No abstract available

[en] Spectrograms were taken in the direction of the apparent minor axis of the peculiar galaxy NGC 2685. Measurements along the [O II] lambda 3727 emission feature within 10'' from the center show that the line-of-sight velocity of the ionized gas increases by approximately equal to 250 km s^-1 from the NW side to SE side of the inner region of the galaxy

[en] The observations of the ionized gas in nuclei of galaxies and the interpretation of the observed data in terms of physical conditions of the gas are reviewed. The ambiguities and uncertainties both in the observations and interpretation are outlined. Comparison is made between optical line intensities in the spectra of normal H II regions and planetary nebulae on one hand and the spectra of nuclei of galaxies on the other hand. The causes of the differences between the spectra of these various types of ionized gas regions are briefly discussed. 21 refs

[en] 20 quasars with redshifts in the range 2-2.7 have been observed with a spectral resolution of 7 A, for a statistical study of the properties of the emission lines and also to find interesting candidates for detailed studies. In three of the four quasars with the narrowest CIV lines, the emission feature at 1909 A is resolved nicely into the two lines Si III] λ 1892 and C III] λ 1909 suggesting that in many cases the Fe III UV 34 triplet is not a dominant contributor to this feature. In the fourth one the 1909 A feature is weak and low-contrast. In the quasar 0353-38 which was found by Osmer to have anomalous abundances and in particular a high N/C ratio, we find that the CIV line is narrower than [N III] λ 1750. In the gas producing the broadest component of the emission line the ratio N/C is twice as large as previously determined by Osmer, but appears normal in the region emitting the narrow component. Four low ionization absorption line systems are found with z ranging from 0.55 to 1.28, two of these systems being in the same quasar (0254-40)

[en] 3C 273 is the most extensively studied quasar both from the ground and from space. Recent satellite observations have given important information on the overall electromagnetic spectrum of 3C 273 in the γ-ray, X-ray, and UV ranges. The most salient results are: (i) the energy per decade of frequency emitted by 3C 273 is nearly constant between 6000 Angstroem and 500 MeV and is approx. equal to 20 x 10⁴⁶ erg s^-1 for H = 50 km s^-1 Mpc^-1; (ii) there is no absorption in the soft X-ray range in contrast to the X-ray spectrum of Seyfert nuclei; (iii) the optical and UV spectra cannot be fitted by power-law spectra only, and the energy distribution in this range suggests that a substantial fraction of the energy in the UV is emitted as black-body radiation at approx. equal to 20 000 K. If the peculiar shape of the UV spectrum is indeed caused by black-body radiation, then an estimate of the energy emitted under this form is 2.5 x 10⁴⁶ erg s^-1, corresponding to an optically thick disk of approx. equal to 10¹⁶ cm in diameter. The UV spectrum of 3C 273 shows absorption lines at zero redshift caused by interstellar matter in the disk and halo of our Galaxy. The strength of CIV lambda1550 in absorption indicates the presence of a hot outer region in the halo. Extragalactic objects with mostly continuous UV spectra, such as 3C 273, are very promising UV sources which allow us to observe the absorbing material over the entire line of sight throughout the galactic halo. (orig.)

[en] Observations of the time variations of the emission lines in Seyfert nuclei, and in particular in NGC 4151, the galaxy that has been the most extensively studied in the ultraviolet, are reviewed. The line intensity and line profile variations in NGC 4151 allow the structure of the broad-line region to be understood. The variations are consistent with a model where the optical thickness, the distance from the central continuum source, and the velocity of the clouds forming the broad-line region are correlated, the cloud with the highest velocities and smaller optical thickness being closer to the center. It is argued that the prominent C IV 1550 absorption lines in NGC 3516 and NGC 4151 are not caused by clouds in the broad-line region. The absorber is probably an outflowing sheet of gas covering a large fraction of the broad-line region and located more than one light year away from the continuum source. 27 references

No abstract available

[en] Low-dispersion spectrograms have been obtained for 22 galaxies noted as 'Extremely Compact' in the Catalogue of Galaxies and of Clusters of Galaxies published by Zwicky and collaborators and radial velocities are given for 14 of them. Ten galaxies have emission lines spectra and one of them (0934 + 01) is a new Seyfert-type galaxy with broad hydrogen lines and narrow forbidden lines. K and H lines at nearly zero velocity are seen on the spectra of two galaxies and presumably originate from galactic stars projected on the galaxy nuclei. (orig.)

No abstract available

[en] The authors report the first observations of variability in the ultraviolet spectrum of the quasar 3C273 (redshift, z=0.158) as observed by the International Ultraviolet Explorer in the period 1978-84. The flux at lambdasub(observed)=1,675 A increased by 1.25 between April and June 1982, then decreased by a factor 2 between June 1982 and April 1983. The amplitude of these variations and the constancy of the intensity of the Lyα emission line during the same period are indications that the ultraviolet variations are caused by variations of the black body and/or non-thermal components. The flux variations are accompanied by variations of the spectral shape. An interpretation is presented of the observed variability in terms of a discontinuous and variable distribution of the temperature on the photosphere emitting the ultraviolet continuum. (author)