Sparse Aperture Masking (SAM) at NAOS/CONICA on the VLT

TL;DR

The paper introduces the implementation and initial results of Sparse Aperture Masking (SAM) mode on the VLT's CONICA camera, demonstrating its advantages in high-fidelity imaging and detection of faint companions, especially when combined with polarimetry.

Contribution

It presents the new SAM operational mode on VLT/CONICA, showcasing its capabilities for improved imaging and circumstellar structure detection.

Findings

SAM mode provides superior PSF calibration and atmospheric noise rejection.

High-resolution imaging reveals new structures around evolved stars.

SAM combined with polarimetry uncovers previously unseen features.

Abstract

The new operational mode of aperture masking interferometry has been added to the CONICA camera which lies downstream of the Adaptive Optics (AO) corrected focus provided by NAOS on the VLT-UT4 telescope. Masking has been shown to deliver superior PSF calibration, rejection of atmospheric noise and robust recovery of phase information through the use of closure phases. Over the resolution range from about half to several resolution elements, masking interferometry is presently unsurpassed in delivering high fidelity imaging and direct detection of faint companions. Here we present results from commissioning data using this powerful new operational mode, and discuss the utility for masking in a variety of scientific contexts. Of particular interest is the combination of the CONICA polarimetry capabilities together with SAM mode operation, which has revealed structures never seen before in the immediate circumstellar environments of dusty evolved stars.