S. Wyckoff

Abundances in comet Halley at the time of the spacecraft encounters

Spectrophotometric observations of Comet Halley obtained in March 1986 at the time of the spacecraft encounters with the comet are described, and the column densities derived from the integrated emission band fluxes are presented. The scale lengths are determined from the spatial profiles of the observed species. Production rates are derived and the parent identities and abundance ratios of the studied species are discussed. The data indicate that the abundance of the primordial condensate NH3 comprises about 0.2 percent of the total volatile fraction of the comet nucleus. The ratio of production rates Q(NH2)/Q(H2O) = 0.003 indicates that Q(NH3)/Q(H2O) is roughly 0.3 percent, which is nearly 10 times lower than the value determined from Giotto ion mass spectrometer data. The production rate Q(CH)/Q(H2O) of 0.007 and the CH spatial profile indicate that CH cannot derive entirely from direct photodissociation of CH4.

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.

Quasar Galaxies: Two-Dimensional Image Deconvolutions

Studies of quasar images which have adequate spatial resolution and reach sufficiently faint surface brightness levels indicate that virtually all low redshift (z ≲ 0.6) quasars are surrounded by faint nebulosities extending ∿ 3–20 arcsec from the quasar nucleus (at 26 R mag arcsec-2) (Wyckoff et al. 1980, 1981, Hutchings et al. 1981, Wehinger et al. 1983). Furthermore, the average integrated absolute magnitude and average metric diameter of the quasar nebulosities (quasar nucleus removed) are roughly those expected for galaxies at the corresponding (cosmological) quasar distances. Moreover, statistical support for the cosmological interpretation of the redshifts as well as the galaxy interpretation of the fuzz was found in correlations between the angular isophotal diameters of the quasar nebulosities and the redshifts, and between the integrated apparent magnitudes and the angular isophotal diameters (Wyckoff et al. 1981). Spectroscopic observations of quasar fuzz now convincingly support the galaxy interpretation for the quasar nebulosities (Boroson and Oke 1982, Oke et al. 1983).

VLA and Optical Mapping of the Quasar PKS 0812+020

Observations are reported of the remarkable object PKS 0812+020, the first quasar found to have optical emission in one of its radio lobes. A distinct radio jet is also seen, and there is radio and optical evidence that the quasar is near the center of a galaxy cluster.

Characteristics of Nebulosity Associated with Parkes Quasars

A sample of 13 out of 15 low redshift (0.1 ≤ z ≤ 0.6) radio-loud quasars have been resolved on large-scale (19 arcsec mm-1), sky-limited (µR ∿ 26.5 mag sec-2) Kodak IIIa-F photographs obtained .with the ESO 3.6-m telescope. The QSO images were analyzed by digitally subtracting the plate background and the point-spread function defined by images of nearby (≤ 1 arcmin) field stars having magnitudes comparable to the quasars (Δm ≲ 0.3 mag). The resolved nebulosities underlying the QSO images have isophotal diameters in the range θ ∿ 7 to 40 arcsec, with surface brightnesses µR ∿ 22–26 mag sec-1, and integrated apparent red magnitudes ∿ 16–21.