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Session 40 - Starburst Galaxies.
Display session, Wednesday, June 11
South Main Hall,
High resolution near infrared array images of the nuclear regions of two merging galaxy systems, NGC 1614 and NGC 520, are presented. The broadband photometric images at 1.25, 1.65, and 2.23 micron wavelengths and the CO bandhead (2.3 microns) absorption index measurements are used to investigate the spatial distribution of starburst activity and extinction in the central regions of these merging systems. The broadband near infrared colors of each of these objects indicate an anomalously red composition, even when corrected for extinction using extinction models ranging from a uniform foreground screen of absorbing material to a distribution of absorbing material fully mixed with the infrared emission sources. This red color may indicate the presence of substantial amounts of hot dust (1000 K) in the merger cores; in the case of NGC 1614, 3 micron continuum measurements by Mizutani, et al. (1994) allow us to estimate the contribution of such hot dust grains to the shorter wavelength near infrared colors. Once that contribution, negligible at 1.25 and 1.65 microns but not at 2.23 microns, is subtracted, the nuclear colors are consistent, within the photometric uncertainties, with red giant and supergiant colors. This, along with the strong CO bandhead index measured for the nuclei of these galaxies, indicates that starbursts containing large numbers of red supergiant stars are responsible for the near infrared emission in these merger cores. No indication of an underlying unresolved central engine is seen from the near infrared broadband emission in either galaxy.
Program listing for Wednesday