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We estimate the spatial clustering of faint galaxies in an extensive new redshift survey performed using the automatic fibre positioner (Autofib) on the Anglo-Australian Telescope. The survey comprises 1100 galaxies within a magnitude range of 17

Considerable evidence exists for a relationship between the optical narrow-line region (the NLR) and the nuclear non-thermal radio emission in Seyfert galaxies. In a previous paper we introduced a model for the NLR, which we here develop and describe more fully, in which the linear motions of the radio components drive bowshocks into the ambient nuclear medium. The cooled shocked gas, photoionized by the UV nuclear continuum, produces the optical NLR emission. The radio components may take the form of bubbles of plasma ejected from the nucleus, or may represent the working surfaces of jets

The formation of nano-particles in silica glass by ion implantation has attracted great attentions because of the applications for visible luminescence and nonlinear optical devices. Ion implantation is a unique technique for producing nano-particles, with the advantages of high controllability of beam position, depth and distribution of projectiles, concentration, high purity and ability to overcome low solubility restrictions.Optical grade silica glasses were used as the substrates. Ion implantation was performed with a 1.7 MV tandem-type ion accelerator (NEC 5SDH-II pelletron accelerator) of NERIN. The substrates were implanted with 1.0 MeV O+ and 1.8 MeV Cu+. Projected ranges were calculated by SRIM-2000 to be 1.5 μm (for O+) and 1.4 μm (for Cu+). Samples were cooled with liquid nitrogen to reduce the beam heating. The ion current densities of O+ and Cu+ were 6 and 2 μA/cm2, respectively.

On a etudie la relation qui existe entre l'emission radio et le gaz qui emet les raies, au moyen de trois techniques differentes: l'interferometrie a tres longue base, l'observation en bande etroite de haute resolution angulaire et la spectroscopie a longue fente, de haute dispersion

Ajustement des sections transversales de photoionisation de plusieurs ions d'interet astrophysique tels que N 2+ , N 3+ , O 4+ , Al + , Si 2+ et S 4+

Observations spectroscopiques haute resolution des raies d'emission [O III] a λ 4959 et λ 5007 A pour 13 noyaux actifs de galaxies de l'hemisphere Sud. Les caracteristiques des profils de ces raies sont etudiees et discutees individuellement

On presente les observations de la structure cinematique du gaz [OI] λ6300 dans un champ de 3,8×2,9 min arc 2 du voisinage de la nebuleuse de Kleinman-Low. Les modeles d'objets de Herbig-Haro ne permettent pas d'interpreter les objets du type Orion. On propose donc deux nouveaux modeles pour leur formation

La methode du couplage fort est utilisee pour calculer les forces de collision pour les transitions dans O 2+ , 2s 2 2p 2 3 P- 1 D, 3 P- 1 S, 1 D- 1 S et 2s 2 2p 2 3 P-2s2p 3 5 S 0 , et les sections efficaces pour la photoionisation de O + 2s 2 2p 34 S 0

Copyright Royal Astronomical Society. [Full text of this article is not available in the UHRA]

On presente de nouvelles observations de la raie O III λ 5592 A dans la nebuleuse planetaire NGC 3918. On propose un modele pour le processus d'echange de charge impliquant O 3+ et H dans cette nebuleuse et NGC 7662. On a obtenu une temperature electronique pour l'oxygene neutre T e (0°)=10000 (±1000)K pour NGC 3918

Le gradient d'abondance dans M33 est etudie sur la base d'observations spectroscopiques IPCS et CCD des raies d'emission dans les regions HII, en utilisant O I I, O I II, S I I et S I II dans l'etendue λλ3700-9600 A pour affiner les abondances en oxygene dans les regions internes et etudier le comportement de S/O

The magnitude of superexchange interaction of the MnO crystal is calculated according to the methods proposed previously. Various mechanisms of superexchange interaction are taken into consideration. Overlaps between neighbouring ions are assumed to be small and the energy of the crystal is developed in powers of 8, the overlap integral between manganese and oxygen ions. The superexchange interaction of all mechanisms appears from 8 4 terms and it is concluded from calculation that the Slater mechanism may play a dominant role in MnO. The numerical value of magnitude of interaction agrees with experiment in the order of magnitude. Several discussions about superexchange interactions of other substances, particularly of MnFg and LaMnOs, are given.

Accurate collision strengths for the semi-forbidden transitions C/sup +/ , N/sup 2+/ 2s/sup 2/2p /sup 2/P/sup o/--2s2p/sup 2/ /sup 4/P, and N/sup +/, O/ sup 2+/ 2s/sup 2/2p/sup 2/ /sup 3/P--2s2p/sup 3/ /sup 5/S/sup o/, were calculated using the close coupling approximation and allowing for configuration interaction. Effective collision strengths are presented for these transitions as a function of electron temperature Te. The signiflcance of these results, for various quasar models, is discussed. (auth)