The GECKOS Survey: revealing the formation history of a barred galaxy via structural decomposition and resolved spectroscopy

Fraser-McKelvie, A, Gadotti, DA, Fragkoudi, F, de Sá-Freitas, C, Martig, M ORCID: 0000-0001-5454-1492, Davis, T, Elliott, R, Fisher, D, Hayden, MR, van de Sande, J and Watts, AB The GECKOS Survey: revealing the formation history of a barred galaxy via structural decomposition and resolved spectroscopy. Astronomy & Astrophysics. ISSN 0004-6361 (Accepted)

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Abstract

Disentangling the (co-)evolution of individual galaxy structural components remains a difficult task, owing to the inability to cleanly isolate light from spatially overlapping components. In this pilot study of PGC044931, observed as part of the GECKOS survey, we utilise a VIRCAM H-band image to decompose the galaxy into five photometric components, three of which dominate by contributing > 50% of light in specific regions: a main disc, a boxy/peanut bulge, and a nuclear disc. When the photometric decompositions are mapped onto MUSE observations, we find remarkably good separation in stellar kinematic space. All three structures occupy unique locations in the parameter space of the ratio of the light-weighted stellar line-of-sight mean velocity and velocity dispersion (V⋆/σ⋆), and the high-order stellar skew (h3). These clear and distinct kinematic behaviours allow us to make inferences about the formation histories of the individual components from observations of the mean stellar ages and metallicities of the three components. A clear story emerges: the main disc built over a sustained and extended star formation phase, possibly partly fuelled by gas from a low metallicity reservoir. Early on, that disc formed a bar that buckled and subsequently formed a nuclear disc in multiple and enriched star-formation episodes. This result is an example of how careful photometric decompositions, combined with spatially well-resolved stellar kinematic information, can help separate out age-metallicity relations of different components and therefore disentangle the formation history of a galaxy. The results of this pilot study can be extended to a differential study of all GECKOS survey galaxies to assert the true diversity of Milky Way-like galaxies.

Item Type:	Article
Uncontrolled Keywords:	5101 Astronomical Sciences; 51 Physical Sciences
Subjects:	Q Science > QB Astronomy Q Science > QC Physics
Divisions:	Astrophysics Research Institute
Publisher:	EDP Sciences
Related URLs:	Preprint
Date of acceptance:	6 November 2025
Date of first compliant Open Access:	6 November 2025
Date Deposited:	06 Nov 2025 15:53
Last Modified:	06 Nov 2025 16:15
URI:	https://researchonline.ljmu.ac.uk/id/eprint/27514

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