Astrophys. J., 863, L7-L7 (2018/August-2)
BST1047+1156: an extremely diffuse and gas-rich object in the Leo I group.
MIHOS J.C., CARR C.T., WATKINS A.E., OOSTERLOO T. and HARDING P.
Abstract (from CDS):
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 ∼2 kpc in radius, it has a peak surface brightness of µB = 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 fg = 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.
© 2018. The American Astronomical Society. All rights reserved.
galaxies: evolution - galaxies: groups: individual: Leo I - galaxies: interactions - galaxies: irregular - galaxies: structure
Table 1: [MCW2018] BST J1047+1156 N=1.
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