NACO/SAM observations of sources at the Galactic Center

TL;DR

This paper demonstrates a novel calibration method for sparse aperture masking interferometry with adaptive optics, enabling high-resolution imaging of crowded fields near the Galactic Center without the need for separate calibrator stars.

Contribution

It introduces a new in-field calibration technique for SAM+AO observations, improving efficiency and robustness in crowded and variable atmospheric conditions.

Findings

First NaCo/SAM images reconstructed with the new calibration method

The method effectively handles unstable atmospheric conditions

Calibration without interspersed reference star observations

Abstract

Sparse aperture masking (SAM) interferometry combined with Adaptive Optics (AO) is a technique that is uniquely suited to investigate structures near the diffraction limit of large telescopes. The strengths of the technique are a robust calibration of the Point Spread Function (PSF) while maintaining a relatively high dynamic range. We used SAM+AO observations to investigate the circumstellar environment of several bright sources with infrared excess in the central parsec of the Galaxy. For our observations, unstable atmospheric conditions as well as significant residuals after the background subtraction presented serious problems for the standard approach of calibrating SAM data via interspersed observations of reference stars. We circumvented these difficulties by constructing a synthesized calibrator directly from sources within the field-of-view. When observing crowded fields, this novel method can boost the efficiency of SAM observations because it renders interspersed calibrator observations unnecessary. Here, we presented the first NaCo/SAM images reconstructed using this method.