Understanding Galaxy Evolution Through Emission Lines

By Lisa J. Kewley, D. Nicholls, R. Sutherland. Annual Review of Astronomy and Astrophysics, 2019

287 citations recorded by the source corpus.

We review the use of emission lines for understanding galaxy evolution, focusing on excitation source, metallicity, ionization parameter, ISM pressure, and electron density. We discuss the physics, benefits, and caveats of emission line diagnostics, including the effects of theoretical model uncertainties, diffuse ionized gas, and sample selection bias. In anticipation of upcoming telescope facilities, we provide new self-consistent emission line diagnostic calibrations for complete spectral coverage from the UV to the IR. These diagnostics can be used in concert to understand how fundamental galaxy properties have changed across cosmic time. We conclude the following: ▪ The UV, optical, and IR contain complementary diagnostics that can probe the conditions within different nebular ionization zones. ▪ Accounting for complex density gradients and temperature profiles is critical for reliably estimating the fundamental properties of Hii regions and galaxies. ▪ Diffuse ionized gas can raise metallicity estimates, flatten metallicity gradients, and introduce scatter in ionization parameter measurements. ▪ New 3D emission line diagnostics successfully separate the contributions from star formation, AGN, and shocks using integral field spectroscopy. We summarize with a discussion of the challenges and major opportunities for emission line diagnostics in the coming years.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/1798bc8459bb31806dcedaae8c61179ac3a33c80

How researchers see this paper

The researchers whose trusted networks rank it highest, strongest advocate first. Every researcher gets a different order.

In Astronomy and Astrophysics

1. P. Hopkins
2. L. Hernquist
3. P. V. van Dokkum
4. Richard S. Ellis
5. T. Treu
6. C. Conroy
7. R. Maiolino
8. M. Franx

In Instrumentation

1. P. V. van Dokkum
2. T. Treu
3. G. Brammer
4. M. Franx
5. Richard S. Ellis
6. R. Maiolino
7. C. Conroy
8. A. Fontana

Citations in the corpus

• Cool outflows in galaxies and their implications (2020, methodology): “The technical challenge of disentangling the different sources of excitation in the gas (AGN, star formation, shocks) will still remain, but great strides have been made in recent years to resolve this problem by using the full suite of sophisticated photoionization and shock models in combination w”
• Host Galaxy Properties and Offset Distributions of Fast Radio Bursts: Implications for Their Progenitors (2020, background): “This allows us to assess the dominant source of ionization and distinguish between typical SF galaxies, low-ionization nuclear emissionline region (LINER) galaxies, and AGNs (see Kewley et al. 2019, for a recent review).”
• The GLASS-JWST Early Release Science Program. I. Survey Design and Release Plans (2022, background): “Gas-phase metallicities are one of the key probes of this cycle as they are sensitive to the flow of material from galaxies into the circumgalactic medium (CGM; see Maiolino & Mannucci 2019; Kewley et al. 2019 for recent reviews).”