Work

Time-dependent metal ionization and the persistence of collisionally excited emission lines in the diffuse ionized gas of star-forming galaxies

Year: 2024

Type: article

Abstract: ABSTRACT We extend our time-dependent hydrogen ionization simulations of diffuse ionized gas to include metals important for collisional cooling and diagnostic emission lines. The combination of heating from supernovae and time-dependent collisional and photoionization from mid-plane OB stars produces emission line intensities (and emission line ratios) that follow the trends observed in the Milky Way and other edge-on galaxies. The long recombination times in low-density gas result in persistent large volumes of ions with high ionization potentials, such as O iii and Ne iii. In particular, the vertically extended layers of Ne iii in our time-dependent simulations result in [Ne iii] 15 $\mu$m/[Ne ii] 12 $\mu$m emission line ratios in agreement with observations of the edge-on galaxy NGC 891. Simulations adopting ionization equilibrium do not allow for the persistence of ions with high ionization states and therefore cannot reproduce the observed emission lines from low-density gas at high altitudes.

Source: Monthly Notices of the Royal Astronomical Society

DOI: 10.1093/mnras/stae2549

Authors: Lewis McCallum, Kenneth Wood, Robert Benjamin, Dhanesh Krishnarao, Bert Vandenbroucke

Institutions: University of St Andrews, University of Wisconsin–Whitewater, Colorado College, Leiden University, Leiden Observatory

Language: English

Topic: Galaxies: Formation, Evolution, Phenomena

Subfield: Astronomy and Astrophysics

Field: Physics and Astronomy

Domain: Physical Sciences

Open Access status: gold

Estimated APC paid: $3,012

Funders: National Aeronautics and Space Administration, Space Telescope Science Institute, Science and Technology Facilities Council