Tsunefumi Mizuno 1

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Gamma-Ray Particle Gamma-Ray Particle Astrophysics:Astrophysics:

the first year of the the first year of the Fermi Gamma-ray Fermi Gamma-ray Space TelescopeSpace Telescope

Tsunefumi MizunoTsunefumi MizunoHiroshima Univ.Hiroshima Univ.

on behalf of the Fermi on behalf of the Fermi CollaborationCollaboration

September 02, 2009, Kobe, JapanSeptember 02, 2009, Kobe, Japan

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Plan of the Talk Plan of the Talk

• Review of the high energy gamma-ray missions• Highlights of the Fermi’s first year results:

Gamma-ray bursts implication on fundamental physics and UHECRs properties of jets with highest

Galactic cosmic-rays and dark matter 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

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Review of High-Energy Gamma-ray Review of High-Energy Gamma-ray Astrophysics MissionsAstrophysics Missions

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Fermi_PIC2009.pptGeV Gamma-ray Astrophysics(E = a few 10s MeV to ~100 GeV)

• 1967 to 1968 -- OSO-3 : First detection of -rays from the Gal. plane• 1972 to 1973 -- SAS-2 : Crab, Vela, and Geminga• 1975 to 1982 -- COS-B : >=20 -ray sources

EGRET:(on the Compton Gamma Ray Observatory)271 (>5) -ray sources + detailed map of the Galaxy

1991 -- 2000

A new gamma-ray satellite every 10 or 15 years

• 2007 to present -- AGILE• 2008 to present -- Fermi

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H.E.S.S., Namibia

CANGAROO III, Australia

MAGIC II, Canary islands, Spain

VERITAS, Arizona, USA

HESS galactic survey

Nearly 100 sources under study.

TeV -ray Astrophysics withAtmospheric Cherenkov Imager Arrays (E >= 100 GeV)

Very important but not covered by this talk. See, e.g., talk by Schwanke in PIC 08

CTA (2013~)

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Fermi LaunchFermi Launch

• Launched from Cape Canaveral Air Station on June 11, 2008• Science Operation on Aug 4, 2009• Orbit: 565 km, 26.5o (low BG)

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Large Area Telescope (LAT) on FermiLarge Area Telescope (LAT) on Fermi

• Tracker: Si-strip detectors & W convertersIdentification and direction measurement of -rays

• Calorimeter: hodoscopic CsI scintillatorsEnergy measurement

• ACD: segmented plastic scintillatorsBG rejection

Technology developed through HEP experimentsSee Atwood et al. (ApJ 697, 1071, 2009) for detail

20 MeV to >= 300 GeVFOV: 2.4 sr

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Gamma-ray Burst Monitor (GBM) on FermiGamma-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

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Highlights from Fermi’s 1Highlights from Fermi’s 1stst year (1): year (1): Gamma-ray BurstsGamma-ray Bursts

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Gamma-Ray Bursts Overview (1)Gamma-Ray Bursts Overview (1)

• Discovered in 1967• Cosmological origin (BeppoSAX, BATSE)

Large apparent energy release: Eiso ~ 1052 - 1054 erg Large Lorentz factor of jet: >= 100 (a few for -QSO and ~10 for AGN) Energetics may be consistent with origin of UHECRs

• Peak in ~ MeV gamma-rays Band function: smoothly joins two power-laws Synchrotron radiation of ultra-relativistic electrons in jet?

0.01 0.1 1 10 100 MeV

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Gamma-Ray Bursts Overview (2)Gamma-Ray Bursts Overview (2)

2 s

T90 (duration) in seconds

• 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

• 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 limit on Lorentz invariance violation search for the clue of UHECRs probe the extragalactic background light (star formation in early universe)

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241 GBM GRBs9 LAT GRBs129 In Field-of-view of LAT

Fermi GRB Skymap (as of Jun. 29, 2009)Fermi GRB Skymap (as of Jun. 29, 2009)

Abdo et al.Sci.323, 1688 (2009)

Abdo et al., submitted to Nature(arXiv:0908.1832)

• 7 long + 2 short GRB by GBM+LAT, from 8 keV to tens of GeV• Short & long GRBs: similar phenomenology at high energy?

