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Structure Formation 2

Structure Formation 2. Press-Schechter formalism. How do we find the halo mass-function from the power spectrum?. Recap: Structure Formation 1. Recap: Structure Formation 1. Recap: Structure Formation 1. Collapse of a perturbation. Rms mass fluctuations. Press – Schechter.

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Structure Formation 2

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  1. Structure Formation 2 Press-Schechter formalism How do we find the halo mass-function from the power spectrum?

  2. Recap: Structure Formation 1

  3. Recap: Structure Formation 1

  4. Recap: Structure Formation 1

  5. Collapse of a perturbation

  6. Rms mass fluctuations

  7. Press – Schechter • Press-Schechter theory: The fraction of mass in collapsed objects more massive than M is related to the fraction of the volume in which the smoothed initial density field is above some density threshold.

  8. Press - Schechter Probability of having a value between δ and δ+dδ Fraction of mass in collapsed objects:

  9. Halo mass function Press-Schechter 1974

  10. PS prediction PS gives a good prediction of the mass function but there are problems Does not take into account accretion of subhaloes in the non-linear stages PS argued multiplication by a factor 2 to compensate Works reasonably well, see fig

  11. Halo bias – peaks within peaks • PS picture also does not take into account the preferential formation of matter peaks within large scale fluctuations

  12. Halo bias

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