R. S. Roger

The radio emission from the Galaxy at 22 MHz

We present maps of the 22MHz radio emission between declinations -28d and +80d, covering ~73% of the sky, derived from observations with the 22MHz radiotelescope at the Dominion Radio Astrophysical Observatory (DRAO). The resolution of the telescopt (EWxNS) is 1.1d x 1.7d secant(zenith angle). The maps show the large scale features of the emission from the Galaxy including the thick non-thermal disk, the North Polar Spur (NPS) and absorption due to discrete HII regions and to an extended band of thermal electrons within 40d of the Galactic centre. We give the flux densities of nine extended supernova remnants shown on the maps.

The synthesis telescope at the Dominion Radio Astrophysical Observatory

We describe an aperture synthesis radio tele- scope optimized for studies of the Galactic interstellar medium (ISM), providing the ability to image extended structures with high angular resolution over wide elds. The telescope produces images of atomic hydrogen emis- sion using the 21-cm H i 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 1 0 and 3:4 0 at the respective frequencies. A full synthesis can achieve a con- tinuum sensitivity (rms) of 0.28 mJy/beam at 1420 MHz and 3.8 mJy/beam at 408 MHz, and the 256-channel H i spectrometer has an rms sensitivity of 3.5B 0:5 sin K per channel, for total spectrometer bandwidth B MHz and declination . The tuning range of the telescope permits studies of Galactic and nearby extragalactic objects. The array uses 9 m antennas, which provide very wide elds 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 incorpo- rated 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 corre- lator systems in detail, together with calibration and ob- serving strategies that make this instrument an ecient survey machine.

IRAS 23545 + 6508, a dissociating star - Prototype for a new observational class

The paper presents observations of a compact H I source coincident with a strong, far-infrared source, IRAS 23545 + 6508. It is believed that this object is representative of a new observational class which traces stars in the range of spectral types from B1 to B5 which are embedded in molecular clouds. Using methods based on birthrate statistics and other data, it is estimated that there are of order 1000 such sources within a radius of 2 kpc of the sun. 42 refs.