Accession Number : AD0696118

Title :   THE 21 CM ABSORPTION PROFILES OF DR 21 AND THE SOURCE NEAR NGC 6857,

Corporate Author : CALIFORNIA INST OF TECH PASADENA OWENS VALLEY RADIO OBSERVATORY

Personal Author(s) : Thompson,A. R. ; Colvin,R. S. ; Hughes,M. P.

Report Date : 1969

Pagination or Media Count : 26

Abstract : The 21 cm absorption profiles of two dense thermal sources, DR 21 and the source near NGC 6857 have been obtained using the interferometer at the Owens Valley Radio Observatory. DR 21 shows absorption over a range of radial velocities from +18 to -20 km/sec (with respect to the local standard of rest), although on the basis of the observed radial velocity and the usual model for galactic rotation one would not expect to find galactic clouds with negative radial velocities between the sun and the source. The neighboring source DR 23 does not appear to show appreciable negative-velocity absorption. Three explanations for the observations of DR 21 are discussed. The radio source previously identified with NGC 6857 has been reported by Rubin and Turner (1969) to be centered 1 ft north of the nebula, at a position that coincides with the small planetary nebula K 3-50. The ionized hydrogen absorption for the source extends from +20 to -33 km/sec and a distance between 7.5 and 9.6 kpc is deduced. (Author)

Descriptors :   (*RADIO ASTRONOMY, NEBULAE), (*NEBULAE, ABSORPTION SPECTRA), GALAXIES, STARS, INTERSTELLAR MATTER, LINE SPECTRA, EXTRATERRESTRIAL RADIO WAVES, ASTRONOMY, PLANETARY ATMOSPHERES, RADIO INTERFEROMETERS, HYDROGEN, IONS, RECOMBINATION REACTIONS, THERMODYNAMICS, RANGE(DISTANCE), VELOCITY, MICROWAVE SPECTROSCOPY

Subject Categories : Astronomy
      Astrophysics

Distribution Statement : APPROVED FOR PUBLIC RELEASE