2009/02/12 by Timothy Robishaw, Carl Heiles · 1 citation
Physics and Astronomy · #Astronomy and Astrophysical Research #Radio Astronomy Observations and Technology #Superconducting and THz Device Technology #astro-ph.GA #astro-ph.IM
paper · pdf · doi:10.1086/597985
39 pages, 20 figures, accepted for publication in PASP
arxiv created 2009/02/12 · openalex publication_date 2009/03/01 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/30
We use observational data to show that 21 cm line profiles measured with the Green Bank Telescope (GBT) are subject to significant inaccuracies. These include ∼10% errors in the calibrated gain and significant contribution from distant sidelobes. In addition, there are ∼60% variations between the GBT and Leiden/Argentine/Bonn 21 cm line profile intensities, which probably occur because of the high main-beam efficiency of the GBT. Stokes V profiles from the GBT contain inaccuracies that are related to the distant sidelobes. We illustrate these problems, define physically-motivated components for the sidelobes, and provide numerical results showing the inaccuracies. We provide a correction scheme for Stokes I 21 cm line profiles that is fairly successful, and provide some rule-of-thumb comments concerning the accuracy of Stokes V profiles.