Research Note

Limits on the H I content of the dwarf galaxy Hydra II

¹ California Institute of Technology, 1200 E. California Blvd, Pasadena, CA 91125, USA
² Oregon Institute of Technology, 3201 Campus Drive, Klamath Falls, OR 97601, USA
³ National Radio Astronomy Observatory, Green Bank, WV 24494, USA
e-mail: jlockman@nrao.edu
⁴ Physics and Astronomy Department, Vanderbilt University, PMB 401807, 2401 Vanderbilt Place, Nashville, TN 37240, USA
⁵ Associated Universities Inc, Av. Nueva Costanera 4091, Suite 502, Vitacura Santiago, Chile
⁶ Department of Physics, Florida International University, Miami, FL 33199, USA
⁷ National Radio Astronomy Observatory, PO Box O, Socorro, NM 87801, USA
⁸ Department of Physics and Astronomy, The University of Toledo, 2825 West Bancroft Street, Toledo, OH 43606, USA
⁹ Department of Physics and Astronomy, York University, 4700 Keele Street, Toronto, Ontario, M3J 1P3, Canada

Received: 8 September 2015
Accepted: 27 October 2015

Abstract

Sensitive 21 cm H I  observations have been made with the Green Bank Telescope toward the newly-discovered Local Group dwarf galaxy Hydra II, which may lie within the leading arm of the Magellanic Stream. No neutral hydrogen was detected. Our 5σ limit of M_HI ≤ 210 M_⊙ for a 15 km s^-1 linewidth gives a gas to luminosity ratio M_HI/ L_V ≤ 2.6 × 10^-2M_⊙L_⊙^-1. The limits on H I  mass and M_HI/L_V are typical of dwarf galaxies found within a few hundred kpc of the Milky Way. Whatever the origin of Hydra II, its neutral gas properties are not unusual.