Metal-Poor Star-Forming Clumps in Cosmic Noon Galaxies: Evidence for Gas Inflow and Chemical Dilution Using JWST NIRISS

TL;DR

This study uses JWST NIRISS data and a new analysis tool called Sleuth to investigate the metallicity and star formation in galaxy clumps at cosmic noon, revealing evidence of gas inflow and chemical dilution.

Contribution

It introduces Sleuth, a novel method for extracting spatially resolved properties from slitless grism data, enabling detailed analysis of galaxy clumps at high redshift.

Findings

Star-forming clumps have ~0.1 dex lower metallicity than their surroundings.

Clumps show increased star formation activity.

Metallicity dilution of about 20% suggests gas inflow.

Abstract

The formation and evolution of galaxies are intricately linked to the baryon cycle, which fuels star formation while shaping chemical abundances within galaxies. Investigating the relationship between star formation and metallicity for large samples of galaxies requires expensive IFU surveys or sophisticated tools to analyze grism data. Here we analyze JWST NIRISS slitless grism data using Sleuth, a tool that forward models and infers spatially resolved physical properties from grism data, including observations from JWST NIRISS/NIRCam and future grism data like that from the Roman Space Telescope. Sleuth enables extraction of high-quality emission line maps from slitless spectra, overcoming contamination and spatially varying stellar populations, which previously limited such studies. Utilizing Sleuth with data from the CAnadian NIRISS Unbiased Cluster Survey (CANUCS), we investigated the relationship between metallicity and star formation in the star-forming clumps of galaxies at 0.6 < z < 1.35. We analyzed a sample of 20 galaxies, extracted high-quality emission line maps with Sleuth, and analyzed, in detail, the spatially resolved properties of star-forming clumps. Using $H\alpha$, [SII], and [SIII] emission line maps, we examined the spatially resolved metallicities, ionization, and star formation rates of our sample. Our findings reveal that these star-forming clumps show lower metallicities ($\sim$ 0.1 dex) than their surrounding galactic environments, indicating a metallicity dilution of 20 $\%$ within the clumps' gas. Our analysis indicates that these clumps exhibit intensified star formation and reduced metallicity, likely due to the inflow of metal-poor gas. These clumps illustrate the dynamic relationship between star formation and chemical enrichment within galaxies.