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Main Authors:	Rossi, Luca, Buttitta, Chiara, Doll, Goran, Iodice, Enrichetta, Gullieuszik, Marco, Sarzi, Marc, Mirabile, Marco, Hartke, Johanna, Arnaboldi, Magda, Calvi, Rosa, Cantiello, Michele, Corsini, Enrico Maria, D'Ago, Giuseppe, Falcón-Barroso, Jesús, Fonzo, Francesca, Forbes, Duncan A., Hilker, Michael, La Marca, Antonio, Loni, Alessandro, Mieske, Steffen, Paolillo, Maurizio, Rejkuba, Marina, Spavone, Marilena, Spiniello, Chiara
Format:	Preprint
Published:	2026
Subjects:	Astrophysics of Galaxies
Online Access:	https://arxiv.org/abs/2605.27109
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author	Rossi, Luca Buttitta, Chiara Doll, Goran Iodice, Enrichetta Gullieuszik, Marco Sarzi, Marc Mirabile, Marco Hartke, Johanna Arnaboldi, Magda Calvi, Rosa Cantiello, Michele Corsini, Enrico Maria D'Ago, Giuseppe Falcón-Barroso, Jesús Fonzo, Francesca Forbes, Duncan A. Hilker, Michael La Marca, Antonio Loni, Alessandro Mieske, Steffen Paolillo, Maurizio Rejkuba, Marina Spavone, Marilena Spiniello, Chiara
author_facet	Rossi, Luca Buttitta, Chiara Doll, Goran Iodice, Enrichetta Gullieuszik, Marco Sarzi, Marc Mirabile, Marco Hartke, Johanna Arnaboldi, Magda Calvi, Rosa Cantiello, Michele Corsini, Enrico Maria D'Ago, Giuseppe Falcón-Barroso, Jesús Fonzo, Francesca Forbes, Duncan A. Hilker, Michael La Marca, Antonio Loni, Alessandro Mieske, Steffen Paolillo, Maurizio Rejkuba, Marina Spavone, Marilena Spiniello, Chiara
contents	This paper presents a detailed analysis of a gas-rich star-forming ultra-diffuse galaxy (UDG) as part of the ESO Large Programme 'Looking into the faintEst WIth MUSE (LEWIS)'. Among the UDGs in the LEWIS sample, UDG 6 is the only galaxy that hosts a significant amount of ionised gas with evidence of emission lines, suggesting recent star-forming activity. The main goal of this work is to constrain the formation history of this UDG by comparing its properties with the main formation scenarios proposed for this extreme class of galaxies. We adopted integral field spectroscopy from MUSE to derive the morphology and the structural properties of the stellar and gas components of UDG 6. We applied spectral fitting and Voronoi tessellation algorithms to the MUSE data-cube to derive the kinematics and properties of the gas and stellar component. Moreover, we derived the GCs populations' properties by applying a multi-band spectrophotometric analysis. We confirmed that UDG 6 is a member of Hydra I cluster. It is characterised by a regular and elongated shape and contains a significant dust content, a metal-poor ionised gas fraction and an underlying old-to-intermediate stellar component. Evidence of local and clumpy star-forming activity has been revealed through the analysis of emission line, and an arc-like tidal feature was discovered from unsharp masking analysis. UDG 6 might originate from a 'puffed-up dwarf' whose stellar content has been stretched out to larger radii, passively evolving into a more diffuse galaxy. Being located in a dynamically active region of the cluster, characterised by tidal features and stripping phenomena, we suggest that the environmental processes have played a role in shaping the properties of UDG 6. A tidal interaction with a nearby galaxy might have triggered recent star-formation activity, without dramatically altering the coherent gas rotation in UDG 6.
format	Preprint
id	arxiv_https___arxiv_org_abs_2605_27109
institution	arXiv
publishDate	2026
record_format	arxiv
spellingShingle	Looking into the faintEst WIth MUSE (LEWIS): Exploring the nature of ultra-diffuse galaxies in the Hydra-I cluster. VI. A star-forming UDG in Hydra I: a rare UDG or a transition phase? Rossi, Luca Buttitta, Chiara Doll, Goran Iodice, Enrichetta Gullieuszik, Marco Sarzi, Marc Mirabile, Marco Hartke, Johanna Arnaboldi, Magda Calvi, Rosa Cantiello, Michele Corsini, Enrico Maria D'Ago, Giuseppe Falcón-Barroso, Jesús Fonzo, Francesca Forbes, Duncan A. Hilker, Michael La Marca, Antonio Loni, Alessandro Mieske, Steffen Paolillo, Maurizio Rejkuba, Marina Spavone, Marilena Spiniello, Chiara Astrophysics of Galaxies This paper presents a detailed analysis of a gas-rich star-forming ultra-diffuse galaxy (UDG) as part of the ESO Large Programme 'Looking into the faintEst WIth MUSE (LEWIS)'. Among the UDGs in the LEWIS sample, UDG 6 is the only galaxy that hosts a significant amount of ionised gas with evidence of emission lines, suggesting recent star-forming activity. The main goal of this work is to constrain the formation history of this UDG by comparing its properties with the main formation scenarios proposed for this extreme class of galaxies. We adopted integral field spectroscopy from MUSE to derive the morphology and the structural properties of the stellar and gas components of UDG 6. We applied spectral fitting and Voronoi tessellation algorithms to the MUSE data-cube to derive the kinematics and properties of the gas and stellar component. Moreover, we derived the GCs populations' properties by applying a multi-band spectrophotometric analysis. We confirmed that UDG 6 is a member of Hydra I cluster. It is characterised by a regular and elongated shape and contains a significant dust content, a metal-poor ionised gas fraction and an underlying old-to-intermediate stellar component. Evidence of local and clumpy star-forming activity has been revealed through the analysis of emission line, and an arc-like tidal feature was discovered from unsharp masking analysis. UDG 6 might originate from a 'puffed-up dwarf' whose stellar content has been stretched out to larger radii, passively evolving into a more diffuse galaxy. Being located in a dynamically active region of the cluster, characterised by tidal features and stripping phenomena, we suggest that the environmental processes have played a role in shaping the properties of UDG 6. A tidal interaction with a nearby galaxy might have triggered recent star-formation activity, without dramatically altering the coherent gas rotation in UDG 6.
title	Looking into the faintEst WIth MUSE (LEWIS): Exploring the nature of ultra-diffuse galaxies in the Hydra-I cluster. VI. A star-forming UDG in Hydra I: a rare UDG or a transition phase?
topic	Astrophysics of Galaxies
url	https://arxiv.org/abs/2605.27109

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