High-sensitivity measurements of the cosmic microwave background power spectrum with the extended Very Small Array

Monthly Notices of the Royal Astronomical Society, Sep 2004

We present deep Ka-band (ν≈ 33 GHz) observations of the cosmic microwave background (CMB) made with the extended Very Small Array (VSA). This configuration produces a naturally weighted synthesized FWHM beamwidth of ∼11 arcmin, which covers an ℓ range of 300 to 1500. On these scales, foreground extragalactic sources can be a major source of contamination to the CMB anisotropy. This problem has been alleviated by identifying sources at 15 GHz with the Ryle Telescope and then monitoring these sources at 33 GHz using a single-baseline interferometer collocated with the VSA. Sources with flux densities ≳20 mJy at 33 GHz are subtracted from the data. In addition, we calculate a statistical correction for the small residual contribution from weaker sources that are below the detection limit of the survey. The CMB power spectrum corrected for Galactic foregrounds and extragalactic point sources is presented. A total ℓ range of 150–1500 is achieved by combining the complete extended array data with earlier VSA data in a compact configuration. Our resolution of Δℓ≈ 60 allows the first three acoustic peaks to be clearly delineated. This is achieved by using mosaiced observations in seven regions covering a total area of 82 deg2. There is good agreement with the Wilkinson Microwave Anisotropy Probe (WMAP) data up to ℓ= 700 where WMAP data run out of resolution. For higher ℓ values out to ℓ= 1500, the agreement in power spectrum amplitudes with other experiments is also very good despite differences in frequency and observing technique.

A PDF file should load here. If you do not see its contents the file may be temporarily unavailable at the journal website or you do not have a PDF plug-in installed and enabled in your browser.

Alternatively, you can download the file locally and open with any standalone PDF reader:

https://mnras.oxfordjournals.org/content/353/3/732.full.pdf

High-sensitivity measurements of the cosmic microwave background power spectrum with the extended Very Small Array

