  We present the formation of a Kinematically Decoupled Core (KDC) in an
elliptical galaxy, resulting from a major merger simulation of two disk
galaxies. We show that although the two progenitor galaxies are initially
following a prograde orbit, strong reactive forces during the merger can cause
a short-lived change of their orbital spin; the two progenitors follow a
retrograde orbit right before their final coalescence. This results in a
central kinematic decoupling and the formation of a large-scale (~2 kpc radius)
counter-rotating core (CRC) at the center of the final elliptical-like merger
remnant (M*=1.3x10^11 Msun), while its outer parts keep the rotation direction
of the initial orbital spin. The stellar velocity dispersion distribution of
the merger remnant galaxy exhibits two symmetrical off-centered peaks,
comparable to the observed "2-sigma galaxies". The KDC/CRC consists mainly of
old, pre-merger population stars (older than 5 Gyr), remaining prominent in the
center of the galaxy for more than 2 Gyr after the coalescence of its
progenitors. Its properties are consistent with KDCs observed in massive
elliptical galaxies. This new channel for the formation of KDCs from prograde
mergers is in addition to previously known formation scenarios from retrograde
mergers and can help towards explaining the substantial fraction of KDCs
observed in early-type galaxies.
