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Title: DISCOVERY OF A GAS-RICH COMPANION TO THE EXTREMELY METAL-POOR GALAXY DDO 68

We present H I spectral-line imaging of the extremely metal-poor galaxy DDO 68. This system has a nebular oxygen abundance of only ∼3% Z {sub ☉}, making it one of the most metal-deficient galaxies known in the local volume. Surprisingly, DDO 68 is a relatively massive and luminous galaxy for its metal content, making it a significant outlier in the mass-metallicity and luminosity-metallicity relationships. The origin of such a low oxygen abundance in DDO 68 presents a challenge for models of the chemical evolution of galaxies. One possible solution to this problem is the infall of pristine neutral gas, potentially initiated during a gravitational interaction. Using archival H I spectral-line imaging obtained with the Karl G. Jansky Very Large Array, we have discovered a previously unknown companion of DDO 68. This low-mass (M{sub H} {sub I} = 2.8 × 10{sup 7} M {sub ☉}), recently star-forming (SFR{sub FUV} = 1.4 × 10{sup –3} M {sub ☉} yr{sup –1}, SFR{sub Hα} < 7 × 10{sup –5} M {sub ☉} yr{sup –1}) companion has the same systemic velocity as DDO 68 (V {sub sys} = 506 km s{sup –1}; D = 12.74 ± 0.27 Mpc) and is located at a projected distance of ∼42 kpc. New H I maps obtained with the 100 m Robert C. Byrd Green Bank Telescope provide evidence that DDOmore » 68 and this companion are gravitationally interacting at the present time. Low surface brightness H I gas forms a bridge between these objects.« less
Authors:
;  [1] ; ;  [2] ; ;  [3] ;  [4] ;  [5] ;  [6] ; ; ; ;  [7] ;  [8] ;  [9] ; ;  [10] ;  [11] ;  [12] ;  [13]
  1. Department of Physics and Astronomy, Macalester College, 1600 Grand Avenue, Saint Paul, MN 55105 (United States)
  2. Australia Telescope National Facility, CSIRO Astronomy and Space Science, P.O. Box 76, NSW 1710, Epping (Australia)
  3. Minnesota Institute for Astrophysics, University of Minnesota, Minneapolis, MN 55455 (United States)
  4. Department of Physics and Astronomy, University of Alabama, P.O. Box 870324, Tuscaloosa, AL 35487-0324 (United States)
  5. National Radio Astronomy Observatory, P.O. Box 2, Green Bank, WV 24944 (United States)
  6. Osservatorio Astronomico di Padova—INAF, Vicolo dell'Osservatorio 5, I-35122 Padova (Italy)
  7. Department of Astronomy, Indiana University, 727 East Third Street, Bloomington, IN 47405 (United States)
  8. Raytheon Company, 1151 E. Hermans Road, Tucson, AZ 85756 (United States)
  9. Astrophysics, Cosmology and Gravity Centre (ACGC), Department of Astronomy, University of Cape Town, Private Bag X3, Rondebosch 7701 (South Africa)
  10. Dipartimento di Fisica e Astronomia Galileo Galilei, Universitá degli Studi di Padova, Vicolo dell'Osservatorio 3, I-35122 Padova (Italy)
  11. School of Physics, Astronomy, and Computational Science, George Mason University, Fairfax, VA 22030 (United States)
  12. Department of Physics and Astronomy, University of San Francisco, 2130 Fulton Street, San Francisco, CA 94117 (United States)
  13. Department of Astronomy, University of Maryland, CSS Bldg., Rm. 1024, Stadium Drive, College Park, MD 20742-2421 (United States)
Publication Date:
OSTI Identifier:
22365846
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal Letters; Journal Volume: 787; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; BRIGHTNESS; DISTANCE; ELEMENT ABUNDANCE; GALAXIES; GRAVITATIONAL INTERACTIONS; HYDROGEN IONS; LUMINOSITY; MASS; MATHEMATICAL SOLUTIONS; METALLICITY; METALS; OXYGEN; STARS; SURFACES; TELESCOPES