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H. Bushouse, S. Arribas, R. A. Lucas (STScI), L. Colina (IAC/CSIC), K. D. Borne (GMU)
We have obtained BVI imaging of a sample of 19 low redshift Very Luminous Infrared Galaxy (VLIRG) systems. Most of these objects exhibit morphological features similar to those found in Ultraluminous Infrared Galaxies (ULIRGs), which suggests that they, like ULIRGs, are also undergoing strong interactions and mergers. We have obtained photometry for the VLIRG systems, the individual galaxies, and their nuclei, and the relative behavior of these groups has been studied in color-magnitude diagrams. The observed colors and magnitudes for both the systems and the nuclei lay in well defined sequences parallel to the reddening vector, with most of the nuclei having redder colors than the galaxy disks. The nuclei typically comprise 10% of the total flux of the system in B and 13% in I. Comparisons of the photometric properties of the VLIRG sample with previously studied samples of ULIRGs show that the sequences for the nuclei and the systems agree well with those for cool ULIRGs. The nuclei sequence also agrees with that for warm ULIRGs, though the latter shows a much larger scatter in both luminosity and color. The photometric properties of the VLIRG and ULIRG samples, considered as a whole, are indistinguishable at optical wavelengths. However, when considering young and old systems separately, according to an interaction classification scheme, the young VLIRGs seem to be more luminous and bluer than old VLIRG systems, which is contrary to what is found for ULIRG samples. If confirmed with larger samples, this behavior suggests that the final evolution of all LIRGs depends on luminosity, and that this process can be probed at optical wavelengths.
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Bulletin of the American Astronomical Society, 35#5
© 2003. The American Astronomical Soceity.