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GRB080916C Prompt Emission (<=100s)GRB080916C Prompt Emission (<=100s)• z=4.35 +/- 0.15 (GROND; GCN8257)

• More than 3000 LAT photons, 145 above 100 MeV and 14 above 1 GeV

• Delayed HE onset (1st peak not seen > 100 MeV)

Opacity effect (->e+e-)? But no evidence of spectral cutoff

• Single Band-function dominant for 6 decades of energy

Lack of prominent SSC component implies high magnetic field or high e

8-260 keV

260 keV-5 MeV

LAT (all)

>100 MeV

>1 GeV

0 20 40 60 80s

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Long-Lived HE EmissionLong-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? Angle-dependent scattering effects?

Flux in LAT/GBM bands• E>100 MeV

index = -1.2 +/- 0.2• E= 50 -300 keV

index: ~-0.6 => ~-3.3(at ~T0+55s)

Photon Index (LAT only)no significant evolution (Epeak gradually decreases)

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Constraints on Bulk Lorentz FactorConstraints on Bulk Lorentz Factor• Large luminosity and short variability time imply large optical depth due to -> e+e- (compactness problem)

Small emission region: R ~ ct (E) ~ (11/180)TN>1/E/4R2

(1 GeV) ~ 7x1011 for a typical GRB of fluence=10-6 erg/cm2, z=1, t=1 s

• Relativistic motion ( >> 1) can reduce optical depth Lager emission region: R ~ 2ct Reduced photon # densities: N>1/E ∝ 2+2 (note: ~ -2.2)

Blue shift of energy threshold: Eth ∝ Blue shift of spectrum: N(E) = (E)+1

Overall reduction of optical depth:2+2 / 2-2-6.4 (<=10-12 for =100)

• Limit from GRB 080916C: 890±21≳ (Largest ever observed as of May 2009)

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Limits on Lorentz Invariance Violation (LIV)Limits on Lorentz Invariance Violation (LIV)

GRB080916C: 13.2 GeV @ T0+16.5 s MQG, 1 > (1.5±0.2) x 1018 GeV/c2, 1/10 of the Plank mass and the highest as of May 9, 2009.

min MQG

(GeV)

Pulsar

(Kaaret 99)

GRB

(Ellis 06)

GRB

(Boggs 04)

AGN

(Biller 98)

AGN

(Aharonian 08)

GRB080916C Planck mass

1015 1016 1017 1018 1019

• Some QG models violate Lorentz invariance. A high-energy photon would arrive after a low-energy one emitted simultaneously.

(Jacob & Piran 2008. n=1 for linear LIV)

16.5 s

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GRB090510 (1)GRB090510 (1)

Abdo et al. 2009Submitted to Nature(arXiv:0908.1832)

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GRB095010 (2)GRB095010 (2)

0 0.5 1 1.5 2 (s)

10

1GeV

0.1

0.01

• Time vs. photon energyLAT all eventsE>100 MeV

• Short GRB with > 150 photons above 100 MeV• 31 GeV @ ~T0+0.83s

• Solid and dotted line are LIV for n=1 and 2, respectively• Several assumptions of tstart indicated by different colors

• Even the conservative case (black line) implies MQG, 1 > 1.19 MPlanck

• Other important findings deviation from Band function highest Epeak: 5.1 MeV (Band+PL model fit) delayed onset of LAT emission by 0.1-0.2 s highest min (~1200)

Preliminary

Preliminary

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Highlights from Fermi’s 1Highlights from Fermi’s 1stst year (2): year (2): Direct Measurements of Galactic Direct Measurements of Galactic

CR ElectronsCR Electrons

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Fermi_PIC2009.pptIntroduction (1):Introduction (1):What Can We Learn from HE eWhat Can We Learn from HE e--/e/e++ and p/p ? and p/p ?

• Inclusive spectra: e- + e+ Electrons, unlike protons, lose energy rapidly by Synchrotron and Inverse Compton: at very high energy they probe the nearby sources

• Charge composition: e+/(e- + e+) and p/(p + p) ratios e+ and p are produced by the interactions of high-energy cosmic rays with the interstellar matter (secondary production) There might be signals from additional (astrophysical or exotic) sources

• Different measurements provide complementary information of the origin, acceleration and propagation of cosmic rays

All available data must be interpreted in a coherent scenario

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Fermi_PIC2009.pptIntroduction (2):Introduction (2):Positron and Antiproton Fraction: 2008-09Positron and Antiproton Fraction: 2008-09

• Antiproton fraction consistent with secondary production• Anomalous rise in the positron fraction above 10 GeV• Several different viable interpretations (>200 papers over the last year)

PAMELA positron and antiprotonNature 458, 607 (2009)PRL 102, 051101 (2009)

1 GeV 10 100

See also Nature 456, 362 (2008) and PRL 101, 261104 (2008) for pre-Fermi CRE spectrum by ATIC and HESS.

