James Webb Space Telescope Feed Post

Brown Dwarf Candidates in the JADES and CEERS Extragalactic Surveys | JADES-GS-BD-10

Proper motion measurements between the HST WFC3 or Spitzer IRAC2 and JWST NIRCam observations. We plot even sources, and for each source we plot the HST WFC3 or Spitzer IRAC2 thumbnail in the left panel and the JWST NIRCam thumbnail in the right panel, with the filter being used shown in the bottom left. We also plot a scale bar in the left panels, above the filter name. In each panel, the centroid measured for the source from the HST or Spitzer observations is shown with a blue circle, and the centroid for the source from the JWST observations is shown in a red circle. The offset, in arcseconds, is provided. For JADES-GS-BD-5, because the Spitzer IRAC2 image has a different WCS than the JADES NIRCam mosaic, we measure the raw centroid and label it with a square symbol, and the centroid corrected to the JADES WCS is plotted with a circle, along with the corresponding separation. 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 1µm - 2.5µm colors and red 3µm - 4.5µm colors that arise from molecular absorption in the atmospheres of Teff< 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.