paper

A Ringed Dwarf LINER 1 Galaxy Hosting an Intermediate-mass Black Hole with Large-scale Rotation-like Hα Emission

arXiv:1702.01033 · doi:10.3847/1538-4357/aa5eb6

Abstract

We report the discovery of a 20-kpc-sized Hα emission in SDSS J083803.68+540642.0, a ringed dwarf galaxy (M = -17.89 mag) hosting an accreting intermediate-mass black hole at z=0.02957. Analysis of the HST images indicates that it is an early-type galaxy with a featureless low-surface brightness disk (μ0 = 20.39 mag arcsec in the V band) and a prominent, relatively red bulge (V - I = 2.03, Re = 0.28 kpc 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 Hα emission is consistent with a rotational gaseous disk, with a mean blueshifted velocity of 162 km s and mean redshifted velocity of 86 km s . According to our photoionization calculations, the large-scale Hα 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 Hα-emitting gas are created by the tidal accretion in a collision-and then merger-with a gas-rich galaxy of a comparable mass.

5 figures, 2 tables; Accepted for publication in The Astrophysical Journal

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