Diffuse Gamma-Ray Emission

Su Yang

2010.1.12

•Telescopes

•Examples

•Our work

• angular resolution: 0.1d@1TeV, 0.14d@200 GeV (68% containment radius)

• energy range: 100 GeV to >30 TeV • energy resolution: 15% at 1 TeV• source location accuracy: 50’’

VERITAS (Very Energetic Radiation Imaging Telescope Array System): 4*12*345

• energy resolution: 15% (Index~0.1; Flux~20%)• energy range: 0.1-10 TeV• PSF: 0.03/0.06d• FOV: 5d

H.E.S.S. (High Energy Stereoscopic System): 4*13*382

• CR density (M82)~500*CR density (our Galaxy): SNe & Winds from massive stars

Chandra;Spitzer; Hubble;

Fermi (PSR J2229+6114) 3EG J2227+6122

CO (-6, -4 km/s)

Radio

SNR G106.3+2.7 (60*24’; D~0.8kpc; Boomerang)

0.4d

Fermi

OH

CO (-20,20km/s)

PWN

Radio

Magic

IC443: 1.5kpc, 45’; CXOU J061705.3+222127;

(VER J0616.9+2230 ~ Magic J0616+225 ~ Milagro; 0FGL J0617.4+2234 ~ 3EG J0617+2238; )

EGRET

• IC: L(0.3-2.0TeV)~4E32 erg/sE (rotation)~1-50E36 erg/s

• Synchrotron cooling:Time (E)~ 1.3E7 (B/uG)-2 (E/GeV)-1 kyrE(electron)~20TeV, B~5uG Time~30 kyr(Abdo et al., 2010, B(Cas A)>=0.1mG)

• Hadronic CRs Particles were accelerated prior to the shock h

itting the MC ？ Or an energy-dependent rate of diffusion of CR

s out of the MC ？

VERITAS

HESS

EGRET+GLAST

VERITAS

(Northern Sky)

AGN, BIN, PWN, starburst galaxy, SNR, UNID

Fermi (GLAST: Gamma-ray Large Area Space Telescope): 2008-06-11

>9000 sources 271 sources

1-10GeV excess?

Dark Matter? Variations of the Galaxy’s CR spectra? Unresolved point sources? Instrumental effects?

10-15%

The DGE (diffuse Galactic emission): CRs (protons, electrons) the ISM (Pi0-decay + bremsstrahlung), and radiation field (IC);

(Abdo et al., 2010, B(Cas A)>=0.1mG)

(Abdo et al., 2010, B(Cas A)>=0.1mG)

Leptonic model Hadronic model

1, The Fermi Gamma-Ray Space Telescope Discovers the Pulsar in the Young Galactic Supernova Remnant CTA 1. Science, 2008, 322, 1218 2, Discovery of Pulsed gamma-Rays from the Young Radio Pulsar PSR J1028–5819 with the Fermi Large Area Telescope. ApJ, 2009, 695, L72 3, Fermi Large Area Telescope Observations of the Vela Pulsar. ApJ, 2009, 696, 1084 4, Measurement of the Cosmic Ray e++e- Spectrum from 20GeV to 1TeV with the Fermi Large Area Telescope. PRL, 2009, 102, 1101 5, Pulsed Gamma Rays from the Millisecond Pulsar J0030+0451 with the Fermi Large Area Telescope. ApJ, 2009, 699, 1171 6, Discovery of Pulsations from the Pulsar J0205+6449 in SNR 3C 58 with the Fermi Gamma-Ray Space Telescope. ApJ, 2009, 699, L102 7, Pulsed Gamma-rays from PSR J2021+3651 with the Fermi Large Area Telescope. ApJ, 2009, 700, 1059 8, Detection of 16 Gamma-Ray Pulsars Through Blind Frequency Searches Using the Fermi LAT. Science, 2009, 325, 8409, Pulsed Gamma-rays from PSR J2021+3651 with the Fermi Large Area Telescope. ApJ, 2009, 700, 1059 10, Fermi LAT Observation of Diffuse Gamma Rays Produced Through Interactions Between Local Interstellar Matter and High-energy Cosmic Rays. ApJ, 2009, 703, 1249