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The Nature of Compact Objects in Active Galactic Nuclei The Nature of Compact Objects in Active Galactic Nuclei
Proceedings of the 33rd Herstmonceux Conference, held in Cambridge, July 6-22, 1992
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Spectroscopy of the Extended Emission Line Regions in NGC 4388

from I - Evidence and Implications of Anisotropy in AGN

Published online by Cambridge University Press:  04 August 2010

Ismael Pérez-Fournon
Affiliation:
Instituto de Astrofísica de Canarias, 38200, La Laguna, Tenerife, Spain
Baltasar Vila-Vilaó
Affiliation:
Instituto de Astrofísica de Canarias, 38200, La Laguna, Tenerife, Spain
José A. Acosta-Pulido
Affiliation:
Instituto de Astrofísica de Canarias, 38200, La Laguna, Tenerife, Spain
J. Ignacio González-Serrano
Affiliation:
Departamento de Física Teórica, Universidad de Cantabria, Santander, Spain
Marc Balcells
Affiliation:
Observatorio del Roque de los Muchachos, La Palma, Tenerife, Spain
Andrew S. Wilson
Affiliation:
Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, U.S.A.
Zlatan Tsvetanov
Affiliation:
Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218, U.S.A.
Andrew Robinson
Affiliation:
University of Cambridge
Roberto Juan Terlevich
Affiliation:
Royal Greenwich Observatory, Cambridge
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Summary

Abstract

We present and discuss the results of long-slit spectroscopic observations of the extended emission line regions (EELR) in NGC4388, a Seyfert 2 galaxy in which extended, off-nuclear broad Hα emission (FWZI ≈ 4000 km s−1) has been reported (Shields & Filippenko 1988). These features have been interpreted as scattered radiation from a Seyfert 1 nucleus that is obscured along our line of sight. Our spectroscopic observations cover a large fraction of the inner part of the EELR, including some of the positions where the presence of broad lines has been claimed. Broad wings in the Hα + [NII] λλ6548, 6583 complex are also present in our data but they can be explained by the superposition of several narrow components. However, we cannot, at present, exclude the possibility that an intrinsically broad component to Hα exists at some locations. The implications of our results for unified models of Seyfert galaxies are briefly discussed.

Introduction

NGC4388 is a high-inclination Seyfert 2 galaxy with bright EELR (Colina et al. 1987, Pogge 1988, Corbin et al. 1988). Radio observations reveal a double-peaked source close to the apparent optical nucleus and more extended emission aligned roughly perpendicular to the galaxy disk (Stone et al. 1988, Hummel & Saikia 1991). The axis of the cone-like, high-excitation gas is almost perpendicular to the galaxy disk and close to that of the extended radio emission (Pogge 1988, Corbin et al. 1988), suggesting that the EELR are photoionized by nuclear radiation which escapes preferentially along and around the radio axis.

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The Nature of Compact Objects in Active Galactic Nuclei
Proceedings of the 33rd Herstmonceux Conference, held in Cambridge, July 6-22, 1992
, pp. 40 - 43
Publisher: Cambridge University Press
Print publication year: 1994

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