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/ Cannon et al., 2006, MNRAS, 372, 425

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.

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.

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

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).

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

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.

Eisenstein et al (ApJ, 633, 560) `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 UniverseMotivation

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

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.

SDSS DR6: 8417 deg 2, 1,271,680 spectra, 790,860 gal

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.

20’’

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 degs 2  92% spectroscopic completeness

(P. Weilbacher) 2dFGRSSDSS LRG 2SLAQ

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.

represents the excess probability of finding a PAIR of galaxies compared with a random distribution: Power Law behaviour: Measure the redshift-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 The 2 Point Correlation Function , slope r 0, correlation length

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

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 = b 2  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) The 2 Point Correlation Function

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.

2SLAQ LRG Redshift-space 2PCF 2SLAQ LRGs at redshift z = 0.55, r 0 =7.45 +/ h -1 Mpc SDSS LRGs (Zehavi et al. 2005) at z=0.28, r 0 =9.80+/-0.20 h -1 Mpc 2dFGRS Luminous Early-Type (Hawkins et al. 2003; Norberg et al. 2002), at redshift z≈0.1, r 0 ≈6 h -1 Mpc

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

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. Alcock-Paczynski Test

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)  (z) Cosmological Constraints

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.

Baryon Acoustic Oscillations In the tightly coupled baryon-photon fluid prior to Recombination, acoustic waves create a characteristic scale – the sound horizon, R S. At Recombination, v s  0, wave stalls and the imprint of R S, (BAO), is frozen (but still evolves gravitationally) in the matter, and later, galaxy correlation functions. R s (z=1089) can be determined accurately with CMB (148 Mpc), so BAO become a very promising standard ruler, D A (z) and H(z). Wayne Hu, Martin White,

Future LSS BAO LRG Projects What you need (minimum):  Large volume of Universe (>1 Gpc 3 )  Large number of objects ( ) 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)

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

LRG riz-selection 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

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

AAOmega LRG Correlation function w p (  ) projection of 3-D  (s) AAOmega LRG r 0 = 9.03+/-0.93 AAOmega LRGs sample now comparable to SDSS LRGs for LSS studies However…

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.

Baryon Oscillation Spectroscopic Survey PI: David Schlegel, part of “SDSS-III”  Use existing 2.5m telescope, upgrade optics and spectrographs  1.5x10 6 LRGs, 0.2<z<0.8 over 10,000 deg 2  160,000 Ly  Forests from QSO sightlines, 2.3<z<2.8, 8,000 deg 2 d A to 1, 1.1 and 1.5% at z~0.35, 0.6, 2.5 Due to start imaging in latter half 2008, spectroscopy 2009

Conclusions 2SLAQ LRG Survey complete, >13,000 LRG spectroscopic redshifts, 0.4 < z < SLAQ LRGs have r 0 =7.45+/-0.35 h -1 Mpc. Using dynamical (peculiar velocity) and geometric (Alcock-Paczynski) information find:  M = and  (z=0.55) = Alcock-Paczynski test, v. complimentary to BAOs SDSS riz-band selection pushes =0.7 Future Projects, e.g. BOSS (LRG & Ly  ) Survey

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.