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 Physical Society Meeting Konan University, Japan
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 Fermi Prospect Japan Physical Society Meeting, SEP 12, 2009, Konan Univ. Japan 2 /22
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 l ʼ Energie 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 Fermi Prospect Japan Physical Society Meeting, SEP 12, 2009, Konan Univ. Japan 3 /22
Predecessor, EGRET ✤ EGRET: 1991–2000 ❖ 271 gamma-ray sources (Hartman et al. 1999) • Only 38% (101 sources) have clear “identifications” EGRET all-sky (galactic coordinates) E>100 MeV Fermi Prospect Japan Physical Society Meeting, SEP 12, 2009, Konan Univ. Japan 4 /22
The LAT 3 Month All-Sky Map ✤ 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 3 month LAT all-sky E>200 MeV arXiv:0902.1340 Fermi Prospect Japan Physical Society Meeting, SEP 12, 2009, Konan Univ. Japan 5 /22
LAT Bright AGN Sample (LBAS) ✤ 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°) FSRQ BLLac Uncertain Radio galaxies 57 FSRQ 42 BL Lac 6 of Uncertain class 2 Radio Galaxies Fermi Prospect Japan Physical Society Meeting, SEP 12, 2009, Konan Univ. Japan 6 /22
Source Associations +90 Class Number FSRQ 62 180 1 8 2 90 0 7 0 0 BL Lac 46 Radio galaxy 11 Other blazar 2 Radio/X-ray pulsar 15 � 90 LAT γ -ray pulsar 14 Unassociated AGN Pulsar X � ray binary Globular cluster HMXB 2 Globular cluster 1 Θ 95% ~0.14° LMC 1 (EGRET ~0.62°) 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 Fermi Prospect Japan Physical Society Meeting, SEP 12, 2009, Konan Univ. Japan 7 /22
Source Associations +90 Class Number 30 Galactic Latitude [deg] FSRQ 62 15 180 1 8 2 90 0 7 0 0 BL Lac 46 0 Radio galaxy 11 � 15 � 30 Other blazar 2 90 75 60 45 30 15 0 345 330 315 300 285 270 Galactic Longitude [deg] Radio/X-ray pulsar 15 � 90 LAT γ -ray pulsar 14 Unassociated AGN Pulsar X � ray binary Globular cluster HMXB 2 Globular cluster 1 Θ 95% ~0.14° LMC 1 (EGRET ~0.62°) 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 Fermi Prospect Japan Physical Society Meeting, SEP 12, 2009, Konan Univ. Japan 7 /22
Cosmic Particle Accelerators ✤ 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 8 /22
High-Energy Emissions from GRB (Past) ✤ EGRET observations of delayed Gonzalez, Nature 2003 424, 749 HE gamma-ray emissions ❖ It is not straightforward to explain by -18 – 14s conventional electron synchrotron models EGRET/TASC ❖ Proton acceleration? BATSE 14 – 47s Origin of UHECR? 47 – 80s Hurley et al. 1994 Two γ >GeV @~T 0 80 – 113s 18 GeV γ @ ~T 0 +75 min 113 – 211s Fermi Prospect Japan Physical Society Meeting, SEP 12, 2009, Konan Univ. Japan 9 /22
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 Dingus et al. 1997 Composite spectrum of 5 EGRET Bursts Fermi Prospect Japan Physical Society Meeting, SEP 12, 2009, Konan Univ. Japan 10 /22
Common Feature of LAT GRBs # of events # of events delayed Long-lived Extra HE GRB duration Redshift > 100 MeV > 1 GeV HE onset HE emission component ✔ ✔ 080825C long ~10 0 — ✔ ✔ 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 Fermi Prospect Japan Physical Society Meeting, SEP 12, 2009, Konan Univ. Japan 11 /22
LAT Localization ✤ Precise LAT localization is critical for successful follow-up observations of afterglow inclination LAT stat. measured GRB 080916C GRB Redshift angle error error 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 Fermi Prospect Japan Physical Society Meeting, SEP 12, 2009, Konan Univ. Japan 12 /22
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 • τ γγ ~ 3.6 for 13 GeV @ z=4.35, τ γγ ~ 5.7 for 33 GeV @ z=1.82 with Stecker model Fermi Prospect Japan Physical Society Meeting, SEP 12, 2009, Konan Univ. Japan 13 /22
SNR/PWN Associations with LAT ✤ Potential associations in LAT 3-month bright source list Age Molecular 0FGL Name l b Associations (x10 3 y) 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) ? ✔ 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 ✔ J1923.0+1411 49.13 -0.40 SNR G49.2-0.7 (W51C) ~20 X J1954.4+2838 65.30 0.38 SNR G65.1+0.6 40~140 ✤ 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 14 /22
Fermi Observations of SNR ✤ Common feature of potential SNRs observed by Fermi ❖ Middle aged SNRs (~10 4 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) Fermi Prospect Japan Physical Society Meeting, SEP 12, 2009, Konan Univ. Japan 15 /22
Recommend
More recommend
