Title: Ultra-High Energy Cosmic-Ray Origin in Light of First Results from the Pierre Auger Observatory and the Fermi Gamma-ray Space Telescope
1Ultra-High Energy Cosmic-Ray Origin in Light of
First Results from the Pierre Auger Observatory
and the Fermi Gamma-ray Space Telescope
- Charles D. Dermer
- Space Science Division
- US Naval Research Laboratory, Washington, DC
- charles.dermer_at_nrl.navy.mil
- Colloquium at the School of Physics and Astronomy
- University of Minnesota, Minneapolis, MN
- November 12, 2008
2Outline
- Cosmic Rays and Ultra-High Energy Cosmic Rays
(UHECRs) - Pierre Auger Observatory Results and
Implications - Criteria for UHECR sources
- Extragalactic
- Emissivity (gt1044 ergs Mpc-3 yr-1)
- Power (gt 1046 ergs s-1)
- Extragalactic Gamma Ray Sources
- Fermi Gamma Ray Space Telescope
- Radio Galaxies and Blazars as Sources of the
UHECRs - Gamma-Ray Bursts as Sources of the UHECRs
see Dermer, Razzaque, Finke, Atoyan (2008)
3Cosmic Rays
- Cosmic rays energetic cosmic particles composed
mainly of protons and ions - Cosmic rays an important particle background in
the space radiation environment
- Particle radiations
- Cosmic Rays
- Solar Energetic Particles
- Neutrinos
- Photon Radiations
- Radio emission (cosmic ray electrons)
- X-rays and g rays (cosmic ray electrons,
protons, and ions) -
- The recent deployment of radiation detectors and
telescopes on ground and in space is providing
new data sets for analysis and interpretation to
solve the problem of cosmic-ray origin
Discovery of cosmic rays by Victor Hess in 1912
4Cosmic Rays and Space Radiations
- Cosmic Ray Origin Fundamental Unsolved Problem
in Astronomy - Galactic Cosmic Rays
- (accelerated by Supernova Remnants?)
- Ultra-high Energy Cosmic Rays (discovered by
Auger and Rossi in the 1930s) - Cosmic rays do not point directly to their
sources, because of magnetic fields in space. - Gamma rays indicate sites of high-energy
particles, but can be attenuated by matter or
other photons at the source or in transit from
the source to Earth. - Neutrinos would unambiguously point to the
sources of the cosmic rays, but are faint and
difficult to detect. - The solution to this problem can therefore only
be achieved by jointly analyzing high-energy
space radiations, including gamma rays, cosmic
rays, and neutrinos
5Highest Energy Cosmic Rays
Knee Feature at 31015 eV Second Knee at 41017
eV Ankle Feature at 51018 eV GZK Cutoff at
61019 eV (predicted by Greisen, Zatsepin, and
Kuzmin in 1968)
- Origin sources of cosmic rays
- Acceleration how accelerated to high energies
- Propagation transport of cosmic rays
- Reception detection at Earth and in space
2-1 through 2-n of N
6Greisen-Zatsepin-Kuzmin (GZK) Cutoff
- Photopion production cross section
- p g ? p po, n po
-
- Photo-ion disintegration cross sections
- (Giant dipole resonance) N g ? N? p, n, a
CMB photons reach threshold for p production for
E 1020 eV protons
7Extragalactic Origin of UHECRs
Galactic Disk Magnetic Field 2 5 mG Thickness
200 pc Galactic Halo Magnetic Field 0.1
mG Thickness 1 5 kpc
Lorentz force equation for a particle with charge
Q Ze and energy E Larmor radius
Hillas 1984
Particle with energy E 60 EeV 60x1018 eV
- Hillas Condition Sources of UHECRs must have rL
lt source size - Rules out many classes of potential UHECR
sources, flare stars, white dwarfs, normal
neutron stars, Galactic sources (if protons),
8Pierre Auger Observatory
Flux (gt 1020 eV) 1 particle/km2/century Ni
Flurorescence Detectors Spectroscopy Detectors
(1600 SDs spaced 1.5 km apart) Angular
resolution 1o for E gt 10 EeV Energy
uncertainty 22 for E gt 10 EeV
(Auger Collaboration, Science Magazine, November
2007)
Auger Observatory in Mendoza province in
Argentina
92007 Birth of Charged Particle Astronomy
All-sky projection Galactic Center at (0,0)
Arrival directions of highest energy cosmic rays
(gt61019 eV open circles) correlated with active
galaxies (AGNs) () within 100 Mpc Cen A,
radio galaxies, also radio-quiet AGN
Deflection in Galactic magnetic field ? protons
or light nuclei
10GZK Horizon Distance for Protons
- MFP for Energy Loss vs. Horizon Distance
11Local Emissivity of UHECRs
12UHECR Emissivity
Yamamoto et al. (2007)
1020 0.2 1019 1.2 1018 3.5 1017 40
Sources of UHECRs need to have a local luminosity
density (emissivity) of ?1044 ergs/Mpc3-yr
13UHECR Acceleration by Sources of Relativistic
Winds
Proper frame () energy density of relativistic
wind with luminosity L
x
Maximum particle energy
G
Lorentz contraction ? DR G DR R R/ G
What sources have L gt Lg gt 1046 ergs s-1?
