EDP Sciences Journals List
Advanced Search
Subscriber Authentication Point
Home All issues Volume 436/ 1 Article

Free access article

Issue A&A
Volume 436, Number 1, June II 2005
Page(s) L5 - L8
Section Letters
DOI http://dx.doi.org/10.1051/0004-6361:200500109



A&A 436, L5-L8 (2005)
DOI: 10.1051/0004-6361:200500109

Letter

Discovery of 10 $\mu$m silicate emission in quasars

Evidence of the AGN unification scheme
R. Siebenmorgen1, M. Haas2, E. Krügel3 and B. Schulz4

1  European Southern Observatory, Karl-Schwarzschildstr. 2, 85748 Garching b. München, Germany
    e-mail: rsiebenm@eso.org
2  Astronomisches Institut, Ruhr-Universität, Universitätsstr. 150, 44780 Bochum, Germany
3  Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, Postfach 2024, 53010 Bonn, Germany
4  IPAC, California Institute of Technology (Caltech), Pasadena, CA 91125, USA

(Received 16 March 2005 / Accepted 10 April 2005)

Abstract
According to the unified scheme, AGN are surrounded by a dust-torus, and the observed diversity of AGN properties results from the different orientations relative to our line of sight. The strong resonance of silicate dust at 10 $\mu$m is therefore, as expected, seen in absorption towards many type-2 AGN. In type-1 AGN, it should be seen in emission because the hot inner surface of the dust torus becomes visible. However, this has not been observed so far, thus challenging the unification scheme or leading to exotic modifications of the dust-torus model. Here we report the discovery of the 10 $\mu$m silicate feature in emission in two luminous quasars with the Infrared Spectrograph of the Spitzer Space Telescope.


Key words: galaxies: active -- galaxies: nuclei -- galaxies: quasars: general -- galaxies: quasars: individual: 3C 249.1 -- galaxies: quasars: individual: 3C 351

SIMBAD Objects



© ESO 2005

What is OpenURL?

The OpenURL standard is a protocol for transmission of metadata describing the resource that you wish to access. An OpenURL link contains article metadata and directs it to the OpenURL server of your choice. The OpenURL server can provide access to the resource and also offer complementary services (specific search engine, export of references...). The OpenURL link can be generated by different means.
  • If your librarian has set up your subscription with an OpenURL resolver, OpenURL links appear automatically on the abstract pages.
  • You can define your own OpenURL resolver with your EDPS Account. In this case your choice will be given priority over that of your library.
  • You can use an add-on for your browser (Firefox or I.E.) to display OpenURL links on a page (see http://www.openly.com/openurlref/). You should disable this module if you wish to use the OpenURL server that you or your library have defined.