Early- and late-stage mergers among main sequence and starburst galaxies
  at 0.2<z<2
  We investigate the fraction of close pairs and morphologically identified
mergers on and above the star-forming main sequence (MS) at 0.2$\leq z\leq$2.0.
The novelty of our work lies in the use of a non-parametric morphological
classification performed on resolved stellar mass maps, reducing the
contamination by non-interacting, high-redshift clumpy galaxies. We find that
the merger fraction rapidly rises to $\geq$70% above the MS, implying that --
already at $z{\gtrsim}1$ -- starburst (SB) events ($\Delta_{\rm MS}\geq$0.6)
are almost always associated with a major merger (1:1 to 1:6 mass ratio). The
majority of interacting galaxies in the SB region are morphologically
disturbed, late-stage mergers. Pair fractions show little dependence on
MS-offset and pairs are more prevalent than late-stage mergers only in the
lower half of the MS. In our sample, major mergers on the MS occur with a
roughly equal frequency of $\sim$5-10% at all masses ${\gtrsim}
10^{10}M_{\odot}$. The MS major merger fraction roughly doubles between $z=0.2$
and $z=2$, with morphological mergers driving the overall increase at
$z{\gtrsim}1$. The differential redshift evolution of interacting pairs and
morphologically classified mergers on the MS can be reconciled by evolving
observability timescales for both pairs and morphological disturbances. The
observed variation of the late-stage merger fraction with $\Delta_{\rm MS}$
follows the perturbative 2-Star Formation Mode model, where any MS galaxy can
experience a continuum of different SFR enhancements. This points to a
starburst-merger connection not only for extreme events, but also more moderate
bursts which merely scatter galaxies upward within the MS, rather than fully
elevating them above it.
