Journal Article

On the nature of the absorber in IRAS 09104+4109: the X-ray and mid-infrared view

C. Vignali, E. Piconcelli, G. Lanzuisi, A. Feltre, C. Feruglio, R. Maiolino, F. Fiore, J. Fritz, V. La Parola, M. Mignoli and F. Pozzi

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 416, issue 3, pages 2068-2077
Published in print September 2011 | ISSN: 0035-8711
Published online September 2011 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2011.19181.x
On the nature of the absorber in IRAS 09104+4109: the X-ray and mid-infrared view

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We present a long (≈76 ks) Chandra observation of IRAS 09104+4109, a hyperluminous galaxy, optically classified as a type 2 active galactic nuclei (AGN) hosted in a cD galaxy in a cluster at z= 0.442. We also report on the results obtained by fitting its broad-band spectral energy distribution. The Compton-thick nature of this source (which has been often referred to as an ‘archetype’ of Compton-thick type 2 quasars) was formerly claimed on the basis of its marginal detection in the Phoswich Detection System (PDS) instrument onboard BeppoSAX, being then disputed using XMM–Newton data. Both Chandra analysis and optical/mid-infrared (IR) spectral fitting are consistent with the presence of heavy (≈1–5 × 1023 cm−2), but not extreme (Compton-thick) obscuration. However, using the mid-IR and the [O iii] emission as proxies of the nuclear hard X-ray luminosity suggests the presence of heavier obscuration. The 54-month Swift BAT map shows excess hard X-ray emission likely related to a nearby (z= 0.009) type 2 AGN, close enough to IRAS 09104+4109 to significantly enhance and contaminate its emission in the early BeppoSAX PDS data.

Keywords: galaxies: active; galaxies: nuclei; quasars: general; quasars: individual: IRAS 09104+4109

Journal Article.  9141 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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