Neutral interstellar gas in the lower galactic halo

Journal Article · Thu Sep 15 04:00:00 EDT 1983 · Astrophys. J.; (United States)

DOI:https://doi.org/10.1086/161317· OSTI ID:5401586

Albert, C E

Optical interstellar absorption lines of Ti II, Ca II, and Na I, and the 21 cm emission line of H I have been observed at high resolution and high detection sensitivity toward nine pairs of nearly aligned distant halo stars and foreground disk stars with well-determined distances. Analysis of the column densities, velocities, and the directly determined variation of the titanium abundances with z-distance leads to a general picture of the neutral interstellar material in the lower galactic halo. Two types of gas with distinct distribution, kinematics, and abundances are found: a thick, low-velocity disk (type A) extending from the plane to well beyond the thin disk of OB stars, and a high-velocity, much less strongly depleted gas (type B) observed only at high z-distances, which constitutes at least 24% of the mass of the halo gas. The observed velocity distribution does not agree well with that predicted by a model corotating halo. The possible origins of the observed gas and its connection with QSO absorption lines are discussed.

• Research Organization: Yerkes Observatory, University of Chicago
• OSTI ID: 5401586
• Journal Information: Astrophys. J.; (United States), Journal Name: Astrophys. J.; (United States) Vol. 272:2; ISSN ASJOA
• Country of Publication: United States
• Language: English

Related Subjects

640105* -- Astrophysics & Cosmology-- Galaxies
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ABSORPTION SPECTRA
ABUNDANCE
ALKALI METALS
CALCIUM IONS
CHARGED PARTICLES
COSMIC GASES
COSMIC RADIO SOURCES
ELEMENTS
EMISSION SPECTRA
FLUIDS
FUNCTIONS
GALAXIES
GASES
HYDROGEN
INTERSTELLAR GRAINS
IONS
LINE WIDTHS
METALS
MILKY WAY
NONMETALS
PARTICLES
QUASARS
RADIAL VELOCITY
SODIUM
SPECTRA
SPECTRAL DENSITY
SPECTRAL FUNCTIONS
TITANIUM IONS
VELOCITY