First-Epoch Proper Motion Radio Observations on the Galactic Spur.

Abstract

view Abstract Citations References Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS First-Epoch Proper Motion Radio Observations on the Galactic Spur. Ellis, Fred Edward Abstract or any large arc-like object, implies proper motion if the object is not too old. The proper motion would be proportional directly to the tangent of the angular radius and inversely to the age. For example, if the Spur were associated with the "supernova" of A.D. 1006 the proper motion would be about 4 min of arc per year. Background radiation maps are not suitable as proper motion material. Scan profiles are desired. To be along the direction of greatest anticipated proper motion the scan path must follow a radius of the circle which best fits the obj ect. If the observation includes a discrete source as a coordinate marker and only relative position measures attempted, precession, correction for time constant, and conversion from indicated to true coordinates are unnecessary. The observing program is more self-contained if it includes pairs of scans made in opposite directions through the same discrete source. Such pairs of proper motion observations simultaneously carry information on telescope pointing errors, time constant, and antenna beam. To investigate observing techniques and to obtain first-epoch material for the Spur, observations were made in spring 1965 using the National Radio Astronomy Observatory 300-ft meridian telescope at 750 and 1415 Mc/sec. Declination scans at 2.5 min of arc per second included north-going and south- going scans through 3C310, 3C315, and 3C318. On 750 Mc/sec the ridge, seen on lower frequencies in this region at 180 declination, is conspicuous but because of the faintness of the Spur, an individual scan would not be useful for a position measurement. Only noise is seen on any individual 1415 Mc/sec record. Averaging of the digital records is in progress. Publication: The Astronomical Journal Pub Date: 1965 DOI: 10.1086/109658 Bibcode: 1965AJ.....70S.674E full text sources ADS |