1. Discovery of  rays from Star-Forming Galaxies New class of nonthermal sources/gamma-ray galaxies (concept of temperature breaks down at high energies) From cosmic-ray interactions, not black holes How to accelerate energetic particles by natural processes? Fermi particle acceleration mechanism Fermilab, Batavia, IL Enrico Fermi (1901-1954) Charles Dermer, Naval Research Laboratory 2009 Fermi Conference Press conference, Feb. 2, 2009

2. Gamma Ray Galaxies: Black-Hole Powered Two classes: 1.Active galaxies: Nearly 700 GeV, 1 25 TeV; including 7 GeV and TeV radio galaxies 2.Star forming galaxies: Milky Way, LMC, others? LAT 1 year sky image 2 1 talk, B. Lott 2 talk, J. Ormes Gamma-ray luminosity of blazars: > trillion Solar luminosities

3. Gamma Ray Galaxies: Cosmic-ray/supernova powered Two classes: 1.Active galaxies: Nearly 700 GeV, 1 25 TeV; including 7 GeV and TeV radio galaxies 2.Star-forming galaxies: Milky Way, LMC, others? LAT 1 year sky image 2 1 talk, B. Lott 2 talk, J. Ormes Gamma-ray luminosity of Milky Way: ~100,000 Solar luminosities

4. Why is this important? Solve the problem of the origin of the cosmic radiation Cosmic rays: energetic cosmic particles composed mainly of protons and ions Cosmic rays: an important particle background in the space radiation environment 1.Cannot be trapped in the Solar cavity 2.Motions bent by magnetic field: do not point back to their sources 3.Cosmic rays make gamma rays by colliding with gas and dust 4.Cosmic rays are believed to be accelerated by supernova remnants 5.Identifying sites of cosmic ray acceleration in the Milky Way by gamma rays is hard because of “forest and trees” problem 6.Starburst galaxies should be more gamma-ray luminous than normal galaxies Cosmic rays: the most energetic particles in the universe Sources of –Light elements Li, Be, B –Galactic radio emission –Galactic gamma-ray emission –Galactic pressure –Terrestrial 14 C –Genetic mutations –Radiation effects on satellites Discovery of cosmic rays by Victor Hess in 1912

5. The  -ray/cosmic-ray connection Nearby, low luminosity star-forming gamma-ray galaxies (millions x Solar luminosity) : powered by supernovae explosions and collapse to neutron stars? Distant, highly luminous active gamma-ray galaxies (trillions x Solar luminosity) : powered by black holes? Why so many detected black-hole powered gamma-ray galaxies (distant and therefore very luminous), and so few detected star-forming gamma-ray galaxies (nearby and therefore weak)? Fermi mechanism predicts that highest energy particles made by sources with largest compactness = luminosity/size Large compactness found in stellar core collapse to a neutron star forming supernovae and supernova remnants TeV  ray/keV X-ray image of SNR RX J1713.7−3946

6. Sources of the highest energy radiations Very highest energy radiations, including ultra-high energy cosmic rays, made by black holes 1. stellar core collapse to a black hole (gamma ray burst) 2. rotating supermassive black holes 3. microquasars in galaxies Huge compactness found near accreting black holes, especially if rotating Ultra-high energy cosmic rays from Centaurus A?

7. Backup Slides

8. New Eyes in the Gamma-ray Sky paint a new picture of the universe Fermi Gamma-ray Space Telescope: launched 11 June 2008 Very Energetic Radiation Imaging Telescope Array System (VERITAS) First light of 4-telescope array in 2007 Fermi LAT measures GeV (giga, or Billion electron Volts) photons in scanning mode VERITAS (HESS, MAGIC) measures TeV (trillion electron Volt) photons in pointing mode Fermi Large Area Telescope (LAT) and Gamma ray Burst Monitor (GBM)

9. Gamma Ray Galaxies: Large Magellanic Cloud Previously detected with the EGRET Experiment on the Compton Observatory, establishing that GeV cosmic rays are not universal Fermi mapping of the LMC shows distribution of sources of cosmic rays First GeV map of star- forming galaxy other than Milky Way Strong gamma-ray emission near 30 Doradus

10. Gamma Ray Galaxies: Large Magellanic Cloud Previously detected with the EGRET Experiment on the Compton Observatory, establishing that GeV cosmic rays are not universal Fermi mapping of the LMC shows distribution of sources of cosmic rays First GeV map of star- forming galaxy other than Milky Way Strong gamma-ray emission near 30 Doradus Described by Jürgen Knödlseder

11. Discovery of Gamma-ray Emitting Starburst Galaxies Starburst galaxies M82 and NGC 253 (about 10 Million lt-yrs) (supernova rate  10 × Milky Way’s gas mass  2 × less than Milky Way) Why not Andromeda (M31)? Described by Keith BechtolDescribed by Niklas Karlsson