1994A&A...286..535L

Observations are presented of high resolution interstellar Na D line profiles towards 10 stars in the globular cluster M 55 and 6 foreground stars which lie within 3deg from the cluster. The spectral region containing the K I (λ 7699 A) line is simultaneously recorded but this line is detected only towards one of the foreground stars as a component having a relatively high K I/Na I abundance ratio. Two principal components are observed towards the cluster stars at velocities of ≃ +1 and +15 km/s and weaker higher velocity gas is detected at ≃ -21, +33 and +55 km/s. The +1 km/s component is at a distance of ≲100 pc and we suggest that this is part of an extensive region of diffuse gas which connects the molecular and dark clouds observed closer to the galactic plane. The +15 km/s component lies at a distance between 130 to 300 pc and is identified with an anomalous velocity arc observed in HI. The higher velocity gas components are at a distance >700 pc. From a comparison with our previous observations in the general direction of the Carina-Sagittarius arm we suggest that these features have an origin in spiral arm gas, in which case their detection towards M 55 places them some 600 to 800 pc from the galactic plane.