Observations of Nearby Interstellar Gas and Dust in the Direction toward the Globular Cluster omega Centauri

Abstract

High-resolution spectra of Na I D interstellar lines are presented for six stars which lie within 4°.0 of the globular cluster ω Centauri and at distances in the approximate range 100-600 pc. For one star (HD 116226) we discuss also the Ca II K line profile and spectra obtained with lUE. Sky flux images of the ω Cen field show considerable structure in the dust emission, and they reveal IR emission associated with faint nebulosity detected in the optical region. The spectral observations reveal gas components having negative LSR velocities between about -11 and -7 km s^-1 and, in general, stronger positive velocity features between about 0.5 and 4.0 km s^-1. These absorption features are produced by the nearby gas and may be associated with the region between the Sco-Cen expanding shell and the Local Bubble. The material responsible for the nebulosity probably forms part of this relatively nearby complex of gas and dust, and the source of the illumination is discussed.