Collaborative Research: Gaseous Halos of Nearby Galaxies as Clues to Galaxy Evolution

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Dr Rand and Dr. Walterbos will search for warm ionized and neutral gas away from the mid-plane of a couple of dozen nearby edge-on spiral galaxies. This diffuse gas rotates more slowly than the denser cool gas in the equatorial plane of the disk; this lag is still not understood, and may hold a clue to the origin of the gas. The team will use the new multi-slit mode of the ARC 3.5-m telescope to measure emission lines of ionized hydrogen from this gas in 7 edge-on galaxies that have vigorous star formation and two with lower rates of starbirth. They will also complete and analyze maps in the 21cm line of neutral hydrogen for four galaxies observed in B and C arrays with the National Radio Astronomy Observatory's Very Large Array, and will use the Westerbork array in the Netherlands to make deep observations for a further eight galaxies. The velocity information in these 'data cubes' will be used to distinguish off-plane gas from a warp or other structure, and to determine its rotation. The aim is to use the velocity information to determine whether the off-plane gas is newly falling in, or has been ejected from the star-forming disk. This research would form the basis for two PhD theses. Both the University of New Mexico and New Mexico State University are Hispanic-serving institutions, and the astronomers at New Mexico State University are particularly active in public outreach.