The NGC 454 system: anatomy of a mixed on-going merger
  This paper focuses on NGC 454, a nearby interacting pair of galaxies
(AM0112-554, RR23), composed of an early-type (NGC 454 E) and a star forming
late-type companion (NGC 454 W). We aim at characterizing this wet merger
candidate via a multi-lambda analysis, from near-UV to optical using
SWIFT-UVOT, and mapping the Halpha intensity (I) distribution, velocity (Vr),
and velocity dispersion (sigma) fields with SAM+Perot-Fabry at SOAR
observations. Luminosity profiles suggest that NGC 454 E is an S0. Distortions
in its outskirts caused by the on-going interaction are visible in both optical
and near-UV frames. In NGC 454 W, the NUV-UVOT images and the Halpha show a set
of star forming complexes connected by a faint tail. Halpha emission is
detected along the line connecting NGC 454 E to the NGC 454 main HII complex.
We investigate the (I-sigma), (I-Vr ) (Vr-sigma) diagnostic diagrams of the HII
complexes, most of which can be interpreted in a framework of expanding
bubbles. In the main HII complex, enclosed in the UV brightest region, the gas
velocity dispersion is highly supersonic reaching 60 km/s. However, Halpha
emission profiles are mostly asymmetric indicating the presence of multiple
components with an irregular kinematics. Observations point towards an advanced
stage of the encounter. Our SPH simulations with chemophotometric
implementation suggest that this mixed pair can be understood in terms of a 1:1
gas/halos encounter giving rise to a merger in about 0.2 Gyr from the present
stage.
