A rest-frame near-IR study of clumps in galaxies at 1 < z < 2 using JWST/NIRCam: connection to galaxy bulges

TL;DR

This study uses JWST/NIRCam imaging to analyze the presence and properties of galactic clumps at 1<z<2, revealing their connection to galaxy bulges and their detection in near-IR, which informs galaxy evolution models.

Contribution

It provides the first rest-frame near-IR analysis of clumps in high-redshift galaxies, linking clump presence to bulge development and galaxy stability.

Findings

Clumps are detectable in near-IR with ~60% spatial overlap with UV/optical.

A strong negative correlation exists between galaxy clumpiness and bulge strength.

The correlation varies between optical and near-IR, indicating different formation modes.

Abstract

A key question in galaxy evolution has been the importance of the apparent `clumpiness' of high redshift galaxies. Until now, this property has been primarily investigated in rest-frame UV, limiting our understanding of their relevance. Are they short-lived or are associated with more long-lived massive structures that are part of the underlying stellar disks? We use JWST/NIRCam imaging from CEERS to explore the connection between the presence of these `clumps' in a galaxy and its overall stellar morphology, in a mass-complete ($log\,M_{*}/M_{\odot} > 10.0$) sample of galaxies at $1.0 < z < 2.0$. Exploiting the uninterrupted access to rest-frame optical and near-IR light, we simultaneously map the clumps in galactic disks across our wavelength coverage, along with measuring the distribution of stars among their bulges and disks. Firstly, we find that the clumps are not limited to rest-frame UV and optical, but are also apparent in near-IR with $\sim 60\,\%$ spatial overlap. This rest-frame near-IR detection indicates that clumps would also feature in the stellar-mass distribution of the galaxy. A secondary consequence is that these will hence be expected to increase the dynamical friction within galactic disks leading to gas inflow. We find a strong negative correlation between how clumpy a galaxy is and strength of the bulge. This firmly suggests an evolutionary connection, either through clumps driving bulge growth, or the bulge stabilizing the galaxy against clump formation, or a combination of the two. Finally, we find evidence of this correlation differing from rest-frame optical to near-IR, which could suggest a combination of varying formation modes for the clumps.