Brown Dwarf Candidates in the JADES and CEERS Extragalactic Surveys

TL;DR

This study identifies twenty-one brown dwarf candidates using JWST data, analyzing their properties and motions to distinguish them from high-redshift galaxies, and discusses their implications for understanding low-mass stars in our galaxy.

Contribution

First identification of brown dwarf candidates in JWST extragalactic surveys with detailed modeling and proper motion analysis.

Findings

Twenty-one brown dwarf candidates identified.

Proper motion observed in seven candidates, indicating galactic origin.

Distinct color signatures from high-redshift galaxies.

Abstract

By combining the JWST/NIRCam JADES and CEERS extragalactic datasets, we have uncovered a sample of twenty-one T and Y brown dwarf candidates at best-fit distances between 0.1 - 4.2 kpc. These sources were selected by targeting the blue 1$\mu$m - 2.5$\mu$m colors and red 3$\mu$m - 4.5$\mu$m colors that arise from molecular absorption in the atmospheres of T$_{\mathrm{eff}} < $ 1300K brown dwarfs. We fit these sources using multiple models of low-mass stellar atmospheres and present the resulting fluxes, sizes, effective temperatures and other derived properties for the sample. If confirmed, these fits place the majority of the sources in the Milky Way thick disk and halo. We observe proper motion for seven of the candidate brown dwarfs with directions in agreement with the plane of our galaxy, providing evidence that they are not extragalactic in nature. We demonstrate how the colors of these sources differ from selected high-redshift galaxies, and explore the selection of these sources in planned large-area JWST NIRCam surveys. Deep imaging with JWST/NIRCam presents an an excellent opportunity for finding and understanding these very cold low-mass stars at kpc distances.