Testing cosmological models with the Integrated Sachs-Wolfe effect

Testing cosmological models with the Integrated Sachs-Wolfe effect

Alvise Raccanelli, Institute of Cosmology and Gravitation,

Portsmouth

Outline:

•The standard model of cosmology•CMB anisotropies•The ISW effect•Why the ISW is a good test for cosmological models•Results and ongoing projects

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Observations of Supernovae Type Ia told us that the universe is accelerating

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The Universe is accelerating; this is caused by something different from the usual gravity

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Hu & White 2004

After the Big Bang, the Universe was hot and dense, and photons were strongly coupled to electrons and protons

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Before the recombination, photons are coupled with matter, so they can not travel to us

The Universe is hot and dense

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After the recombination, photons are free to travel towards us

The Universe become colder and less dense, and at one point protons and electrons form hydrogen (recombination)

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The Last Scattering Surace: why CMB is important

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CMB Experiments

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WMAP

Planck

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The Planck First Light

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Better Power Spectrum at small scale

The Planck BlueBook 2005

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ISW effect: evolving gravitational potential

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Galaxies form inside gravitaional wells left after inflation

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Travelling from the last scattering surface to us, photons pass through gravitational wells. If the potential is static, they will exit with the same energy they had when they entered. If the well is stretched by the dark

energy, photons will experience a shift in energy (and so in temperature)

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But this effect is small compared to other CMB anisotropies

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so we need to cross-correlate this temperature shift with something that can trace potential wells. Galaxies are a biased

tracer of potential wells

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This part tells us where is matter

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This part tells us how the gravitational potential change

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ISW can be used to test the gravitational or the galaxies part:

•Changing the filter of the galaxies allow to test models for the bias relating the visible matter to the mass (including Dark Matter) and the redshift distribution of galaxies

•Changing the filter of the gravitational part allow to test models of gravity

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Results:

Raccanelli et al. 08

Testing Galaxy distribution and bias models

Work with G. De Zotti, S. Matarrese, M. Negrello, A. Bonaldi, G. Tormen

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Results:Testing new Galaxy distribution models

Massardi et al. 10

Work with G. De Zotti, M. Massardi, M. Negrello, A. Bonaldi, S. Ricciardi

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Ongoing projects:•Test of Unified Dark Matter models(with D. Bertacca, D. Pietrobon, S. Matarrese, T. Giannantonio, N. Bartolo, O. Piattella)

•Test of Modified Gravity Models(with F.P. Silva, K. Koyama, T. Giannantonio, G.-B. Zhao)

•ISW with LOFAR data(with W. Percival, M. Jarvis, D. Bacon, S. Rawlings, F. Abdalla)

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Preliminary results for testing UDM models

Bertacca et al., in preparation

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Kobayashi et al. 09

In some modified gravity scenarios we expect a negative cross-correlation, due to the “stronger” dark energy

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Conclusions

• The ISW is a good test for testing different cosmologies•The incoming data from CMB and Large Scale Structure observations will allow a better estimation of cosmological parameters

Alvise RaccanelliTesting cosmological models with the ISW