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BAO and Tomography of the SDSS

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BAO and Tomography of the SDSS. Alex Szalay Haijun Tian Tamas Budavari Mark Neyrinck. SDSS Redshift Samples. Main Galaxies 8 00K galaxies, high sampling density, but not too deep Volume is about 0.12 Gpc 3 Luminous Red Galaxies 100K galaxies, color and flux selected - PowerPoint PPT Presentation
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BAO and Tomography of the SDSS Alex Szalay Haijun Tian Tamas Budavari Mark Neyrinck
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Page 1: BAO and Tomography  of the SDSS

BAO and Tomography of the SDSS

Alex SzalayHaijun Tian

Tamas BudavariMark Neyrinck

Page 2: BAO and Tomography  of the SDSS

SDSS Redshift Samples

Main Galaxies◦ 800K galaxies, high sampling density, but

not too deep◦ Volume is about 0.12 Gpc3

Luminous Red Galaxies◦ 100K galaxies, color and flux selected◦ mr < 19.5, 0.15 < z < 0.45, close to

volume-limitedQuasars

◦ 20K QSOs, cover huge volume, but too sparse

Page 3: BAO and Tomography  of the SDSS

Finding the Bumps – DR4Eisenstein et al (2005) – LRG

sample

Page 4: BAO and Tomography  of the SDSS

Primordial Sound Waves in SDSSPower Spectrum(Percival et al 2006, 2007)SDSS DR6+2dF

SDSS DR5

800K galaxies

Page 5: BAO and Tomography  of the SDSS

(r) from linear theory + BAOMixing of 0 , 2 and 4

◦Along the line of sight)()(

21)(

0

22 kPkrjkdkr nn

)(35

8)(7

43

4)(53

21)( 4

2

2

2

0

2)( rrrrs

r

Page 6: BAO and Tomography  of the SDSS
Page 7: BAO and Tomography  of the SDSS

2D SymmetryThere is a planar symmetry:

◦Observer+ 2 galaxiesThus 2D correlation of a slice is

the sameWe usually average over cosVery little weight along the

axis:◦Sharp of features go away

Page 8: BAO and Tomography  of the SDSS

Tomography of SDSSSDSS DR7 Main Galaxy Sample

◦Limit distances to 100<r<750 h-1 Mpc

Cut 3D data into thin angular slices◦Project down to plane (only 2D info)◦Different widths (2.5, 5, 10 deg)◦Rotate slicing direction by 15

degreesAnalyze 2D correlation function (,)

Average over angle for 1-D correlations

Page 9: BAO and Tomography  of the SDSS

Why correlation function?For a homogeneous isotropic process,

the correlation function in a lower dimsubset is identical

There are subtleties:◦With redshift space distortions the process is

not fully homogeneous and isotropicRedshift space distortions and ‘bumps’

◦Distortions already increase the ‘bumps’◦Any effects from the ‘slicing’?

Page 10: BAO and Tomography  of the SDSS

Projection and Slicing Theorem

Nmmm FSPF

The basis of CAT-SCAN / Radon xform

Page 11: BAO and Tomography  of the SDSS
Page 12: BAO and Tomography  of the SDSS

Slices of finite thicknessProject redshift-space power

spectrum with a corresponding window function

sinc(kzR)Anisotropic power spectrum

◦There is a thickness-dependent effect

◦Thinner slices give bigger boost

Page 13: BAO and Tomography  of the SDSS

Millennium 64Mpc

Page 14: BAO and Tomography  of the SDSS

Millennium 16Mpc

Page 15: BAO and Tomography  of the SDSS

Millennium 4Mpc

Page 16: BAO and Tomography  of the SDSS

Millennium 1Mpc

Page 17: BAO and Tomography  of the SDSS

2.5 deg slices (702 total)

Page 18: BAO and Tomography  of the SDSS

5 deg slices

Page 19: BAO and Tomography  of the SDSS

10 deg slices

Page 20: BAO and Tomography  of the SDSS

10 deg, in 3D

Page 21: BAO and Tomography  of the SDSS

Full 3D correlation function

Page 22: BAO and Tomography  of the SDSS

Full 3D no Great Wall

Page 23: BAO and Tomography  of the SDSS

2.5 deg slices (702 total)

Page 24: BAO and Tomography  of the SDSS

(r) along the line of sight

0 20 40 60 80 100 120 140 160 180 200-0.05

-0.04

-0.03

-0.02

-0.01

0

0.01

0.02

0.03

0.04

0.05

Average of all 2.5 degree slices

Page 25: BAO and Tomography  of the SDSS

3D along the line

Page 26: BAO and Tomography  of the SDSS

No Great Wall

Page 27: BAO and Tomography  of the SDSS

(r) along the line of sightThe correlation function along a

1D line:◦Pencilbeam

Corresponding power spectrum◦Projection of P(s)(k) onto a single axis

Page 28: BAO and Tomography  of the SDSS

Computations on GPUsGenerated 16M randoms with

correctradial and angular selection for SDSS-N

Done on an NVIDIA GeForce 260 card

400 trillion galaxy/random pairsBrute force massively parallel

code muchfaster than tree-code

All done inside the JHU SDSS database

2D correlation function is now DB utility

Page 29: BAO and Tomography  of the SDSS

SummaryRedshift space distortions amplify featuresLower dimensional subsets provide further

amplification of ‘bumps’ at 107-110h-1MpcBoost much stronger along the line of sightUsing these techniques we have strong

detection of BAO in SDSS DR7 MGSEffect previously mostly seen in LRGsTrough at 55h-1Mpc is a harmonic,

sharpness indicates effects of nonlinear infall

Bump at 165h-1Mpc puzzling

Page 30: BAO and Tomography  of the SDSS

Millennium galaxies

Page 31: BAO and Tomography  of the SDSS

Cosmology usedM = 0.279L = 0.721K = 0.0h = 0.701w0 = -1


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