Early Results from GLASS-JWST. XIII. A Faint, Distant, and Cold Brown Dwarf
Santini, Paola; Castellano, Marco; Fontana, Adriano; Treu, Tommaso; Glazebrook, Karl; Nanayakkara, Themiya; Burgasser, Adam J.; Vulcani, Benedetta; Wang, Xin; Nonino, Mario; Grillo, Claudio; Rosati, Piero; Morishita, Takahiro; Vanzella, Eros; Mercurio, Amata; Merlin, Emiliano; Paris, Diego; Bradac, Marusa; Polenta, Gianluca; Bonchi, Andrea; Lepinzan, Marius
Italy, Australia, United States, Slovenia
Abstract
We present the serendipitous discovery of a late T-type brown dwarf candidate in JWST NIRCam observations of the Early Release Science Abell 2744 parallel field. The discovery was enabled by the sensitivity of JWST at 4 μm wavelengths and the panchromatic 0.9-4.5 μm coverage of the spectral energy distribution. The unresolved point source has magnitudes F115W = 27.95 ± 0.15 and F444W = 25.84 ± 0.01 (AB), and its F115W-F444W and F356W-F444W colors match those expected for other known T dwarfs. We can exclude it as a reddened background star, high redshift quasar, or a very high redshift galaxy. Comparison with stellar atmospheric models indicates a temperature of T eff ≈ 650 K and surface gravity $\mathrm{log}g\approx 5.25$ , implying a mass of 0.03 M ⊙ and age of 5 Gyr. We estimate the distance of this candidate to be 570-720 pc in a direction perpendicular to the Galactic plane, making it a likely thick disk or halo brown dwarf. These observations underscore the power of JWST to probe the very low-mass end of the substellar mass function in the Galactic thick disk and halo. *Based on data collected with JWST.