High angular resolution near-infrared integral field observations of
  young star cluster complexes in NGC1365
  This paper presents and examines new near-infrared integral field
observations of the three so-called 'embedded star clusters' located in the
nuclear region of NGC1365. Adaptive-optics- corrected K-band data cubes were
obtained with the ESO/VLT instrument SINFONI. The continuum in the K-band and
emission lines such as HeI, Bracket-gamma, and several H2 lines were mapped at
an achieved angular resolution of 0.2arcsec over a field of 3x3arcsec^2 around
each source. We find that the continuum emission of the sources is spatially
resolved. This means that they are indeed cluster complexes confined to regions
of about 50pc extension. We performed robust measurements of the equivalent
width of the CO absorption band at 2.3micro and of Bracket-gamma. For the main
mid-infrared bright sources, the data only allow us to determine an upper limit
to the equivalent width of the CO bands. Under the assumption of an
instantaneously formed standard initial mass function Starburst99 model, the
new measurements are found to be incompatible with previously published
mid-infrared line ratios. We show that an upper mass limit of 25 to 30 solar
masses, lower than the typically assumed 100solar masses, allows one to simply
remove this inconsistency. For such a model, the measurements are consistent
with ages in the range of 5.5Myr to 6.5Myr, implying masses in the range from 3
to 10 x 10^6 solar masses. We detect extended gas emission both in HII and H2.
We argue that the central cluster complexes are the sources of excitation for
the whole nebulae, through ionisation and shock heating. We detect a blue wing
on the Bracket-gamma emission profile, suggesting the existence of gas outflows
centred on the cluster complexes. We do not find any evidence for the presence
of a lower mass cluster population, which would fill up a 'traditional' power
law cluster mass function.
