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N. A. Reddy, S. Jogee, N. Z. Scoville (Caltech)
The study of starburst and AGN phenomena is central to determining the powering mechanisms of ultraluminous infrared galaxies (ULIRGs). Of particular interest is IRAS 17208-0014, a ULIRG which has a very high infrared luminosity (> 1012 L\odot) , shows evidence of being primarily powered by star formation, and appears to be in a dynamically interesting merger phase. We present a study of the circumnuclear activity, stellar populations, and evolutionary phase of IRAS 17208 based on multi-wavelength data including OVRO high resolution (1.0''x 0.7'') CO (2-1) observations, near-infrared NICMOS images, optical broadband and H\alpha images, and Keck optical spectra. Extended optical tidal tails suggest IRAS 17208 is a merger of two high angular momentum systems. The merger may be advanced as the inner 10 kpc shows an r1/4 light profile typical of ellipticals, and NICMOS images reveal only one nucleus. A massive (several 1010 M\odot) disk of cold molecular gas undergoing vigorous star formation appears to be powering the luminosity in the inner few kpc. We derive the circumnuclear star formation rate using radio continuum, far-infrared, and optical tracers. We also estimate the ages, masses, and extinction of the very bright compact stellar clusters, revealed by NICMOS images in the inner kpc region. These are reminiscent of super star clusters found in nearby starbursts and are postulated to be proto globular systems.
The author(s) of this abstract have provided an email address for comments about the abstract: nar@astro.caltech.edu