The highly ionized warm/hot intergalactic medium (WHIM) permeating the vast space of the cosmic filaments is one of the least explored baryon contents in the local Universe. The properties of the WHIM in long cosmic filaments with lengths reaching up to 20-100Mpc, which account for >80% of the total filament volume and 50% of the baryonic mass, remain to be explored. In this work, we examine the emission properties of the WHIM in long cosmic filaments using the deepest SRG/eROSITA All-Sky Survey data available. By stacking the X-ray emission from 8000 cosmic filaments traced by the galaxy distribution by the SDSS, we detect the X-ray emission in the filament. After correcting for the emission from the unresolved point sources and extended low-mass haloes, the detection of the WHIM component remains statistically significant. We further stack the eROSITA X-ray spectra and obtain the first-ever broadband 100 eV resolution spectrum of cosmic filaments at the source frame. The best-fit mean gas temperature of the WHIM component is 10^6.8 K.
BIO
Dr. Xiaoyuan Zhang works as a postdoc researcher at Max-Planck Institute for extraterrestrial Physics. He obtained his PhD degree in Leiden University and SRON in 2022. He has research interests in multiple aspects of galaxy clusters and ICM astrophysics.
