A benchmark for multi-conjugated AO: VLT-MAD observations of the young
  massive cluster Trumpler 14
  MAD is the first multi-conjugated adaptive optics system at the VLT. We
present H and Ks observations of the young massive cluster Trumpler 14
revealing the power of MCAO systems by providing a homogeneous Strehl ratio
over a large field of view. Mean Strehl ratios of 6.0 and 5.9 per cent with
maximum Strehl ratios of 9.8 and 12.6 per cent in H and Ks, respectively, show
significant improvement of the spatial PSF stability compared to
single-conjugated adaptive optics systems. Photometry of our observations cover
a dynamic range of ~10 mag including 2-3 times more sources than comparable
seeing-limited observations. The colour-magnitude diagram reveals that the
massive cluster originated in a recent starburst-like event 1+/-0.5 Myr ago. We
tentatively detect hints for an older population of 3 Myr suggesting that low
intensity star formation might have been going on in the HII region for a few
Myr. We derive the luminosity function and mass function between 0.1 M_sun and
3.2 M_sun and identify a change of the power law slope of the mass function at
m_c~0.53(+0.12/-0.10) M_sun. The MF appears shallow with power law slopes of
Gamma1=-0.50+/-0.11 above m_c and Gamma2=0.63+/-0.32 below m_c.
