Far-Infrared Counterpart to the Optical and H i Plume in the Leo Triplet of Galaxies: NGC 3623, NGC 3627, and NGC 3628

March 1991 • 1991ApJ...370..176H

Authors • Hughes, D. H. • Appleton, P. N. • Schombert, J. M.

Abstract • A study of the infrared emission in the Leo triplet of interacting galaxies is presented. We have applied a new background subtraction routine to IRAS-calibrated raw detector data (CRDD) covering a 4 deg^2^ field centered on the triplet of galaxies. We report the discovery of an extragalactic IR counterpart at 60 and 100 microns to the previously known optical and H I tidal plume associated with NGC 3628. The IR plume has a ratio I_100 microns_/N_H_ of 7 +/- 4 x 10^- 15^ Jy sr^-1^/(H I atoms cm^-2^), in striking agreement with Galactic cirrus clouds and a dust-to-gas ratio of 3.3 x 10^-5^. We show that these values are consistent with the tidal model of the plume formation. The IR plume also exhibits a gradient of decreasing temperature along the plume away from NGC 3628 which can be explained by a dilution of the stellar optical and UV radiation field. In addition to the Leo triplet galaxies, we also detected with remarkable success almost all background late-type galaxies in the field.

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Phil Appleton

Senior Scientist