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The signature of the nearby universe on the very high energy (diffuse) gamma sky. Bergen, November 2006. Troels Haugbølle. [email protected]. Collaborators: Alessandro Cuoco, Hannestad S, Miele G, Serpico P D, Tu H. Institute for Physics & Astronomy, Århus University. - PowerPoint PPT Presentation
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The signature of the nearby universe on the very high energy (diffuse) gamma skyBergen, November 2006
Troels Haugbølle
Institute for Physics & Astronomy, Århus University
Collaborators: Alessandro Cuoco, Hannestad S, Miele G, Serpico P D, Tu H
The diffuse cosmic gamma ray sky(as seen by EGRET)
Energy spectra
Angular distribution
Why interest us for the diffuse -ray sky?
● Glast is flying very soon (fall 2007) (energy range 10 MeV -> 500 GeV)
Why interest us for the diffuse -ray sky?
● Glast is flying very soon (fall 2007) (energy range 10 MeV -> 500 GeV)● Several ground based surveys are in operation
or planned●Milagro, HAWC, ARGO... Energy range > 500 GeV
Why interest us for the diffuse -ray sky?
● Glast is flying very soon (fall 2007) (energy range 10 MeV -> 500 GeV)● Several ground based surveys are in operation
or planned●Milagro, HAWC, ARGO... Energy range > 500 GeV
● Using the angular distribution and spectra of the flux, we can learn about the sources - be it AGNs, micro quasars, pulsars, decaying dark matter or ...
Other gamma-ray observatories(with small field-of-view though)
CANGAROO III(Australia & Japan)
Spring 20044 telescopes 10
meters ØWoomera, Australia
Windhoek, NamibiaHESS
(Germany & France)
Summer 20024 (16)
telescopes12 meters Ø
Roque delos Muchachos, Canary Islands
MAGICMAGIC(Germany, Spain, Italy)(Germany, Spain, Italy)
Summer 2003Summer 20031 telescope 17 meters 1 telescope 17 meters
ØØMontosa Canyon,Arizona
VERITAS(USA &
England)2005?
7 telescopes10 meters Ø
Gamma Ray Propagation
Photon interactions at TeV energies give a gamma horizon comparable in size to the GZK horizon
The main interaction is:
-> e+e-
Pair production with e+e- cascading.
The gamma photons scatter on the extra- galactic background light.
10 TeV
1 TeV
100 GeV
=1
Given the density of sources and the energy spectrum g[E] the intensity is
For low z the flux above an threshold energy Ecut is
where W(E,z) is the window function
Gamma Ray Propagation
W
z
3TeV1TeV
300GeV
Window Function
Using the large scale structure to predict the
distribution of the -ray fluxThe SDSS survey
1Gpc
The SDSS survey
1Gpc
Using the large scale structure to predict the
distribution of the -ray flux
The large scale structure- on a sphere -
The large scale structure- on a sphere -
QuickTime™ and a decompressor
are needed to see this picture.
The PSCz survey
Quality compared to the 2MASS:
• About 15.000 Gal. in PSCz against 1.5 millions in 2MASS, and less sky coverage.
• ...but better redshifts quality: Spectroscopic redshifts available in PSCz with negligible errors
• For 2MASS only photometry is available from which photometric redshifts are calculable only with great errors (typically 20-30%)
Mask and sky distribution of the PSCz sources
Redshift distribution and selection function
W
z
3TeV1TeV
3GeV
Window Function
=
Combine W(E,z) and survey
+
Synthetic sky maps(low-l angular powerspectrum)
Synthetic sky maps(low-l angular powerspectrum)
Green band: 1- Shot noise Points: alm from PSCz
The angular powerspectrum for high l
Using N-Body simulations or the Halo model we can repeat the analysis of the PSCz catalog.But without masks, noise, or resolution problems.
Halo Model
N-body Simulation
Summary● Observations: GLAST is flying soon. Ground
based survey telescopes are planned or working● Theory: Due to pair production the very high
energy gamma rays originate at low redshift● Hypothesis: Sources are sitting in the cosmic
web. But how are they correlated with matter? ● Analysis: Using large redshift surveys with well
understood systematics, we can make skymaps of the diffuse ray sky in different scenarios
● Prediction: Using N-body/halo models we can predict the form of the angular powerspectrum for high l. Using surveys we can predict the low l
● Conclusion: Correlating the -ray sky with the large scale structure we learn about the sources
Summary● Observations: GLAST is flying soon. Ground
based survey telescopes are planned or working● Theory: Due to pair production the very high
energy gamma rays originate at low redshift● Hypothesis: Sources are sitting in the cosmic
web. But how are they correlated with matter? ● Analysis: Using large redshift surveys with well
understood systematics, we can make skymaps of the diffuse ray sky in different scenarios
● Prediction: Using N-body/halo models we can predict the form of the angular powerspectrum for high l. Using surveys we can predict the low l
● Conclusion: Correlating the -ray sky with the large scale structure we learn about the sources
Green band: 1- Shot noise Points: alm from PSCz