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Clustering of Luminous Red Galaxies and Applications to Cosmology

Clustering of Luminous Red Galaxies and Applications to Cosmology. Nic Ross (Penn State) Research Progress Meeting LBNL 8th November 2007. Ross et al., 2007, MNRAS, 381, 573 Ross et al., 2007, MNRAS submitted, astro-ph/0704.3739 Cannon et al., 2006, MNRAS, 372, 425. Outline of talk.

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Clustering of Luminous Red Galaxies and Applications to Cosmology

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  1. Clustering of Luminous Red Galaxies and Applications to Cosmology NicRoss (Penn State) Research Progress Meeting LBNL 8th November 2007 Ross et al., 2007, MNRAS, 381, 573 Ross et al., 2007, MNRAS submitted, astro-ph/0704.3739 Cannon et al., 2006, MNRAS, 372, 425

  2. Outline of talk • Motivation • The 2dF-SDSS LRG And QSO (2SLAQ) Survey • Clustering techniques • 2SLAQ LRG Clustering results and z-space distortions • The AAOmega LRG Pilot Survey • Future BAO Surveys, The B.O.S.S.

  3. Outline of talk • Motivation • The 2dF-SDSS LRG And QSO (2SLAQ) Survey • Clustering techniques • 2SLAQ LRG Clustering results and z-space distortions • The AAOmega LRG Pilot Survey • Future BAO Surveys, The B.O.S.S.

  4. What is the Universe made of? 4% Baryonic matter “Dark Energy” ~26% Dark matter ~70% Evidence from: SNeIa, CMB, LSS, (Clusters)

  5. Motivation • Luminous Red Galaxies (LRGs) provide a very good observational sample to test models of galaxy formation and evolution. • Excellent tracers of Large Scale Structure (LSS).

  6. Motivation, observations vs. models • Semi-Analytic Model predictions - lines, LRG Observations - stars; z=0.24 (L), z=0.50 (R) • Almedia et al. 2007 (astro-ph/0710.3557)

  7. Motivation • Luminous Red Galaxies (LRGs) provide a very good observational sample to test models of galaxy formation and evolution. • Excellent tracers of Large Scale Structure (LSS). • 2 Point Correlation Function (2PCF) simple but powerful statistic.

  8. Motivation • `Bump’ in the 2 Point Correlation Function at ~100 h-1 Mpc • Due to ``baryon acoustic oscillations’’ • Can be used as a Standard Ruler, determine geometry of the Universe Eisenstein et al. 2005 (ApJ, 633, 560)

  9. Motivation • Luminous Red Galaxies (LRGs) provide a very good observational sample to test models of galaxy formation and evolution. • Excellent tracers of Large Scale Structure. • 2 Point CF simple but powerful statistic. • Redshift-space distortions can provide cosmological parameter constraints via Alcock-Paczyncski and clustering evolution (explained in due course) • 2SLAQ extending SDSS LRGs to 0.4<z<0.8. • Extended redshift arm led to photo-z calibration • Proof of concept for future LRG studies e.g. BOSS

  10. Outline of talk • Motivation • The 2dF-SDSS LRG And QSO (2SLAQ) Survey • Clustering techniques • 2SLAQ LRG Clustering results and z-space distortions • The AAOmega LRG Pilot Survey • Future BAO Surveys, The B.O.S.S.

  11. SDSS DR6: 8417 deg2, 1,271,680 spectra, 790,860 gal

  12. LRG Photometric Selection, gri-bands • Method: Use SDSS photometry, gri-bands, to select intrinsically luminous (L > 3L*) red galaxies from z0.0 to 0.8. • Bruzual and Charlot (2003) evolutionary model tracks superimposed on the SDSS data. • Star/galaxy separation from SDSS images. Some red M-type stars remain.

