October
2026
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2026MNRAS.552g1653P
Authors
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Popp, Jürgen J.
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Dickinson, Hugh
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Serjeant, Stephen
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Fortson, Lucy F.
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Géron, Tobias
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Mehta, Vihang
Abstract
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Massive, star-forming clumps are regions of intensive star formation that are commonly observed in high-redshift ($z \gt 1$) galaxies. Observations of low-redshift clumpy galaxy analogues are rare but the availability of wide-field galaxy survey data makes the detection of large clumpy galaxy samples much more feasible. We present a population of 12 790 star-forming clumps detected in a mass-complete sample of 5395 star-forming galaxies at redshifts $z\le 0.32$, located in the XMM-LSS, E-COSMOS, and DEEP2-3 fields observed by the Hyper Suprime-Cam Subaru Strategic Survey and CFHT Large Area U-band Deep Survey (CLAUDS). The clumps were detected using an improved version of our deep learning (DL)-based object detection framework which uses the ZOOBOT foundation DL model as a `backbone' feature extractor. We determined the fraction of star-forming galaxies hosting at least one off-centre clump ($f_{\mathrm{clumpy}}$) based on a clump definition that requires a clump--galaxy flux ratio in the CLAUDS u-band of $\ge 8{{\ \rm per\ cent}}$. We estimate $f_{\mathrm{clumpy}}$ to decrease from $\sim$31 per cent at $z\sim 0.3$ to $\sim$23 per cent at $z \sim 0.1$, which aligns well with a low-redshift extrapolation of the clumpy fraction that is measured using high-redshift observations. At fixed redshift, $f_{\mathrm{clumpy}}$ is negatively correlated with the stellar mass and positively correlated with the specific star formation rate (sSFR) of the host galaxies. When the clump definition is changed to include only clumps with a stellar mass of $M_{\mathrm{cl}} \ge 10^7 \, \mathrm{M}_\odot$, we observe a highly increased clumpy fraction of $\sim$60 per cent that tends to increase with the stellar mass of the host galaxies but does not show a dependence on the sSFR of the host galaxies.
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