HIGH-RESOLUTION CA-II OBSERVATIONS OF THE LOCAL INTERSTELLAR-MEDIUM

High-resolution absorption measurements (lambda/DELTAlambda approximately 150,000) of the interstellar Ca II K line observed toward 46 early-type stars in the local interstellar medium (LISM) are presented. Ca II was detected in 36 of the 46 stars with 82 individual cloud components identified. As opposed to previous observations of the Na I D line, Ca II was detected to most of the stars closer than 50 pc, except in the region of the Galactic quadrant l = 180-degrees-270-degrees, which also contains the empty line of sight to beta CMa at 220 pc. The mean local standard of rest velocity of the 82 Ca II components is 0.9 km s-1 with an rms of 9.4 km s-1, implying that the LISM clouds are associated with the motion of the solar neighborhood and not the Sun. An analysis of the component velocities for coherent motion of the 44 components known to be closer than 50 pc does not support the hypothesis that Ca II velocities are correlated across large angular scales as a result of the Sun being embedded in a few local clouds. However, if the present data are combined with other nearby Ca II component velocities taken from the literature, then a cloud centered approximately at l = 90-degrees, b = -40-degrees moving coherently with the local interstellar wind vector is supported at a significance level of 99%. The Ca II data have been combined with Na I data for the same stars to produce a N(Na I)/N(Ca II) ratio for each identified absorption feature. This ratio plotted against the local standard of rest velocities of the clouds shows that the Routly-Spitzer effect exists down to +/- 10 km s-1, which supports grain desorption/destruction models that are efficient at returning calcium to the gas phase at these low velocities.