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Astron. Astrophys. 338, 8-14 (1998)

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1. Introduction

Dust and stars in the Milky Way obscure a large fraction of the extragalactic sky, creating a "Zone of Avoidance" (ZOA) in the distribution of galaxies. In an effort to reduce the size of the ZOA and thus coming closer towards an all-sky distribution of galaxies, we have embarked on a deep optical galaxy search behind the southern Milky Way (Kraan-Korteweg & Woudt 1994). This has led to the recognition that ACO 3627 (Abell et al. 1989), also called the Norma cluster after the constellation it is located in, is a massive, nearby cluster of galaxies at the core of the Great Attractor (GA) [FORMULA] km s-1 ) (Kraan-Korteweg et al. 1996). The Norma cluster appears to be the central, dominant component of a "great wall"-like structure and would be the most prominent overdensity of galaxies in the southern sky, were it not obscured by the Milky Way (Woudt et al. 1997).

Recent observations of the Norma cluster with the ROSAT PSPC have confirmed the massive nature of ACO 3627; it is the 6th brightest cluster in the ROSAT sky (Böhringer et al. 1996). The X-ray contours furthermore suggest the existence of a subcluster. The merging scenario is independently supported by the radio continuum emission of the central cD galaxy PKS1610-608. The emission from this wide-angle-tail (WAT) radio source (Jones & McAdam 1992) seems to encircle the X-ray subcluster (see Fig. 3 of Kraan-Korteweg et al. 1997) and is indicative of a strong motion of the cluster gas due to the ongoing merging process (Jones & McAdam 1996, Burns et al. 1994).

Roughly [FORMULA] from the centre of this cluster - taken as the central cD galaxy PKS1610-608 - we have identified a Seyfert 1 galaxy. It is a member of ACO 3627. In the following sections we describe the various observations of this galaxy: the discovery of the galaxy in Sect. 2, the multicolour photometry obtained at the South African Astronomical Observatory (SAAO) in Sect. 3, the spectroscopy obtained at the European Southern Observatories (ESO) and the SAAO in Sect. 4, the H I observations obtained with the 64m radio telescope of the Parkes Observatory of the Australian Telescope National Facility (ATNF) in Sect. 5, and the X-ray data from ROSAT PSPC observations in Sect. 6. The results are summarized and discussed in the last section.

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© European Southern Observatory (ESO) 1998

Online publication: September 8, 1998