alexander kappes uw-madison 4 th tevpa workshop, beijing (china) sep. 24 – 28, 2008 the hunt for...
TRANSCRIPT
![Page 1: Alexander Kappes UW-Madison 4 th TeVPA Workshop, Beijing (China) Sep. 24 – 28, 2008 The Hunt for the Sources of the Galactic Cosmic Rays — A multi-messenger](https://reader036.vdocuments.us/reader036/viewer/2022062421/56649e505503460f94b475a5/html5/thumbnails/1.jpg)
Alexander KappesUW-Madison
4th TeVPA Workshop, Beijing (China)Sep. 24 – 28, 2008
The Hunt for the Sources ofthe Galactic Cosmic Rays
—A multi-messenger approach
![Page 2: Alexander Kappes UW-Madison 4 th TeVPA Workshop, Beijing (China) Sep. 24 – 28, 2008 The Hunt for the Sources of the Galactic Cosmic Rays — A multi-messenger](https://reader036.vdocuments.us/reader036/viewer/2022062421/56649e505503460f94b475a5/html5/thumbnails/2.jpg)
Alexander Kappes, TeV Workshop, Beijing 2
Outline
Energetics of Galactic CRs and source candidates
The missing PeVatrons and the Milagro skymap
Neutrino fluxes from Galactic CR source candidates
Sep. 28, 2008
![Page 3: Alexander Kappes UW-Madison 4 th TeVPA Workshop, Beijing (China) Sep. 24 – 28, 2008 The Hunt for the Sources of the Galactic Cosmic Rays — A multi-messenger](https://reader036.vdocuments.us/reader036/viewer/2022062421/56649e505503460f94b475a5/html5/thumbnails/3.jpg)
Alexander Kappes, TeV Workshop, BeijingSep. 28, 2008 3
Energetics of Cosmic Rays
• Galactic component:– GeV – PeV– rE ≈ 10-12 erg cm-3
# ≈ 4×10-14 cm-3
– similar to energy density in light and magnetic field
• Transition: somewhere between 107 and 109 GeV
• Extra-Galactic component:– > EeV– ~10-19 erg cm-3
extragalacticgalactic
J.K. Becker
![Page 4: Alexander Kappes UW-Madison 4 th TeVPA Workshop, Beijing (China) Sep. 24 – 28, 2008 The Hunt for the Sources of the Galactic Cosmic Rays — A multi-messenger](https://reader036.vdocuments.us/reader036/viewer/2022062421/56649e505503460f94b475a5/html5/thumbnails/4.jpg)
Alexander Kappes, TeV Workshop, Beijing 4
• Even after 100 years sources of (Galactic) cosmic rays (CRs) unknown(CRs not back-traceable due to Galactic magnetic field)
• Multi-messenger astronomy is key:
Neutrino telescopes:✓Unambiguous prove for CR
acceleration✗Still under development✗No sources found yet
g-Cherenkov telescopes:✓Very mature✓Discovered many (Galactic) sources✗Problem of synch/IC-pion ambiguity
not overcome yet
Multi-messenger Astronomy: Cosmic Rays, g-Rays and Neutrinos
Sep. 28, 2008
p + p() → p + X 9 m + nm 9 e + ne + nm
p + p() → p0 + X 9
p gCR Photon field
p pCR IM
Flux ratios (for E-2): (p+p) (p+ )g
€
φ(ν ) ≈1
2φ(γ )
€
φ(ν ) ≈1
8φ(γ )
AND
![Page 5: Alexander Kappes UW-Madison 4 th TeVPA Workshop, Beijing (China) Sep. 24 – 28, 2008 The Hunt for the Sources of the Galactic Cosmic Rays — A multi-messenger](https://reader036.vdocuments.us/reader036/viewer/2022062421/56649e505503460f94b475a5/html5/thumbnails/5.jpg)
Alexander Kappes, TeV Workshop, Beijing 5
Estimate of Gamma Flux from pp Interactions
Sep. 28, 2008
€
Qγ (>1TeV ) ≈ c nCR λ pp−1 Eπ
E p≈10−29cm−3s−1 nIM
cm−3
⎛
⎝ ⎜
⎞
⎠ ⎟
(nIM spp)
spp ≈ 40 mb
≈ 4×10-14 cm-3 for E-2; ≈ 0.2
• Steady Galactic CR density (~10-12 erg cm-3) requires 1041 erg s-1 (finite CR containment time)
• Corresponds to release of 1050 erg in CRs every 30 years• Emissivity in g-rays for interaction of CRs with interstellar medium:
energy released in CRs
€
Lγ (>1TeV ) ≈ QγW
ρE≈1033s−1 W
1050erg
⎛
⎝ ⎜
⎞
⎠ ⎟
≈ 10-12 erg cm-3F. Halzen, arXiv:0809.1874
![Page 6: Alexander Kappes UW-Madison 4 th TeVPA Workshop, Beijing (China) Sep. 24 – 28, 2008 The Hunt for the Sources of the Galactic Cosmic Rays — A multi-messenger](https://reader036.vdocuments.us/reader036/viewer/2022062421/56649e505503460f94b475a5/html5/thumbnails/6.jpg)
Alexander Kappes, TeV Workshop, Beijing 6
Estimate of Gamma Flux from pp Interactions cont’d
Sep. 28, 2008
Source candidates with known TeV g-ray emission:
• Supernovae (release ~1051 erg every ~30 years):- nIM 100 – 1000 cm-3 in star-forming regions where SN typically occur
- why don’t we see more SNe in TeV, why have all SNe cutoffs << 100 TeV?
