High Resolution Mid-Infrared Imaging of Ultraluminous Infrared Galaxies

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Session 23 -- Emission-Line, Starburst and Ultra-Luminous Galaxies
Oral presentation, Monday, 2:30-4:00, Wheeler Room

[23.06] High Resolution Mid-Infrared Imaging of Ultraluminous Infrared Galaxies

J. W. Miles, T. L. Hayward, and J. R. Houck (Cornell University)

We have obtained 0.5 arcsecond resolution multi-wavelength mid-infrared images of a sample of 10 infrared ultraluminous galaxies using the new instrument SpectroCam-10 at the Palomar 5~m telescope. The galaxies in the sample have $L_{\rm FIR} > 10^{11}L_\odot$ and small beam 10~$\mu$m fluxes $>$ 200~mJy. We are attempting to isolate the extended starburst component of these galaxies from the unresolved nuclear component. With this information, we can place constraints on models of the nuclear activity, and help to distinguish whether the nuclear energy generation mechanism is due to a compact starburst or a monster.

The results are mixed: some of the galaxies in the sample are unresolved point sources, some have multiple unresolved nuclei, some have faint extended emission surrounding an unresolved nucleus, and others are extended with no unresolved bright nucleus. Most evidently have a considerable starburst component. Comparisons with nonthermal radio continuum maps show a strong spatial correlation between the radio and infrared fluxes. Multi-wavelength broadband images yield color maps and show varying amounts of 10~$\mu$m silicate absorption.

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