A multi-wavelength investigation of spiral structures in $z > 1$ galaxies with JWST

TL;DR

This study uses JWST data to analyze spiral structures in galaxies at redshift > 1, revealing their origins and characteristics, including density waves, shocks, and interactions, similar to local universe phenomena.

Contribution

Introduces a systematic method for quantifying spiral arms at high redshift using JWST data, revealing the diverse origins of spiral structures at $z > 1$.

Findings

Detection of offsets indicating density waves in most spiral arms.

Identification of spiral shocks and tidal interactions as formation mechanisms.

Evidence of stochastic star formation in some arms.

Abstract

Recent JWST observations have revealed the prevalence of spiral structures at $z > 1$. Unlike in the local Universe, the origin and the consequence of spirals at this epoch remain unexplored. We use public JWST/NIRCam data from the COSMOS-Web survey to map spiral structures in eight massive ($> 10^{10.5}\,\rm M_{\odot}$) star-forming galaxies at $z_{\rm spec} \sim 1.5$. We present a method for systematically quantifying spiral arms at $z>1$, enabling direct measurements of flux distributions. Using rest-frame near-IR images, we construct morphological models accurately tracing spiral arms. We detect offsets ($\sim 0.2 - 0.8\,\rm kpc$) between the rest-frame optical and near-IR flux distributions across most arms. Drawing parallels to the local Universe, we conclude that these offsets reflect the presence of density waves. For nine out of eighteen arms, the offsets indicate spiral shocks triggered by density waves. Five arms have offsets in the opposite direction and are likely associated with tidal interactions. For the remaining cases with no detected offsets, we suggest that stochastic 'clumpy' star formation is the primary driver of their formation. In conclusion, we find a multi-faceted nature of spiral arms at $z > 1$, similar to that in the local Universe.