Evidence for X-Ray Emission from a Large-Scale Filament of Galaxies?

Area of Science:

• Cosmology
• Astrophysics
• X-ray Astronomy

Background:

• Cosmological simulations predict a significant baryonic mass fraction exists as diffuse, X-ray-emitting gas (105-107 K) in low-density cosmic structures.
• This intergalactic gas is crucial for reconciling the observed baryon deficit compared to the standard Big Bang model predictions.

Purpose of the Study:

• To present the discovery and analysis of a large-scale filamentary structure.
• To investigate the presence and properties of diffuse, X-ray-emitting gas in the intergalactic medium.

Main Methods:

• Analysis of a deep ROSAT PSPC X-ray field.
• Examination of I-band galaxy surface density.
• Detection and characterization of a 5-sigma significance, half-degree filamentary structure.

Main Results:

• Discovery of a filamentary structure evident in both galaxy distribution and unresolved X-ray emission.
• Estimated diffuse X-ray surface brightness of ~1.6x10-16 ergs s-1 cm-2 arcmin-2 (0.5-2 keV).
• The observed properties are comparable to predictions for intercluster gas.

Conclusions:

• The detected filament represents a potential direct detection of the elusive diffuse baryonic component.
• This discovery supports cosmological models and helps resolve the cosmic baryon count discrepancy.