2001MNRAS.327..841C

I present very high resolution (R=400000 and R=880000) observations of interstellar Caii absorption lines towards eight early-type stars situated within 15° of α Oph on the sky. I confirm an earlier result that the interstellar structure responsible for the anomalously strong Caii absorption towards α Oph has a spatial extent of ≲1pc (and is probably very much smaller). Many discrete interstellar absorption components are apparent in these high-resolution data, but while several have velocities in the range expected for the local interstellar medium (LISM), no convincing detections of either the local interstellar cloud (LIC), or the so-called G cloud, were made. In the former case, I argue that the relatively weak LIC components are masked by components arising in more distant clouds, but which have LISM-like velocities owing to the pervasive influence of outflow from the Sco-Cen association. The non-detection of the G cloud is more problematical, and I tentatively argue that, previous claims notwithstanding, this feature does not extend to galactic latitudes as high as +15° in this direction.