14Gamma Ray Sources
Compton Gamma-Ray Observatory Pioneering g-ray
space observatory (1991 2000)
270 EGRET sources (3EG) 25 blazars with 5
Spark Chamber Gamma Ray Bursts ground-based
TeV 70 High Confidence Blazars telescopes LMC,
Cen A, NGC 6251 (? see Mukherjee et al. 2002)
15Fermi Gamma-ray Space Telescope
- International space mission devoted to the study
of the high-energy gamma rays from the universe - Successfully launched on June 11,
2008
from Cape Canaveral - Formerly, the Gamma ray Large Area Space
Telescope (GLAST)
Circular orbit, 565 km altitude (96 min period),
25.6 deg inclination
16The Fermi Observatory
- Large Area Telescope (LAT)?
- 20 MeV to gt300 GeV
- onboard and ground burst triggers, localization,
spectroscopy - Gamma-ray Burst Monitor (GBM)?
- 12 NaI detectors (8 keV to 1 MeV)?
- onboard trigger, onboard and ground
localizations, spectroscopy - 2 BGO detectors (150 keV to 30 MeV)?
- spectroscopy
Spectral observations over 7 orders of magnitude
in energy
17Pair Conversion Technique
?
The anti-coincidence shield vetos incoming
charged particles.
Photon converts to an ee- pair in one of the
conversion foils
The directions of the charged particles are
recorded by particle tracking detectors, the
measured tracks point back to the source.
The energy is measured in the calorimeter
Tracker angular resolution is determined
by multiple scattering (at low energies) gt Many
thin layers position resolution (at high
energies) gt fine pitch detectors Calorimeter Eno
ugh X0 to contain shower, shower leakage
correction. Anti-coincidence detector Must have
high efficiency for rejecting charged particles,
but not veto gamma-rays
18First Light Sky Map (June 30 July 4, 2008)
Equivalent to full year of data from the Compton
Observatory!
- All sky projection bright central band shows g
rays from cosmic-ray interactions in our Galaxy - Already detected many blazars and GRBs
- Identification of localized sources of radiation
requires detailed spectral and background analysis
NASA Fermi First Light Press Conference August
26, 2008 http//www.nasa.gov/mission_pages/GLAST/n
ews/glast_findings_media.html
19 The Gamma Ray Sky
2-1 through 2-n of N
20Relativistic Jet Sources of UHECRs
Nonthermal g rays ? nonthermal particles
intense photon fields
- Leptonic jet model optical/X-rays/soft g-rays
are nonthermal lepton synchrotron - Hadronic jet model
- Photomeson production
- second g-ray component
Large Doppler factors required for g-rays to
escape
21UHECRs from Radio Galaxies and Blazars
22Radio Galaxies and Blazars
Cygnus A
FRII/FSRQ
L 1045 x (f/10-10 ergs cm-2 s-1) ergs s-1
Mrk 421, z 0.031
FRI/BL Lac
3C 279, z 0.538
FRI/II dividing line at radio power ?1042 ergs s-1
L 5x1048 x (f/10-9 ergs cm-2 s-1) ergs s-1
3C 296
BL Lacs optical emission line equivalent widths
lt 5 Å
23Blazar g-ray Emissivity
gt100 MeV g-Ray fluence
Dermer 2007
24Flaring Blazar Sources
- Automated search for flaring sources on 6 hour, 1
day and 1 week timescales.
PKS 1502106 z 1.84
Preliminary
25Leptonic Blazar Modeling
Observer
q
Ejection of relativistic plasma from supermassive
black hole
BLR clouds
G
Relativistically Collimated Plasma Outlfows
Dusty Torus
W
Accretion Disk
SMBH
G
Ambient Radiation Fields
z 0.538
BL Lac vs. FSRQ
Böttcher et al. 2007
26Photo-hadronic Blazar Jet Models
Possible photon targets for p
??? Internal synchrotron radiation
External accretion disk radiation (UV) (i)
direct accretion disk radiation (ii)
accretion disk radiation scattered in the
broad-line region (Atoyan Dermer 2001)
quasi-isotropic, up to RBLR 0.1-1 pc Impact
of the external accretion disk radiation
component high p?-rates lower threshold
energies ???????????????prot?????????MeV/(1-
cos?) ??
