UNRAVELING THE MYSTERIES OF THE LEO RING: AN ABSORPTION LINE STUDY OF AN UNUSUAL GAS CLOUD

• Published in: The Astrophysical journal Vol. 790; no. 1; pp. 1 - 9
• Main Authors: Rosenberg, J L, HAISLMAIER, KARL, Giroux, M L, Keeney, B A, Schneider, S E
• Format: Journal Article
• Language: English
• Published: United States 20.07.2014
• Subjects: ABSORPTION; Accretion; ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; Clouds; DENSITY; Estimates; EVOLUTION; FEEDBACK; GALAXIES; Hubble Space Telescope; HYDROGEN; INTERGALACTIC SPACE; METALLICITY; MODIFICATIONS; Origins; QUASARS; SPACE; Spectrographs; TELESCOPES
• ISSN: 0004-637X; 1538-4357
• DOI: 10.1088/0004-637X/790/1/64

Since the discovery of the large (2 x 10 super(9) M sub([middot in circle])) intergalactic cloud known as the Leo Ring in the 1980s, the origin of this object has been the center of a lively debate. Determining the origin of this object is still important as we develop a deeper understanding of the accretion and feedback processes that shape galaxy evolution. We present Hubble Space Telescope/Cosmic Origins Spectrograph observations of three sightlines near the ring, two of which penetrate the high column density neutral hydrogen gas visible in 21 cm observations of the object. These observations provide the first direct measurement of the metallicity of the gas in the ring, an important clue to its origin. Our best estimate of the metallicity of the ring is ~10% Z sub([middot in circle]), higher than expected for primordial gas but lower than expected from an interaction. We discuss possible modifications to the interaction and primordial gas scenarios that would be consistent with this metallicity measurement.