# UV-Bright Star-Forming Clumps and Their Host Galaxies in UVCANDELS at 0.5 $\leq$ z $\leq$ 1

**Authors:** Alec Martin, Yicheng Guo, Xin Wang, Anton M. Koekemoer, Marc Rafelski, Harry I. Teplitz, Rogier A. Windhorst, Anahita Alavi, Norman A. Grogin, Laura Prichard, Ben Sunnquist, Daniel Ceverino, Nima Chartab, Christopher J. Conselice, Y. Sophia Dai, Avishai Dekel, Johnathan P. Gardner, Eric Gawiser, Nimish P. Hathi, Matthew J. Hayes  
**arXiv:** [2308.00041](https://arxiv.org/abs/2308.00041)  
**Date:** 2023-07-31  
**Summary page:** https://www.summarizepaper.com/en/paper/2308.00041v1/

## Key points

- Giant star-forming clumps are significant in star-forming galaxies and provide insights into galaxy formation and evolution.
- Uncertainty exists regarding the demographics of these clumps and their host galaxies.
- The study uses images from UVCANDELS taken by HST/WFC3 to detect and analyze giant star-forming clumps at redshifts ranging from 0.5 to 1.
- The authors construct a clump sample with higher luminosity than local HII regions.
- Approximately 35% of low-mass galaxies contain at least one off-center clump, decreasing to 22% for intermediate and high-mass galaxies.
- Clumpy SFGs tend to have higher star formation rates (SFRs) and bluer colors for low- and intermediate-mass galaxies, while high mass clumpy SFGs tend to be larger in size but have similar density profiles as non-clumpy SFGs.
- More luminous star-forming regions are found in more luminous, smaller-sized, and/or higher specific star formation rate galaxies.
- The study provides insights into the demographics of giant star-forming clumps at intermediate redshifts and highlights differences between clumpy and non-clumpy SFGs of different mass ranges.
- Further research is needed to understand the underlying mechanisms driving these differences.

## Summary

Giant star-forming clumps are a significant characteristic of star-forming galaxies (SFGs) and provide valuable insights into galaxy formation and evolution. However, there is still uncertainty surrounding the basic demographics of these clumps and their host galaxies. In this study, the authors utilize images from the Ultraviolet Imaging of the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey (UVCANDELS) taken by the Hubble Space Telescope's Wide Field Camera 3 (HST/WFC3) in order to detect and analyze giant star-forming clumps in galaxies at redshifts ranging from 0.5 to 1. By focusing on this particular redshift range, the authors bridge two epochs when clumps are known to be common (at cosmic high-noon, z ~ 2) and rare (in the local universe). They construct a clump sample that has a rest-frame 1600 Å luminosity three times higher than the most luminous local HII regions. The results show that approximately 35 ± 3% of low-mass galaxies (with a stellar mass less than log[M*/M⊙] < 10) contain at least one off-center clump. This fraction decreases to 22 ± 3% for intermediate-mass galaxies (with stellar masses ranging from log[M*/M⊙] = 10 to log[M*/M⊙] = 10.5), as well as for high-mass galaxies (with stellar masses greater than log[M*/M⊙] > 10.5), which is consistent with previous studies. Comparing clumpy SFGs with non-clumpy SFGs of similar mass, it is observed that low- and intermediate-mass clumpy SFGs tend to have higher star formation rates (SFRs) and bluer rest-frame U–V colors while high mass clumpy SFGs tend to be larger in size compared to non–clumpy SFGs but exhibit similar Sersic indices indicating a similar underlying density profile. Furthermore, this study investigates how the ultraviolet (UV) luminosity of star–forming regions correlates with physical properties of their host galaxies; on average more luminous star–forming regions are found in galaxies that are also more luminous, smaller in size, and/or have higher specific star formation rates while they tend to be located closer to galactic center of their host galaxies. In conclusion, this study provides valuable insights into demographics of giant star–forming clumps and their host galaxies at intermediate redshifts highlighting differences in properties between clumpy and non–clumpy SFGs of different mass ranges as well as shedding light on relationship between UV luminosity and galaxy properties; further research is needed to understand underlying mechanisms driving these differences and reconcile them with current galaxy formation scenarios.