EDP Sciences
Free Access
Issue
A&A
Volume 391, Number 2, August IV 2002
Page(s) L21 - L24
Section Letters
DOI https://doi.org/10.1051/0004-6361:20021039


A&A 391, L21-L24 (2002)
DOI: 10.1051/0004-6361:20021039

Letter

NGC 5506 unmasked as a Narrow Line Seyfert 1:

A direct view of the broad line region using near-IR spectroscopy
N. M. Nagar1, E. Oliva1, 2, A. Marconi1 and R. Maiolino1

1  INAF, Arcetri Observatory, Largo E. Fermi 5, Florence 50125, Italy
2  INAF, Telescopio Nazionale Galileo, Aptdo de Correos, 565, 38700 Santa Cruz de La Palma, Canary Islands, Spain

(Received 12 May 2002 / Accepted 13 July 2002)

Abstract
This letter presents incontrovertible evidence that NGC 5506 is a Narrow Line Seyfert 1 (NLSy1). Our new 0.9-1.4  $\mu$m spectrum of its nucleus clearly shows the permitted $\ion{O}{I}$ $\,\lambda 1.1287~\mu$m line (with full width at half maximum <2000 km s -1) and the "1 micron $\ion{Fe}{II}$ lines". These lines can only originate in the optically-thick broad line region (BLR) and, among Seyfert nuclei the latter series of lines are seen only in NLSy1s. The obscuration to the BLR, derived from a rough estimate of the $\ion{O}{I}$ $\,\lambda 1.1287~\mu$m/ $\ion{O}{I}$ $\,\lambda$8446 ratio and from the reddening of the near-IR Paschen lines, is $A_{\rm V}\,>\,5$. Together, these results make NGC 5506 the first identified case of an optically-obscured NLSy1. This new classification helps explain its radio to X-ray properties, which until now were considered highly anomalous. However, interesting new concerns are raised: e.g., NGC 5506 is unusual in hosting both a "type 1" AGN and a nuclear water vapor megamaser. As the brightest known NLSy1, NGC 5506 is highly suitable for study at wavebands less affected by obscuration.


Key words: line: formation -- line: identification -- galaxies: active -- galaxies: individual: NGC 5506 -- galaxies: Seyfert -- galaxies: infrared

Offprint request: N. Nagar, neil@arcetri.astro.it




© ESO 2002

Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.

Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.

Initial download of the metrics may take a while.