In this paper long slit spectroscopy and broad band imaging of the intermediate Seyfert galaxies Mkn 423 and Mkn 739 are presented. The analysis of the extranuclear emissions reveals that Mkn 423 and Mkn 739 are undergoing a strong burst of star formation spread over a kpc-sized scale. Although the morphological appearance of Mkn 423 is suggestive of a galaxy of type Sa/SBa with a giant HII region (component B), the peculiar kinematics of Mkn 423 and the very large Hα luminosity of component B suggest that this system could be the result of an ongoing merging of two galaxies. The resolution ~2 A FWHM of the spectra taken in the range 4000-5500 A allowed to resolve substructures in the Hβ and [OIII]λλ4959,5007 line profiles, permitting an analysis of the circumnuclear regions of these objects. The narrow line spectrum of Mkn 423 originates in two partially resolved blobs, of high ionization degree, which are likely to be the optical counterpart of two radio emitting sources or which are associated with the NLR and circumnuclear gas ionized by the central source. Mkn 739 shows extended high-ionization gas up to a distance ~4 h^-1^ kpc from the Seyfert nucleus. This gas is photoionized by the active nucleus itself, and it is in a kinematical status (probably in outflow) different from that of the low ionization gas associated with star formation. The high ionization degree observed as far as ~2 h^-1^ kpc from the Seyfert nucleus suggests that the central ionizing source is most probably anisotropic.
The Merging Seyfert Galaxies MARKARIAN:423 and MARKARIAN:739
RAFANELLI, PIERO;
1993
Abstract
In this paper long slit spectroscopy and broad band imaging of the intermediate Seyfert galaxies Mkn 423 and Mkn 739 are presented. The analysis of the extranuclear emissions reveals that Mkn 423 and Mkn 739 are undergoing a strong burst of star formation spread over a kpc-sized scale. Although the morphological appearance of Mkn 423 is suggestive of a galaxy of type Sa/SBa with a giant HII region (component B), the peculiar kinematics of Mkn 423 and the very large Hα luminosity of component B suggest that this system could be the result of an ongoing merging of two galaxies. The resolution ~2 A FWHM of the spectra taken in the range 4000-5500 A allowed to resolve substructures in the Hβ and [OIII]λλ4959,5007 line profiles, permitting an analysis of the circumnuclear regions of these objects. The narrow line spectrum of Mkn 423 originates in two partially resolved blobs, of high ionization degree, which are likely to be the optical counterpart of two radio emitting sources or which are associated with the NLR and circumnuclear gas ionized by the central source. Mkn 739 shows extended high-ionization gas up to a distance ~4 h^-1^ kpc from the Seyfert nucleus. This gas is photoionized by the active nucleus itself, and it is in a kinematical status (probably in outflow) different from that of the low ionization gas associated with star formation. The high ionization degree observed as far as ~2 h^-1^ kpc from the Seyfert nucleus suggests that the central ionizing source is most probably anisotropic.
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