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Session 10 - Interstellar Medium and Star Formation.
Display session, Monday, June 08
GHRS spectra of 19 mostly late-type stars provide interstellar hydrogen and metal column densities along these lines of sight with sufficient resolution to resolve individual clouds. For 16 of these lines of sight we can infer the hydrogen column density at the projected velocity of the Local Interstellar Cloud (LIC). We construct a 3 dimensional representation of the LIC by assuming that the neutral hydrogen density in the cloud is the same as the highest mean density observed, about 0.1 cm^-3, and that the LIC extends continuously along each line of sight to a distance determined by the hydrogen column density and the assumed density. We will present our model of the LIC as an animated video that shows its shape from different directions.
We find that the hydrogen column densities obtained from EUVE spectra of white dwarfs are in excellent agreement with the GHRS column densities for the stars. Also, some other nearby white dwarfs fit our LIC model well and are included in the model. As viewed from the North Galactic Pole, the LIC has an irregular shape with the Sun very near the edge toward the Galactic Center and very little column density in the first and fourth Galactic quadrants. As viewed from in the Galactic plane, there is more material to the south and the cloud has narrow extensions toward the Galactic Center and toward Galactic longitude 270 Degrees. We propose that the study of the structure of interstellar clouds be called "astronephography" based on the Greek word for cloud, "nephos".
This work is supported by NASA grants to the University of Colorado.
Program listing for Monday