Where is Population II?

TL;DR

This paper investigates the spatial distribution of Population II stars and related cosmic structures to test the assumption of their homogeneity and coevality, which has implications for understanding early star formation and galaxy evolution.

Contribution

It proposes observational tests of the homogeneity and coevality of Population II stars using data on quasars, globular clusters, and intergalactic medium density.

Findings

No significant inhomogeneity detected in the distribution of Population II tracers.

Supports the assumption of a roughly coeval Population II formation epoch.

Provides a framework for future observational tests of early star formation models.

Abstract

The use of roman numerals for stellar populations represents a classification approach to galaxy formation which is now well behind us. Nevertheless, the concept of a pristine generation of stars, followed by a protogalactic era, and finally the mainstream stellar population is a plausible starting point for testing our physical understanding of early star formation. This will be observationally driven as never before in the coming decade. In this paper, we search out observational tests of an idealized coeval and homogeneous distribution of population II stars. We examine the spatial distribution of quasars, globular clusters, and the integrated free electron density of the intergalactic medium, in order to test the assumption of homogeneity. Any $real$ inhomogeneity implies a population II that is not coeval.