On Measuring Accurate 21-cm Line Profiles with the Robert C. Byrd Green Bank Telescope

Abstract

We use observational data to show that 21 cm line profiles measured with the Green Bank Telescope (GBT) are subject to significant inaccuracy. 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.

arXiv comment39 pages, 20 figures, accepted for publication in PASP

Cited by in corpus (6)

• Discovery of the Interstellar Chiral Molecule Propylene Oxide (CH${}_3$CHCH${}_2$O)
• GASS: The Parkes Galactic All-Sky Survey. II. Stray-Radiation Correction and Second Data Release
• Accurate Galactic 21-cm H I measurements with the NRAO Green Bank Telescope
• Understanding synthesis imaging dynamic range
• The Neutral Hydrogen Bridge between M31 and M33
• Mapping the Extended HI Distribution of Three Dwarf Galaxies