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W.C. Keel (U. Ala.)
I present two-band HST STIS imaging of ongoing mass transfer in the interacting galaxy pair NGC 1409/10 (where NGC 1410 is the Seyfert galaxy often listed as III Zw 55). Archival snapshot WFPC2 imaging from the survey by Malkan et al. showed a dust feature stretching between the galaxies, apparently being captured by NGC 1409. The new images allow estimates of the mass being transferred and rate of transfer. An absorption lane typically 0.25" (100 pc) wide with a representative optical depth \tauB = 0.2 cuts across the spiral structure of NGC 1410, crosses the 7-kpc projected space between the nuclei, wraps in front of and, at the limits of detection, behind NGC 1409, and becomes a denser (\tauB = 0.4) polar ring around the core of NGC 1409. Models for the light distribution in the two galaxies allow a crude three-dimensional recovery of the dust structure, supporting the front/back geometry derived from colors and extinction estimates. The whole feature contains of order 5000 solar masses in dust, implying about 8 \times 105 solar masses of gas. Incorporating the projected velocity difference between nuclei for a timescale, this suggests a very modest mass transfer rate averaging about 0.02 solar masses per year unless we are particularly unlucky in viewing angle. Curiously, this demonstrable case of mass transfer seems to be independent of the occurrence of a Seyfert nucleus, since the Seyfert galaxy in this pair is the donor of the material.
This work was support by NASA through STScI grant GO-8147.01-97A.
The author(s) of this abstract have provided an email address for comments about the abstract: keel@bildad.astr.ua.edu