Atomic Data and Spectral Models for FeII

TL;DR

This paper provides comprehensive atomic data and spectral models for Fe II, including transition rates and collision strengths, to improve astrophysical spectral analysis in IR, optical, and UV regions.

Contribution

It introduces new calculations of Fe II atomic data using advanced multiconfiguration methods and compares their effectiveness for spectral modeling.

Findings

Benchmark spectral models for Fe II emission and absorption.

Validated atomic data against observed astronomical spectra.

Provided diagnostic line ratios and emissivities for spectroscopy.

Abstract

We present extensive calculations of radiative transition rates and electron impact collision strengths for Fe II. The data sets involve 52 levels from the $3d\,^7$, $3d\,^64s$, and $3d\,^54s^2$ configurations. Computations of $A$-values are carried out with a combination of state-of-the-art multiconfiguration approaches, namely the relativistic Hartree--Fock, Thomas--Fermi--Dirac potential, and Dirac--Fock methods; while the $R$-matrix plus intermediate coupling frame transformation, Breit--Pauli $R$-matrix and Dirac $R$-matrix packages are used to obtain collision strengths. We examine the advantages and shortcomings of each of these methods, and estimate rate uncertainties from the resulting data dispersion. We proceed to construct excitation balance spectral models, and compare the predictions from each data set with observed spectra from various astronomical objects. We are thus able to establish benchmarks in the spectral modeling of [Fe II] emission in the IR and optical regions as well as in the UV Fe II absorption spectra. Finally, we provide diagnostic line ratios and line emissivities for emission spectroscopy as well as column densities for absorption spectroscopy. All atomic data and models are available online and through the AtomPy atomic data curation environment.