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Fermi-LAT Capability for CR Electrons• Candidate electrons pass through 12.5 X0 on average ( Tracker and Calorimeter added together)

• Simulated residual hadron contamination (5-21% increasing with the energy) is deducted from resulting flux of electron candidates

• Effective geometric factor (Gf) exceeds 2.5 [m2 sr] for 30 GeV to 200 GeV, and decreases to ~1 [m2 sr] at 1 TeV. Gf times exposure has already reached several x 107 [m2 sr s]. (very high statistics)

• Full power of all LAT subsystems is in use: Tracker, Calorimeter and ACD act together

Geometric Factor (Gf)

Residual hadron contamination 20 GeV 100 GeV 1 TeV

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Fermi-LAT Electron Spectrum

Abdo et al. Phys. Rev. Let. 102, 181101 (2009)

Cited 38 times within a month

APS Viewpoint

Total statistics collected for 6 months of Fermi LAT observations

~4.5 million candidate electrons above 20 GeV

> 400 candidate electrons in last energy bin (770-1000 GeV)

Harder spectrum (spectral index: -3.04) than previously thought

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Implication from Fermi-LAT CRE (1)

Old “conventional” CRE Model

New “conventional” CRE models

0=2.54

0=2.42 0=2.33

Fermi CRE spectrum can be reproduced by the “conventional” Galactic cosmic-ray source model, with harder injection spectral index (-2.42) than in a pre-Fermi conventional model (-2.54). All that within our current uncertainties, both statistical and systematic.

for detail, seeD. Grasso et al. arXiv:0905.0636 (accepted by Astroparticle Physics)

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Implication from Fermi-LAT CRE (2)

New “conventional” CRE models

Old “conventional” CRE Model

Now include recent PAMELA result on positron fraction

• Qualitative approach: the harder primary CRE spectrum is, the steeper secondary-to-primary e+/e- ratio should be. PAMELA shows the opposite.

Precise Fermi measurement increases the discrepancy between a purely secondary origin for positrons, and the positron fraction measured by PAMELA.

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Implication from Fermi-LAT CRE (3)

An example of the fit to both Fermi and PAMELA data with Monogem and Geminga with a nominal choice for the e+/e- injection parameter (blue lines). Works well.

(Discrepancy in positron fraction in low energy can be understood as the charge-sign effect of solar modulation)

It is becoming clear that we are dealing with at least 3 distinct origins of HE e-/e+

Uniformly distributed distant sources, likely SNRs.

Unavoidable e+e- production by CRs and the ISM

And those that create positron excess at high energies. Nearby (d<1 kpc) and Mature (104 - 106 yr) pulsars?

“conventional” sources

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Dark Matter InterpretationDark Matter Interpretation

• We need local sources (astrophysical or exotic). The origin is still unclear but is strongly constrained by Fermi data (+ others)

What said about pulsars is applicable to dark matter as sources of e- and e+. PAMELA and Fermi data tighten the DM constraints, favoring pure e+e-, lepto-philic, or super-heavy DM models.

likely excludedpreferred

100 GeV 1 TeVDM mass

10-22

10-26

10-24

v [cm3/s]

10-19

10-23

10-21

pure e+e- Models lepto-philic Super-heavy DM

• More results from Fermi-LAT are coming. Extending energy range to 5 GeV – 2 TeV and searching for the CRE anisotropy at a 1 % level.

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Highlights from Fermi’s 1Highlights from Fermi’s 1stst year (3): year (3): Galactic Diffuse Gamma-ray Galactic Diffuse Gamma-ray Emission (Indirect Probe of Emission (Indirect Probe of

Galactic CRs)Galactic CRs)

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Cosmic-Rays Overview

V. Hess, 1912

Energy (eV)

Flu

x (m

2 s

r s

GeV

)-1

1 particle/m2/sec

Knee

1 particle /m2/yr

Ankle

1 particle/km2/yr

• Discovered by V. Hess in 1912• Globally power-law spectrum with some structures (knee and ankle)

hint of the origin• Large energy density (~1 eV cm-3): comparable to UB and Urad

• UHECRs : not covered by this talk in detail small scale anisotropy

Auger Collaboration, Sci. 318, 938 (2007)18/27 events > 5.6 x 1019 eV correlate with nearby AGNs. See also arXiv:0906.2347

Galactic

Extragalactic

G or EG?

