0 v 1 1 7 M ar 2 00 1 Gas Distribution and Starburst Activity in the Widely Separated Interacting Galaxies NGC 6670

We present high resolution H I 21 cm line, 20 cm radio continuum, and CO(1–0) line observations of the luminous infrared galaxy NGC 6670. NGC 6670 consists of two edge-on disk galaxies (NGC 6670E and NGC 6670W) with a projected nuclear separation of ∼ 16 kpc. While there are no optically identified tidal features and the molecular disks are not distorted much, we have detected a 90 kpc long H I tail which suggests that the galaxies are interacting and have already experienced at least one close encounter. The galaxies appear to be gravitationally bound and in a prograde-prograde orbit, which is the most efficient for producing tidal tails. Our observations suggest that the H I at larger galactic radii has been ejected to form the tails and the remnant H I disks have been perturbed by the interaction. In particular, we find that the H I disk of NGC 6670E appears to have been nearly destroyed. We conclude that the previous encounter between the galaxies had a large impact parameter and that the system is still in an early stage of interaction. Even though NGC 6670 is in an early stage of interaction, we find that there is evidence for nuclear starbursts already present. The CO(1–0) observations show large molecular gas reservoirs in the central regions and the 20 cm radio continuum observations reveal enhanced star formation activity in the nuclear regions of both galaxies. Academia Sinica Institute of Astronomy and Astrophysics, P.O. Box 1-87, Nankang, Taipei, Taiwan IPAC, MS 100-22, Caltech, 770S Wilson Ave., Pasadena, CA 91125, USA Laboratory for Astronomical Imaging, Department of Astronomy, University of Illinois, 1002 W. Green Street, Urbana, IL 61801, USA Current address: Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822, USA