Evidence for a Tidal Interaction in the Seyfert Galaxy Markarian 315

Summary

ABSTRACT

We have detected a diffuse, continuum knot which may be a reminant nucleus, in the inner regions of Markarian 315. This knot is associated with a complex, ring-like structure in both the continuum and ionized gas emission. The occurance of this feature in combination with an extensive, ionized streamer, or tidal tail, and highly non-circular kinematics in the ionized gas, suggests that this galaxy has suffered a disruptive, tidal interaction whose influence extends well into the inner one kiloparsec region.

INTRODUCTION

Markarian 315 (Markarian and Lipovetskii 1971) (also IIZwl87), is a moderately luminous Seyfert 1.5 galaxy (Koski 1978). It has a redshift of 11,820 km s^-1 relative to the galactic center and M_v= –21.6 (Sargent 1970). For this discussion, we adopt a scale of 0.57 h^-l kpc arcsec^-1.

Radio frequency images of Markarian 315 show that it is a steep spectrum source with a diffuse morphology and a total extent of 2.9 h^-l kpc (Wilson and Willis 1980; Ulvestad, et al. 1981). This extended structure is the largest in the sample of Seyfert galaxies studied by these authors. (These typically ranged between 0.4 and 1.0 h^-l kpc). It is, however, consistent with an extended starburst in the galaxy and the IRAS fluxes are also consistent with this interpretation (MacKenty 1989).

MacKenty (1986) discovered an extraordinary, 80 kpc, streamer of ionized gas emerging from near the nucleus, extending in a straight line for 60 kpc then bending back in a hook. He suggested two possible origins for this feature: a tidal interaction or a dormant radio jet.