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CRs and Galactic Diffuse Gamma-RaysCRs and Galactic Diffuse Gamma-Rays

e+-

X,γISM

diffusiondiffusion energy losses energy losses reaccelerationreacceleration convectionconvection etc.etc.

π0

synchrotron

bremssHESS

SNR SNR RX J1713-3946RX J1713-3946

B

Pulsar,-QSO

PPHeHe

CNOCNO

Chandra, Suzaku, Radio telescopes

A powerful probe to study CRs in distant locations

HE -rays are produced via interactions between Galactic cosmic-rays (CRs) and the interstellar medium (or interstellar radiation field)

IC

HESS, Fermi

gas

gas

ISRF

e+-

π+-

(CR Accelerator) (Interstellar space) (Observer)

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Fermi_PIC2009.pptOutstanding Question: Outstanding Question: EGRET GeV ExcessEGRET GeV Excess

• EGRET observations showed excess emission > 1 GeV everywhere in the sky when compared with models based on directly measured CR spectra• Potential explanations

Unexpectedly large variations in cosmic-ray spectra over Galaxy Dark Matter Unresolved sources (pulsars, SNRs, …) Instrumental

• Fermi-LAT is able to confirm or deny this phenomena

Hunter et al. 1997

~100% difference above 1 GeV

0.1 1 10 GeV

|b|=6°-10°

|b|=2°-6°

|b|<=2°

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Intermediate Latitude Region seen by LATIntermediate Latitude Region seen by LAT

|b|=10°-20°

0.1 1 10 GeV

EGRETLAT

• |b|=10°-20°: avoid Gal. plane but still have high statistics• EGRET spectrum extracted for the same region

• LAT spectrum is significantly softer and does not confirm the EGRET GeV excess • Strongly constrains the DM interpretation

Preliminary

PreliminaryAbdo et al. submitted to PRLPorter et al. 2009 (arXiv:0907.0294)

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Probing CRs using Gamma-rays from ISMProbing CRs using Gamma-rays from ISM

• Correlation with gas column density reveals the CR spectrum Method go back to SAS-2/COS-B era

• Fermi-LAT’s high performance + CR propagation model (e.g. GALPROP) to predict IC

Sensitivity significantly improved

ISM(e.g., LAB HI survey)

(http://www.astro.uni-bonn.de/~webaiub/english/tools_labsurvey.php)

Gamma-ray intensity(Fermi LAT data)

High latitude region:Detailed study of local CRs (most of the gas is close to solar system)

Galactic plane: CR gradient in the Galaxy (need to resolve point sources)

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Accurate Measurements of Local CRsAccurate Measurements of Local CRs

electron-bremsstrahlung

nucleon-nucleon

LAT datamodel from the LIS

• Prove that local CR nuclei spectra are close to those directly measured at the Earth

• Best quality -ray spectrum in 100 MeV-10 GeV (Tp = 1-100 GeV)

• Agree with the model prediction from the local interstellar spectrum (LIS)

Mid-high lat. region in 3rd quadrant:• small contamination of IC and molecular gas• correlate -ray intensity and HI gas column density

Abdo et al. 2009, accepeted by ApJ(arXiv:0908.1171) contact author: TM

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CR Distribution in GalaxyCR Distribution in Galaxy

CR source distribution from -rays(Strong & Mattox 1996)

SNR distribution

(Case & Bhattacharya 1998)

0 5 10 15 kpc

Pulsar distribution(Lorimer 2004)

sun

• CR distribution is a key to understand

their origin and propagation• distribution of SNRs not well measured• Previous Gamma-ray data suggests a

flatter distribution than SNR/pulsar

distributions (e.g., Strong et al. 2004)

Gal.Center

Inner Galaxy

OuterGalaxy

• Fermi-LAT is able to map out CR distributions in the Galaxy with unprecedented accuracy• Work in progress. (arXiv:0907.0304 and arXiv:0907.0312)

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Highlights from Fermi’s results (4): Highlights from Fermi’s results (4): Selected Galactic and Extragalactic Selected Galactic and Extragalactic Objects as a Key to Understand CRsObjects as a Key to Understand CRs

