Measuring dark energy from galaxy surveys
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Measuring dark energy from galaxy surveys. Carlton Baugh Durham University London 21 st March 2012. Galaxies to cosmological parameters. Connecting dark matter to linear theory. Linear perturbation theory. Evolved matter distribution: MXXL. Angulo et al. 2012.

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Measuring dark energy from galaxy surveys

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Measuring dark energy from galaxy surveys

Measuring dark energy from galaxy surveys

Carlton Baugh

Durham University

London 21st March 2012


Galaxies to cosmological parameters

Galaxies to cosmological parameters


Connecting dark matter to linear theory

Connecting dark matter to linear theory

Linear perturbation theory

Evolved matter distribution: MXXL

Angulo et al. 2012


Connecting galaxies to mass

Connecting galaxies to mass

H-a

H-band

Orsi et al. 2010


A hybrid tool to study dark energy

A hybrid tool to study dark energy

Galaxy formation simulation

N-body simulation


Bias and nonlinear effects

Bias and nonlinear effects

Angulo et al. 2008


Scale dependent biases

Scale dependent biases

Dark matter

Linear theory

Angulo et al. 2008


Scale dependent rsd

Scale dependent RSD

Linear theory

Jennings et al. 2011


Scale dependent rsd1

Scale dependent RSD

Jennings et al. 2011


The need for improved rsd models

The need for improved RSD models

Using linear theory leads to systematic errors similar to difference in signal

Jennings et al. 2011


Measuring de using galaxy pairs

Measuring DE using galaxy pairs

Marinoni & Buzzi 2010

Peculiar motions distort apparent

distribution of pair angles:

Jennings et al. 2012


A probe of dark energy

A probe of dark energy

  • Peculiar velocities give distortion in pair angle distribution

  • Probe of Hubble expansion

  • Distortion sensitive to nature of dark energy

  • Distinguish models with same BAO and halo mass function

  • Requires simulations

    Jennings et al. 2012


Why build a mock catalogue

Why build a mock catalogue?

A synthetic galaxy can catalogue be used to:

  • Test estimators: e.g. Galaxy clustering, photo-z, group-finders

  • Devise new statistics: e.g. pair distortions

  • Uncover systematic effects (we already know the right answer)

  • Estimate errors

  • Generate predictions for different dark energy cosmologies


What is a mock catalogue

What is a mock catalogue?

STEP 2

STEP 1

Combine with galaxy

formation model

N-body simulation

A priori calculation

of baryon physics

Millennium, Horizon, MICE, MXXL

e.g. GALFORM; GALICS, LGALAXIES; MORGANA

Springel et al. 2005, Teyssier et al. 2009;

Fosalba et al 2008; Angulo et al. 2012

Cole et al. ;Hatton etal; de Lucia et al; Monaco +


Constructing observer s past lightcone

Constructing observer’s past lightcone

STEP 3

Build galaxy catalogue on observer’s past

lightcone.

redshift

e.g. Blaizot et al 2005; Fosalba et al.

Kitzbichler & White; Merson et al.


A pply survey window function

Apply survey “window function”

  • Apply angular footprint

  • Apply scanning mask

  • Incorporate sampling

  • Redshift completeness (synergy with OU-SIM)

  • Steps 1, 2, 3 generic

  • Step 4 is survey specific


Synthetic images

Synthetic images


Measuring dark energy from galaxy surveys

Merson et al. 2012


Measuring dark energy from galaxy surveys

Merson et al. 2012


Measuring dark energy from galaxy surveys

Merson et al. 2012


Summary

Summary

  • Hybrid tool: N-body and galaxy formation sims

  • Linear theory not accurate enough for Euclid on large-scales

  • Scale dependent: nonlinearities, bias, RSD

  • Mock catalogues will help refine estimators

  • Devise new tests


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