The SRG/eROSITA all-sky survey. X-ray emission from the warm-hot phase gas in long cosmic filaments
Abstract
The properties of the warm-hot intergalactic medium (WHIM) in the cosmic filaments are among the least quantified in modern astrophysics. eROSITA All Sky Survey (eRASS) provides us with a unique opportunity to study the X-ray emission of the WHIM. We applied both imaging and spectroscopic stacking techniques to the data of the first four eRASS scans to inspect the X-ray emissions from 7817 cosmic filaments identified from Sloan Digital Sky Survey optical galaxy samples. We obtained a 9-sigma significant detection of the total X-ray signal from filaments in the 0.3-1.2 keV band. We introduce a novel method to estimate the contamination fraction from unmasked X-ray halos, active galactic nuclei, and X-ray binaries that are associated with galaxies in filaments. We found an approximately 40% contamination fraction by these unmasked sources, suggesting that the remaining 60% of the signal could be from the WHIM and a 5.4-sigma detection significance of the WHIM. Moreover, we modeled the temperature and baryon density contrast of the detected WHIM by fitting the stacked spectrum and surface brightness profile. The best-fit temperature log(T/k)=6.84+/-0.07 obtained by using a single temperature model is marginally higher than the simulation results, which could be due to the fitting of a single temperature model on a multi-temperature spectrum. The best-fit baryon density contrast log\Delta_b=1.88+/-0.18 generally agrees with the X-ray emitting phases in the IllustrisTNG simulation, suggesting that the broadband X-ray emission traces the high temperature and density end of the entire WHIM population.
- Publication:
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arXiv e-prints
- Pub Date:
- May 2024
- DOI:
- 10.48550/arXiv.2406.00105
- arXiv:
- arXiv:2406.00105
- Bibcode:
- 2024arXiv240600105Z
- Keywords:
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- Astrophysics - High Energy Astrophysical Phenomena;
- Astrophysics - Cosmology and Nongalactic Astrophysics
- E-Print:
- 15+7 pages, 11+7 figures, submitted to A&