Engineering topics

Weedman, D. W.

Publications and source records attributed to Weedman, D. W..

6 records

NASA NTRS1985

IUE observations of a starburst disk and the detectability of high redshift galaxies

The high-surface-brightness inner disk of NGC 1068 has been observed with the IUE to determine the ultraviolet spectrum and surface brightness profile. This disk is explained by an intense starburst, requiring formation of 1-2 massive stars/yr, so it is a good prototype for seeking at early epochs in the universe. Calculations of isophotal diameter as a function of redshift are presented. It is found that this disk could be resolved to z of about 0.3 from the ground or to z of about 2.0 with the Hubble Space Telescope. For z greater than about 1.3, such a disk is more easily observable than a large, normal galaxy.

Weedman, D. W.↗

NASA NTRS1981

NGC 7714 - The prototype star-burst galactic nucleus

New X-ray, ultraviolet (IUE), optical, and radio (VLA) observations are presented for the bright nucleus galaxy NGC 7714. All data are explainable as resulting from intense star-formation activity in this nucleus - a star burst. The X-ray and radio luminosities are explained by supernova remnants arising from the massive stars, and approximately 10,000 supernova remnants are required in a volume of 280 pc radius. It is thought that NGC 7714 is typical of a significant class of emission-line galaxies. It is pointed out that individual supernovae should be observable in this, or similar nuclei, because they are expected to occur at rates approaching one per year.

Weedman, D. W.↗

NASA NTRS1980

Colors and magnitudes predicted for high redshift galaxies

Ultraviolet observations of nearby galaxies with the ANS are used to derive ultraviolet spectra for different galaxy types. These spectra are used with existing visible spectrophotometry to calculate K-corrections, and to predict colors and magnitudes for various galaxy types as a function of redshifts, to z = 2. No evolutionary effects are considered. It appears that the first-ranked cluster galaxies on blue emulsions should be spirals for z greater than or approximately equal to 0.5.

Coleman, G. D.↗

NASA NTRS1979

Spectrophotometry of Michigan-Tololo quasars

The Michigan-Tololo sample of quasars is discussed using observational data for 48% of this sample. Emission-line quasar characteristics are confirmed for 80% of the objects observed, including at least four new quasars with spectral features indicative of 'supernova-like' outflow. Approximately 73% of the redshifts predicted from the discovery plates are found to be accurate, with a mean error in z of 0.03; a large range of z (from about 0.1 to 3.16) is represented in the sample. The interpretation of the observed redshift distribution for quasars is strongly dependent upon the significance ascribed to wavelength-dependent selection effects. It appears that the behavior of the comoving quasar density above z = 2.0 may be represented by a constant or an exponential increase.

Lewis, D. W.↗

NASA NTRS1979

Spectrophotometry of Michigan-Tololo quasars

Emission-line quasar characteristics are confirmed for 80% of the objects observed, including at least four new quasars with spectral features indicative of supernova-like outflow. Approximately 73% of the redshifts predicted from the discovery plates are found accurate with a mean error in z of 0.03, and a large range of z (from about 0.1 to 3.16) is represented in the sample. The observed redshift distribution for quasars is marginally consistent with a constant co-moving quasar density above z approximately 2.0. The shape of the redshift distribution may be used as an isotropy probe with a cosmic time resolution of a few times one-hundred million years in the early universe; therefore, continued surveys of this sort are important even if accurate magnitudes are not determined.

Lewis, D. W.↗

NASA NTRS1978

Ultraviolet observations and the extended spectrum of NGC 4151

Five-channel ultraviolet photometry of the Seyfert galaxy NGC 4151 was obtained at three epochs with the ANS. These data are combined with other recent results to illustrate the spectrum of the nucleus of NGC 4151 from 34 microns to 20 MeV, with corrections for galaxy contamination. It is found that no other part of the spectrum has a slope like the best-fitting power law for the X-rays. The C IV emission-line flux is measured; the C IV/H-beta ratio is between 5 and 8, which is similar to the ratio in quasars.

Wu, C.-C.↗