Abstract
We report new observations of Na I and Ca II interstellar absorption in a nearby (230 ^ 30 pc) southern high-latitude —lament obtained at a spectroscopic resolution of D0.32 km s~1 using HD 22252 as the background probe. Complex absorption is present for both species with total column densities of N(Ca II) D 1.3 ) 1012 cm~2 and N(Na I) ( 7 ) 1012 cm~2. Over a velocity range of 25 km s~1 we —nd 11 Ca II velocity components loosely grouped into three velocity aggregates. Unusually narrow Ca II absorption is present with b-values in the range 0.25¨0.5 km s~1; such small values are rarely dis- covered. Each of these narrow Ca II components has an associated broader component at a slightly shifted velocity. Finally, there are two Ca II clouds with large b-values (D 5k m s~1) but no detectable Na I that —ank the three aggregates. At our particular intercept we may be observing the —lament edge-on and seeing cold interior condensations each with a warm outer shellall contained within a further exterior envelope of ionized gas. We estimate that a typical interior condensation will have a linear dimension d in the range 104 d 6 ) 104 AU and a pressure nT of 1.5 nT 9 ) 104 cm~3 K, but with large uncertainties. This result is consistent with the picture of small and relatively dense cloud cores expanding into the local bubble. Subject headings: ISM: kinematics and dynamicsline: pro—lesstars: individual (HD 22252)
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