English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

Spectroscopic studies of extreme-ionization galaxies (EIGs) are critical toour understanding of exotic systems throughout cosmic time. These EIGs exhibitspectral features requiring >54.42 eV photons: the energy needed to fullyionize helium into He2+ and emit He II recombination lines. They are likely keycontributors to reionization, and they can also probe exotic stellarpopulations or accretion onto massive black holes. To facilitate the use ofEIGs as probes of high ionization, we focus on ratios constructed from strongrest-frame UV/optical emission lines, specifically [O III] 5008, H-beta, [NeIII] 3870, [O II] 3727,3729, and [Ne V] 3427. These lines probe the relativeintensity at energies of 35.12, 13.62, 40.96, 13.62 eV, and 97.12,respectively, covering a wider range of ionization than traced by other commonrest-frame UV/optical techniques. We use ratios of these lines ([Ne V]/[Ne III]= Ne53 and [Ne III]/[O II]), which are closely separated in wavelength, andmitigates effects of dust attenuation and uncertainties in flux calibration. Wemake predictions from photoionization models constructed from Cloudy that use abroad range of stellar populations and black hole accretion models to explorethe sensitivity of these line ratios to changes in the ionizing spectrum. Wecompare our models to observations from the Hubble Space Telescope and JamesWebb Space Telescope of galaxies with strong high-ionization emission lines atz ~ 0, z ~ 2, and z ~ 7. We show that the Ne53 ratio can separate galaxies withionization from 'normal' stellar populations from those with AGN and even'exotic' Population III models. We introduce new selection methods to identifygalaxies with photoionization driven by Population III stars orintermediate-mass black hole accretion disks that could be identified inupcoming high-redshift spectroscopic surveys.

Using [Ne V]/[Ne III] to Understand the Nature of Extreme-Ionization Galaxies