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: II. Westerbork observations of the fields around 3C 196 and the North Celestial Pole
Astronomy and Astrophysics, Volume 522, No. 6, Article A67, Year 2010
Notification
URL copied to clipboard!
Description
Context. In the coming years a new insight into galaxy formation and the thermal history of the Universe is expected to come from the detection of the highly redshifted cosmological 21 cm line. Aims. The cosmological 21 cm line signal is buried under Galactic and extragalactic foregrounds which are likely to be a few orders of magnitude brighter. Strategies and techniques for effective subtraction of these foreground sources require a detailed knowledge of their structure in both intensity and polarization on the relevant angular scales of 1-30 arcmin. Methods. We present results from observations conducted with the Westerbork telescope in the 140-160 MHz range with 2 arcmin resolution in two fields located at intermediate Galactic latitude, centred around the bright quasar 3C  196 and the North Celestial Pole. They were observed with the purpose of characterizing the foreground properties in sky areas where actual observations of the cosmological 21 cm line could be carried out. The polarization data were analysed through the rotation measure synthesis technique. We have computed total intensity and polarization angular power spectra. Results. Total intensity maps were carefully calibrated, reaching a high dynamic range, 150000:1 in the case of the 3C 196 field. No evidence of diffuse Galactic emission was found in the angular power spectrum analysis on scales smaller than ∼10 arcmin in either of the two fields. On these angular scales the signal is consistent with the classical confusion noise of ∼3 mJy beam-1. On scales greater than 30 arcmin we found an excess of power attributed to the Galactic foreground with an rms of 3.4 K and 5.5 K for the 3C 196 and the NCP field respectively. The intermediate angular scales suffered from systematic errors which prevented any detection. Patchy polarized emission was found only in the 3C 196 field whereas the polarization in the NCP area was essentially due to radio frequency interference. The polarized signal in the 3C 196 field is close to the thermal noise for angular scales smaller than ∼10 arcmin. On scales greater than 30 arcmin it has an rms value of 0.68 K. The polarized signal appears mainly at rotation measure values smaller than 4 rad m-2. Conclusions. In regard of the detection of the cosmological 21 cm line, we conclude that Galactic total intensity emission lacks small-scale power, which is below the confusion noise level at the angular resolution of 2 arcmin. Galactic polarization, given its relative weakness and its small rotation measure values, is less severe than expected as a contaminant of the cosmological 21 cm line. © 2010 ESO.
Authors & Co-Authors
Bernardi, Gianni
Netherlands, Groningen
Rijksuniversiteit Groningen
United States, Cambridge
Harvard-smithsonian Center for Astrophysics
de Bruyn, A. Ger
Netherlands, Groningen
Rijksuniversiteit Groningen
Netherlands, Dwingeloo
Netherlands Foundation for Research in Astronomy
Harker, Geraint J.A.
Netherlands, Groningen
Rijksuniversiteit Groningen
Brentjens, Michiel A.
Netherlands, Dwingeloo
Netherlands Foundation for Research in Astronomy
Ciardi, Benedetta
Germany, Garching Bei Munchen
Max Planck Institute for Astrophysics
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
Japan, Tokyo
The University of Tokyo
Yatawatta, Sarod B.
Netherlands, Groningen
Rijksuniversiteit Groningen
Zaroubi, Saleem
Netherlands, Groningen
Rijksuniversiteit Groningen
Statistics
Citations: 102
Authors: 14
Affiliations: 6
Identifiers
Doi:
10.1051/0004-6361/200913420
ISSN:
14320746
Research Areas
Environmental