Area Spectroscopy of the Extended Emission-Line Region in the Seyfert Galaxy NGC 3516

Abstract

We performed an area spectroscopic observation of the extended emission-line region (EELR) in the Seyfert 1 galaxy NGC 3516 with the Spectronebulagraph of Okayama Astrophysical Observatory. The whole EELR, including the northern detached component which lies apart by 20″ (4 kpc) from the nucleus, was scanned with a 4.′5 long slit. From the resulting data cube we reproduced pure narrow emission-line images of Hβ [O III], Hα, [N II], and [S II]. From these images it has been found that the excitation is higher toward the northern detached component from the nucleus, and probably also toward the opposite direction. The northern detached component is ionized by power-law ionizing radiation as well as a Z-shaped component. From the kinematics, the northern detached component lies on the galactic disk. There is a considerable deficit of ionizing photons toward the line of site in spite of the fact that the broad-line region can be clearly seen from us. It seems that collimation of the ionizing radiation from the nucleus is caused in or inside the broad line region. Thus, a simple version of the current unified scheme of Seyfert nuclei may not apply to this typical Seyfert 1 galaxy, as in the case of the NGC 4151.