Performance Assessment of the KASI-Deep Rolling Imaging Fast-optics Telescope pathfinder

TL;DR

The paper evaluates the K-DRIFT telescope's ability to detect low surface brightness features, demonstrating its high efficiency and low photometric uncertainties in observing faint galactic structures.

Contribution

It introduces a new optimized telescope design with a linear astigmatism free-three mirror system and assesses its performance in detecting faint LSB features.

Findings

Surface brightness limit of ~28.5 mag arcsec$^{-2}$ achieved

Able to identify faint stellar streams around NGC 5907

Low PSF wing levels with some internal reflections within 6 arcmin

Abstract

In a $\Lambda$CDM universe, most galaxies evolve by mergers and accretions, leaving faint and/or diffuse structures, such as tidal streams and stellar halos. Although these structures are a good indicator of galaxies' recent mass assembly history, they have the disadvantage of being difficult to observe due to their low surface brightness (LSB). To recover these LSB features by minimizing the photometric uncertainties introduced by the optical system, we developed a new optimized telescope named K-DRIFT pathfinder, adopting a linear astigmatism free-three mirror system. Thanks to the off-axis design, it is expected to avoid the loss and scattering of light on the optical path within the telescope. To assess the performance of this prototype telescope, we investigate the photometric depth and capability to identify LSB features. We find that the surface brightness limit reaches down to $\mu_{r,1\sigma}\sim28.5$ mag arcsec$^{-2}$ in $10^{\prime\prime}\times10^{\prime\prime}$ boxes, enabling us to identify a single stellar stream to the east of NGC 5907. We also examine the characteristics of the point spread function (PSF) and find that the PSF wing reaches a very low level. Still, however, some internal reflections appear within a radius of $\sim$6 arcmin from the center of sources. Despite a relatively small aperture (0.3 m) and short integration time (2 hr), this result demonstrates that our telescope is highly efficient in LSB detection.