We present an analysis of the nuclear infrared (IR, 1.6–18 μm) emission of the ultraluminous IR galaxy UGC 5101 to derive the properties of its active galactic nucleus (AGN) and its obscuring material. We use new mid-IR high angular resolution (0.3–0.5 arcsec) imaging using the Si-2 filter (λC = 8.7 μm) and 7.5–13 μm spectroscopy taken with CanariCam (CC) on the 10.4 m Gran Telescopio CANARIAS. We also use archival Hubble Space Telescope/NICMOS and Subaru/COMICS imaging and Spitzer/IRS spectroscopy. We estimate the near- and mid-IR unresolved nuclear emission by modelling the imaging data with GALFIT. We decompose the Spitzer/IRS and CC spectra using a power-law component, which represents the emission due to dust heated by the AGN, and a starburst component, both affected by foreground extinction. We model the resulting unresolved near- and mid-IR, and the starburst subtracted CC spectrum with the CLUMPY torus models of Nenkova et al. The derived geometrical properties of the torus, including the large covering factor and the high foreground extinction needed to reproduce the deep 9.7 μm silicate feature, are consistent with the lack of strong AGN signatures in the optical. We derive an AGN bolometric luminosity Lbol ~ 1.9 × 1045 erg s−1 that is in good agreement with other estimates in the literature.

Document Type


Publication Date


Notes/Citation Information

Published in Monthly Notices of the Royal Astronomical Society, v. 454, no. 4, p. 3577-3589.

This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©: 2015 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.

Digital Object Identifier (DOI)


Funding Information

This work has been partly supported by Mexican CONACyT under research grant CB-2011-01-167291. MMP acknowledges support by the CONACyT PhD fellowship programme. AA-H and AH-C acknowledge financial support from the Spanish Plan Nacional de Astronom´ıa y Astrof´ısica under grant AYA2012-31447, which is partly funded by the FEDER programme, and the Universidad de Cantabria through the Augusto G. Linares programme. CRA is supported by a Marie Curie Intra European Fellowship within the 7th European Community Framework Programme (PIEF-GA-2012-327934). IG-B ackowledges financial support from the Instituto de Astrof´ısica de Canarias through Fundaci ´on La Caixa and from the Spanish Ministry of Science and Innovation (MICINN) through project PN AYA2013-47742-c4-2-P (Estallidos).