Statistical characteristics of the observed metal systems and problems of reionization

TL;DR

This study examines metal systems in quasar spectra to understand their properties, distribution, and implications for cosmic reionization, revealing thermal broadening dominance, typical protogalaxy sizes, and the limited role of stars in reionization.

Contribution

It provides detailed analysis of metal system properties, their spatial distribution, and implications for reionization, highlighting the need for additional UV sources beyond stellar contributions.

Findings

Metal Doppler parameters indicate thermal broadening dominance.

Metal systems are located in regions of 0.1-0.25h^{-1} Mpc, typical of protogalaxies.

Metal abundances suggest stars alone cannot account for reionization.

Abstract

We analyze basic properties of about 200 metal systems observed in high resolution spectra of 9 quasars by Boksenberg, Sargent & Rauch (2003). The measured Doppler parameters for the hydrogen and carbon lines are found to be different by a factor $\sim\sqrt{m_C/ m_H}$ what indicates the domination of the thermal broadening and high degree of relaxation for majority of the observed metal systems. The analysis of the mean separation of the metal systems confirms that they can be located in regions with the typical proper size $R_{cl}\sim 0.1 - 0.25h^{-1}$ Mpc what corresponds to the typical sizes of protogalaxies with the baryonic masses $M_b\approx 10^9-10^{10}M_\odot$. The metal abundances observed at redshifts $z=3 - 6$ within both IGM and galaxies are found to be quite similar to each other what indicates the strong interaction of young galaxies with the IGM and the important role of dwarf satellites of host galaxies in such interaction. On the other hand, this metal abundance can be considered as the integral measure of nuclear reactions within any stars what in turn restricts the contribution of the stars to the creation of ionizing UV background. Available now estimates of these abundances demonstrate that attempts to explain the reionization of the Universe as a byproduct of the process of synthesis of metals only are problematic and a significant contribution of unobserved and/or non thermal UV sources seems to be required.