Multi-layered model-based characterisation of the local-Universe galaxy data from the GAMA survey
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arXiv
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| Natura: | Preprint |
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2026
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| author | Dai, Fan Maitra, Ranjan Baldry, Ivan K. |
| author_facet | Dai, Fan Maitra, Ranjan Baldry, Ivan K. |
| contents | Understanding the formation and evolution of galaxy populations requires robust classification and characterisation techniques that jointly account for internal galaxy properties and environment. We analyse $5,306$ galaxies from the Galaxy And Mass Assembly (GAMA) survey, described by stellar mass, specific star formation rate, $u-r$ colour, half-light radius, Sérsic index, and a combined environmental measure given by the optimal density. Unlike distance-based unsupervised clustering methods, our framework provides a probabilistic characterisation of galaxy populations, accommodates heavy-tailed feature distributions, and captures dependence among observables through latent factors. We model the sample using a $t$-mixture of factor analysers with group-specific latent structures (M$t$FAD), and then apply model-estimated overlap-based syncytial clustering (MOBSynC) to merge weakly separated groups and recover higher-level population structure. The first stage identifies eight simple clusters. The third and the fourth groups lie on the red, low-star-forming sequence and correspond to environmentally quenched and mass-quenched systems, respectively, while the sixth group traces the massive end of the star-forming sequence, and the seventh group appears to represent a more heterogeneous population that may include transition objects. The remaining groups populate the low- to intermediate-mass blue sequence, including both compact and more extended star-forming galaxies. The second MOBSynC stage merges the simple clusters into two compound groups: a red sequence formed by the third and the fourth groups, and the rest merging to form a broad blue sequence. Our results show that the familiar red-blue bimodality of local galaxies contains additional physically meaningful substructure linked to quenching pathway, morphology, and environment. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2605_23596 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | Multi-layered model-based characterisation of the local-Universe galaxy data from the GAMA survey Dai, Fan Maitra, Ranjan Baldry, Ivan K. Astrophysics of Galaxies 62H05, 62H12, 62H20, 62H25, 62H30, 62P35 G.3; I.2; I.5; I.6; J.2 Understanding the formation and evolution of galaxy populations requires robust classification and characterisation techniques that jointly account for internal galaxy properties and environment. We analyse $5,306$ galaxies from the Galaxy And Mass Assembly (GAMA) survey, described by stellar mass, specific star formation rate, $u-r$ colour, half-light radius, Sérsic index, and a combined environmental measure given by the optimal density. Unlike distance-based unsupervised clustering methods, our framework provides a probabilistic characterisation of galaxy populations, accommodates heavy-tailed feature distributions, and captures dependence among observables through latent factors. We model the sample using a $t$-mixture of factor analysers with group-specific latent structures (M$t$FAD), and then apply model-estimated overlap-based syncytial clustering (MOBSynC) to merge weakly separated groups and recover higher-level population structure. The first stage identifies eight simple clusters. The third and the fourth groups lie on the red, low-star-forming sequence and correspond to environmentally quenched and mass-quenched systems, respectively, while the sixth group traces the massive end of the star-forming sequence, and the seventh group appears to represent a more heterogeneous population that may include transition objects. The remaining groups populate the low- to intermediate-mass blue sequence, including both compact and more extended star-forming galaxies. The second MOBSynC stage merges the simple clusters into two compound groups: a red sequence formed by the third and the fourth groups, and the rest merging to form a broad blue sequence. Our results show that the familiar red-blue bimodality of local galaxies contains additional physically meaningful substructure linked to quenching pathway, morphology, and environment. |
| title | Multi-layered model-based characterisation of the local-Universe galaxy data from the GAMA survey |
| topic | Astrophysics of Galaxies 62H05, 62H12, 62H20, 62H25, 62H30, 62P35 G.3; I.2; I.5; I.6; J.2 |
| url | https://arxiv.org/abs/2605.23596 |