Near-IR clumps and their properties in high-z galaxies with JWST/NIRCam

TL;DR

This study uses JWST/NIRCam near-infrared imaging to identify and analyze stellar clumps in high-redshift galaxies, revealing their properties, distribution, and relation to galaxy classification, with implications for galaxy evolution.

Contribution

It introduces a stellar-mass based clump detection method in near-IR, providing new insights into clump properties and their distribution in $z>1$ galaxies, independent of UV-based methods.

Findings

Near-IR detects more and different clumps than UV, with only 28% overlap.

85% of UV clumps have near-IR counterparts, indicating a strong correlation.

Clump masses range from 10^{7.5} to 10^{9.5} solar masses, influencing galaxy core gas inflow.

Abstract

Resolved stellar morphology of $z>1$ galaxies was inaccessible before JWST. This limitation, due to the impact of dust on rest-frame UV light, had withheld major observational conclusions required to understand the importance of clumps in galaxy evolution. Essentially independent of this issue, we use the rest-frame near-IR for a stellar-mass dependent clump detection method and determine reliable estimations of selection effects. We exploit publicly available JWST/NIRCam and HST/ACS imaging data from CEERS, to create a stellar-mass based picture of clumps in a mass-complete sample of 418 galaxies within a wide wavelength coverage of $0.5-4.6\,\mu$m and a redshift window of $1 < z < 2$. We find that a near-IR detection gives access to a larger, and possibly different, set of clumps within galaxies, with those also detected in UV making up only $28\%$. Whereas, $85\%$ of the UV clumps are found to have a near-IR counterpart. These near-IR clumps closely follow the UVJ classification of their respective host galaxies, with these hosts mainly populating the star-forming regime besides a fraction of them ($16\%$) that can be considered quiescent. The mass of the detected clumps are found to be within the range of $10^{7.5-9.5}\,\rm M_{\odot}$, therefore expected to drive gas into galaxy cores through tidal torques. The clump stellar mass function is found to have a slope of $-1.50 \pm 0.14$, indicating a hierarchical nature similar to that of star-forming regions in the local Universe. Finally, we observe a radial gradient of increasing clump mass towards the centre of galaxies.