2013AJ....146...15G
ALFALFA Discovery of the Nearby Gas-rich Dwarf Galaxy Leo P. I. H I Observations
Giovanelli, Riccardo ( Center for Radiophysics and Space Research, Space Sciences Building, Cornell University, Ithaca, NY 14853, USA ); Haynes, Martha P. ( Center for Radiophysics and Space Research, Space Sciences Building, Cornell University, Ithaca, NY 14853, USA ); Adams, Elizabeth A. K. ( Center for Radiophysics and Space Research, Space Sciences Building, Cornell University, Ithaca, NY 14853, USA ); Cannon, John M. ( Department of Physics and Astronomy, Macalester College, Saint Paul, MN 55105, USA ); Rhode, Katherine L. ( Department of Astronomy, Indiana University, Bloomington, IN 47405, USA ); Salzer, John J. ( Department of Astronomy, Indiana University, Bloomington, IN 47405, USA ); Skillman, Evan D. ( Minnesota Institute for Astrophysics, University of Minnesota, Minneapolis, MN 55455, USA ); Bernstein-Cooper, Elijah Z. ( Department of Physics and Astronomy, Macalester College, Saint Paul, MN 55105, USA ); McQuinn, Kristen B. W. ( Minnesota Institute for Astrophysics, University of Minnesota, Minneapolis, MN 55455, USA ) show affiliations
The Astronomical Journal, Volume 146, Issue 1, article id. 15, 6 pp. (2013).
Published in Jul 2013
The discovery of a previously unknown 21 cm H I line source identified as an ultra-compact high velocity cloud in the ALFALFA survey is reported. The H I detection is barely resolved by the Arecibo 305 m telescope ~4' beam and has a narrow H I linewidth (half-power full width of 24 km s-1). Further H I observations at Arecibo and with the Very Large Array corroborate the ALFALFA H I detection, provide an estimate of the H I radius, ~1' at the 5 × 1019 cm-2 isophote, and show the cloud to exhibit a velocity field which, if interpreted as disk rotation, has an amplitude of sime9.0 ± 1.5 km s-1. In other papers, Rhode et al. show the H I source to have a resolved stellar counterpart and ongoing star forming activity, while Skillman et al. reveal it as having extremely low metallicity: 12 + log (O/H) = 7.16 ± 0.04. The H I mass to stellar mass ratio of the object is found to be 2.6. We use the Tully-Fisher template relation in its baryonic form to obtain a distance estimate D_{Mpc}=1.3^{+0.9}_{-0.5}. Additional constraints on the distance are also provided by the optical data of Rhode et al. and McQuinn et al., both indicating a distance in the range of 1.5 to 2.0 Mpc. The three estimates are compatible within their errors. The object appears to be located beyond the dynamical boundaries of, but still in close proximity to the Local Group. Its pristine properties are consistent with the sedate environment of its location. At a nominal distance of 1.75 Mpc, it would have an H I mass of ~= 1.0 × 106 M , a stellar mass of ~= 3.6 × 105 M , and a dynamical mass within the H I radius of ~= 1.5 × 107 M . This discovery supports the idea that optically faint—or altogether dark—low mass halos may be detectable through their non-stellar baryons.
Keywords:
Astronomy: galaxies: distances and redshifts; galaxies: halos; galaxies: luminosity function; galaxies: photometry; galaxies: spiral; mass function; radio lines: galaxies
arXiv: Astrophysics - Cosmology and Extragalactic Astrophysics; Astrophysics - Galaxy Astrophysics
Graphics
Feedback