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Fermi_PIC2009.pptIntroduction: Introduction: -ray objects seen -ray objects seen by the LATby the LAT

Class Number

FSRQ 64

BL Lac 46

Radio galaxy 2

Other blazar 9

Radio/X-ray pulsar 15

LAT γ-ray pulsar 15

HMXB 2

Globular cluster 1

LMC 1

Special cases (SNRs, PWNe)

13

Unidentified 37

• Variety of objects in the LAT bright source list (Abdo et al. ApJS 183, 46, 2009)• >=200 sources. More than 80% are identified (EGRET:~30%)

• Here I will pickup SNRs, LMC and Blazars and briefly discuss their implications for CRs.

• Many other very important objects and topics will not be discussed. (See LAT publications, please)

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Fermi LAT Study on SNRsFermi LAT Study on SNRs

• SNRs are the most favored explanations for the origin of Galactic CRs.Diffusive shock acceleration in SNR shell. Sufficient to supply CRs up to knee.

• Significant progress in recent years in keV and TeV observation of young SNRs.• Key issues to be addressed by Fermi-LAT:

Searching for pion signatures & measuring total energy content per SNR

• Several possible associations to SNRs in the LAT bright source list including

W44: (T. Tanaka et al. proc. ICRC 2009) Middle age (2000 yr), Mixed Morphology, 3 kpc Interactions with Molecular Cloud EGRET Fermi-LAT: (0FGL J1855.9+0126: 3 month data yield 39)

W51C: (Y. Uchiyama et al. proc. ICRC 2009) Middle age (20000 yr), 6 kpc Interactions with MC HESS (Fiasson et al. 2009, no spectrum) Fermi-LAT: (0FGL J1923.0+1411: 3 month data yield 23

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W51C: The Fermi Source is “Extended”W51C: The Fermi Source is “Extended”

• Mean surface brightness (2-8 GeV) as a function of distance from the SNR center vs. Fermi-LAT PSF => Spatially extended

R

(Note) PSF of Fermi LAT depends heavily on energy. The PSF shape above is obtained by taking account of the energy distribution (not presented).

Black contours: ROSAT X-ray (0.1-2.4 keV)Green contours: VLA 1.4 GHzColor: Fermi-LAT count map (2-8 GeV)

Preliminary

Preliminary0.6 deg

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Spatial Extent of W44Spatial Extent of W44

Smoothed Count Map (>1 GeV) Profile along the rectangleContributions form the diffuse backgrounds

and nearby sources are subtracted

• For both W44 and W51C, gamma-rays are spatially “extended” & positionally coincident with SNRs. The luminosity is found to be very large.• Spectral analysis will be presented in a refereed journal

Black Cross: Pulsar (PSR B1853+01) location

Red: Observed CountsBlack: Expected Profile for a Point Source

Preliminary

Preliminary

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Local Group GalaxiesLocal Group Galaxies

• LMC detection: CR density is inferred to be similar to MW• SMC non-detection: CR density is smaller than in the MW• M31 non-detection: has to have smaller CR density than the MW

(size M31>MW)

EGRET Observation Summary:

• First direct evidence that CRs

(E<Eknee) are Galactic and not universal

• Key issues not fully addressed yet CR propagation in each Galaxy detailed comparison of CR densities

among galaxies

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Fermi-LAT Resolved the LMCFermi-LAT Resolved the LMC

• 161 days of survey data, ~ 1300 events above 100 MeV• Gamma-ray is clearly extended, with the maximum consistent with the massive star-forming region 30 Doradus

CRATES J060106-703606

30 Doradus

Dust map (SFD)

Preliminary

Preliminary

Gal. latitude

Gal. longitude

adaptively smoothed 100 MeV - 10 GeV counts map (s.n.r. = 5)

Detailed study of spatial and energy distribution is in progress

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LAT Bright AGN Sample (LBAS)

• 125 non-pulsar sources at |b|>10o

• 106 high-confidence (P>90%) associations with AGNs 11 lower-confidence (40%<P<90%) associations 9 unidentified (3EG: 96/181 at |b|>10o)

Only ~30% of the bright Fermi AGNs were detected by EGRET. The Sky changes!

