Abstract
Abstract We report the discovery of a 20 kpc sized emission in SDSS J083803.68+540642.0, a ringed dwarf galaxy ( mag) hosting an accreting intermediate-mass black hole at z = 0.02957. Analysis of the Hubble Space Telescope images indicates that it is an early-type galaxy with a featureless low-surface brightness disk ( mag arcsec−2 in the V band) and a prominent, relatively red bulge (V − I = 2.03, or 0.″48) that accounts for ≈81% of the total light in the I band. A circumgalactic ring of a diameter 16 kpc is also detected, with a disperse shape on its south side. The optical emission lines reveal the nucleus to be a broad-line LINER. Our MMT longslit observation indicates that the kinematics of the extended emission is consistent with a rotational gaseous disk, with a mean blueshifted velocity of 162 and mean redshifted velocity of 86 . According to our photoionization calculations, the large-scale emission is unlikely to be powered by the central nucleus or by hot evolved (post-AGB) stars interspersed in the old stellar populations, but by in situ star formation; this is vindicated by the line-ratio diagnostic of the extended emission. We propose that both the ring and large-scale -emitting gas are created by the tidal accretion in a collision—and then merger—with a gas-rich galaxy of a comparable mass.
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