  13. 20’’

  14. SDSS LRG vs. 2SLAQ LRG N(z) • SDSS LRG sky density is 12 deg-2 • 2SLAQ LRG sky density is 53 deg-2 • Same populations, different redshifts • 2SLAQ LRG Survey: • 13,121 LRGs • 17.5 < i < 19.8 • 80 fields giving total area 180 degs2 • 92% spectroscopic completeness

  15. SDSS LRG 2dFGRS 2SLAQ (P. Weilbacher)

  16. Outline of talk • Motivation • The 2dF-SDSS LRG And QSO (2SLAQ) Survey • Clustering techniques • 2SLAQ LRG Clustering results and z-space distortions • The AAOmega LRG Pilot Survey • Future BAO Surveys, The B.O.S.S.

  17. The 2 Point Correlation Function • represents the excess probability of finding a PAIR of galaxies compared with a random distribution: • Power Law behaviour: • Measure theredshift-space CF which include peculiar velocities due to cluster infall and random motions leading to “redshift-space distortions”. • Can measure  in two dimensions, with ,perpendicular and ,parallel, to line-of-sight where, and effects of z-space distortions seen , slope r0, correlation length

  18. The 2 Point Correlation Function a=0 kms-1 =0 a=0 kms-1  =0.4  (along the l.o.s.) Hawkins et al. (2003, MNRAS, 346, 78) a=500 kms-1 =0 a=500 kms-1  =0.4  (perpendicular to the l.o.s.)

  19. The 2 Point Correlation Function • Redshift-space, (s), and Real-space, (r), CFs related by (Kaiser 1987): • Also,  and M related (Peebles 1980; Lahav1991; Peacock+ 2001; Hawkins+ 2003; Zehavi+ 2002) where b is the `linear bias parameter’, which is the ratio of galaxy to (underlying) mass fluctuations; g = b2 m • This linear bias, b, important because it reduces the fractional error due to shot noise, i.e. b , no. of objects needed  (e.g. Blake&Glazebrook, 2003; Tegmark 2006)

  20. Outline of talk • Motivation • The 2dF-SDSS LRG And QSO (2SLAQ) Survey • Clustering techniques • 2SLAQ LRG Clustering results and z-space distortions • The AAOmega LRG Pilot Survey • Future BAO Surveys, The B.O.S.S.

  21. 2SLAQ LRG Redshift-space 2PCF • 2SLAQ LRGs at redshift z = 0.55, r0=7.45 +/- 0.35 h-1 Mpc • SDSS LRGs (Zehavi et al. 2005) at z=0.28, r0=9.80+/-0.20 h-1 Mpc • 2dFGRS Luminous Early-Type (Hawkins et al. 2003; Norberg et al. 2002), at redshift z≈0.1, r0≈6 h-1 Mpc

  22. 2SLAQ 2-D Correlation Function, (,)  (along the l.o.s.) (perpendicular to the l.o.s.)

  23. Alcock-Paczynski Test • Ratio of observed radial size to angular size, varies with cosmology: • Have an intrinsically isotropic structure (e.g. the clustering of galaxies) and observe the radial/angular ratio (A&P, 1979; Ballinger, Peacock, Heavens ’96; Popowski+’98; Hoyle+’02; da Angela+’05; Kim&Croft+’07) • Pros: Geometric test to determine ;no messy galaxy evolution; v. complimentary to BAOs. • Cons: Peculiar velocities also affect isotropic structure.

  24. Cosmological Constraints 1.0 • Compare data to range of test cosmologies • Degeneracy along M-, recall • Additional info: e.g. (z=0), 2dFGRS (Hawkins+ 2003) •  = 0.45 • M =0.25 M(0) 0 0 1.0 +0.10 (z) - 0.15

  25. Outline of talk • Motivation • The 2dF-SDSS LRG And QSO (2SLAQ) Survey • Clustering techniques • 2SLAQ LRG Clustering results and z-space distortions • The AAOmega LRG Pilot Survey • Future BAO Surveys, The B.O.S.S.

