A benchmark for multi-conjugated AO: VLT-MAD observations of the young massive cluster Trumpler 14

TL;DR

This paper demonstrates the effectiveness of the MAD multi-conjugated adaptive optics system at the VLT by observing the young cluster Trumpler 14, revealing improved image stability, deeper photometry, and insights into the cluster's star formation history.

Contribution

First application of the VLT-MAD system to observe a young massive cluster, showing enhanced PSF stability and deeper photometry compared to traditional AO systems.

Findings

Achieved mean Strehl ratios of ~6% in H and Ks bands.

Detected a young starburst population approximately 1 Myr old.

Derived the cluster's mass function with a change in slope at ~0.53 M_sun.

Abstract

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.