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Mid-infrared observations of the ultraluminous galaxies IRAS14348-1447, IRAS19254-7245, and IRAS23128-5919

V. Charmandaris·O. Laurent·E. Le Floc'h·I. F. Mirabel·M. Sauvage·S. Madden·P. Gallais·L. Vigroux·C. J. Cesarsky
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Abstract

We present a study of the three ultraluminous infrared galaxies IRAS14348-1447, IRAS19254-7245, and IRAS23128-5919, based on mid-infrared (MIR) spectro-imaging (5-18microns) observations performed with ISOCAM. We find that the MIR emission from each system, which consists of a pair of interacting late type galaxies, is principally confined to the nuclear regions with diameters of 1-2kpc and can account for more than 95% of their IRAS 12micron flux. In each interacting system, the galaxy hosting an active galactic nucleus (AGN) dominates the total spectrum and shows stronger dust continuum (12-16microns) relative to the Unidentified Infrared Band (UIB) emission (6-9microns), suggestive of its enhanced radiation field. The MIR dominant galaxy also exhibits elevated 15micron/Halpha and 15micron/K ratios which trace the high extinction due to the large quantities of molecular gas and dust present in its central regions. Using only diagnostics based on our mid-infrared spectra, we can establish that the Seyfert galaxy IRAS19254-7245 exhibits MIR spectral features of an AGN while the MIR spectrum of the Seyfert (or LINER) member of IRAS23128-5919 is characteristic of dust emission principally heated by star forming regions.

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V. Charmandaris, O. Laurent, E. Le Floc'h, I. F. Mirabel, M. Sauvage, S. Madden, P. Gallais, L. Vigroux, C. J. Cesarsky. 2002-06-10. Mid-infrared observations of the ultraluminous galaxies IRAS14348-1447, IRAS19254-7245, and IRAS23128-5919. https://doi.org/10.1051/0004-6361%3A20020879

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