Uncertainties in Theoretical HeI Emissivities: HII Regions, Primordial Abundance, and Cosmological Recombination

TL;DR

This paper quantifies uncertainties in theoretical helium I emissivities across different astrophysical conditions, revealing significant errors that impact primordial abundance estimates and cosmological models.

Contribution

It provides the first comprehensive uncertainty analysis of atomic data for He I emissivities using Monte Carlo methods under various astrophysical conditions.

Findings

Uncertainties can be as large as or larger than current measurement errors.

Systematic effects on primordial helium abundance calculations are identified.

Errors in cosmological recombination emissivities are comparable to recent model effects.

Abstract

A number of recent works in astronomy and cosmology have relied upon theoretical He I emissivities, but we know of no effort to quantify the uncertainties in the atomic data. We analyze and assign uncertainties to all relevant atomic data, perform Monte Carlo analyses, and report standard deviations in the line emissivities. We consider two sets of errors, which we call "optimistic" and "pessimistic." We also consider three different conditions, corresponding to prototypical Galactic and extragalactic H II regions and the epoch of cosmological recombination. In the extragalactic H II case, the errors we obtain are comparable to or larger than the errors in some recent $Y_p$ calculations, including those derived from CMB observations. We demonstrate a systematic effect on primordial abundance calculations; this effect cannot be reduced by observing a large number of objects. In the cosmological recombination case, the errors are comparable to many of the effects considered in recent calculations.