X-ray emission from clusters and groups of galaxies

Area of Science:

• Cosmic Evolution
• Astrophysics
• Galaxy Clusters

Background:

• Recent advancements in X-ray imaging and spectroscopy enable mass determination of galaxy clusters.
• Most baryonic mass in rich clusters resides in gas, with gas-to-star ratios varying significantly.
• Baryonic fractions in clusters often exceed theoretical limits, conflicting with the standard cosmological model (Omega = 1) and Big Bang nucleosynthesis.

Purpose of the Study:

• To investigate the mass, mass profiles, and baryonic fractions of galaxy clusters and groups using X-ray data.
• To determine chemical abundances (Fe, O, Si) in these structures and infer their origins.
• To assess the contribution of galaxy groups to the universe's mass density and understand their properties.

Main Methods:

• Utilizing X-ray imaging and spectroscopy to analyze galaxy clusters and groups.
• Calculating mass and mass profiles out to the virial radius.
• Measuring baryonic fractions and elemental abundances (Iron, Oxygen, Silicon).

Main Results:

• Baryonic fractions in clusters vary significantly and often exceed the Omega = 1 prediction.
• Iron abundances range from 0.2-0.45 solar, while Oxygen and Silicon range from 0.6-1.0 solar in low-redshift systems.
• Galaxy groups contribute substantially to the universe's mass density, with some exhibiting large X-ray halos and properties matching X-ray temperatures.

Conclusions:

• The observed baryonic fractions challenge the standard cosmological model.
• Elemental abundances suggest enrichment from Type II supernovae, indicating their crucial role in early cosmic evolution.
• Galaxy groups are significant contributors to cosmic mass density and display properties consistent with X-ray observations.