SHIELD: neutral gas kinematics and dynamics
- Department of Physics and Astronomy, Macalester College, 1600 Grand Avenue, Saint Paul, MN 55105 (United States)
- ASTRON, the Netherlands Institute for Radio Astronomy, Postbus 2, 7990 AA, Dwingeloo (Netherlands)
- Department of Astronomy, University of Wisconsin, 475 N Charter Street, Madison, WI 53706 (United States)
- Center for Astrophysics and Planetary Science, Space Sciences Building, 122 Sciences Drive, Cornell University, Ithaca NY 14853 (United States)
- SKA South Africa, Radio Astronomy Research Group, 3rd Floor, The Park, Park Road, Pinelands, 7405 (South Africa)
- Minnesota Institute for Astrophysics, School of Physics and Astronomy, 116 Church Street, S.E., University of Minnesota, Minneapolis, MN 55455 (United States)
- Department of Astronomy, Indiana University, 727 East Third Street, Bloomington, IN 47405 (United States)
- Cray, Inc., 380 Jackson Street, Suite 210, St. Paul, MN 55101 (United States)
- Raytheon Company, 1151 E. Hermans Road, Tucson, AZ 85756 (United States)
- Astrophysics, Cosmology and Gravity Centre (ACGC), Department of Astronomy, University of Cape Town, Private Bag X3, Rondebosch 7701 (South Africa)
- Physics Department, Knox College, 2 East South Street, Galesburg, IL 61401 (United States)
- National Radio Astronomy Observatory, P.O. Box O, 1003 Lopezville Road, Socorro, NM 87801 (United States)
- Department of Physics and Astronomy, University College London, Gower Place, London WC1E 6BT (United Kingdom)
We present kinematic analyses of the 12 galaxies in the “Survey of H i in Extremely Low-mass Dwarfs” (SHIELD). We use multi-configuration interferometric observations of the H i 21 cm emission line from the Karl G. Jansky Very Large Array (VLA){sup 22} to produce image cubes at a variety of spatial and spectral resolutions. Both two- and three-dimensional fitting techniques are employed in an attempt to derive inclination-corrected rotation curves for each galaxy. In most cases, the comparable magnitudes of velocity dispersion and projected rotation result in degeneracies that prohibit unambiguous circular velocity solutions. We thus make spatially resolved position–velocity cuts, corrected for inclination using the stellar components, to estimate the circular rotation velocities. We find v{sub circ} ⩽ 30 km s{sup −1} for the entire survey population. Baryonic masses are calculated using single-dish H i fluxes from Arecibo and stellar masses derived from HST and Spitzer imaging. Comparison is made with total dynamical masses estimated from the position–velocity analysis. The SHIELD galaxies are then placed on the baryonic Tully–Fisher relation. There exists an empirical threshold rotational velocity, V {sub rot} < 15 km s{sup −1}, below which current observations cannot differentiate coherent rotation from pressure support. The SHIELD galaxies are representative of an important population of galaxies whose properties cannot be described by current models of rotationally dominated galaxy dynamics.
- OSTI ID:
- 22868439
- Journal Information:
- Astrophysical Journal, Vol. 832, Issue 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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