Atomic Physics with the Goddard High Resolution Spectrograph on the Hubble Space Telescope. IV. Relative Oscillator Strengths for Singly Ionized Nickel

Abstract

Absorption lines of trace metals like nickel are often used to measure the metallicity and depletion in H I regions within our Galaxy and others. Ultraviolet absorption lines from the dominant ion, Ni II, are generally weak, making them a convenient tool to study metallicity and depletion in these environments. As an aid for studies of dust evolution in galaxies, we obtained an adjusted set of precise relative oscillator strengths for Ni II lines occurring at ultraviolet wavelengths. This set of f-values was derived from curves of growth for interstellar absorption toward ρ Oph A, χ Oph, and ζ Oph. In all, absorption from 12 lines was analyzed. Comparison with the compilation of Morton reveals good agreement for the stronger lines but significant differences for the weakest ones.

Based on observations obtained with the NASA/ESA Hubble Space Telescope through the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555.