  26. Baryon Acoustic Oscillations • In the tightly coupled baryon-photon fluid prior to Recombination, acoustic waves create a characteristic scale – the sound horizon, RS. • At Recombination, vs 0, wave stalls andthe imprint of RS, (BAO), is frozen (but still evolves gravitationally) in the matter, and later, galaxy correlation functions. • Rs(z=1089) can be determined accurately with CMB (148 Mpc), so BAO become a very promising standard ruler, DA(z) and H(z). • Wayne Hu, http://background.uchicago.edu/~whu/ • Martin White, http://cdm.berkeley.edu/doku.php?id=baopages

  27. Future LSS BAO LRG Projects • What you need (minimum): • Large volume of Universe (>1 Gpc3) • Large number of objects (105 - 106) • Our Idea: • ~300,000 LRG redshift surveyover • ~3,500 sq. degs. (95 deg-2) • with redshift 0.5 < z < 1.0 • Requirements: • Imaging from SDSS and VST-ATLAS • LRGs down to i < 20.5 in ~1 hour • 4m-class telescope, reasonable site • Multi-object spectrograph • (Australian)

  28. AAOmega • AAOmega, 392 fibre MOS, on 4m AAT • Blue and Red arms • 5600-8800Å  4000 Å @ z = 0.4 - 1.2 (~0.9). • `Large’ ~200 night proposal • Use LRGs to measure BAO at <z>=0.7 • Pilot Program 03 Mar 2006 – 07 Mar 2006

  29. Again, use SDSS imaging • Select in riz-bands, down to i<20.5 (cf. 2SLAQ i<19.8) • High stellar contamination, can do better • Panels show selection areas and model tracks LRG riz-selection

  30. AAOmega LRG Pilot Run • Mean redshift, <z>=0.68 • Exposure times to get absorption line redshifts varied from 1 to 3 hours, (typically 1.67hrs)

  31. AAOmega LRG Correlation function wp() projection of 3-D (s) AAOmega LRG r0 = 9.03+/-0.93 AAOmega LRGs sample now comparable to SDSS LRGs for LSS studies However…

  32. Outline of talk • Motivation • The 2dF-SDSS LRG And QSO (2SLAQ) Survey • Clustering techniques • 2SLAQ LRG Clustering results and z-space distortions • The AAOmega LRG Pilot Survey • Future BAO Surveys, The B.O.S.S.

  33. Baryon Oscillation Spectroscopic Survey • PI: David Schlegel, part of “SDSS-III” • Use existing 2.5m telescope, upgrade optics and spectrographs • 1.5x106 LRGs, 0.2<z<0.8 over 10,000 deg2 • 160,000 Ly Forests from QSO sightlines, 2.3<z<2.8, 8,000 deg2 • dAto 1, 1.1 and 1.5% at z~0.35, 0.6, 2.5 • Due to start imaging in latter half 2008, spectroscopy 2009

  34. Conclusions • 2SLAQ LRG Survey complete, >13,000 LRG spectroscopic redshifts, 0.4 < z < 0.8. • 2SLAQ LRGs have r0=7.45+/-0.35 h-1 Mpc. • Using dynamical (peculiar velocity) and geometric (Alcock-Paczynski) information find: M=0.25+0.10-0.15 and (z=0.55) = 0.45+0.05-0.03 • Alcock-Paczynski test, v. complimentary to BAOs • SDSS riz-band selection pushes <zLRG>=0.7 • Future Projects, e.g. BOSS (LRG & Ly) Survey

  35. Credits • Tom Shanks, Jose da Angela, Phil Outram, Alastair Edge, David Wake (Durham) • Bob Nichol (Portsmouth) • Russell Cannon, Scott Croom, Rob Sharp (AAO) • Michael Drinkwater, Isaac Roseboom, Kevin Pimbblet (UQ) • Daniel Eisenstein (Arizona) • John Peacock (Edinburgh) • And Nikhil P. and Martin W. for inviting me.

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