Fermi Gamma Ray Space Telescope:
Launch+509
Roger Blandford
KIPACStanford(With considerable help from Fermi teammembers working at Stanford)

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A Cosmic Reflection on Fermi’s First Year
• Goals– To summarize the main published and preprinted astrophysical and cosmologicalconclusions from Fermi– To compare these to community expectations at the time of the First Symposium– To ignore genuine instrument, data and pure observing accomplishments– To avoid previewing results that will be presented here and/or published soon
– To avoid prognostication on what Fermi should do in the next nine years!

• Organization (from First Symposium).
– Stars– Jets
• Active Galactic Nuclei• Gamma Ray Bursts• Galactic Superluminals– Pulsars– Supernova Remnants– Backgrounds

The Scientific Bottom Lines3

GLAST -> Fermi GST(2007)
Pre-launch expectations
LAT• 0.02 - 300 GeV• 2.5 sr, 0.3 - 0.9m2• 5o - 5’resolution• Δln E ~ 0.1• 3 x 10-9 cm-2 s-1 (>0.1 GeV, point source)• 109 photons (3Hz)• All sky every 3hr

GBM• 0.01-30 MeV• 9sr, 100 cm2.
• 1o resolution• Δln E ~ 0.1• 1000 GRBs

Sources after a decade• 10,000 Active Galactic Nuclei• 100 Gamma Ray Bursts• 100 Pulsars• 100 Supernova Remnants• 10 Galaxies• 10 Clusters of Galaxies• 10 X-Ray Binaries• ? Unidentified Sources

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Stars (2007)
• Sun

Share

– Flares– Solar minimum->maximum– Observe neutrons– Radiation hazard• Minutes!

• 3 HMXBDubus
Cortina
Hermsen– LSI+61 303• NS-Be• P=27d• e ~0.7• i ~ 60o
– PWN orbiting Be excretion disk?
– Other Binaries– Cygnus Region5Stars• LS I+61 303, LS 5039
– HMXB: 26.6d e~0.6, Be, 3.9d, e~0.3, O6 +BH/NS– Also seen as TeV sources but temporally and spectrally distinct– Reasons for modulation• Absorption by stellar radiation and wind
• Eccentric orbit => variable flux to scatter• Anisotropy of inverse Compton scattering, back scattering stronger• Equatorial disk for hadronic emission– Are we observing modified pulsar emission or jets from BH

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Padovani, Celotti

Jet Physics (2007)• Blazar–––AGN classification
Blazar sequence (10-4 of galaxies)• FR2->FR1?
• GLAST observe more RG
Variability Wagner• M87• Mk 501 Mazin• Contrary evolutions Fukazawa• GRB–––Long - collapsars; short- NS coalescence??
Butler Briggs
Late emission, plateau, chromatic breaks
Hurley et
Faster than Blazar jets

• Jet Physics––––––

Ptran, Granot

TaylorEmission mechanism
SSC vs EC
Opacity, location Baring
Bulk Comptonization and Cooling
Composition, Structure, Confinement
Impactal. 1994

Extended/Delayedemission

7AGN• Demography:– 200 source list >10σ @ 3month;– ~1000 today– Spectroscopic campaign going well

• Multi wavelength campaigns well organized and delivering– Radio (OVRO <1000 sources per day), Optical (polarimetry), X-ray, TeV• Comparable numbers of BL Lacs, FSRQ
– BL Lac – closer, dimmer, more numerous, evolve less…

• <ten percent of GeV background– Star-forming galaxies could dominate background– cf LMC8AGN• Specific sources– FSRQ:3C454.3, 1454-354• X 100, ~1d variation; γVLBI~16,; 2GeV break– BL Lac: PKS 2155-304• Low state; not SSC– RG: NGC 1275, M87, Cen A• Variability => not cluster; misdirected jets
– NLQ/S:J0948+0022• Behavior depends upon Eddington ratio?

