Journal Article

Probing the nuclear and circumnuclear activity of NGC 1365 in the infrared<sub>⋆</sub>

A. Alonso-Herrero, M. Sánchez-Portal, C. Ramos Almeida, M. Pereira-Santaella, P. Esquej, S. García-Burillo, M. Castillo, O. González-Martín, N. Levenson, E. Hatziminaoglou, J. A. Acosta-Pulido, J. I. González-Serrano, M. Pović, C. Packham and A. M. Pérez-García

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 425, issue 1, pages 311-324
Published in print September 2012 | ISSN: 0035-8711
Published online September 2012 | e-ISSN: 1365-2966 | DOI:
Probing the nuclear and circumnuclear activity of NGC 1365 in the infrared⋆

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We present new far-infrared (70–500 μm) Herschel Photodetector Array Camera and Spectrometer (PACS) and Spectral and Photometric Imaging Receiver (SPIRE) imaging observations as well as new mid-IR Gemini/Thermal-Region Camera Spectrograph imaging (8.7 and 18.3 μm) and spectroscopy of the inner Lindblad resonance (ILR) region (R < 2.5 kpc) of the spiral galaxy NGC 1365. We complemented these observations with archival Spitzer imaging and spectral mapping observations. The ILR region of NGC 1365 contains a Seyfert 1.5 nucleus and a ring of star formation with an approximate diameter of 2 kpc. The strong star formation activity in the ring is resolved by the Herschel/PACS imaging data, as well as by the Spitzer 24 μm continuum emission, [Ne ii] 12.81 μm line emission, and 6.2 and 11.3 μm PAH emission. The active galactic nucleus (AGN) is the brightest source in the central regions up to λ ∼ 24 μm, but it becomes increasingly fainter in the far-infrared when compared to the emission originating in the infrared clusters (or groups of them) located in the ring. We modelled the AGN unresolved infrared emission with the clumpy torus models and estimated that the AGN contributes only to a small fraction (∼5 per cent) of the infrared emission produced in the inner ∼5 kpc. We fitted the non-AGN 24–500 μm spectral energy distribution of the ILR region and found that the dust temperatures and mass are similar to those of other nuclear and circumnuclear starburst regions. Finally we showed that within the ILR region of NGC 1365, most of the ongoing star formation activity is taking place in dusty regions as probed by the 24 μm emission.

Keywords: galaxies: evolution; galaxies: individual: NGC 1365; galaxies: nuclei; galaxies: Seyfert; galaxies: structure; infrared: galaxies

Journal Article.  10726 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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