The signature of the nearby universe on the very high energy (diffuse) gamma skyBergen, November 2006

Troels Haugbølle

haugboel@phys.au.dk

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 -

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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