NEUTRAL HYDROGEN ABSORPTION AND EMISSION IN THE QUASAR GALAXY PAIR 3C-275.1 NGC-4651/

3C 275.1 and NGC 4651 make a particularly interesting quasar/galaxy pa iring because of the alignment of such a strong radio emitter behind t he outer H I disk of a relatively undisturbed spiral galaxy. This prov ides an opportunity to study the spin-temperature characteristics of a tomic hydrogen at low column densities, in an apparently star-free env ironment. We previously reported a tentative detection of absorption a gainst the quasar based on VLA C-array observations; we have now made more sensitive maps of the H I emission from NGC 4651 with the VLA D-a rray, and we have attempted to confirm the weak H I absorption against the quasar at higher spatial and spectral resolution in VLA B-array. The possible absorption feature against this quasar appears to be weak er than we previously suspected, even though it seems fairly clear tha t H I emission is present close to the line of sight to the quasar. Th e weakness of the possible absorption seems also to confirm the trend found in previous observations that where strong absorption lines are seen, the galaxies show evidence of disturbance. The possible detectio n of (or limits on) absorption suggest that the neutral gas in the out er disk is quite warm. We use the absorption and emission measurements to set lower limits on the combination of heating inputs outside the star-forming regions of a disk galaxy and/or the intensity of the cosm ic background radiation around 100 eV.