GBT22B-353

SPC: Mapping the GBT Beam using Pulsars

Abstract

Over the past 20 years, there have been numerous projects that have sought to map HI in the Milky Way and in the circumgalactic medium of nearby galaxies using the GBT. Stray radiation is one of the main limiting factors in deriving accurate fluxes for sources and in properly localizing emission in the halos of galaxies instead of in their disks. While the unblocked optics of the GBT minimize sidelobes, they do not completely eliminate them as the L-band feedhorn is too small for the secondary reflector. Boothroyd et al. (2011) has mapped the far sidelobes of the GBT L-band feed, but was unable to map the inner beam due to the limited dynamic range of the receiver when observing the Sun. We propose to map the inner square degree of the GBT beam using a pulsar to provide in situ On and Off measurements, as has been done at Parkes, and will allow us to measure the beam down to -40 dB from the peak response. When combined with the Boothroyd et al. beam maps, these data will permit for even higher dynamic range imaging of HI (and other sources) with the GBT.

Investigators

Name	Institution
D.J. Pisano *	Cape Town, University of
Ryan Lynch	Green Bank Observatory
Jay Lockman	Green Bank Observatory
Nickolas Pingel	Wisconsin at Madison, University of; Indiana University; Australian National University

* indicates the PI