58 FSRQ42 BL Lac4 of Uncertain class2 Radio Galaxies

Abdo et al. ApJ 700, 597 (2009)

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Population of the LAT AGNsPopulation of the LAT AGNs

3x1029 W Mpc-3

• 42 BL Lacs and 58 FSRQs (EGRET: 14 and 46)• BL Lac has harder spectrum than FSRQ (1.99 +/- 0.22 vs. 2.40 +/- 0.17)• V/Vmax test (Schmidt 1968) indicates the positive evolution for FSRQ

(more sources or brighter sources at earlier time)• Local emissivity

ℓBL ≥ 1031 W Mpc-3, ℓFSRQ ≈ 1030 (ℓUHECR ≈ 3x1029; Waxman & Bahcall 1999) BL Lacs are favored as the origin of UHECRs (if AGNs are the sources)

S. Razzaque, J. Finke and C. Dermer

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SummarySummary• Presented a very biased summary of gamma-ray particle astrophysics

• Long history of more than 40 years. Significant progresses in recent years by Air Cherenkov Telescopes and Fermi.

• Fermi view of GRBs: >240 GRBs, 9 detected by LAT (as of June 2009) GRB080916C & GRB090510

strongly constrains the bulk Lorentz factor, Lorentz invariance, etc..• CR electrons by Fermi + PAMELA and other data.

Local sources are required. Nearby mature pulsars. Constrains on DM scenario

• Diffuse gamma-rays as a probe of Galactic CRs non-GeV-excess. Local CRs close to those measured at the Earch. Is able to map out CR distribution in the Galaxy

• Found extended sources positionally associated with SNR. Resolved LMC for the first time. BL Lacs are favored (than FSRQs) as the origin of UHECR.

Thank you for your attention!

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Backup SlidesBackup Slides

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• No conclusive evidence of extra HE component– Probability of no extra component is ~1%– Effect of EBL

• HE absorption• Transparency:

0.03–1.0(model dependent)

• Single Band-functiondominant for 6 decades of energy band

• Lack of prominent SSC component implies– High magnetic field

• εe/εB 0.1≲– Epeak,SSC 10 GeV (γ≫ e 100)≫

Band function

Band + power law

Time bin ‘d’

GBM NaI

GBM BGO

LAT

synchrotron synchrotron SSCSSC

EEp,SSCp,SSCEEp,synp,syn γγee

22νν FFνν

νν

~ε~εee /ε/εBB

GRB 080916C SpectrumGRB 080916C Spectrum

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FOM for CRE MeasurementFOM for CRE Measurement

Exposure factor (effectively) determines the # of countsEf(E) = Gf(E)*Tobs

L. Baldini

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LAT vs pre-Fermi ModelLAT vs pre-Fermi Model

Preliminary

Preliminary

• Compare with a CR propagation

model prediction based on pre-

Fermi CR data (Strong et al. 2004,

Porter et al. 2008) π0-decay, e-Brems, Inverse Compton

• Source and isotropic (w/ residual

BG) component come from fitting

the data to the sky above 30 deg

latitude with model fixed • Although there is a uniform

excess above the model, data is

reasonably reproduced by the

model

The model is successful considering it is a priori

pre-Fermi model

LATmodel total

0-decay

ICe-Brems

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Correlation with the HI Column DensityCorrelation with the HI Column Density

• Mask point sources (52 total) and subtract the residual point source

contributions. Also subtract the IC contributions.• Correlation from 100 MeV to 10 GeV. The slope gives the -ray

emissivity spectrum of local HI gas produced through interactions

with CRs.

400-566 MeV

HI column density (1020 cm-2)

(error bars are statistical only)

E2 x

-r

ay

Inte

ns

ity

HI column density (1020 cm-2)

1.6-2.3 GeV400-560 MeV

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Fermi View on W51C RegionFermi View on W51C Region

Black contours: ROSAT X-ray (0.1-2.4 keV)Green contours: VLA 1.4 GHzColor: Fermi-LAT count map (2-8 GeV)

X-ray:• Thermal emission by shock-heated plasma (kT=0.2 keV)• Central region due to cloud evapolation?

Radio:• Peaks are HII region• Synchrotron radiation is well matched with thermal X-rays

GeV gamma-ray:• Origin?• Very high luminosity (~4 x 1035 erg/s) using 6 kpc

Preliminary

Preliminary

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Fermi_PIC2009.ppt

Fermi-LAT Image of W44Fermi-LAT Image of W44

Fermi-LAT Smoothed Count Map (Front Evnets; 2-10 GeVBlack cross: location of PSR B1853+01

Spatially Extended??

Preliminary

Preliminary