the signature of the nearby universe on the very high energy (diffuse) gamma sky

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