• Binaries: only few observed up to now; again cutoffs << 100 TeV (absorption?)not visible in Milagro map
• Pulsar wind nebula: thought to accelerate (mainly) electrons
• Maybe something unknown!?
€
EdNγdE
(>1TeV ) =Lγ
4π d2≈10−12 −10−11cm−2s−1 W
1050erg
⎛
⎝ ⎜
⎞
⎠ ⎟nIMcm−3
⎛
⎝ ⎜
⎞
⎠ ⎟d
kpc
⎛
⎝ ⎜
⎞
⎠ ⎟
−2
The sources of the Galactic CR should have fluxes visible to current g-ray detector(in particular, they have to show up in the Milagro sky map)
![Page 7: Alexander Kappes UW-Madison 4 th TeVPA Workshop, Beijing (China) Sep. 24 – 28, 2008 The Hunt for the Sources of the Galactic Cosmic Rays — A multi-messenger](https://reader036.vdocuments.us/reader036/viewer/2022062421/56649e505503460f94b475a5/html5/thumbnails/7.jpg)
Alexander Kappes, TeV Workshop, BeijingSep. 28, 2008 7
The Missing PeVatrons
• SNRs generally considered as best candidates for Galactic cosmic ray accelerators
• But no SNR spectrum extends above a few 10 TeV(“knee” corresponds to ~300 TeV)
• Possible reason: “Direct” high energy -ray emission only in first few hundred years
• Detection still possible by observing secondary -rays produced in nearby clouds
• Milagro-like experiments better suited than Cherenkov telescopes
Gabici & Aharonian, arXiv:0705.3011
400 yr
2000 yr8000 yr
32000 yr
at 1 Kpc
2000 yr
Cherenkov telescopes(e.g. HESS, Magic)
Air shower arrays(Milagro)
(104 solar masses)
8000 yr
10 TeV
![Page 8: Alexander Kappes UW-Madison 4 th TeVPA Workshop, Beijing (China) Sep. 24 – 28, 2008 The Hunt for the Sources of the Galactic Cosmic Rays — A multi-messenger](https://reader036.vdocuments.us/reader036/viewer/2022062421/56649e505503460f94b475a5/html5/thumbnails/8.jpg)
Alexander Kappes, TeV Workshop, BeijingSep. 28, 2008 8
2007 Milagro Sky Survey At 12 TeV
• Several sources along Galactic plane• Large accumulation in the Cygnus region• Additional small “cluster” at l = 40°
MGRO J2019+37
C2
MGRO J2031+41 J1852+01
MGRO J1908+06
C1
![Page 9: Alexander Kappes UW-Madison 4 th TeVPA Workshop, Beijing (China) Sep. 24 – 28, 2008 The Hunt for the Sources of the Galactic Cosmic Rays — A multi-messenger](https://reader036.vdocuments.us/reader036/viewer/2022062421/56649e505503460f94b475a5/html5/thumbnails/9.jpg)
Alexander Kappes, TeV Workshop, BeijingSep. 28, 2008 9
Milagro:• Spectrum extends
up to 100 TeV !
