Changes In Line Profiles Research Articles

An Interferometric Investigation of the Spatial Distribution and Motion of the Neutral Hydrogen in Seven External Galaxies.

view Abstract Citations References Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS An Interferometric Investigation of the Spatial Distribution and Motion of the Neutral Hydrogen in Seven External Galaxies. Seielstad, G. A. ; Whiteoak, J. B. ; Radhakrishnan, V. ; Fomalont, E. B. Abstract A preliminary investigation of the spatial distribution and motion of the neutral hydrogen in seven external galaxies has been carried out using the twin-element interferometer of the Owens Valley Radio Observatory with an east- west baseline of 100 ft. A traveling-wave maser, donated by the Bell Telephone Laboratories, was employed in one channel of the interferometer output, and a conventional crystal receiver in the other. The bandwidth in each channel was 100 kc/sec. The galaxies studied were NGC 55, 300, 2403, 3109,4214, 4244, and Holmberg II. For most of these galaxies, comparison of the line profiles with single- dish measurements made at Harvard indicates that resolution effects have already become noticeable. For some of the galaxies, notably NGC 2403, the shape of the line profile changes as the galaxy rotates with respect to the fringe system of the interferometer. These changes have yielded information regarding the distribution of neutral hydrogen with the galaxy. Phase measurements as a function of frequency have been converted into rotation curves. In Holmberg II there is no evidence of systematic motion. In the other cases, the rotation curves indicate solidbody rotation in the central portions of the galaxies. For a few cases the rotation curve was determined to the point where departures from linearity became evident. From the rotation curves, estimates of the total masses were obtained. Publication: The Astronomical Journal Pub Date: 1965 DOI: 10.1086/109587 Bibcode: 1965AJ.....70R.147S full text sources ADS |

Short Period Investigations in Spark Discharges

With the help of an automatic electronic switch placed between phototube and recorder of a spectrograph, the intensities as function of time of a series of spectrum lines produced in a spark have been recorded. The changes as function of the position in the gap were also investigated. There is an extensive afterglow which in general decays faster for the higher stages of ionization. The continuous background has the same characteristics as the spectrum of the surrounding gas. The changes in self-absorption excitation and line profile were also studied as function of time and partly correlated with the fundamental processes responsible for the afterglow.