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Cosmic Chronometers: Unveiling the Universe's Secrets

Explore the latest findings on cosmic measurements combining BAO and SN data, revealing age and evolution constraints of the universe. Discover discrepancies and potential resolutions. Analyze cosmological relationships and parameters for a deeper understanding of cosmic evolution.

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Cosmic Chronometers: Unveiling the Universe's Secrets

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  1. Combining Different Measurements Bob Nichol, ICG Portsmouth Tommaso Giannantonio, H-J Seo, Dan Carson, Hubert Lampeitl*, Josh Frieman, Bruce Bassett, Mat Smith, Will Percival (for SDSS Collaboration) * see poster

  2. BAO with Redshift Measure ratio of volume averaged distance D0.35 /D0.2 = 1.812 ± 0.060 Flat CDM = 1.67 Systematics (damping, BAO fitting) also ~1Next set of measurements will need to worry about this 99.74% detection z~0.2 143k + 465k 79k z~0.35 Percival et al. (2006) Percival et al. 2007

  3. Cosmological Constraints Flatness assumed, constant w With CMB Only D0.35 /D0.2 W w= P/ 3 1 Favors w<-1 at 1.4 2 m

  4. Cosmological Constraints Flatness assumed m = 0.249 ± 0.018 w = -1.004 ± 0.089 With CMB Only D0.35 /D0.2 W W w= P/ 3 1 D0.35 /D0.2 = 1.66 ± 0.01 2 m m

  5. 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

  6. Revisit with SDSS SNe Only look at measurements at z<0.4 • 500 Ia’s • 102 from 05 • LCDM line • 2s contours • q0 = -0.34 (2s) SDSS BAO points

  7. Cosmological Constraints Only look at measurements at z<0.4 • ISW (z<0.4) • Peacock et al Flat wCDM W SNe BAO w= -1 (15% stat & sym) SDSS BAO points

  8. Curvature Only look at measurements at z<0.4 • ISW (z<0.4) • Peacock et al

  9. Distance Duality Returning to BAO and SN discrepancy?

  10. Cosmic Chronometers Age 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)

  11. Cosmic Chronometers II Age of galaxies constraints age of universe (Jimenez & Loeb 2002) ALL FLAT raw t(z) HST TSR ISW WMAP

  12. Differential Ages H(z) We find H(z=0.2) ~ 80 +/- 12 km/s Same value as Gaztanaga et al. but not yet competitive in error

  13. Tension remains between BAO and SN (over same redshift range). But ~2s at best Cosmic Chronometers provide constraints on age-redshift relation (thus h and Wm). 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.) Conclusions

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