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Hewitt, A.

Publications and source records attributed to Hewitt, A..

6 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1993

A revised and updated catalog of quasi-stellar objects

The paper contains a catalog of all known quasi-stellar objects (QSOs) with measured emission redshifts, and BL Lac objects, complete to 1992 December 31. The catalog contains 7315 objects, nearly all QSOs including about 90 BL Lac objects. The catalog and references contain extensive information on names, positions, magnitudes, colors, emission-line redshifts, absorption, variability, polarization, and X-ray, radio, and infrared data. A key in the form of subsidiary tables enables the reader to relate the name of a given object to its coordinate name, which is used throughout the compilation. Plots of the Hubble diagram, the apparent magnitude distribution, the emission redshift distribution, and the distribution of the QSOs on the sky are also given.

Hewitt, A.↗
NASA NTRS1991

An optical catalog of extragalactic emission-line objects similar to quasi-stellar objects

A catalog of 935 galaxies which have optical properties similar to those of QSOs is given. A subsidiary table of cross-identifications enables the reader to relate the name of a given object to its coordinate name. Most of the objects appear to be nonstellar. The majority, more than 700, have redshifts z = 0.2 or less, and have mostly been classified as Seyfert galaxies, N systems, or radio galaxies. The Hubble diagram for all of the objects with z = 0.2 or less is shown. The redshift distribution peaks at z = 0.025, but there are about 200 powerful radio galaxies in the extended tail of the distribution which have z greater than 0.2. There is a separate and distinct peak in the redshift distribution at z = 0.06.

Hewitt, A.↗
NASA NTRS1990

Associations between quasi-stellar objects and galaxies

A table is presented here listing all close pairs of QSOs and galaxies that were found in a computer-aided search of catalogs of QSOs and bright galaxies and an extensive search of the literature. There is a large excess of pairs with separations of 2 arcmin lor less, or about 60 kpc, over the numbers expected if the configurations were accidental. The angular separation for 392 pairs adds to the evidence for physical association, and it is shown that selection effects are not important. A general rule is stated that QSOs tend to lie in the vicinity of normal galaxies much more often than is expected by chance whether or not the galaxies and the QSOs have the same redshifts. It is emphasized that this rule cannot be explained in terms of gravitational microlensing, and it is concluded that some part of the redshift of all classes of active nuclei is not associated with the expansion of the universe.

Burbidge, G.↗
NASA NTRS1990

The redshift peak at z = 0.06

A catalog of galaxies whose optical spectra contain strong broad emission lines and continua, probably of nonthermal origin, has been completed. The catalog contains about 900 objects, about 700 of which have z of 0.2 or less. A histogram of the redshift distribution for all of the objects in the redshift range 0.02-0.2 and with a large peak at z = 0.06 is shown. Possible interpretations of the peak, which was first seen in 1968, are considered. It is concluded that the only way to explain the peak (and others like it that make up a series of peaks) and still maintain the cosmological redshift hypothesis is to go to cosmological models in which the universe has a multiply connected topology.

Burbidge, G.↗
NASA NTRS1980

High resolution imaging at large telescopes

Image recovery at a resolution limited only by diffraction is now possible at large telescopes. The theory of speckle image reconstruction is explained and the current status of a video recording and digitization system for the reconstruction procedure is described. Potential applications of the process when used with very large telescopes are discussed. The constraints on telescope design imposed by these techniques are listed.

Nisenson, P.↗