Derivation of the cosmological density parameter Omega0 from large-scale flows

Area of Science:

• Cosmology
• Astrophysics
• Galaxy Dynamics

Background:

• Determining the cosmological density parameter (Omega0) is crucial for understanding the universe's expansion and fate.
• Large-scale galaxy flows provide a unique probe for Omega0, independent of cosmic microwave background methods.
• Previous studies yielded varying Omega0 values, necessitating robust and consistent measurement techniques.

Purpose of the Study:

• To review and synthesize methods for Omega0 determination using large-scale galaxy flows.
• To assess the consistency of results obtained from Infrared Astronomical Satellite (IRAS) data.
• To discuss potential biases and challenges in Omega0 measurements from galaxy surveys.

Main Methods:

• Review of methods utilizing galaxy distribution maps to predict peculiar velocities.
• Comparison of density fields from IRAS galaxy data with peculiar velocities from optical distance methods.
• Analysis of a new study using the complete IRAS point source catalog.

Main Results:

• Consistent Omega0 estimates around 0.7 +/- 0.1 derived from multiple independent analyses of IRAS data.
• Alternatively, results are consistent with Omega0 = 1 if a bias parameter b = 1.2 +/- 0.1 is considered.
• New study using the full IRAS catalog yields results corroborating previous IRAS-based findings.

Conclusions:

• IRAS data provides reliable and consistent Omega0 measurements, favoring values around 0.7.
• Discrepancies with optical studies may stem from biases in elliptical galaxy selection.
• Further investigation into waveband optimization, bias, and luminosity function universality is warranted.