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Published February 1, 1990 | Published
Journal Article Open

The near-infrared morphology of ultraluminous infrared galaxies


Near-infrared images at 1.25 μm, 1.65 μm, and 2.2 μm have been obtained of nine galaxies from the IRAS Bright Galaxy Sample with infrared luminosities L_(IR) ≥ 10^(12) L_☉. Two of the 2.2 μm images reveal previously undetected double nuclei, increasing the number of close double nuclei known for this sample from two to four. For three of these four sources, the colors of both nuclei are substantially different from those of normal spiral galaxies, indicating that the high activity state in high-luminosity mergers tends to occur in both nuclei. Three sources show 2.2 μm emission that is more centrally concentrated than the emission at 1.3 μm, a result that can be explained as the effects of dust emission and/or extinction or, alternatively, as the result of direct emission at 2.2 μm from the accretion disk of a central active galactic nucleus. Implications of these results for the model that galaxy collisions lead to quasar formation are briefly discussed. Finally, from the frequency and separation of the double nucleus sources, the lifetime of the ultraluminous phase of galaxies is estimated to be ~ 4 x 10^8 yr.

Additional Information

© 1990 American Astronomical Society. Received 1989 September 6; accepted 1989 November 16. We thank the night assistants at the Hale telescope, J. Carasco and S. Staples, and the entire staff at Palomar Observatory. S. Lin made substantial contributions to the construction of the near-infrared camera, and V. Heron wrote most of the data acquisition software for the camera. Discussions with S. Phinney and W. Sargent were most helpful, as were the suggestions provided by the referee, G. Wynn-Williams. Ground-based infrared astronomy at Caltech is supported by a grant from the NSF.

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Published - 1990ApJ___349L__39C.pdf


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