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arXiv · 2605.15361

Clumps in spiral galaxies at $z \lesssim 3$: Disentangling two spatial modes of star formation

Ilia V. Chugunov·Alexander A. Marchuk
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Abstract

At high redshifts, star formation in galaxies is more often concentrated in clumps than in spiral arms. Although clumps are actively studied, it is rarely done considering spiral arms as objects for study as well, and the connection between clumps and spirals remains understudied. We used a sample of 159 spiral galaxies at $0.1 \leq z \leq 3.3$ observed by HST and JWST. Using the residual images from photometric models with spiral arms constructed before, which was not done previously, we have done identification of clumps and measured their properties with photometric decomposition, finding 3003 clumps in overall, and performing SED fitting for a fraction of them. We examined the overall properties of clumps, focusing on the properties of spiral structure. We found that clumps luminosities, masses and sizes are smaller than commonly accepted in literature, either for the reason spiral arms were modelled separately, or because clumps in spiral galaxies are different compared to clumpy ones. We demonstrate the connection between clumps and spirals, in particular clumps are spatially concentrated towards spirals and various parameters of clumps and spirals correlate. Also, clumps in spiral arms tend to be smaller but brighter compared to clumps in inter-arm area, but their colours are similar. There are also some differences between clumps and spirals such as colour, emphasizing the importance of their separate analysis. Our results probably indicate that spiral arms stimulate the formation of clumps, although star formation properties of clumps in spiral arms is not changed compared to inter-arm region.

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Ilia V. Chugunov, Alexander A. Marchuk. 2026-05-14. Clumps in spiral galaxies at $z \lesssim 3$: Disentangling two spatial modes of star formation. https://arxiv.org/abs/2605.15361

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