The photoionization of extended narrow-line regions in Seyfert galaxies by the radiation produced in a thick accretion disk is studied. The emission-line spectrum is calculated for a range of black hole masses, varying the values of the ionization parameter and the disk size. It is found that models with a million solar masses fit observations of

The discovery of a very high velocity, low-intensity gas feature in the giant extragalactic H II region NGC 5471 is reported. A broad component in the emission lines of H-alpha + forbidden N II 6548, 6584 A is located within an area less than 1 arcsec in diameter at the position known as knot C. The broad component is characterized by its low

As part of a systematic survey for the search of high velocity gas in giant extragalactic H II regions, the authors have observed the five largest and brightest H II regions in M101. They have found two types of peculiar emission profiles: (1) a broadening of the Hα emission line at low intensity, in excess of the values expected for the typical

Ultraviolet IUE spectra and infrared JHKL photometry of FG Sge obtained over the period 1982-1989 indicate that the cooling rate of the star observed until about 1980 seems to have stopped and that an increase of the effective temperature may have occurred, this being a significant change in the evolutionary path traced so far. The current spectral

The peculiar galaxy NGC 520 (Arp 157) is often interpreted as an interacting pair of galaxies. The identification of the two bulges and overall morphology of the two galaxies has long been a puzzle which the authors attempt to solve here. New longslit optical spectroscopy and near-infrared images of NGC 520 are presented. These data suggest that

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