Skip to content
Home
About Us
Resources
Profiles Metrics
Authors Directory
Institutions Directory
Top Authors
Top Institutions
Top Sponsors
AI Digest
Contact Us
Menu
Home
About Us
Resources
Profiles Metrics
Authors Directory
Institutions Directory
Top Authors
Top Institutions
Top Sponsors
AI Digest
Contact Us
Home
About Us
Resources
Profiles Metrics
Authors Directory
Institutions Directory
Top Authors
Top Institutions
Top Sponsors
AI Digest
Contact Us
Menu
Home
About Us
Resources
Profiles Metrics
Authors Directory
Institutions Directory
Top Authors
Top Institutions
Top Sponsors
AI Digest
Contact Us
Publication Details
AFRICAN RESEARCH NEXUS
SHINING A SPOTLIGHT ON AFRICAN RESEARCH
Foregrounds for observations of the cosmological 21 cm line: I. First westerbork measurements of Galactic emission at 150 MHz in a low latitude field
Astronomy and Astrophysics, Volume 500, No. 3, Year 2009
Notification
URL copied to clipboard!
Description
Context. The cosmological 21 cm line promises to be a formidable tool for cosmology, allowing the investigation of the end of the so-called dark ages, when the first galaxies formed.Aims. Astrophysical foregrounds are expected to be about three orders of magnitude greater than the cosmological signal and therefore represent a serious contamination of the cosmological 21 cm line. Detailed knowledge of both their intensity and polarization structure on the relevant angular scale of 1-30 arcmin will be essential for extracting the cosmological signal from the data.Methods. We present the first results from a series of observations conducted with the Westerbork telescope in the 140-160 MHz range with a 2 arcmin resolution aimed at characterizing the properties of the foregrounds for epoch of reionization experiments. The polarization data were analysed through the rotation measure synthesis technique. We computed total intensity and polarization angular power spectra.Results. For the first time we have detected fluctuations in the Galactic diffuse emission on scales greater than 13 arcmin at 150 MHz, in the low Galactic latitude area known as Fan region, centred at α = 3h10m, δ = 65°30'. Those fluctuations have an rms of 14 K. The total intensity power spectrum shows a power-law behaviour down to ℓ ∼900 with slope βℓI = -2.2 ± 0.3. The detection of diffuse emission at smaller angular scales is limited by residual point sources. We measured an rms confusion noise of ∼3 mJy beam-1. Diffuse polarized emission was also detected for the first time at this frequency. The polarized signal shows complex structure both spatially and along the line of sight. The polarization power spectrum is not affected by residual point sources and is only limited by the thermal noise. It shows a power-law behaviour down to ℓ ∼2700 with slope βℓP = -1.65 ± 0.15. The rms of polarization fluctuations is 7.2 K on 4 arcmin scales.Conclusions. The measured total intensity fluctuations are used to estimate the foreground contamination on the cosmological signal. By extrapolating the spectrum of total intensity emission, we find a contamination of δT = √ℓ(ℓ + 1)CℓI/2π ∼ 5.7 K on 5 arcmin scales and a corresponding rms value of ∼18.3 K at the same angular scale. The level of the polarization power spectrum is δT ∼ 3.3 K on 5 arcmin scales. However, the Fan region cannot be taken as representative of other sky regions, given its exceptionally bright polarized signal, but is likely to represent an upper limit on the sky brightness at moderate and high Galactic latitude. © 2009 ESO.
Authors & Co-Authors
Bernardi, Gianni
Netherlands, Groningen
Rijksuniversiteit Groningen
de Bruyn, A. Ger
Netherlands, Groningen
Rijksuniversiteit Groningen
Netherlands, Dwingeloo
Netherlands Foundation for Research in Astronomy
Brentjens, Michiel A.
Netherlands, Dwingeloo
Netherlands Foundation for Research in Astronomy
Ciardi, Benedetta
Germany, Garching Bei Munchen
Max Planck Institute for Astrophysics
Harker, Geraint J.A.
Netherlands, Groningen
Rijksuniversiteit Groningen
Jelić, Vibor
Netherlands, Groningen
Rijksuniversiteit Groningen
Koopmans, Léon V.E.
Netherlands, Groningen
Rijksuniversiteit Groningen
Labropoulos, Panagiotis
Netherlands, Groningen
Rijksuniversiteit Groningen
Offringa, André R.
Netherlands, Groningen
Rijksuniversiteit Groningen
Pandey, Vishhambhar N.
Netherlands, Groningen
Rijksuniversiteit Groningen
Schaye, Joop
Netherlands, Leiden
Universiteit Leiden
Thomas, Rajat Mani
Netherlands, Groningen
Rijksuniversiteit Groningen
Yatawatta, Sarod B.
Netherlands, Groningen
Rijksuniversiteit Groningen
Zaroubi, Saleem
Netherlands, Groningen
Rijksuniversiteit Groningen
Statistics
Citations: 168
Authors: 14
Affiliations: 4
Identifiers
Doi:
10.1051/0004-6361/200911627
ISSN:
14320746
Research Areas
Environmental