ABSTRACT

We describe the results of an imaging and spectrophotometric investigation of the mixed elliptical-spiral pair Kar 29 (≡ VV 347 ≡ Arp 119). The spiral component (≡ Mrk 984) shows a strong, extended, LINER-like emission line spectrum. Each line is partly resolved into at least four components, redshifted with respect to the underlying galaxy, and covering δvr ∼ 1,300 km s-1. Line ratios indicate that the dominant ionization mechanism is provided by shocks or a mixture of shocks and photoionization by hot stars. One possible interpretation involves a nearly polar crossing of the spiral disk by the elliptical, with the line emitting gas stripped and accelerated toward the elliptical. Some of the data are however better explained if the large δvr between the line components is due to the disk impact of an additional small companion.

INTRODUCTION AND OBSERVATIONS

Interaction between galaxies produces a wide variety of observable phenomena; however, most of them are not yet fully understood in physical terms. One important challenge is to explain the response of the gaseous component of a disk galaxy to strong perturbations.

Long slit CCD spectra of the spiral (classified as Sc pec or Sdm)/elliptical (E5) pair of giant galaxies Kar 29 were obtained at KPNO, San Pedro Martir and ESO. Slits were oriented (1) along the major axis of the pair (P.A. = 8°), (2) along the major axis of the spiral (116°), (3) and at P.A. = 82° (with the slit centered on the knot closest to the nucleus), during several observing runs in 1991/92.