IRAS observations of AGN candidates at low flux levels

IRAS additional observations were used to obtain a sample of point sources at much fainter flux levels than hitherto available through the IRAS Point Source Catalogue. This sample is being used to compile an incomplete but representative catalogue of faint IRAS candidate Active Galactic Nuclei (AGNs) and to study the evolution of the infrared bright galaxies. Ground based follow up observations (optical spectroscopy) are mainly hampered by identification confusion

The nature of the emission-line nebulae in powerful far-infrared galaxies

The authors discuss their program of narrow-band (H alpha + (NII)) imaging of a sample of 30 powerful far-infrared galaxies (FIRG's) chosen to have far-infrared spectral energy distributions similar to the prototype FIRG's Arp 220, NGC 3690, NGC 6240, and M82. The emission-line nebulae of these IR color-selected sample (ICSS) galaxies as a class are both impressively large (mean half light radius, r approx. 1.3 Kpc, and mean diameter, D approx. 16 Kpc) and luminous (L sub TOT approx. 10(exp 8) solar lumninosity; uncorrected for internal extinction). The mean total H alpha + (NII) luminosity of the FIRG's is comparable to that found for pairs of optically selected interacting galaxies (Bushouse, Lamb, and Werner 1988), but is a factor of approx. 5 greater than that of isolated spirals (Kennicutt and Kent 1983). Only approx. 25 percent of the nearby (z approx. less than 0.10) FIRG's have morphologies suggesting that large HII-regions contribute significantly to their emission-line appearance. The broad-band morphologies of our IR color-selected galaxies fall into three major categories. Nearly 75 percent are single galaxy systems, with the remaining FIRG's being either multiple nuclei systems, or members of interacting pairs. Since the authors saw few (10 percent) currently interacting FIRG's, yet many (80 percent) with highly distorted continuum morphologies, their IR color criteria may be preferentially selecting galaxies that have undergone highly inelastic, rapidly merging interactions

PKS 1004+13: A High-Inclination, Highly-Absorbed Radio-Loud QSO -- The First Radio-Loud BAL QSO at Low Redshift?

The existence of BAL outflows in only radio-quiet QSOs was thought to be an important clue to mass ejection and the radio-loud - radio-quiet dichotomy. Recently a few radio-loud BAL QSOs have been discovered at high redshift. We present evidence that PKS 1004+13 is a radio-loud BAL QSO. It would be the first known at low-redshift (z = 0.24), and one of the most radio luminous. For PKS 1004+13, there appear to be broad absorption troughs of O VI, N V, Si IV, and C IV, indicating high-ionization outflows up to about 10,000 km/s. There are also two strong, broad (~500 km/s), high-ionization, associated absorption systems that show partial covering of the continuum source. The strong UV absorption we have detected suggests that the extreme soft-X-ray weakness of PKS 1004+13 is primarily the result of absorption. The large radio-lobe dominance indicates BAL and associated gas at high inclinations to the central engine axis, perhaps in a line-of-sight that passes through an accretion disk wind.Comment: To appear in Ap.J. Letters, 1999 (June or July); 4 pages, 5 figure

Propeller propulsion integration, phase 1

A bibliography was compiled of all readily available sources of propeller analytical and experimental studies conducted during the 1930 through 1960 period. A propeller test stand was developed for the measurement of thrust and torque characteristics of full scale general aviation propellers and installed in the LaRC 30 x 60 foot full scale wind tunnel. A tunnel entry was made during the January through February 1980 period. Several propellers were tested, but unforseen difficulties with the shaft thrust torque balance severely degraded the data quality

Starburst-driven superwinds from infrared galaxies

New data is presented that indicate that strong far infrared galaxies commonly have largescale emission line nebulae whose properties are suggestive of mass outflows (superwinds), presumably driven by the high supernova rate associated with the central starburst. These data include longslit spectra of M82 which show that the radial variation of the gas pressure in the emission line nebula is in excellent agreement with a previous wind model. The M82 nebula also has a LINER spectrum, consistent with shock heating. Morphologically and spectroscopically similar emission line nebulae were found in NGC253, and Arp 220 and NGC6240. A longslit spectroscopic investigation was conducted of 20 additional very powerful far-infrared galaxies and found that they generally have spatially extended emission line nebulae whose spectra closely resemble that of the M82 nebula. If the superwind interpretation is correct, it could have many important consequences in extragalactic astronomy

Deceleration of Relativistic Radio Components and the morphologies of Gigahertz Peaked Spectrum Sources

A relativistic radio component, which moves in a direction close to the sky plane, will increase in flux density when it decelerates. This effect is the basis for the qualitative model for GPS galaxies we present in this paper, which can explain their low-variability convex spectrum, their compact double or compact symmetric morphology, and the lack of GPS quasars at similar redshifts. Components are expelled from the nucleus at relativistic speeds at a large angle to the line of sight, and are decelerated (eg. by ram-pressure or entrainment of the external gas) before contributing to a mini-lobe. The young components are Doppler boosted in the direction of motion but appear fainter for the observer. The non-relativistic mini-lobes dominate the structure and are responsible for the low variability in flux density and the convex radio spectrum as well as the compact double angular morphology. Had the same source been orientated at a small angle to the line of sight, the young components would be boosted in the observer's direction resulting in a flat and variable radio spectrum at high frequencies. Hence the characteristic convex spectrum of a GPS source would not be seen. These sources at small angles to the line of sight are probably identified with quasars, and are not recognized as GPS sources, but are embedded in the large population of flat spectrum variable quasars and BL Lac objects. This leads to a deficiency in GPS/CSOs identified with quasars.Comment: 11 pages, LaTeX, accepted by A&A 26/Jan/199