arXiv subjects

A. C. Goncalves

Publications and source records attributed to A. C. Goncalves.

22 records · Page 2Linked to original sources

arXiv1998

On the QSO content of the First Byurakan Survey and the completeness of the Palomar Green Survey

The second part of the First Byurakan Survey is aimed at detecting all bright (B < 16.5) UV-excess starlike objects in a large area of the sky. By comparison with major X-ray and radio surveys we tentatively identified as QSOs 11 FBS objects. We made spectroscopic observations of nine of them. We found six new QSOs bringing the total number of known QSOs in this survey to 42. By comparison with the Palomar Green (PG) QSO survey, we found that the completeness of this last survey is of the order of 70% rather than 30-50% as suggested by several authors.

astro-ph↗

arXiv1998

The emission-line spectrum of KUG 1031+398 and the Intermediate Line Region controversy

We present results based on the analysis of optical spectra of the Narrow-Line Seyfert 1 (NLS1) galaxy KUG 1031+398, for which evidence was reported of a line-emitting region "intermediate" (both in terms of velocity and density) between the conventional Broad and Narrow Line Regions (BLR and NLR, respectively). From our observations and modeling of the spectra, we get a consistent decomposition of the line profiles into four components: an extended H II region with unresolved lines, two distinct Seyfert-type clouds identified with the NLR, and a relatively narrow "broad line" component emitting only Balmer lines but no forbidden lines. Therefore, although we find this object to be exceptional in having line-emission from the BLR with almost the same width as the narrow lines, our interpretation of the data does not support the existence of an "intermediate" line region (ILR).

astro-ph↗

arXiv1998

NGC 5252 - a Liner undercover

Ground based long slit spectroscopic observations of the nuclear region of NGC 5252, and Hubble Space Telescope (HST) Faint Object Spectrograph (FOS) spectra of the nucleus and two bright knots located 0.36" NE and 0.31" SW from it, show that the nuclear region exhibits the characteristics of a Liner with exceptionally strong [OI] emission, all lines being broad (FWHM ~ 1100 km/s), while the gas outside the nucleus has a typical Seyfert 2 spectrum with relatively narrow lines (FWHM ~ 200-300 km/s). We suggest that all the emitting gas is photoionized by the hidden non-thermal nuclear source detected through near-infrared (Kotilainen & Prieto 1995) and X-ray (Cappi et al. 1996) observations, the ionizing continuum, in the case of the central Liner, being "filtered" by a matter-bounded highly ionized cloud, hidden from our view by the same material obscuring the central continuum source.

astro-ph↗

arXiv1997

Miscellaneous observations of active galactic nuclei. II

We observed 37 AGN candidates and classified them on the basis of their spectroscopic properties; three are confirmed QSOs, one is a BL Lac object, nine are Seyfert 1 galaxies, four Seyfert 2s, while twenty are HII regions.

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