BST1047+1156: An Extremely Diffuse and Gas-rich Object in the Leo I Group

J. Christopher Mihos*, Christopher T. Carr, Aaron E. Watkins, Tom Oosterloo, Paul Harding

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

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Abstract

We report the detection of diffuse starlight in an extragalactic H I cloud in the nearby Leo I galaxy group. We detect the source, BST1047+1156, in both broadband optical and the Galaxy Evolution Explorer (GALEX) ultraviolet (UV) light. Spanning similar to 2 kpc in radius, it has a peak surface brightness of mu(B) = 28.8 mag arcsec(-2), making it the lowest surface brightness object ever detected via integrated light. Although the object is extremely gas rich, with a gas fraction of f(g) = 0.99, its peak H I column density is well below levels where star formation is typically observed in galaxies. Nonetheless, BST1047+1156 shows evidence for young stellar populations: along with the detected UV emission, the object is extremely blue, with B - V = 0.14 +/- 0.09. The object has two tidal tails and is found embedded within diffuse gas connecting the spiral galaxy M96 to the group's extended H I Leo Ring. The nature of BST1047+1156 is unclear. It could be a disrupting tidal dwarf, recently spawned from star formation triggered in the Leo I group's tidal debris. Alternatively, the object may have been a pre- existing galaxy-the most extreme example of a gas-rich field low surface brightness galaxy known to date-which had a recent burst of star formation triggered by encounters in the group environment.

Original languageEnglish
Article numberL7
Number of pages6
JournalAstrophysical Journal Letters
Volume863
Issue number1
DOIs
Publication statusPublished - 10-Aug-2018

Keywords

  • galaxies: evolution
  • galaxies: groups: individual (Leo I)
  • galaxies: interactions
  • galaxies: irregular
  • galaxies: structure
  • STAR-FORMATION LAW
  • CLUSTER DWARF GALAXIES
  • M96 GROUP
  • NEARBY GALAXIES
  • MASS FRACTIONS
  • DISK GALAXIES
  • VIRGO CLUSTER
  • MILKY-WAY
  • HI
  • POPULATION

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