Imaging the dense stellar cluster R136 with VLT-MAD

TL;DR

This paper assesses the performance of the MAD adaptive optics system in imaging the dense stellar cluster R136, demonstrating its capabilities in high-resolution near-infrared observations despite challenging observing conditions.

Contribution

It provides the first detailed evaluation of MAD's imaging performance in a crowded stellar environment using natural guide stars at high airmass.

Findings

Achieved Strehl ratios of 15-30% in Ks-band.

Reached 5 sigma sensitivities of Ks=21.75 and H=22.25.

Demonstrated effective adaptive optics correction in a complex field.

Abstract

We evaluate the performance of the Multi-conjugate Adaptive optics Demonstrator (MAD) from H and Ks imaging of 30 Doradus in the Large Magellanic Cloud. Maps of the full-width half maximum (FWHM) of point sources in the H and Ks images are presented, together with maps of the Strehl ratio achieved in the Ks-band observations. Each of the three natural guide stars was at the edge of the MAD field-of-view, and the observations were obtained at relatively large airmass (1.4-1.6). Even so, the Strehl ratio achieved in the second pointing (best-placed compared to the reference stars) ranged from 15% to an impressive 30%. Preliminary photometric calibration of the first pointing indicates 5 sigma sensitivities of Ks=21.75 and H=22.25 (from 22 and 12 min exposures, respectively).