Clustering in the Sloan Digital Sky Survey. Bob Nichol (ICG, Portsmouth) Many SDSS Colleagues. Outline. Statistics of clustering SDSS overview and update What have we learnt from p(k)? Caution about fair samples Features in p(k)? The Future. Clustering in the Universe.
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Clustering in the Sloan Digital Sky Survey
Bob Nichol (ICG, Portsmouth)
Many SDSS Colleagues
Measuring the distribution of matter in the Universe is a fundamental goal of physics as it tests theories of gravity and the creation of mass in the Universe
Alternatively, can express the correlation function in terms of the power spectrum of density fluctuations
On large scales, we expect fluctuation to be small so perturbation theory can be applied. On small scales, the density field will be highly evolved and non-linear (see CMBfast)
ADD DEFINITION OF Tk and primodial P(k)
The “break” gives
mh2 due to horizon at matter-radiation equality
k / mh2 Mpc-1
Therefore, like the CMB power spectrum, precision measurements of P(k) provide important information on the contents of the Universe
DR2: 367,000 spectra, 3324 sq degs (half-way)
Done 07/2005: ~700,000 spectra, 8000 sq degs
Extension (2005-2007): Legacy, SNe, Galaxy
The inclusion of the “SDSS Great Wall” (Gott et all. 2003) has a 40% effect on P(k)
mh = 0.213 (11% error), assuming h=0.72 and spatially flat
Combine with CMB data (spatially flat), then we require Dark Energy to fill the Universe!
Large Scale P(k)Have we been the beyond the “break”? Hard as fluctuation are small (linear regime) demanding homogeneous photometry and selection of galaxies over large volumes
Luminous Red Galaxies (Massive Ellipticals) maybe the answer
Using hydro sims, for k < (1 Mpc)-1, the shape of Pflux(k) matches primordial P(k) (see Croft et al. 1998)
P(k,z) At higher z, the effect of non-linear evolution on the primordial P(k) is less. Use the “Lyman-alpha forest” to measure P(k) at high z.
Ned Wright’s webpage
Seljak et al. (2004)Using CMB+lensing+Pgalaxy(k)+Pflux(k), Seljak et al. (2004) reconstructed the primordial and observed P(k) over largest possible range of scales.
Max Tegmark Webpage
Pprimordial(k) = kn
Dip in Tegmark P(k)! Pope et al. has higher
Miller et al. 2003
2dFGRS smears out the oscillations because of window function.
GWFMOS - 5000 fibres over 1.5 deg FOV on an 8-meter telescope. A million redshifts in 3 years at z>1 (SDSS-like). Design study underway.
k / mh2 Mpc-1
Tbe David Letterman Show July 2003
(See Rob Crittenden’s talk for answer)