The molecular gas content of the advanced S+E merger NGC 4441 - Evidence
  for an extended decoupled nuclear disc?
  Mergers between a spiral and an elliptical (S+E mergers) are poorly studied
so far despite the importance for galaxy evolution. NGC4441 is a nearby
candidate for an advanced remnant of such a merger, showing typical tidal
structures like an optical tail and two shells as well as two HI tails. The
study of the molecular gas content gives clues on the impact of the recent
merger event on the star formation. Simulations of S+E mergers predict
contradictory scenarios concerning the strength and the extent of an induced
starburst. Thus, observations of the amount and the distribution of the
molecular gas, the raw material of star formation, are needed to understand the
influence of the merger on the star formation history. 12CO and 13CO (1-0) and
(2-1) observations were obtained using the Onsala Space Observatory 20m and
IRAM 30m telescope as well as the Plateau de Bure interferometer. These data
allow us to carry out a basic analysis of the molecular gas properties such as
estimates of the molecular gas mass, its temperature and density and the star
formation efficiency. The CO observations reveal an extended molecular gas
reservoir out to ~4kpc, with a total molecular gas mass of ~5x10^8 M_sun.
Furthermore, high resolution imaging shows a central molecular gas feature,
most likely a rotating disc hosting most of the molecular gas ~4x10^8 M_sun.
This nuclear disc shows a different sense of rotation than the large-scale HI
structure, indicating a kinematically decoupled core. (abbreviated)
