The warm-hot intergalactic medium (WHIM) in inter-cluster filaments — A forecast for HUBS observations based on eRASS1 superclusters
Yuanyuan Zhao, Haiguang Xu, Ang Liu, Xiaoyuan Zhang, Li Ji, Jiang Chang, Dan Hu, Norbert Werner, Zhongli Zhang, Wei Cui, Xiangping Wu
arXiv:2410.06836v2 Announce Type: replace
Abstract: Cosmological simulations indicate that nearly half of the baryons in the nearby Universe are in the warm-hot intergalactic medium (WHIM) phase, with about half of which residing in cosmic filaments. Recent observational studies using stacked survey data and deep exposures of galaxy cluster outskirts have detected soft X-ray excess associated with optically identified filaments. However, the physical characteristics of WHIM in filaments remain largely undetermined due to the lack of direct spectral diagnostics. In this work, we aim to select appropriate targets for WHIM characterization through pointing observations with the future Hot Universe Baryon Surveyor (HUBS) mission, which is designed with eV level energy resolution in the 0.1-2.0 keV band and a 1 square degree field-of-view. We built a sample of 1577 inter-cluster filaments based on the first eROSITA All-Sky Survey (eRASS1) supercluster catalog and estimated their soft X-ray emission, and used their modeled geometrical properties and oxygen line intensities to select four most appropriate candidate targets for HUBS observations. By simulating and analyzing their mock observations, we demonstrated that with 200 ks HUBS exposure for each candidate, the gas properties of individual filaments can be accurately determined, with the temperature constrained to +-0.01 keV, metallicity constrained to arXiv:2410.06836v2 Announce Type: replace
Abstract: Cosmological simulations indicate that nearly half of the baryons in the nearby Universe are in the warm-hot intergalactic medium (WHIM) phase, with about half of which residing in cosmic filaments. Recent observational studies using stacked survey data and deep exposures of galaxy cluster outskirts have detected soft X-ray excess associated with optically identified filaments. However, the physical characteristics of WHIM in filaments remain largely undetermined due to the lack of direct spectral diagnostics. In this work, we aim to select appropriate targets for WHIM characterization through pointing observations with the future Hot Universe Baryon Surveyor (HUBS) mission, which is designed with eV level energy resolution in the 0.1-2.0 keV band and a 1 square degree field-of-view. We built a sample of 1577 inter-cluster filaments based on the first eROSITA All-Sky Survey (eRASS1) supercluster catalog and estimated their soft X-ray emission, and used their modeled geometrical properties and oxygen line intensities to select four most appropriate candidate targets for HUBS observations. By simulating and analyzing their mock observations, we demonstrated that with 200 ks HUBS exposure for each candidate, the gas properties of individual filaments can be accurately determined, with the temperature constrained to +-0.01 keV, metallicity constrained to