Bibcode
Rebolo, R.; Vsa Consortium.
Bibliographical reference
Lecture Notes and Essays in Astrophysics, vol. 1, p. 1-22.
Advertised on:
9
2004
Citations
0
Refereed citations
0
Description
We describe the Very Small Array (VSA) and review the recent results on
the angular power spectrum of the Cosmic Microwave Background (CMB)
obtained in the Ka-band (ν ≈ 33 GHz) with this instrument. This
array has covered an ℓ-range of 150 to 1500 with a relatively high
resolution in ℓ compared to previous measurements at ℓ≥ 1000;
this is achieved by using mosaiced observations in 7 regions covering a
total of approximately 82 sq. degrees. Our resolution of Δ ℓ
≈ 60 between ℓ=300 and ℓ = 1500 allows the first 3 acoustic
peaks to be identified. Contamination by extragalactic radiosources
brighter than 20 mJy has been taken into account by simultaneously
monitoring identified sources with a high resolution interferometer. In
addition, it has been performed a statistical correction for the small
residual contribution from weaker sources that are below this flux
limit. There is good agreement between the VSA power spectrum and that
obtained by WMAP and other higher resolution experiments like ACBAR and
CBI.
We have set constraints on cosmological parameters using VSA data and
combinations with other CMB data and external priors. Within the flat
ΛCDM model, the combined VSA+WMAP data without external priors
gives Ω_{b}h^2=0.0234^{+0.0012}_{-0.0014},
Ω_{dm}h^2=0.111^{+0.014}_{-0.016}, h=0.73^{+0.09}_{-0.05},
n_{S}=0.97^{+0.06}_{-0.03}, 10^{10}A_{S}=23^{+7}_{-3} and
τ=0.14^{+0.14}_{-0.07}. We also find evidence for a running spectral
index of density fluctuations, n_{run}=-0.069± 0.032 at a level
of more than 95% confidence. However, inclusion of prior information
from the 2dF galaxy redshift survey reduces the significance of the
result. When a general cosmological model with 12 parameters is
considered we find consistency with other analyses available in the
literature. The evidence for n_{run}<0 is only marginal within this
model. The fraction of dark matter in neutrinos is constrained to
f_{ν}< 0.087 (95% confidence limit) which implies that
m_ν<0.32 eV if all the three neutrino species have the same mass.