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.
Cite
@article{arxiv.1609.05376,
title = {SHIELD: Neutral Gas Kinematics and Dynamics},
author = {Andrew T. McNichols and Yaron G. Teich and Elise Nims and John M. Cannon and Elizabeth A. K. Adams and Elijah Z. Bernstein-Cooper and Riccardo Giovanelli and Martha P. Haynes and Gyula I. G. Józsa and Kristen B. W. McQuinn and John J. Salzer and Evan D. Skillman and Steven R. Warren and Andrew Dolphin and E. C. Elson and Nathalie Haurberg and Jürgen Ott and Amelie Saintonge and Ian Cave and Cedric Hagen and Shan Huang and Steven Janowiecki and Melissa V. Marshall and Clara M. Thomann and Angela Van Sistine},
journal= {arXiv preprint arXiv:1609.05376},
year = {2016}
}
Comments
Accepted for publication by the Astrophysical Journal, high-resolution version and survey data available at https://www.macalester.edu/~jcannon/shield/