scott croom- dark energy and cosmic sound

8/3/2019 Scott Croom- Dark energy and cosmic sound

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Dark energy andcosmic sound

1. The evidence for dark energy.2. Acoustic waves as standard rulers.

3. The WiggleZ Survey.

Scott Croom

(Sydney Institute for Astronomy)


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The fate of the UniverseThe Universe: dark matter

baryons

neutrinos

photons

m>1 m=1 m


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Standard Candles

If we know the intrinsic brightness of anobject we can calculate its distance:

But distance (r) depends on redshift (i.e.

cosmological expansion) and the content ofthe Universe.

Supernovae (in particular type Ia SNe) are

good standard candles.


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Type Ia SNe

Thermo-nucleardetonation of a whitedwarf.

Can outshine theirgalaxy.

Their peak luminosity

is consistent to ~10%.


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An unexpected result

AcceleratingCoasting

Critical

-2.5

log10

(measuredre

lativeSNflux)


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The fate of the Universe

X X X


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Dark Energy whats going on?

One of Key Science Questions for the NewCentury (US National Academies, 2003)

Cosmic acceleration requires new physics:

Cosmological constant: natural scale very wrong (z=0) / Planck = H0

2 h G c5 = 10-122

New theory of gravity?

Quintessence/phantom energy?

Connection to inflation?

Extra dimensions?

New particle interactions?

Dark-matter dark-energy connections?


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The physics of dark energy

The equation of state: w=p/ Normal matter w=0, V-1

Photons w=1/3, V-4/3

Friedmann equations give: Acceleration -(1+3w) w accelerating Universe

Dark Energy:

Cosmological constant: w=-1, V0 Quintessence: w(z)=-1/3 to -1 Phantom energy: w


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Vacuum energy

The cost of space?

Work done = -pdV

Vacuum energy: dE = dV

So dV = -pdV

And w=p/=-1


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Tracker Quintessence, single exp Quintessence, double expQuintessence, Pseudo-Nambu-Goldstone Boson Quintessence,Holographic dark energy, cosmic strings, cosmic domain walls, axion-photon coupling, phantom dark energy, Cardassian model, branecosmology (extra-dimensions), Van Der Waals Quintessence, Dilaton,

Generalized Chaplygin Gas, Quintessential inflation, Unified Darkmatter & Dark energy, superhorizon perturbations, UndulantUniverse, various numerology, Quiessence, general oscillatory models,Milne-Born-Infeld model, k-essence, chameleon, k-chameleon, f(R)gravity, perfect fluid dark energy, adiabatic matter creation, varyingG etc, scalar-tensor gravity, double scalar field, scalar+spinor,Quintom model, SO(1,1) scalar field, five-dimensional Ricci flatBouncing cosmology, scaling dark energy, radion, DGP gravity, Gauss-Bonnet gravity, tachyons, power-law expansion, Phantom k-essence,vector dark energy, Dilatonic ghost condensate dark energy,Quintessential Maldacena-Maoz dark energy, superquintessence,

vacuum-driven metamorphosis, wet dark fluid...

Dark Energy whats going on?


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Issues with SN

Evolution of progenitors?

Host galaxy environments?

Dust? Explosions not understood.

Calibration: Now limited at >1%

Need something else a standard ruler?


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A standard ruler: Cosmic sound

aka: Baryon acoustic oscillations (BAOs)

Baryon wiggles Doppler peaks


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Measuring cosmic sound (1)CMB from WMAP (z=1500)


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Measuring cosmic sound (2)

Galaxy redshift surveys can measurethe 3-D structure of the galaxy

distribution and see the BAOs.

Local galaxy surveys:

Sloan Digital Sky Survey (US). 2dF Galaxy Redshift Survey (Aus/UK).

Eisenstein et al (2005) Cole et al. (2005)


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GA

LAXYSURVEY

Dark energy fixes

apparent size of

ruler C

OSMICMIC

ROWAVEBA

CKGROUND

A cosmic ruler


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The WiggleZ Project

Project aim: 240,000 galaxies over 1000 deg2

Measure the BAO scale to 2% at z~0.5-1.

Test for cosmological constant w=-1 at z~0.5-1.

Method: Target UV selected galaxies forming stars so

easy to see. Observe spectra with the Anglo-Australian

Telescope AAOmega spectrograph target up to400 galaxies at once.


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AAOmega

Spectrograph for the 2-degree Fieldrobotic fibre positioner at the AAT.


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AA hardware


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First BAO detection


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The Universe is accelerating we have no ideawhy!

WiggleZ is the only current high-z project

measuring dark energy via cosmic sound. We target star-forming galaxies selected in the

ultra-violet.

So far: marginal detection of the wiggles?

Only the first step future projects needed toget a fuller answer.

Summary

scott croom- dark energy and cosmic sound

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