Misc,
Ultimate Merging at z~0.1
(2019)cite arxiv:1906.05629Comment: 8 Pages, 12 figures, Letter accepted to A&A.
Abstract
We present a study of 58 double-peaked emission line galaxies for which one
of the components is suppressed in OIII5008 or significantly weaker than the
other one. Accordingly, the two components are classified differently in the
BPT diagram. We show that the strong OIII component coincides with the
stellar velocity and the suppressed component is off-centred in 66% of the
galaxies, while in 12% of them it is the opposite. The analysis of their
morphology reveals that about half of the sample is composed of S0, the rest is
composed in equal part of mergers and late-type galaxies. We discuss that these
characteristics exclude rotating discs and suggest different stages of merging.
It is possible that the number of mergers is underestimated if the double
nuclei are not resolved. Tidal features are detected in the outskirts of some
S0 galaxies. This high fraction of S0 is surprising, as in addition most of the
galaxies are isolated and the others in small groups. All these galaxies,
hosting an AGN component, are massive, lie on the star forming sequence, and
exhibit an enhanced star formation in their centre. While we cannot exclude
outflows, these galaxies exhibit a spectra, which do not correspond to usual
outflow observations characterised by high gas velocities, and the standard
deviations of the two peaks are comparable. In parallel, these characteristics
are compatible with ultimate stages of galaxy merging, where the two nuclei are
too close to be detected or dynamical disturbances might be present in
post-mergers like massive S0.
