Mapping galactic winds and small-scale structure in the circumgalactic medium with Habitable Worlds Observatory

We present a science case for the Habitable Worlds Observatory (HWO) to map the circumgalactic medium (CGM) in emission by targeting ultraviolet emission lines, which trace the 104 to 106K gas engaged in the feedback and accretion mechanisms driving galaxy evolution. Although the CGM–galaxy connection is clearly evident through absorption line experiments and limited work has been done in optical and radio emission from the ground, the nature of this connection is poorly understood with regard to how these cosmic ecosystems exchange matter and energy. We outline a two-pronged experiment with HWO utilizing both multi-object spectroscopy to map kpc-scale CGM structures such as galactic superwinds and integral field spectroscopy to unveil the sub-kpc-scale processes such as thermal instabilities, which are theorized to govern the cool gas reservoirs long detected in pencil-beam absorption surveys.