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

TL;DR

This study analyzes the properties and spatial distribution of star-forming clumps in spiral galaxies across redshifts 0.1 to 3.3, revealing their connection to spiral arms and differences from clumps in non-spiral galaxies.

Contribution

It introduces a novel method of identifying and analyzing clumps within spiral arms using residual images, highlighting their properties and relation to spiral structure.

Findings

Clumps are smaller, brighter, and less massive than previously reported.

Clumps are spatially concentrated towards spiral arms and correlate with spiral parameters.

Clumps in spiral arms are smaller but brighter than in inter-arm regions, with similar colors.

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.