The synthesis telescope at the Dominion Radio Astrophysical Observatory

TLDR

The paper presents an aperture synthesis radio telescope designed to image the Galactic interstellar medium with high angular resolution over wide fields, detailing its receiver, correlator, calibration, and observing strategies that make it an efficient survey instrument. It uses nine 9‑m antennas to generate 21‑cm HI and dual‑band continuum (1420 MHz and 408 MHz) images, including 1420 MHz linear polarization, with synthesized beams of …, a 256‑channel spectrometer, wide fields of view, short baselines for extended structure, and incorporates single‑antenna data for full angular coverage. The system achieves continuum rms sensitivities of 0.28 mJy beam⁻¹ at 1420 MHz and 3.8 mJy beam⁻¹ at 408 MHz, and the 256‑channel HI spectrometer reaches 3.5 K per channel.

Abstract

We describe an aperture synthesis radio telescope optimized for studies of the Galactic interstellar medium (ISM), providing the ability to image extended structures with high angular resolution over wide fields. The telescope produces images of atomic hydrogen emission using the 21-cm HI spectral line, and, simultaneously, continuum emission in two bands centred at 1420 MHz and 408 MHz, including linearly polarized emission at 1420 MHz, with synthesized beams of and at the respective frequencies. A full synthesis can achieve a continuum sensitivity (rms) of 0.28 mJy/beam at 1420 MHz and 3.8 mJy/beam at 408 MHz, and the 256-channel HI spectrometer has an rms sensitivity of 3.5 K per channel, for total spectrometer bandwidth B MHz and declination δ. The tuning range of the telescope permits studies of Galactic and nearby extragalactic objects. The array uses 9 m antennas, which provide very wide fields of view of 3.1° and 9.6° (at the 10% level), at the two frequencies, and also allow data to be gathered on short baselines, yielding extremely good sensitivity to extended structure. Single-antenna data are also routinely incorporated into images to ensure complete coverage of emission on all angular scales down to the resolution limit. In this paper we describe the telescope and its receiver and correlator systems in detail, together with calibration and observing strategies that make this instrument an efficient survey machine.