"Slow-Scanning" in Ground-Based Mid-Infrared Observation

TL;DR

This paper introduces a 'slow-scanning' observational method for ground-based mid-infrared astronomy, replacing traditional chopping techniques with continuous imaging and advanced data processing, demonstrating comparable image quality and improved efficiency.

Contribution

The paper proposes and experimentally validates a novel 'slow-scanning' method that eliminates the need for large tip-tilt mirrors in mid-infrared observations, enhancing efficiency.

Findings

Image quality comparable to traditional chopping for bright sources

Improved observational efficiency over chopping method

Potential applicability to next-generation large telescopes

Abstract

Chopping observations with a tip-tilt secondary mirror have conventionally been used in ground-based mid-infrared observations. However, it is not practical for next generation large telescopes to have a large tip-tilt mirror that moves at a frequency larger than a few Hz. We propose an alternative observing method, a "slow-scanning" observation. Images are continuously captured as movie data, while the field-of-view is slowly moved. The signal from an astronomical object is extracted from the movie data by a low-rank and sparse matrix decomposition. The performance of the "slow-scanning" observation was tested in an experimental observation with Subaru/COMICS. The quality of a resultant image in the "slow-scanning" observation was as good as in a conventional chopping observation with COMICS, at least for a bright point-source object. The observational efficiency in the "slow-scanning" observation was better than that in the chopping observation. The results suggest that the "slow-scanning" observation can be a competitive method for the Subaru telescope and be of potential interest to other ground-based facilities to avoid chopping.