Ongoing mass transfer in the interacting galaxy pair NGC 1409/1410
I present two-band Hubble Space Telescope (HST) STIS imaging and WIYN spectral mapping of ongoing mass transfer in the interacting galaxy pair NGC 1409/1410 ( where NGC 1410 is the Seyfert galaxy also cataloged as III Zw 55). Archival snapshot WFPC2 imaging from the survey by Malkan and coworkers 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 the rate of transfer. An absorption lane typically 0."25 ( 100 pc) wide, with a representative optical depth tau(B) = 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 (tau(B) = 0.4) polar feature around the core of NGC 1409. The combination of extinction data in two passbands allows a crude three-dimensional recovery of the dust structure, supporting the front/back geometry derived from colors and extinction estimates. The whole feature contains on the order of 2 x 10(6) M-. in dust, implying about 3 x 10(8) M-. of gas and requiring a mass transfer rate averaging approximate to 1 M-. yr(-1), 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. Likewise, the recipient shows no signs of recent star formation from incoming gas, although NGC 1410 has numerous luminous young star clusters and widespread Halpha emission.