Electron temperature relations in low metallicity, diffuse, and extraplanar gas of starburst galaxies

Journal article

In this work, we test the validity of – relations in resolved (10–200 pc) measurements of four nearby, low-metallicity (7.25 12 + log(O/H) 8.33), low-mass (10 /M 10), starburst (10 sSFR 10) galaxies. We obtain Very Large Telescope/X-Shooter spectra of NGC 5253, NGC 0625, SBS 0335−052E, and IC 2828, targeting regions within these galaxies with bright point-like sources and diffuse gas. Our observations are designed to extend from the galaxy mid-plane into extraplanar gas likely belonging to galactic winds. We measure electron temperatures from five different auroral lines: [N ii] 5755, [O ii] 7319, 7330, [S ii] 4069, 4076, [S iii] 6312, and [O iii] 4363. We compare the resulting – relations with previous studies of H ii regions in nearby spiral galaxies. Our results show that – relations in low-metallicity starburst galaxies do not significantly deviate from – relations in H ii regions of local spiral galaxies. We do not find significant differences in the diffuse, extraplanar gas. These results suggest that auroral lines provide a reliable metallicity diagnostic not only for high-redshift galaxies but also for the extended diffuse gas in extreme environments like outflows.

Authors: Hamel-Bravo, MJ; Fisher, DB; Berg, DA; Cameron, AJ; Chisholm, J

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: Oxford University Press
• Journal: Monthly Notices of the Royal Astronomical Society
• Volume: 543
• Issue: 2
• Pages: 1322-1338
• Publication date: 2025-09-04
• Acceptance date: 2025-08-28
• DOI: 10.1093/mnras/staf1472
• EISSN: 1365-2966
• ISSN: 0035-8711
• Language: English
• Keywords: galaxies: ISM; galaxies: starburst; galaxies: dwarf