Engineering topics

Wardle, J. F. C.

Publications and source records attributed to Wardle, J. F. C..

6 records

NASA NTRS1993

Is 1308+326 A BL Lacertae object or a quasar?

The active galaxy 1308+326 (z = 0.996) has been classified as a BL Lacertae object because of its nearly featureless optical continuum and high and variable polarization. New VLBI polarization images of 1308+326, however, show both VLBI polarization structure and tentative superluminal motions that are characteristic of quasars rather than BL Lacertae objects. These data strongly suggest that this source is simply a quasar with emission lines of small equivalent width. We discuss the possibility that the optical continuum is enhanced by microlensing in a foreground galaxy, as suggested by Stickel et al.

Gabuzda, D. C.↗

NASA NTRS1992

Radio constraints on the nature of BL Lacertae objects and their parent population

5 GHz VLA observations of 17 BL Lac objects with bright radio cores at both high and low resolution are reported. Extended emission is detected around most objects. None of the sources observed at low resolution show evidence of giant halos on the scale of tens of arcmin. In general, the sources with the most luminous extended emission exhibit FR II characteristics in both morphology and polarization, and less luminous sources exhibit FR I characteristics. Thus, the parent population of the BL Lac objects contains both FR I and FR II radio sources. No BL Lac objects are found that clearly exhibit quasarlike polarization at milliarcsec resolution. This argues against the view that the more luminous BL Lac objects are simply an extension of the quasar/OVV population, or that most BL Lac objects are gravitationally microlensed images of distant quasars. Other properties are generally consistent with the view the BL Lac objects are normal radio galaxies whose jets make a small angle to the line of sight.

Kollgaard, R. I.↗

NASA NTRS1992

A survey of the milliarcsecond polarization properties of BL Lacertae objects at 5 GHz

Consideration is given to millarcsecond-resolution total-intensity and linear polarization maps at 5 GHz presented for 11 BL Lacertae objects. In every BL Lacertae object in which polarization structure was detected, the polarization position angle of the knots is nearly parallel to the VLBI structural axis. The direction of the polarization in the cores of these sources appears to be random. The preferred polarization direction in the jets is explained by the fact that plane perpendicular shock waves are common in these sources; the origin of the absence of the preferred polarization direction in the core components is unclear. These results support an early conclusion that it cannot be the case that a significant number of BL Lacertae objects are gravitationally microlensed images of more distant quasars, since the characteristic VLBI polarization structures observed in these two types of objects are very different.

Gabuzda, D. C.↗

NASA NTRS1986

The linear polarization of 3C 345 at milliarcsecond resolution

A polarization-sensitive 6 cm map of the superluminal quasar 3C 345 with angular resolution 2.5 x 4.7 mas was made using four stations of the US VLBI network. The optically thick core is essentially unpolarized, while both of the knots in the jet are highly polarized. The inner knot C3 has m = 11 percent at electric vector position angle chi = 22 deg, and the outer knot C2 has m = 6 percent at chi = 83 deg. Thus the magnetic field appears to be parallel to the jet near its base and to change direction down the jet.

Wardle, J. F. C.↗

NASA NTRS1983

X-ray studies of quasars with the Einstein Observatory. III The 3CR sample

Using X-ray emission detected by the Einstein Observatory from each of the 33 3CR quasars in Schmidt's complete sample, it is demonstrated that there is a relationship between the X-ray emission and centimeter wavelength radio emission even for steep-spectrum quasars, provided that only the radio emission from the central object is considered. The observations are summarized, and the estimation of the X-ray luminosity distribution, rather narrow compared to the radio and optical luminosity distributions, is presented. The relationship between X-ray and radio emission is discussed, as is the cosmological evolution of the X-ray luminosity function. The relationship between X-ray and optical luminosity provides an explanation for the finding that X-ray selected quasars have lower redshifts than optically selected quasars of the same optical magnitude.

Tananbaum, H.↗

NASA NTRS1982

A new intermediate Seyfert galaxy - X-ray, optical, and radio properties

It is shown that the X-ray source X0459 + 034 is a Seyfert galaxy of intermediate type, and optical spectroscopy and radio observations were performed to study the nature of the object. The object appears almost stellar and slightly diffuse on Palomar Sky Survey prints. The source is identified as a Type 1.5 Seyfert with broad and narrow line components of redshift 0.016 + or - 0.001, according to H-Beta line profile. In addition, the broad line component H-Beta equivalent width is larger than that of the narrow line component by a factor of three. Finally, it is shown that this is a weak radio source with a steep nonthermal spectrum and an angular extent of approximately 3 in., and the composite radio-to-X-ray spectrum suggests that in different spectral regions, different relativistic electron populations or emission mechanisms are contributing factors.

Ghigo, F. D.↗