??7 (solid) ??10 (dashed) ??15
(dot-dashed) (red - without ADR)
(for 1996 flare of 3C 279)
27Blazars as High Energy Hadron Accelerators
Powerful blazars / FR-II Neutrons with En gt 100
PeV and ???rays with E? gt 1PeV take away
5-10 of the total energy injected at RltRBLR
(3C 279)
Synchrotron and IC fluxes from the pair-photon
cascade for the Feb 1996 flare of 3C279
dotted - CRs injected during the flare solid -
neutrons escaping from the blob, dashed -
neutrons escaping from Broad Line Region (ext.
UV) dot-dashed - g rays escaping external UV
field (from neutrons outside the
blob) 3dot-dashed- Protons remaining in the blob
at l RBLR
astro-ph/0610195
Sreekumar et al. (1998)
28Hadronic g-Ray Emission from Blazars
29 UHE neutrons ?-rays energy momentum
transport from AGN core
- UHE ?-ray pathlengths in CMBR
- l?? 10 kpc - 1Mpc
- for En 1016 - 1019 eV
- Neutron decay pathlength
- ld (?n) ?0 c ?n (?0 900 s)
- ? ld 1 kpc - 1Mpc
- for E 1017 - 1020 eV
solid z 0 dashed z 0.5
Detection of single high-energy n from blazars ?
neutral beams could power large-scale jets
30Pictor A
d 200 Mpc l jet 1 Mpc (lproj 240
kpc) Deposition of energy through ultra-high
energy neutral beams (Atoyan and Dermer 2003)
Pictor A in X-rays and radio (Wilson et al, 2001
ApJ 547)
31 Neutrinos expected fluences/numbers
- Expected ?? - fluences calculated for 2 flares,
in 3C 279 and Mkn 501, assuming - proton aceleration rate Qprot(acc) Lrad(obs)
red curves - contribution due to - internal photons, green curves - external
component (Atoyan Dermer 2003) -
- Expected numbers of ?? for IceCube-scale
detectors, per flare - 3C 279 N? 0.35 for ? 6 (solid curve) and
N? 0.18 for ? 6 (dashed) - Mkn501 N? 1.2 10-5 for ? 10 (solid) and N?
10-5 for ? 25 (dashed) - (persistent') ? -level of 3C279 0.1 F?
(flare) , ( external UV for p? ) - ? N?? few - several per year can be expected
from poweful ? FSRQ blazars. -
32UHECRs from GRBs
33Gamma Ray Bursts
- GRB Burst of g rays accompanying black-
- hole formation
- Classes of GRBs
- Long duration GRBs
- (collapse of massive star core)
- Short hard class of GRBs
- (coalescence of compact objects)
- Low luminosity GRBs
All-sky g ray map in Galactic coordinates
(Galactic coordinates)
g-ray Light Curve of GRB
Swift mission discovered that short hard class of
GRBs are related to old stellar population
(Gehrels et al. 2005)
34GRB X-ray/g-ray Emissivity
GRB fluence
gt 20 keV fluence distribution of 1,973 BATSE
GRBs (477 short GRBs and 1,496 long GRBs). 670
BATSE GRBs/yr (full sky)
Vietri 1995 Waxman 1995
(independent of beaming) Baryon loading
(Band 2001)
35Ultra-high Energy Cosmic Rays from Gamma Ray
Bursts
- Proposed Solution to the Origin of Ultra-High
Energy Cosmic Rays - Hypothesis requires that GRBs can accelerate
cosmic rays to energies gt 1020 eV - Injection rate density determined by birth rate
of GRBs early in the history of the universe - High-energy (GZK) cutoff from photopion
interactions with cosmic microwave radiation
photons - Ankle formed by pair production effects
Wick, Dermer, and Atoyan 2004
Test UHECR origin hypothesis by detailed fits to
measured cosmic-ray spectrum
36Effects of Different Star Formation Rates
g-ray signatures of UHECRs at source can confirm
this hypothesis
Hopkins Beacom 2006
37Leptonic GRB Modeling
- Dominant synchrotron radiation at X-g energies
- Two peaks in nFn distribution
- Power-law afterglow decay
- Generic rise in intensity until tdec, followed by
constant or decreasing flux (except in
self-absorbed regime or in synchrotron/SSC trough)
E1054 ergs n0100 cm-3 eB 10-4
- nFn spectra shown at 10i seconds after GRB
- gg opacity included
38GRBs at High Energy Signatures of Hadrons?
