High-resolution observations of the neutral hydrogen absorption and radio continuum emission of the radio source 3C 178.

The radio source 3C 178, which has been identified with the spiral galaxy NGC 2377, has been observed with the Very Large Array. These observations show that the source has a double radio structure with roughly equal unresolved components separated by 24". The radio lobes are offset by 25" and 45", respectively, from the bright nucleus of the galaxy. It is concluded that the radio source is not associated with the galaxy and is possibly a background quasar or radio galaxy.

The neutral hydrogen absorption spectrum of each of the double components was investigated with the NRAO line interferometer. Absorption features having widths of 17-24 km s^-1 were detected against both radio components with features from one component covering a velocity range of 30 km s^-1. Thus the radio source/galaxy pair 3C 178 / NGC 2377 provides a direct analog for 21 cm absorption lines detected in the spectra of quasars, in which the line of sight intersects the disk of a nearly face-on foreground spiral galaxy. 3C 178 may be a physical analog for AO 0235+164 whose absorption spectrum resembles that of 3C 178.