• Strong indicator for proton acceleration in this source
MGRO J1908+06
H.E.S.S.: • E-2 spectrum without
cutoff indication
• Flux @ 1TeV:3.2×10-12 cm-2 s-1 TeV-1
(H.E.S.S. Coll., ICRC’07 proceedings)
![Page 10: Alexander Kappes UW-Madison 4 th TeVPA Workshop, Beijing (China) Sep. 24 – 28, 2008 The Hunt for the Sources of the Galactic Cosmic Rays — A multi-messenger](https://reader036.vdocuments.us/reader036/viewer/2022062421/56649e505503460f94b475a5/html5/thumbnails/10.jpg)
Alexander Kappes, TeV Workshop, BeijingSep. 28, 2008 10
MGRO J2031+41
Milagro:• Flux @ 1TeV for E-2:
2.4×10-12 cm-2 s-1 TeV-1
€
F = (4.5 ± 0.3) ×10−13E−2.0±0.3 (TeV −1cm−2s−1)
MAGIC: • E-2 spectrum• Flux @ 1TeV:
0.45×10-12 cm-2 s-1 TeV-1
• Lower flux probably due to high photon backgroundin Cygnus region
Milagro
(Milagro Coll., ApJ 658:L33, 2007)
(MAGIC Coll., ApJ 675:L25, 2008)
![Page 11: Alexander Kappes UW-Madison 4 th TeVPA Workshop, Beijing (China) Sep. 24 – 28, 2008 The Hunt for the Sources of the Galactic Cosmic Rays — A multi-messenger](https://reader036.vdocuments.us/reader036/viewer/2022062421/56649e505503460f94b475a5/html5/thumbnails/11.jpg)
Alexander Kappes, TeV Workshop, BeijingSep. 28, 2008 11
MGRO J2019+37
VERITAS:• Not seen in first observation:
Fg < 30 mCrab (99% C.L.)
consistency with Milagro requires < 2.2
VERITAS observation
Milagro: • Flux @ 1TeV for E-2:
3.5×10-12 cm-2 s-1 TeV-1
(VERITAS Coll., ICRC’07 proceedings)
(Milagro Coll., ApJ 658:L33, 2007)
![Page 12: Alexander Kappes UW-Madison 4 th TeVPA Workshop, Beijing (China) Sep. 24 – 28, 2008 The Hunt for the Sources of the Galactic Cosmic Rays — A multi-messenger](https://reader036.vdocuments.us/reader036/viewer/2022062421/56649e505503460f94b475a5/html5/thumbnails/12.jpg)
Alexander Kappes, TeV Workshop, BeijingSep. 28, 2008 12
The Role of Neutrino Telescopes
• Several g-ray sources with hard spectra• Photon production ambiguous
• Air-shower array currently only in Northern Hemisphere• Cherenkov telescopes only small field of view (few deg2)
– cover only small part of sky (at a time)
– large photon background in star-forming region (e.g. Cygnus) can hide sources
• Neutrinos unambiguous sign for hadronic acceleration• Neutrino telescope properties very similar to
air shower arrays
– “all sky” sensitivity
– increasing sensitivity with energy (fast decreasing background)
– angular resolution O(1°)
![Page 13: Alexander Kappes UW-Madison 4 th TeVPA Workshop, Beijing (China) Sep. 24 – 28, 2008 The Hunt for the Sources of the Galactic Cosmic Rays — A multi-messenger](https://reader036.vdocuments.us/reader036/viewer/2022062421/56649e505503460f94b475a5/html5/thumbnails/13.jpg)
Alexander Kappes, TeV Workshop, BeijingSep. 28, 2008 13
Gamma and Neutrino Spectra
Spectra for MGRO J1908+06
• E-2 with Milagro normalization assumed (MGRO J1908+06 index = 2.1)
• spectrum cutoff @ 180 TeV
neutrino flux
gamma flux
1 10E (TeV)
100010010-13
10-12
10-11
10-10
E2 flu
x (T
eV s
-1 c
m-2
)
Halzen etal, Phys.Rev. D78, 063004 (2008)
J1852+01MGRO J2019+37MGRO J1908+06MGRO J2031+41
C1C2
Neutrino spectra for all sources
![Page 14: Alexander Kappes UW-Madison 4 th TeVPA Workshop, Beijing (China) Sep. 24 – 28, 2008 The Hunt for the Sources of the Galactic Cosmic Rays — A multi-messenger](https://reader036.vdocuments.us/reader036/viewer/2022062421/56649e505503460f94b475a5/html5/thumbnails/14.jpg)
Alexander Kappes, TeV Workshop, BeijingSep. 28, 2008 14
Significance for MGRO J1908+06
• Source size and detector angular + energy resolution taken into account • Milagro measurements favor lower sensitivity curve (dashed line) • Individual sources probably hard to detect for IceCube
IceCube with 80 strings
observed eventssignal + atm.
