Scale dependence of the primordial spectrum from combining the three-year WMAP, galaxy clustering, supernovae, and Lyman-alpha forests
Abstract
We probe the scale dependence of the primordial spectrum in the light of the three-year WMAP (WMAP3) alone and WMAP3 in combination with the other cosmological observations such as galaxy clustering and type Ia supernova (SNIa). We pay particular attention to the combination with the Lyman-α (Lyα) forest. In contrast to the first-year WMAP (WMAP1), WMAP3's preference for the running of the scalar spectral index on large scales is now fairly independent of the low CMB multipoles \ell . A combination with the galaxy power spectrum from the Sloan Digital Sky Survey (SDSS) prefers a negative running to larger than 2σ, regardless of the presence of the low-\ell CMB (2\le \ell \le 23 ) or not. On the other hand, if we focus on the power law ΛCDM cosmology with only six parameters (matter density Ωmh2, baryon density Ωbh2, Hubble constant H0, optical depth τ, the spectral index, ns, and the amplitude, As, of the scalar perturbation spectrum) when we drop the low-\ell CMB contributions WMAP3 is consistent with the Harrison Zel'dovich Peebles scale-invariant spectrum (ns = 1 and no tensor contributions) at ~1σ. When assuming a simple power-law primordial spectral index or a constant running, in the case when one drops the low-\ell contributions (2\le \ell \le 23 ) WMAP3 is more consistent with the other observations, such as the inferred value of σ8.
- Publication:
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Journal of Cosmology and Astroparticle Physics
- Pub Date:
- May 2007
- DOI:
- 10.1088/1475-7516/2007/05/020
- arXiv:
- arXiv:astro-ph/0608365
- Bibcode:
- 2007JCAP...05..020F
- Keywords:
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- Astrophysics
- E-Print:
- 16 pages, 13 figures Revtex4