IUE and HI observations of gas components towards HD 174632.

Abstract

IUE spectra of gas components towards the nearby star HD 174632 are reported, together with 21-cm H I emission profiles obtained in the direction of the star and at several neighboring positions some 1 deg from the star. These new observations reveal a far more complex velocity structure of the interstellar gas than that reported through optical spectroscopy by Crawford, with components at the approximate LSR velocities -68, -18, -7.7, + 5.5, and + 15.5 km/s. From the optical, UV, and radio data, we show that the star is embedded in diffuse gas of large angular extent, which has a similar velocity to those of the Riegel and Crutcher (1972) cold cloud and the R CrA dark cloud. The -7.7 and +15.5 km/s components are shown to cover an area of sky at least as extensive as the current sampled H I region of roughly 4 sq deg. The +15.5 km/s component is produced by gas that lies beyond the star. The structure and other physical properties of the gas components are discussed.