Combining Different Measurements

Bob Nichol, ICG PortsmouthBob Nichol, ICG PortsmouthTommaso Giannantonio, H-J Seo, Tommaso Giannantonio, H-J Seo, Dan Dan

CarsonCarson, , Hubert LampeitlHubert Lampeitl*, Josh *, Josh Frieman, Bruce Bassett, Mat Smith, Will Frieman, Bruce Bassett, Mat Smith, Will

PercivalPercival

(for SDSS Collaboration)(for SDSS Collaboration)

* see poster

BAO with Redshift

99.74% detection

Percival et al. (2006)

143k + 465k

79kz~0.35

z~0.2

Percival et al. 2007

Measure ratio of volume averaged distance

D0.35 /D0.2 = 1.812 ± 0.060

Flat CDM = 1.67

Systematics (damping, BAO fitting) also ~1Next set of measurements will need to worry about this

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Dv(z) =(1+ z)2czDA(z)2

H (z)

⎡

⎣ ⎢

⎤

⎦ ⎥

1

3

Cosmological Constraints

w=

P/

m

Only D0.35 /D0.2

With CMB

Flatness assumed, constant w

Favors w<-1 at 1.4

W

Cosmological Constraints

1

2

3

W

m

Only D0.35 /D0.2

With CMB

Flatness assumed

W

m

m = 0.249 ± 0.018

w = -1.004 ± 0.089

D0.35 /D0.2 = 1.66 ± 0.01

w=

P/

Discrepancy?

• 2.4 difference between SN & BAO. The BAO want more acceleration at z<0.3 than predicted by z>0.3 SNe

• ~1 possible from details of BAO damping - more complex then we thought

• Assumption of flatness and constant w needs to be revisited

Revisit with SDSS SNeOnly look at measurements at z<0.4

500 Ia’s 102 from 05 LCDM line 2 contours q0 = -0.34 (2)

SDSS BAO points

Cosmological ConstraintsOnly look at measurements at z<0.4

ISW (z<0.4) Peacock et al

SDSS BAO points

W SNe

BAO

Flat wCDM

w= -1 (15% stat & sym)

CurvatureOnly look at measurements at z<0.4

ISW (z<0.4) Peacock et al

Distance DualityReturning to BAO and SN discrepancy?

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DL = (1+ z)2+2α DA

Cosmic ChronometersAge of galaxies constraints age of universe (Jimenez & Loeb 2002)

5500 LRGs

Carson et al. (in prep)

(Using Thomas et al. models, marginalised over alpha-enhancement and metallicity)

Cosmic Chronometers IIAge of galaxies constraints age of universe (Jimenez & Loeb 2002)

raw t(z) HST TSR

ISW WMAP

ALL FLAT

Differential Ages H(z)

We find H(z=0.2) ~ 80 +/- 12 km/s

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H(z) =1

(1+ z)

dz

dt

Same value as Gaztanaga et al. but not yet competitive in error

Conclusions

• Tension remains between BAO and SN (over same redshift range). But ~2 at best

• Cosmic Chronometers provide constraints on age-redshift relation (thus h and m). Also provide constraints on H(z) but not yet competitive

• BOSS could do much better, especially if we can do better on the stellar modeling (Maraston et al.)