The Prevalence of Star-forming Clumps as a Function of Environmental Overdensity in Local Galaxies

Adams, D; Dickinson, H; Fortson, L; Mantha, K; Mehta, V; Popp, J; Scarlata, C; Lintott, C; Simmons, B; Walmsley, M

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The Prevalence of Star-forming Clumps as a Function of Environmental Overdensity in Local Galaxies

Abstract:: At the peak of cosmic star formation (1 ≲ z ≲ 2), the majority of star-forming galaxies hosted compact, star-forming clumps, which were responsible for a large fraction of cosmic star formation. By comparison, ≲5% of local star-forming galaxies host comparable clumps. In this work, we investigate the link between the environmental conditions surrounding local (z < 0.04) galaxies and the prevalence of clumps in these galaxies. To obtain our clump sample, we use a Faster R-CNN object detection network trained on the catalog of clump labels provided by the Galaxy Zoo: Clump Scout project, then apply this network to detect clumps in approximately 240,000 Sloan Digital Sky Survey galaxies (originally selected for Galaxy Zoo 2). The resulting sample of 41,445 u-band bright clumps in 34,246 galaxies is the largest sample of clumps yet assembled. We then select a volume-limited sample of 9964 galaxies and estimate the density of their local environment using the distance to their projected fifth nearest neighbor. We find a robust correlation between environment and the clumpy fraction (f clumpy) for star-forming galaxies (specific star formation rate, sSFR > 10−2 Gyr−1) but find little to no relationship when controlling for galaxies’ sSFR or color. Further, f clumpy increases significantly with sSFR in local galaxies, particularly above sSFR > 10−1 Gyr−1. We posit that a galaxy’s gas fraction primarily controls the formation and lifetime of its clumps, and that environmental interactions play a smaller role.

Publication status:: Published

Peer review status:: Peer reviewed

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APA Style

Adams, D., Dickinson, H., Fortson, L., Mantha, K., Mehta, V., Popp, J., Scarlata, C., Lintott, C., Simmons, B., & Walmsley, M. (2025). The Prevalence of Star-forming Clumps as a Function of Environmental Overdensity in Local Galaxies. The Astrophysical Journal, 979(2).

MLA Style

Adams, D, et al. “The Prevalence of Star-Forming Clumps as a Function of Environmental Overdensity in Local Galaxies.” The Astrophysical Journal, vol. 979, no. 2, 2025.

Chicago Style

Adams, D, H Dickinson, L Fortson, et al. 2025. “The Prevalence of Star-Forming Clumps as a Function of Environmental Overdensity in Local Galaxies.” The Astrophysical Journal 979 (2).
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