9Padovani, Celotti

Jet Physics (2007)• Blazar–––

AGN classification
Blazar sequence (10-4 of galaxies)• FR2->FR1?
• GLAST observe more RG
Variability Wagner• M87• Mk 501 Paneque• Contrary evolutions Fukazawa• GRB–––Long - collapsars; short- NS coalescence??
Butler Briggs
Late emission, plateau, chromatic breaks
Hurley etFaster than Blazar jets

• Jet Physics––––––Ptran, Granot

TaylorEmission mechanism
SSC vs EC
Opacity, location Baring
Bulk Comptonization and Cooling
Composition, Structure, Confinement
Impactal. 1994

Extended/Delayedemission

10GRBs• GBM+LAT+SWIFT+…
– 252 seen by GBM in 1 yr
– 138 in LAT FoV– 9 detected w LAT• z=4.35; not 8.2– 2 short bursts• GeV similar to long (core collapse?) bursts• Are they NS coalescence?
– 3 magnetars• Spectral and temporal properties– Eiso > 3 x 1054 erg– Band +PL;
– Thermal peak?
– GeV emission later and more persistent; early 10 GeV; Late 33 GeV• “Γ” >1000• Resuscitation or afterglow?
– 090510: z=0.9s; t~ 1s; Lorentz invariance confirmed;• linear QG scale, > Planck mass…
– Modest EBL constraints
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Pulsar Physics (2007)• Detection– 100s pulsars?
– 50 RQ pulsars?
– 10 MSP

Harding

JohnstonRansom– RRATS– Blind searches• How do pulsars shine?
– Polar cap vs slot gaps vs outer gaps
– Locate gamma ray and radio emission– Does gamma ray power ~ V?

Spitkovsky• Force free models– Compute pulse profiles for different emission
sites and fit to radio, gamma ray observations– Is the rotating vector model really supported byobservations?
• Orthogonal polarization!
12Pulsars• Abundant– Young (105yr),– Regular(107yr),• 1/50 yr?
– Recycled(109yr)• 8/72 Field MSP• 1/6 x 105 yr?

• 16/50 Radio-Quiet––––cf Geminga
2 subsequently found
CTA1
Dominate low latitude unidentiied EGRET sources 15/36• 47 Tuc– 23 from Radio X-ray– May be seeing 60 in gamma rays
– Not winds13Emission Mechanism• η~0.01-0.5 spin down power• gamma ray beam > radio beam
• High energy cutoff• Outer or slot gap emission• Curvature radiation• Young and MSP• Vela– Cusped profile– Not wind14

Supernova Remnants (2007)• Nonthermal accelerators

Drury– >100TeV– Spectral curvature• Hadronic vs leptonic– n problem or B problem?
– GLAST should decide– Local FIR not CMB?

• Acceleration

SlaneBlandford– PeV-> mG– DSA vs F2 vs ?
– If DSA do not need scattering behind shock!

15Supernova remnants• W51C 3 x 10^4 yr SNR 400 km/s
• Shocked atomic and mol gas• Hadronic emission not leptonic– 10^36 erg/s 5 x 1050 erg in protons• Spectral break– Cooling, acceleration, loss …

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Backgrounds (2007)• Interplanetary–

C-1 starlight–

GeV excess? Cygnus TeV?

• Diffuse interstellar

Digel, Knodelseder, Abdo

• Extragalactic gamma ray background–Sum of sources or new component ?

Dermer• Extragalactic X-ray background–

INTEGRAL reports HEAO-1 spectrum x 1.1• Extragalactic stellar background––

TeV observations vs Spitzer - limits on Pop III contribution?
GLAST will see to greater distance and study evolution––AGN vs GRB
Auger - Hard for UHECR to escape either environment

Hartmann• Extragalactic cosmic ray background• Dark matter annihilation background––Kuhlen, Wai, Koushiappas

Lines?
• No “no go” theorem
Bump• Validation of DM signal will be a challenge• Confusion with PWN etc?
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Backgrounds• 0.1-1000 GeV electrons featureless? spectrum J~E-3.
– No problem yet• No 0.1-10 GeV diffuse excess– Galactic + extragalactic diffuse + unresolved sources– E-2.4• Line, subhalo, rich cluster upper limits

18Summary• Fermi has exceeded the already high expectations for itat the time of the first Symposium in terms of its
performance and the science it has already delivered– stars, AGN, GRB, pulsars, SNR, backgrounds• Fermi, working in combination with an army of othertelescopes, is transforming our view of the high energy
universe– Routine and opportunistic multi-wavelength campaigns are working• It is also advancing our understanding of fundamental
physics by shrinking the range of allowable possibilities– High confidence upper limits are extremely valuable• We will learn much more over the next four days and, wehope, over the next nine years– Time to think hard about how we optimize the science return from the mission

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