In this paper, we review the extended halo material and the circumgalactic medium (CGM), including both dust and gas, and discuss promising science cases that could be realized using the KASI Deep Rolling Imaging Fast Telescope (K-DRIFT). Scattered starlight from cirrus clouds in our Galaxy poses one of the major challenges to studying the low surface brightness features of extragalactic sources. Therefore, it is essential to investigate how to discriminate extragalactic sources from cirrus cloud features. At the same time, interstellar dust clouds themselves are fundamental to understanding dust properties and the interstellar radiation field, both of which are essential for studies of chemical evolution and star formation in our Galaxy. Measuring the reddening of background sources, such as quasars, with K-DRIFT, which benefits from its broad field of view and accurate background subtraction, allows for the effective detection of extended dust in galactic halos, the CGM, and intracluster space. Observations of the Hα emission lines can be used to identify signatures of star formation activity within galaxies, as well as the environmental effects acting on them. Galactic winds driven by active galactic nuclei and starbursts can be traced through Hα emission. Strong ram pressure stripping effectively removes the interstellar medium (ISM) from galaxies. The stripped ISM becomes ionized or dissociated through mixing with the hot intracluster medium (ICM), forming Hα tails. The surface brightness of these Hα tails correlates not only with the presence of star formation in the tails but also the mixing stage of the stripped ISM and ICM. The Hα survey with K-DRIFT will enable the investigation of the evolutionary stages of ram pressure stripped galaxies in cluster environments, as well as the multiphase gas reservoir around galaxies and in the CGM.

Introduction
Dust
    Cirrus Clouds in Our Galaxy
    Extended Halo Dust around Galaxies
    Dust in the Intracluster and Intergalactic Media
Gas
    Halpha Emission from the Ram Pressure Stripped Gas in the Cluster Environments
        Physical Origin of Jellyfish Features
        Halpha Emission from Jellyfish Galaxies
        Mixing of Stripped ISM with ICM
        Halpha Observations in K-DRIFT
    Extended Halpha Emission as a Tracer of the Multiphase Gas Reservoir around Galaxies and in the CGM
Concluding Remarks
    Metallic Absorption/Emission Lines from the CGM
    Relation between the CGM and ICL
Summary
Acknowledgments
References

• Woowon Byun(Korea Astronomy and Space Science Institute, Daejeon 34055, Republic of Korea)
• Jaewon Yoo(Korea Astronomy and Space Science Institute, Daejeon 34055, Republic of Korea)
• Kyungwon Chun(Korea Astronomy and Space Science Institute, Daejeon 34055, Republic of Korea)
• Sang-Hyun Chun(Korea Astronomy and Space Science Institute, Daejeon 34055, Republic of Korea)
• Sungryong Hong(Korea Astronomy and Space Science Institute, Daejeon 34055, Republic of Korea)
• Jae-Woo Kim(Korea Astronomy and Space Science Institute, Daejeon 34055, Republic of Korea)
• Kwang-il Seon(Korea Astronomy and Space Science Institute, Daejeon 34055, Republic of Korea, Department of Astronomy and Space Science, University of Science and Technology, Korea, Daejeon 34113, Republic of Korea) Corresponding author
• Jongwan Ko(Korea Astronomy and Space Science Institute, Daejeon 34055, Republic of Korea, Department of Astronomy and Space Science, University of Science and Technology, Korea, Daejeon 34113, Republic of Korea)
• Hong Soo Park(Korea Astronomy and Space Science Institute, Daejeon 34055, Republic of Korea, Department of Astronomy and Space Science, University of Science and Technology, Korea, Daejeon 34113, Republic of Korea)
• Jihye Shin(Korea Astronomy and Space Science Institute, Daejeon 34055, Republic of Korea, Department of Astronomy and Space Science, University of Science and Technology, Korea, Daejeon 34113, Republic of Korea)
• Jaehyun Lee(Korea Astronomy and Space Science Institute, Daejeon 34055, Republic of Korea, Korea Institute for Advanced Study, Seoul 02455, Republic of Korea)