James Nathaniel Douglas

Optical identifications of radio sources using accurate radio and optical positions

The first results of a program of optical identification of several thousands of radio sources based on the sole criterion of coincidence of accurate radio and optical positions are presented. Radio positions of ~1 arcsec accuracy for 605 radio sources have already been published by Douglas, Bash, Ghiho, Moseley, and Torrence (1973), who give further details of the overall program. Optical positions a re given for 181 objects near some of these and other radio sources, measured with typical rms accuracy of 0.5 arcsec. Of 145 objects within 10 arcsec of the radio positions measured by Douglas et al., 81 are within 3 arcsec, including 38 spectroscopically confirmed QSOs, 15 additional blue stellar objects, and 15 galaxies. Finding charts are given for 43 objects which are within 3 arcsec of the radio positions (5 arcsec for galaxies and blue stellar objects) and for which finding charts do not exist in the literature. The reliability of these new identifications, based on position coincidence alone, is approximately 95%. A number of previously suggested identifications have been rejected on the basis of the new and more accurate radio and optical positions. (auth)

A search for optically variable objects in the Texas Radio Source Survey

The positions of 60,284 radio sources from the University of Texas Radio Astronomy Observatorys survey are compared with those of 14,672 objects from the General Catalog of Variable Stars in the overlap region between -35.8 and +49.1 deg declination. While all the previously known identifications with BL Lac objects, Seyfert galaxies, and supernova remnants in the GCVS were found in the search, no new coincidences were discovered, even though the number of radio sources used is an order of magnitude larger than those used in earlier searches. 22 references.

Interim Report on the Texas Survey

The University of Texas Radio Astronomy Observatory (UTRAO) is engaged in a survey of the entire sky north of −35° declination at various frequencies in the range 335–380 MHz. Primary goals are (i) determination of accurate ~l“) positions for about 50,000 sources, followed by (ii) optical identification of the sources on the basis of exact radio-optical position coincidence; (iii) provision of rough structure models for all listed sources; and (iv) monitor the sky for variable sources on the time scale of 1 to 2 years. The survey is not expected to be a reliable source of absolute flux density information except for those sources known to be unresolved from other work.

The Texas Radio Astrometric Survey

The 5-element Texas Interferometer is engaged in a 365 MHz survey of the sky with a primary goal of establishing positions of about 50000 discrete radio sources with an accuracy of about 1″ in each coordinate. Measurements are made relative to optical positions of identified sources, and the 2000 positions thus far obtained support our expectations of the accuracy of the survey. In a companion program, optical positions of objects near radio source positions are being measured to ± 1/2″ accuracy on glass copies of the Palomar Sky Survey, yielding both improved overall calibration of the radio positions and identification of associated optical objects on the basis of position coincidence alone, without the selection effects usually introduced by auxiliary identification criteria.