray Electron

✤ Recent report by ATIC indicates high energy excess

❖ Could be interpreted as evidence of dark matter

✤ LAT can measure CR electron spectrum with high statistics

❖ All events above ~20 GeV are sent to ground ❖ Hadron rejection > 103, large effective area, long observation

✤ # of citations: ~130 ✤ Next step

❖ Extend lower-end

to ~ 5 GeV

  • Low energy region using

minimum bias events

❖ Extend higher-end

to ~2 TeV

  • Confirm a feature
  • bserved by H.E.S.S.

❖ Anisotropy measurement

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Fermi Prospect Japan Physical Society Meeting, SEP 12, 2009, Konan Univ. Japan

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Cosmic-ray Electron

✤ Recent report by ATIC indicates high energy excess

❖ Could be interpreted as evidence of dark matter

✤ LAT can measure CR electron spectrum with high statistics

❖ All events above ~20 GeV are sent to ground ❖ Hadron rejection > 103, large effective area, long observation

✤ # of citations: ~130 ✤ Next step

❖ Extend lower-end

to ~ 5 GeV

  • Low energy region using

minimum bias events

❖ Extend higher-end

to ~2 TeV

  • Confirm a feature
  • bserved by H.E.S.S.

❖ Anisotropy measurement

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Fermi Prospect Japan Physical Society Meeting, SEP 12, 2009, Konan Univ. Japan

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Extragalactic Diffuse Gamma-ray BG

✤ Mostly due to unresolved sources ✤ Truly diffuse emission may arise from UCHE CRs interactions,

WIMP annihilation, large scale structure formation

✤ Consistent with sum of blazars

❖ Spectrum is compatible with a power law of index γ=2.45 ❖ logN-logS indicates 20–100% of EGB can be accounted for

✤ Flux will decrease as more source are resolved

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✤ EBL is sensitive to star formation history

❖ Complementary to deep galaxy survey

✤ HE gamma rays are sensitive to EBL in IR to UV band

via γγ → e+e− process

❖ EBL will steepen AGN/GRB/EGB spectra above > 10 GeV

Fermi Prospect Japan Physical Society Meeting, SEP 12, 2009, Konan Univ. Japan

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Extragalactic Background Light

21 Hopkins et al. 2007, fesc=0.10 S&B Model ʻCʼ, f=0.02

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Probing EBL with AGN and GRB

✤ Requires many sources at various redshifts to untangle EBL

effect and intrinsic spectra

❖ Fermi will have ~1000 of blazars and ~100 of GRBs with redshift

✤ Distinguish competing models

❖ Observation of 13.2 GeV @ z=4.35, 33.4 GeV @ z=1.82

  • τγγ highly model dependent: 0.03 – 6 ➡ transparency: 100 – 0.3%

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  • Kneiske et al.

(2004) Best Fit Gilmore et al. (2008) Stecker et al. (2006) Baseline Stecker et al. (2006) Fast Evolution Razzaque et al. (2008) z = 4.35

33.4 GeV 13.2 GeV

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Fermi Prospect Japan Physical Society Meeting, SEP 12, 2009, Konan Univ. Japan

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Summary

✤ Fermi LAT demonstrating very exciting science in an early stage

  • f its operations

❖ Already surpassing EGRET in many area

✤ Very exciting science ahead of us ✤ Data are now public

❖ Even data for 090902B are available (while we were writing GCN)

✤ 2nd International Fermi Symposium in Nov/2-5 2009 at DC

❖ http://fermi.gsfc.nasa.gov/science/symposium/2009/

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Fermi Prospect Japan Physical Society Meeting, SEP 12, 2009, Konan Univ. Japan

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Galaxy Clusters

✤ Cosmic rays in galaxy cluster

❖ Origin of UHE cosmic ray due to large scale shock acceleration? ❖ Effect on galaxy cluster formation

✤ Dark matter can also contribute to gamma ray emission ✤ 15 clusters with highest predicted γ-ray flux [Pfrommer 2008]

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Perseus AWM7 Ophiuchu Triangulu NGC5846 Fornax Centauru Hydra A0754 NGC4636 A1367 M49 Coma 3C129 1-month count map Norma

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Upper Limits on Gamma rays from GC

✤ Fermi upper limits on gamma-ray fluxes from galaxy clusters

❖ Improved sensitivity over EGRET for each cluster ❖ Limits are comparable to theoretical predictions of brightest

clusters

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