Engineering topics

Danziger, I. J.

Publications and source records attributed to Danziger, I. J..

3 records

NASA NTRS1995

Dark matter in elliptical galaxies

We present measurements of the shape of the stellar line-of-sight velocity distribution out to two effective radii along the major axes of the four elliptical galaxies NGC 2434, 2663, 3706, and 5018. The velocity dispersion profiles are flat or decline gently with radius. We compare the data to the predictions of f = f(E, L(sub z)) axisymmetric models with and without dark matter. Strong tangential anisotropy is ruled out at large radii. We conclude from our measurements that massive dark halos must be present in three of the four galaxies, while for the fourth galaxy (NGC 2663) the case is inconclusive.

Carollo, C. M.↗

NASA NTRS1984

The medium sensitivity survey - A new sample of X-ray sources with optical identifications and the revised extragalactic log N-log S

Maccacaro et al. (1982) surveyed approximately 50 sq deg in different regions of the sky at medium sensitivity flux levels intermediate between the Uhuru/Ariel V limit and the Einstein deep survey limit. This 'first' medium sensitivity survey (MSS 1) was primarily aimed at the analysis of the source-count relation for extragalactic X-ray sources. The present investigation is concerned with an extension of the MSS 1 on the basis of an analysis of new fields obtained with the aid of the Imaging Proportional Counter (IPC) on board the Einstein Observatory. A parallel optical program to identify all the new sources was also undertaken. X-ray and optical data are presented for this 'second' complete sample of medium sensitivity survey X-ray sources (MSS 2). The log N-log S relation is derived and discussed.

Gioia, I. M.↗

NASA NTRS1983

The Einstein Observatory Medium Sensitivity Survey - Optical identifications for a complete sample of X-ray sources

It is suggested that virtually all the X-ray sources in the Einstein Observatory's Medium Sensitivity Survey flux range can be identified with objects visible on the POSS, on the basis of the complete identification of all sources north of -25 deg declination. There is no evidence for a significant population of 'blank field' X-ray sources at this flux level, and therefore no evidence for any new X-ray source class with very high L(x)/L(v). Most of the quasars detected in the present survey are spectroscopically similar to optical or radio-selected quasars. About 25 percent of the quasar sample, however, had reddish colors, and permitted lines dominated by a narrow-line component. These objects form a second sequence of active galactic nuclei, distinct in their optical properties from the broad line objects.

Stocke, J. T.↗