K-DRIFT Science Theme: Illuminating the Next Era of Galaxy Cluster Science

TL;DR

The paper presents K-DRIFT as a dedicated instrument for probing low-surface-brightness phenomena in galaxy clusters, with a focus on intracluster light (ICL) and faint structures as tracers of cluster assembly and dark matter. It outlines a comprehensive strategy—deep wide-field imaging, narrow-band and NUV follow-up, LSB-focused simulations (including GRT and zoom-in approaches), and ML-enabled detection—to characterize ICL origins, its spatial relation to dark matter, and the dynamical state of clusters. Key contributions include using the Weighted Overlap Coefficient (WOC) to compare ICL and DM distributions, leveraging ICL as a potential DM proxy, and forecasting constraints on SIDM versus CDM through cluster substructure and ICL morphologies. The work emphasizes synergies with LSST, Euclid, SPHEREx, DES, and other surveys to maximize scientific return and enhance cosmological inferences, with a practical plan to reach surface brightness levels down to $ ext{μ}_V ightarrow 29$–$30$ mag arcsec$^{-2}$ for hundreds to thousands of clusters.

Abstract

The KASI Deep Rolling Imaging Fast Telescope (K-DRIFT) is a pioneering instrument designed to explore low-surface-brightness (LSB) phenomena. This white paper presents a compelling array of science cases that showcase K-DRIFT's unique capabilities in unraveling the mysteries of intracluster light (ICL) and other LSB components within galaxy clusters. Exploring the origin of ICL in galaxy clusters and comparing the spatial distributions of ICL and dark matter will offer new insights into galaxy cluster dynamics. Moreover, investigating LSB objects in galaxy clusters, such as LSB structures in the brightest cluster galaxy, ultra-diffuse galaxies, and tidal features, will enhance our understanding of galaxy evolution within the cluster environment. We present our strategies for addressing scientific queries, encompassing LSB observation and analysis techniques, specialized simulations, and machine-learning approaches. Additionally, we examine the potential synergies between K-DRIFT and other ongoing or forthcoming multi-wavelength surveys. This white paper advocates for the recognition and support of K-DRIFT as a dedicated tool for advancing our understanding of the universe's subtlest phenomena.

Figures (4)

• Figure 1: Galaxy cluster images observed with the K-DRIFT Pathfinder. Left: Abell 2199, spanning approximately $25 \times 25$ arcmin$^2$. Right: Coma cluster, spanning approximately $32 \times 32$ arcmin$^2$. In the upper panels, regions with surface brightness brighter than 26.5 mag arcsec$^{-2}$ (the typical ICL detection threshold) are masked and displayed in the lower panels. The K-DRIFT G1 is expected to provide wider FoV and improved image quality.
• Figure 2: Top: the WOC results for different components of galaxy clusters. The three data points with the same symbols come from the three projection angles of each galaxy cluster, which are connected with lines. Bottom: the WOC results for different dynamical state of galaxy clusters. Figure credit from 2022ApJS..261...28Y.
• Figure 3: Mock color images of all cluster light (left) and ICL (right) from the Horizon Run 5 simulation. The top, middle, and bottom panels show the $g-r$, $u-r$, and NUV$-r$ mock color images, respectively. Theses mock color images were produced with a 2 arcsec pixel scale and a 1.5 arcsec PSF FWHM, simulating the anticipated performance of K-DRIFT. Notably, the NUV$-r$ color map exhibits greater variations compared to the $g-r$ and $u-r$ color maps.
• Figure 4: Structures of a GRT cluster of $M_{\rm{200c}} = 2\times10^{14}$$M_{\odot}$ brighter than $\mu_{V} <$ 26.5 mag arcsec$^{-2}$ (left) and $\mu_{V} <$ 31 mag arcsec$^{-2}$ (right).