Interstellar Hα Line Profiles toward HD 93521 and the Lockman Window

摘要

We have used the Wisconsin Hα Mapper (WHAM) facility to measure the interstellar Hα emission toward the high Galactic latitude O star HD 93521 (l = 183.1 deg, b = +62.2 deg). Three emission components were detected along this line of sight. These components have radial velocities of -10, -51, and -90 km s~-1 with respect to the local standard of rest (LSR) and have Hα intensities of 0.20, 0.15, and 0.023 R, respectively, corresponding to emission measures of 0.55, 0.42, and 0.06 cm~-6 pc. We have also mea- sured the Hα emission toward the direction l = 148.5 deg, b = +53.0 deg, which lies in the region of exception- ally low H I column density known as the Lockman Window.