- Little is known about GRB emission above 100 MeV
prior to Fermi Telescope - Prompt HE gamma emission
- Prompt GeV emission with no HE cutoff (combined
with rapid variability) implies highly
relativistic bulk motion - EGRET detections from a few GRBs, e.g. GRB940217
- New HE extra component, with independent
temporal evolution (GRB 941017) inconsistent with
the synchrotron model! (Gonzalez 03)? - Extended or delayed HE emission
- It may require more than one emission mechanism,
and remains one of the unsolved problems - GRB 940217 (EGRET)?
- GRB 080514B (AGILE)?
- HE emission clearly has different time dependence
- What is its spectral shape?
- Need more sensitivity and larger FOV
GRB941017
GRB080514B
-18 to 14 sec 14 to 47 sec 47 to 80 sec
80-113 sec 113-211 sec
39Hadronic GRB Modeling
- Nonthermal Baryon Loading Factor fb 30
Energy injected in protons normalized to GRB
synchrotron fluence
Injected proton distribution
Cooled proton distribution
Escaping neutron distribution
Forms neutral beam of neutrons, g rays, and
neutrinos
40Photohadronic Cascade Radiation Fluxes
Photomeson Cascade
Nonthermal Baryon Loading Factor fb 1
C2
Ftot 3?10-4 ergs cm-2
C3
emits synchrotron (S1) and Compton (C1)
photons emits
synchrotron (S2) and Compton (C2) photons,
etc.
Total
C4
S2
C1
S3
C5
S4
Photon index between -1.5 and -2
MeV
d 100
41Photon and Neutrino Fluence during Prompt Phase
Nonthermal Baryon Loading Factor fb 1
Ftot 3?10-4 ergs cm-2
d 100
- Hard g-ray emission component from
hadronic-induced electromagnetic cascade
radiation inside GRB blast wave - Second component from outflowing high-energy
neutral beam of neutrons, g-rays, and neutrinos
42Neutrinos from GRBs in the Collapsar Model
requires Large Baryon-Loading
Nonthermal Baryon Loading Factor fb 20
(2/yr)
Dermer Atoyan 2003
43GZK neutrinos from UHECRs produced by GRBs
Barwick et al. 2006
44GRB 080916C Luminous Fermi GRB
- 30 deg region around GRB 080916C
- GRB at 48 from the LAT boresight at T0?
- RGB lt100 MeV, 100 MeV - 1 GeV, gt1 GeV
Before the burst (T0-100 s to T0)?
During the burst (T0 to T0100 s)?
Black region out of FoV
45Light Curves of GRB 080916C
PRELIMINARY!
- Light curves arebackground subtracted
- First low energy peak not observed at Large Area
Telescope (LAT) energies - Spectroscopy needs LAT event selection (gt100
MeV)? - 5 intervals for time-resolved spectral
analysis0 3.6 7.7 16 55 100 s - 14 events above 1 GeV
46Multiple detector light curve
PRELIMINARY!
- The bulk of the emission of the 2nd peak is
moving toward later times as the energy increases - Clear signature of spectral evolution
47Spectroscopy of the main LAT peak
Models for GRB 080916C Hadronic
emission Separate Shell Collisions Opacity
Effects
PRELIMINARY!
- Consistent with smooth Band function from 10
keV to 10 GeV - No evidence for any other component
- No evidence for any roll-off
48Summary
UHECRs from GRBs and Radio-Loud AGNs Why
(these) Black Holes? 1. Extragalactic 2.
Powerful 3. Emissivity How to confirm
origin? Association of arrival directions with
sources g-ray signatures of UHECR
acceleration Neutrino emission from GRBs or
Blazars
492005-2015 A Decade of Discovery
-
- Swift Gamma-ray Burst Explorer (NASA 2004 MidEx)
- High Energy Stereoscopic Observatory (HESS)
- (Ground-based g-ray telescope Namibia, 2004)
- Very Energetic Radiation Imaging
- Telescope Array System
- (VERITAS) (Arizona 2007)
- Auger High Energy Cosmic
- Ray Observatory
- (Argentina 2007)
- IceCube NSFs
- South Pole km-scale
- neutrino telescope
- (km-scale design
- sensitivity in 2012)
- Fermi Gamma-ray
- Space Telescope (2008)
Swift
Auger
IceCube
VERITAS