Genesis of morpho-kinematic lopsidedness in minor merger of galaxies
  An $m=1$ lopsided asymmetry is common in disc galaxies. Here, we investigate
the excitation of an $m=1$ lopsidedness in host galaxies during minor mergers
while choosing a set of 1:10 merger models (with varying orbital
configurations, morphology of the host galaxy) from the GalMer galaxy merger
library. We show that a minor merger triggers a prominent $m=1$ lopsidedness in
stars of the host galaxy. The strength of the $m=1$ lopsidedness undergoes a
transient amplification phase after each pericenter passage of the satellite,
in concordance with past findings of exciting an $m=1$ lopsidedness by tidal
encounters. However, once the merger happens, and the post-merger remnant
readjusts itself, the lopsidedness disappears in short time-scale ($\sim$
500-850 Myr). Furthermore, a delayed merger can drive a prolonged ($\sim$2 Gyr)
lopsidedness in the host galaxy. We demonstrate that the $m=1$ lopsidedness
rotates with a well-defined pattern speed which is much slower than the $m=2$
bar pattern speed, and is retrograde with respect to the bar. This gives rise
to a dynamical scenario where the Inner Lindblad resonance of the $m=1$
lopsidedness falls in between the corotation and the Outer Lindblad resonance
of the $m=2$ bar mode. A kinematic lopsidedness also arises in the host galaxy;
the resulting temporal variation closely follows that of the density
lopsidedness. The minor merger also triggers a transient off-centred stellar
disc-dark matter halo configuration due to the tidal encounter with the
satellite.
