Challenges and Techniques for Simulating Line Emission

TL;DR

This paper reviews the challenges and recent advances in simulating emission lines across the spectrum, emphasizing the importance of aligning models with observations for understanding the interstellar and circumgalactic media.

Contribution

It summarizes discussions from a 2018 conference on emission line simulation techniques, highlighting current challenges and recent progress across multiple physical scales.

Findings

Identification of key challenges in line emission modeling

Summary of recent advances in simulation techniques

Emphasis on the importance of observational synergy

Abstract

Modeling emission lines from the millimeter to the UV and producing synthetic spectra is crucial for a good understanding of observations, yet it is an art filled with hazards. This is the proceedings of "Walking the Line", a 3-day conference held in 2018 that brought together scientists working on different aspects of emission line simulations, in order to share knowledge and discuss the methodology. Emission lines across the spectrum from the millimeter to the UV were discussed, with most of the focus on the interstellar medium, but also some topics on the circumgalactic medium. The most important quality of a useful model is a good synergy with observations and experiments. Challenges in simulating line emission are identified, some of which are already being worked upon, and others that must be addressed in the future for models to agree with observations. Recent advances in several areas aiming at achieving that synergy are summarized here, from micro-physical to galactic and circum-galactic scale.