[Paper Review] Detection of Filamentary X-Ray Structure in the Core of the Shapley Supercluster

Andreas Kull, H. Boehringer|ArXiv.org|Dec 16, 1998

Crystallography and Radiation Phenomena6 citations

TL;DR

This paper presents X-ray observations from ROSAT that detect a filamentary structure connecting three central clusters (A3562, A3558, A3556) in the Shapley Supercluster, confirming a physical, extended X-ray-emitting filament. The filament spans at least 17.5 h₅₀⁻¹ Mpc with a total luminosity of ~16×10⁴⁴ h₅₀⁻² erg s⁻¹ in the 0.1–2.4 keV band, providing strong evidence for large-scale structure formation in the supercluster's core.

ABSTRACT

We report on X-ray observations of the core of the Shapley Supercluster. Combining data from pointed observations of the ROSAT PSPC detector and data from the ROSAT All-Sky Survey, the observed region covers an area of $6^\circ imes 3^\circ$. It contains the central clusters A3562, A3558 and A3556. We find clear evidence for X-ray emission connecting the three clusters. This confirms the existence of a filamentary, physical structure embedding the three clusters A3562, A3558 and A3556. We also find evidence for faint emission westwards of A3556. In total, the extension of the filamentary X-ray emission of the core of the Shapley Supercluster amounts up to at least $\sim 17.5 h_{50}^{-1}$ Mpc. The total luminosity in the 0.1-2.4 keV energy band is $\sim 16 imes10^{44} h_{50}^{-2}$ erg s$^{-1}$.

Motivation & Objective

• To investigate the existence of extended X-ray structures connecting the central clusters in the Shapley Supercluster.
• To determine whether the observed X-ray emission forms a physical filament linking the clusters A3562, A3558, and A3556.
• To measure the spatial extent and luminosity of the X-ray-emitting structure in the core region.
• To assess the presence of faint X-ray emission beyond the main cluster complexes, particularly west of A3556.
• To provide observational evidence for large-scale filamentary structure in the densest region of the Shapley Supercluster.

Proposed method

• Combination of pointed ROSAT PSPC observations with data from the ROSAT All-Sky Survey to cover a 6°×3° region.
• Use of X-ray image analysis to detect extended emission features connecting the three central clusters.
• Application of background subtraction and source detection techniques to isolate faint, diffuse X-ray emission.
• Measurement of the spatial extent of X-ray emission using source contour mapping and photometric analysis.
• Calculation of luminosity in the 0.1–2.4 keV energy band using flux integration over the detected emission region.
• Use of cosmological distance scaling with h₅₀ to express physical lengths and luminosities in standard cosmological units.

Experimental results

Research questions

• RQ1 Is there extended X-ray emission connecting the three dominant clusters A3562, A3558, and A3556 in the core of the Shapley Supercluster?
• RQ2 What is the physical extent of the X-ray-emitting structure in the supercluster's central region?
• RQ3 Does the observed X-ray emission represent a physical filament or a chance alignment of clusters?
• RQ4 What is the total X-ray luminosity of the filamentary structure in the 0.1–2.4 keV band?
• RQ5 Are there signs of diffuse X-ray emission extending beyond the immediate vicinity of the main clusters, such as west of A3556?

Key findings

• Clear X-ray emission is detected connecting the three central clusters A3562, A3558, and A3556, confirming a physical filamentary structure.
• The filament extends over at least 17.5 h₅₀⁻¹ Mpc in physical length, indicating a large-scale structure.
• The total X-ray luminosity in the 0.1–2.4 keV band is measured at ~16×10⁴⁴ h₅₀⁻² erg s⁻¹.
• Faint X-ray emission is observed extending westward from A3556, suggesting possible continuation of the filamentary structure.
• The combined data from ROSAT PSPC and the All-Sky Survey provide high dynamic range and sensitivity to detect diffuse, low-surface-brightness emission.
• The results support the existence of a massive, hot, and extended X-ray-emitting structure linking clusters in the densest part of the Shapley Supercluster.