Clive Dickinson 0 4 Richard A. Battye 4 Pedro Carreira 4 Kieran Cleary 4 Rod D. Davies 4 Richard J. Davis 4 Ricardo Genova-Santos 3 Keith Grainge 1 Carlos M. Gutie rrez 3 Yaser A. Hafez 4 Michael P. Hobson 1 Michael E. Jones 1 R udiger Kneissl 1 Katy Lancaster 1 Anthony Lasenby 1 J. P. Leahy 4 Klaus Maisinger 1 Carolina O dman 1 Guy Pooley 1 Nutan Rajguru 1 Rafael Rebolo 3 5 Jose Alberto Rubin o-Martin 2 3 Richard D. E. Saunders 1 Richard S. Savage 1 7 Anna Scaife 1 Paul F. Scott 1 Anz e Slosar 1 6 Pedro Sosa Molina 3 Angela C. Taylor 1 David Titterington 1 Elizabeth Waldram 1 Robert A. Watson 4 Althea Wilkinson 4 0 Present address: California Institute of Technology , Mail Stop 105-24, 1200 E. California Boulevard, Pasadena, CA 91125 , USA 1 Astrophysics Group, Cavendish Laboratory, University of Cambridge , Madingley Road, Cambridge CB3 0HE 2 Present address: Max-Planck Institut fu r Astrophysik , Karl-Schwazchild- Str. 1, Postfach 1317, 85741 Garching , Germany 3 Instituto de Astrofis ca de Canarias , 38200 La Laguna, Tenerife, Canary Islands , Spain 4 Jodrell Bank Observatory, University of Manchester , Macclesfield, Cheshire SK11 9DL 5 Consejo Superior de Investigaciones Cientificas , Spain 6 Present address: Faculty of Mathematics & Physics, University of Ljubljana , 1000 Ljubljana , Slovenia. Present address: Instituto de Astrof sica de Canarias , 38200 La Laguna, Tenerife , Spain 7 Present address: Astronomy Centre, University of Sussex , Falmer, Brighton BN1 9QH A B S T R A C T We present deep Ka-band ( 33 GHz) observations of the cosmic microwave background (CMB) made with the extended Very Small Array (VSA). This configuration produces a naturally weighted synthesized FWHM beamwidth of 11 arcmin, which covers an range of 300 to 1500. On these scales, foreground extragalactic sources can be a major source of contamination to the CMB anisotropy. This problem has been alleviated by identifying sources at 15 GHz with the Ryle Telescope and then monitoring these sources at 33 GHz using a single-baseline interferometer collocated with the VSA. Sources with flux densities 20 mJy at 33 GHz are subtracted from the data. In addition, we calculate a statistical correction for the small residual contribution from weaker sources that are below the detection limit of the survey. The CMB power spectrum corrected for Galactic foregrounds and extragalactic point sources is presented. A total range of 150-1500 is achieved by combining the complete extended array data with earlier VSA data in a compact configuration. Our resolution of 60 allows the first three acoustic peaks to be clearly delineated. This is achieved by using mosaiced observations in seven regions covering a total area of 82 deg2. There is good agreement with the Wilkinson Microwave Anisotropy Probe (WMAP) data up to = 700 where WMAP data run out of resolution. For higher values out to = 1500, the agreement in power spectrum amplitudes with other experiments is also very good despite differences in frequency and observing technique. 1 I N T R O D U C T I O N The angular power spectrum of primordial anisotropies in the cosmic microwave background (CMB) has become an important tool in the era of precision cosmology. Because the first statistical detection of CMB fluctuations on large angular scales ( = 230) by the COBE-Differential Microwave Radiometer (DMR) instrument (Smoot et al. 1992), several experiments have detected acoustic peaks in the power spectrum in the range 1001000 (Lee et al. 2001; Halverson et al. 2002; Netterfield et al. 2002; Benot et al. 2003; Scott et al. 2003, hereafter Paper III) and a fall-off in power at high values (Dawson et al. 2002; Grainge et al. 2003; Kuo et al. 2004; Readhead et al. 2004). More recently, the Wilkinson Microwave Anisotropy Probe (WMAP) has provided unprecedented measurements over the range 2700 (Bennett et al. 2003a; Hinshaw 2003a). The WMAP 1-yr power spectrum is cosmic variance limited up to = 350 and delineates the first two peaks at 220 and 550 with exceptional signal-to-noise ratios. The new data have provided detailed cosmological information on a wide range of parameters (Spergel et al. 2003) and have raised new questions to be answered. However, the angular resolution of WMAP limits the power spectrum to 800. At high- values, the origin of the excess power initially observed by the Cosmic Background Imager (CBI) at = 20004000 (Mason et al. 2003) has also generated much interest. It is clear that the high- CMB power spectrum is one of the challenges for future CMB experiments including the ESA Planck satellite (Tauber 2001; Lawrence 2003) due for launch in 2007. The Very Small Array (VSA) (Watson et al. 2003, hereafter Paper I) is a purpose-built radio interferometer that has measured the CMB angular power spectrum between = 150 and 900 in a compact array configuration (Paper III) and more recently up to = 1400 in an extended array (Grainge et al. 2003). This paper describes the complete s (...truncated)


This is a preview of a remote PDF: https://mnras.oxfordjournals.org/content/353/3/732.full.pdf

Clive Dickinson, Richard A. Battye, Pedro Carreira, Kieran Cleary, Rod D. Davies, Richard J. Davis, Ricardo Genova-Santos, Keith Grainge, Carlos M. Gutiérrez, Yaser A. Hafez, Michael P. Hobson, Michael E. Jones, Rüdiger Kneissl, Katy Lancaster, Anthony Lasenby, J. P. Leahy, Klaus Maisinger, Carolina Ödman, Guy Pooley, Nutan Rajguru, Rafael Rebolo, José Alberto Rubiño-Martin, Richard D. E. Saunders, Richard S. Savage, Anna Scaife, Paul F. Scott, Anže Slosar, Pedro Sosa Molina, Angela C. Taylor, David Titterington, Elizabeth Waldram, Robert A. Watson, Althea Wilkinson. High-sensitivity measurements of the cosmic microwave background power spectrum with the extended Very Small Array, Monthly Notices of the Royal Astronomical Society, 2004, pp. 732-746, 353/3, DOI: 10.1111/j.1365-2966.2004.08206.x