SHARP: The SHARC-II Polarimeter for CSO

摘要

SHARC-II is a 32 x 12 pixel submillimeter camera that is used with the ten-meter diameter Caltech Submillimeter Observatory (CSO) on Mauna Kea. This camera can be operated at either 350 or 450 microns. We developed a module that is installed at the CSO Nasmyth focus in order to convert SHARC-II into a sensitive imaging polarimeter, which we refer to as "SHARP". SHARP splits the incident beam into two orthogonally polarized beams that are then re-imaged onto different halves of the SHARC-II bolometer array. When this removable polarimetry module is in use, SHARC-II becomes a dual-beam 12x12 pixel polarimeter. Sky noise is a significant source of error for submillimeter continuum observations. Because SHARP simultaneously observes two orthogonal polarization components, we are able to eliminate or greatly reduce this source of error. Here we describe the design of SHARP and report preliminary results of tests and observations carried out during our first two runs at CSO in August 2005 and January 2006.