Nikolaos Nikoloudakis Friday lunch talk 12/6/09 Supported by a Marie Curie Early Stage Training Fellowship

 4 clones spectrographs  prime focus of classical 4-m wide-field telescopes  4000 MOS slits over a 1° field (1.5’’ seeing)  Spectral resolution 10 Å (0.52 – 0.72, μm)  galaxy redshifts/night for z up to 0.7 → 1.5 hrs exposure → ~ 5-6 million galaxy z surveys in 200 nights → deg² sky area

 Observational Cosmology via galaxy redshift surveys at z~0.7 → LRGs (i<21) ELGs (i<22)  Measuring Growth of Structure/ z-space distortion.  Measuring the scale of BAO.  XMS Galaxy Evolution Survey.

 i 6 in 1.5hr exposure in ~1.´´5 seeing  i 4 in 1.5hr exposure in ~1.´´5 seeing (Exposure times being checked directly – see later)

Galaxy sky densities  i<20 all galaxies ~2500deg -2  i<21 z~0.5 em+absn galaxies ~5000deg -2  21<i<22 all galaxies ~9000deg -2  21<i<22 z~0.7 OII em galaxies ~5000deg -2  Stripe82 reaches i~22 – so will PanSTARRS!

Acoustic peaks created in the photon-baryon fluid, while photon’s pressure was resisting against the gravitational collapse of perturbations in the density of baryons. Their feature were acoustic waves in early Universe (z<1100), so during recombination, these waves had ‘frozen’ in a scale of ~ 150 comoving Mpc.  They correspond to sounds waves propagating through the primordial photon – baryon fluid in the early Universe → → → New ways to measure : evolution of expansion rate + relative effects of dark energy & dark matter

→ oscillation in the power spectrum P(k) → spike in the two point spatial galaxy – galaxy correlation function ξ The BAO signature has been detected in the local universe: 1. 2dFGRS of z~0.1 galaxies ( Cole et al. 2005) 2. SDSS galaxy samples of z~0.35 LRGs ( Eisenstein et al. 2005).

 Using CMB data we can determine precisely the physical length scale of BAO. → standard ruler that can be measured in the transverse and the radial direction from the distribution of galaxies  The combination of : apparent size + known physical sizes : → angular diameter distance d A → Hubble parameter H(z)  Better constraints in the equation-of-state of the dark energy.

This quantity can measure survey efficiency for detecting BAO, Gravitational Growth Rate and other quantities based on galaxy clustering. The shot noise of the power spectrum must be as low as possible, Errors on P(k) go as 1/sqrt(Veff(k)).

 Luminous Red Galaxies  LRG / 3000 deg^2  170 nights  ž ≈ 0.7  1.5 hrs exposure  Emission Line Galaxies  ELG/ 1000 deg^2  165 nights  ž ≈ 0.6  exposure 1 hrs

 Extra test of GR  Estimator of mass M/L galaxy groups haloes in CDM models Measurement Redshift-space distortions i. at small scales, random peculiar velocities strongly distort the correlation function along the parallel π direction to the line of sight, the known “Fingers-of-God” effect, ii. at large scales the coherent infall causes a flattening to the perpendicular direction σ.

2-D correlation function  WiggleZ AAomega r o= 4.4Mpc/h r o= 10Mpc/h b=1.3 b=2.35 β=0.58 β=0.34

White, Song/&Percival 2008

XMS/NG1dF ELGs 4000deg -2

MOSCA Instrument  3.5-m Cassegrain focus at Calar Alto  FOV 10 x 8 arcmin 2  resolution ~ 28Å  ~ 70 slits/ mask MOSCA data  1 mask/ 2hrs 2 masks/ 1 hr  Green -250 grism  Below average observational conditions  More data needed

15/30 from 2hrs z = 0.95 z = 0.77

4/10 from 2hrs z = 0.62 z = 0.73

 LRGs can give bigger effective volume more quickly than ELGs for 2dF.  XMS/NG1dF is competitive for BAO at scales Mpc  XMS/NG1dF is more competitive for z-space distortions at smaller scales.  Some of the assumptions needed to be tested: exposure times/MOSCA data