Elliot, R., Fisher, D. B., Mazzilli Ciraulo, B., Fraser-McKelvie, A. and Davis, T. A.  ORCID: https://orcid.org/0000-0003-4932-9379
2026.
The GECKOS Survey: Extraplanar ionised gas in star-forming galaxies from eDIG to galaxy-scale winds.
Monthly Notices of the Royal Astronomical Society
548
(3)
, stag672.
10.1093/mnras/stag672
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Abstract
We map the extraplanar gas, with ∼50-200 pc resolution, in nine star-forming galaxies using Multi-Unit Spectroscopic Explorer (MUSE) observations from the GECKOS VLT Large Program targeting edge-on galaxies with similar stellar mass as the Milky Way. The narrow range in stellar mass (±0.35 dex) of the GECKOS sample makes it ideal for studying trends with star formation rate (SFR). We find strong extraplanar emission reaching ∼2-8 kpc from the disk midplane in all targets with SFR >_ 1 M⊙ yr−1. Targets with SFR ≥ 5 M⊙ yr−1 have brighter, more extended Hα emission compared to lower SFR targets. In high-SFR systems, the gas velocity dispersion (σHα) shows a biconical morphology, consistent with the expectation of outflows. This agrees with previous works suggesting high velocity dispersion in a biconical shape is a good means to identify outflows. We find mixed results using line diagnostics ([OIII]5007/Hβ - [NII]/Hα and σHα - [SII]/Hα) to spatially resolve ionisation mechanisms across the extraplanar gas. The highest [NII]/Hα are found in the extraplanar gas of the highest SFR systems , yet main-sequence galaxies have the highest [OIII]/Hβ. While the morphology of [NII]/Hα may be useful to identify outflows, the absolute value of the line ratio alone may not distinguish strong outflows from extraplanar gas of main-sequence galaxies. The ubiquitous extraplanar emission can be interpreted as the result of feedback, in the form of large-scale winds for starbursts or smaller-scale galactic fountains for main-sequence galaxies. Moreover, shock-heating may ionise gas at the interface of the disk and the circumgalactic medium, independent of the source of the gas.
| Item Type: | Article |
|---|---|
| Date Type: | Published Online |
| Status: | Published |
| Schools: | Schools > Physics and Astronomy |
| Additional Information: | Full list of authors available at: https://doi.org/10.1093/mnras/stag672 |
| Publisher: | Oxford University Press |
| ISSN: | 0035-8711 |
| Date of First Compliant Deposit: | 20 April 2026 |
| Date of Acceptance: | 25 March 2026 |
| Last Modified: | 06 May 2026 09:56 |
| URI: | https://orca.cardiff.ac.uk/id/eprint/186488 |
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