signal events
1
2
3
1 10Ethresh (TeV)
100p
valu
e
atm. n
Halzen etal, Phys.Rev. D78, 063004 (2008)10 years
![Page 15: Alexander Kappes UW-Madison 4 th TeVPA Workshop, Beijing (China) Sep. 24 – 28, 2008 The Hunt for the Sources of the Galactic Cosmic Rays — A multi-messenger](https://reader036.vdocuments.us/reader036/viewer/2022062421/56649e505503460f94b475a5/html5/thumbnails/15.jpg)
Alexander Kappes, TeV Workshop, BeijingSep. 28, 2008 15
Significance for stacked Sources
• p-value = 10-4 after 5 years but large error band (not shown)
• Optimal threshold @ 30–40 TeV (determined by loss of signal events)
Halzen etal, Phys.Rev. D78, 063004 (2008)
5 years
10 years
![Page 16: Alexander Kappes UW-Madison 4 th TeVPA Workshop, Beijing (China) Sep. 24 – 28, 2008 The Hunt for the Sources of the Galactic Cosmic Rays — A multi-messenger](https://reader036.vdocuments.us/reader036/viewer/2022062421/56649e505503460f94b475a5/html5/thumbnails/16.jpg)
Alexander Kappes, TeV Workshop, Beijing 16
AMANDA II
• Search for muon neutrinos in 6 Milagro source regionsin AMANDA II 7 year data set (3.8 years livetime)
• Per-source flux sensitivity improved by a factor of 4 compared to fixed-point search for any of the six sources
Sep. 28, 2008
Shown by J. Braun @ COSMOS’08
![Page 17: Alexander Kappes UW-Madison 4 th TeVPA Workshop, Beijing (China) Sep. 24 – 28, 2008 The Hunt for the Sources of the Galactic Cosmic Rays — A multi-messenger](https://reader036.vdocuments.us/reader036/viewer/2022062421/56649e505503460f94b475a5/html5/thumbnails/17.jpg)
Alexander Kappes, TeV Workshop, BeijingSep. 28, 2008 17
Simulated Neutrino Skymap IC80 (5 years)
J1852+01
MGRO J1908+06Gal
actic
Lati
tude
(°)
Galactic Longitude (°)
![Page 18: Alexander Kappes UW-Madison 4 th TeVPA Workshop, Beijing (China) Sep. 24 – 28, 2008 The Hunt for the Sources of the Galactic Cosmic Rays — A multi-messenger](https://reader036.vdocuments.us/reader036/viewer/2022062421/56649e505503460f94b475a5/html5/thumbnails/18.jpg)
Alexander Kappes, TeV Workshop, Beijing 18
Conclusions
• Straight forward calculations show that sources of Galactic CR should show up in Milagro sky-map
• Sources might not be (easily) visible for Cherenkov telescopes– largest energy density might be at several 10 TeV
(interactions of CR in molecular clouds)
– large photon background in SN regions, e.g. Cygnus
• Several Milagro sources show indications for hard E-2 spectra with one (MGRO J1908+06) possibly extending to at least 100 TeV
• Hard to decide from g-ray signal alone whether g-ray sources are CR sources
• Neutrino telescopes can unambiguously identify sources of cosmic rays
• IceCube will be able to detect stacked Milagro sources after several years(individual sources difficult)
Sep. 28, 2008
![Page 19: Alexander Kappes UW-Madison 4 th TeVPA Workshop, Beijing (China) Sep. 24 – 28, 2008 The Hunt for the Sources of the Galactic Cosmic Rays — A multi-messenger](https://reader036.vdocuments.us/reader036/viewer/2022062421/56649e505503460f94b475a5/html5/thumbnails/19.jpg)
Alexander Kappes, TeV Workshop, Beijing 19Sep. 28, 2008
Backup Slides
![Page 20: Alexander Kappes UW-Madison 4 th TeVPA Workshop, Beijing (China) Sep. 24 – 28, 2008 The Hunt for the Sources of the Galactic Cosmic Rays — A multi-messenger](https://reader036.vdocuments.us/reader036/viewer/2022062421/56649e505503460f94b475a5/html5/thumbnails/20.jpg)
Alexander Kappes, TeV Workshop, Beijing 20
TeV Gamma-Ray Sky Map
Sep. 28, 2008
![Page 21: Alexander Kappes UW-Madison 4 th TeVPA Workshop, Beijing (China) Sep. 24 – 28, 2008 The Hunt for the Sources of the Galactic Cosmic Rays — A multi-messenger](https://reader036.vdocuments.us/reader036/viewer/2022062421/56649e505503460f94b475a5/html5/thumbnails/21.jpg)
Alexander Kappes, TeV Workshop, BeijingSep. 28, 2008 21
Simulated Neutrino Skymaps IC80 (5 years)G
alac
tic L
atitu
de (°
)
Galactic Longitude (°)