SHIELD: Neutral Gas Kinematics and Dynamics

Abstract

We present kinematic analyses of the 12 galaxies in the "Survey of HI in Extremely Low-mass Dwarfs" (SHIELD). We use multi-configuration interferometric observations of the HI 21cm emission line from the Karl G. Jansky Very Large Array (VLA) 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 circular velocities <30 km/s for the entire survey population. Baryonic masses are calculated using single-dish HI 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 <15 km/s, 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.

Accepted for publication by the Astrophysical Journal, high-resolution version and survey data available at https://www.macalester.edu/~jcannon/shield/

References in corpus (12)

• High-resolution mass models of dwarf galaxies from LITTLE THINGS
• What is Driving the HI Velocity Dispersion?
• Is there a "too big to fail" problem in the field?
• Kinematic modelling of disk galaxies I. A new method to fit tilted rings to data cubes
• Dwarf Galaxy Dark Matter Density Profiles Inferred from Stellar and Gas Kinematics
• A Catalog of Ultra-compact High Velocity Clouds from the ALFALFA Survey: Local Group Galaxy Candidates?
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• (Almost) Dark HI Sources in the ALFALFA Survey: The Intriguing Case of HI1232+20
• ALFALFA Discovery of the Nearby Gas-rich Dwarf Galaxy Leo P. V. Neutral Gas Dynamics and Kinematics
• SHIELD: Comparing Gas and Star Formation in Low Mass Galaxies
• Oxygen Abundance Measurements of SHIELD Galaxies
• Characterizing the Star Formation of the Low-Mass SHIELD Galaxies from Hubble Space Telescope Imaging

Cited by in corpus (6)

• SHIELD: Comparing Gas and Star Formation in Low Mass Galaxies
• New insights into the interstellar medium of the dwarf galaxy IC 10: connection between magnetic fields, the radio--infrared correlation and star formation
• The Enigmatic (Almost) Dark Galaxy Coma P: Distance Measurement and Stellar Populations from HST Imaging
• The Enigmatic (Almost) Dark Galaxy Coma P: The Atomic Interstellar Medium
• Identifying galaxy candidates in WSRT HI imaging of ultra-compact high velocity clouds
• First Characterization of the Neutral ISM in Two Local Volume Dwarf Galaxies