The GECKOS Survey: extraplanar ionized gas in star-forming galaxies from eDIG to galaxy-scale winds

ABSTRACT We map the extraplanar gas, with $\sim$50–200 pc resolution, in nine star-forming galaxies using Multi-Unit Spectroscopic Explorer (MUSE) observations from the GECKOS VLT Large Programme targeting edge-on galaxies with similar stellar mass as the Milky Way. The narrow range in stellar mass ($\pm 0.35$ dex) of the GECKOS sample makes it ideal for studying trends with star formation rate (SFR). We find strong extraplanar emission reaching $\sim$2-8 kpc from the disc mid-plane in all targets with $\rm {SFR}\ge$1 M$_{\odot }$ yr$^{-1}$. Targets with SFR $\, \ge \,$ 5 M$_{\odot }$ yr$^{-1}$ have brighter, more extended H$\alpha$ emission compared to lower SFR targets. In high-SFR systems, the gas velocity dispersion ($\sigma _{\rm H\alpha }$) 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 ([O iii]$_{5007}$/H $\beta$–[N ii]/H $\alpha$ and $\sigma _{\rm H\alpha }$–[S ii]/H $\alpha$) to spatially resolve ionization mechanisms across the extraplanar gas. The highest [N ii]/H $\alpha$ are found in the extraplanar gas of the highest SFR systems, yet main-sequence galaxies have the highest [O iii]/H $\beta$. While the morphology of [N ii]/H $\alpha$ 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 disc and the circumgalactic medium, independent of the source of the gas.

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Journal
Monthly Notices of the Royal Astronomical Society
Published
2026-04-13
DOI
https://doi.org/10.1093/mnras/stag672
Primary Topic
Galaxies: Formation, Evolution, Phenomena
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article
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article

The GECKOS Survey: extraplanar ionized gas in star-forming galaxies from eDIG to galaxy-scale winds

Amelia Fraser-McKelvie, L. Cortese, Lucas M. Valenzuela, Thomas H. Puzia et al.
Monthly Notices of the Royal Astronomical Society
Galaxies: Formation, Evolution, Phenomena
article

The GECKOS Survey: extraplanar ionized gas in star-forming galaxies from eDIG to galaxy-scale winds

Amelia Fraser-McKelvie, L. Cortese, Lucas M. Valenzuela, Thomas H. Puzia, Timothy A. Davis, Dimitri Alexei Gadotti, Marie Martig, J van de Sande, F Combes, D B Fisher, L A Silva-Lima, M R Hayden, T H Brown, R Elliott, F Pinna, E Emsellem, A D Bolatto, A J Battisti, B Mazzilli Ciraulo, J Bland-Hawthorn, G van de Ven, B Catinella
article en

Abstract

ABSTRACT We map the extraplanar gas, with $\sim$50–200 pc resolution, in nine star-forming galaxies using Multi-Unit Spectroscopic Explorer (MUSE) observations from the GECKOS VLT Large Programme targeting edge-on galaxies with similar stellar mass as the Milky Way. The narrow range in stellar mass ($\pm 0.35$ dex) of the GECKOS sample makes it ideal for studying trends with star formation rate (SFR). We find strong extraplanar emission reaching $\sim$2-8 kpc from the disc mid-plane in all targets with $\rm {SFR}\ge$1 M$_{\odot }$ yr$^{-1}$. Targets with SFR $\, \ge \,$ 5 M$_{\odot }$ yr$^{-1}$ have brighter, more extended H$\alpha$ emission compared to lower SFR targets. In high-SFR systems, the gas velocity dispersion ($\sigma _{\rm H\alpha }$) 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 ([O iii]$_{5007}$/H $\beta$–[N ii]/H $\alpha$ and $\sigma _{\rm H\alpha }$–[S ii]/H $\alpha$) to spatially resolve ionization mechanisms across the extraplanar gas. The highest [N ii]/H $\alpha$ are found in the extraplanar gas of the highest SFR systems, yet main-sequence galaxies have the highest [O iii]/H $\beta$. While the morphology of [N ii]/H $\alpha$ 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 disc and the circumgalactic medium, independent of the source of the gas.

Monthly Notices of the Royal Astronomical SocietyVol. 548(3)
Université Claude Bernard Lyon 1 (FR), École Normale Supérieure de Lyon (FR), Australian National University (AU), Herzberg Institute of Astrophysics (CA), Centre National de la Recherche Scientifique (FR), The University of Sydney (AU), University of Vienna (AT), European Southern Observatory (DE), Universidad de La Laguna (ES), Pontificia Universidad Católica de Chile (CL), Collège de France (FR), Durham University (GB), Université Paris Sciences et Lettres (FR), Observatoire de Paris (FR), UNSW Sydney (AU), Sorbonne Université (FR), Centre de Recherche Astrophysique de Lyon (FR), Universidade Cidade de São Paulo (BR), Instituto de Astrofísica de Canarias (ES), ARC Centre of Excellence for All-sky Astrophysics (AU), International Centre for Radio Astronomy Research (AU), Swinburne University of Technology (AU), Liverpool John Moores University (GB), University of Maryland, College Park (US), Cardiff University (GB), Ludwig-Maximilians-Universität München (DE), University of Oklahoma (US)
National Aeronautics and Space Administration, American Academy of Ophthalmology, European School of Oncology, Science and Technology Facilities Council, Australian Research Council
Openalex Percentile: Top 21%
Galaxies: Formation, Evolution, Phenomena
DOIOpen Access PDFOpenAlex
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