Clouds with a silicate lining: Using JWST spectra to probe atmospheric diversity in young AB Dor L dwarfs

Aims . We present the first full JWST NIRSpec Prism and MIRI LRS 0.6–14 μm ( R ~ 100) spectra and analysis of five ~133 Myr L dwarf members of the AB Doradus moving group and one probable ~500 Myr T dwarf of the Oceanus moving group with known inclination angles between ~23–90°: 2MASS J00470038+6803543, 2MASS J03552337+1133437, 2MASS J06420559+4101599, 2MASS J17410280–4642218, 2MASSW J2206450–421721, and 2MASS J22443167+2043433. Methods . We constructed near-complete spectral energy distributions of each of our objects to measure their bolometric luminosities, and we estimated their fundamental parameters ( T eff , radius, M , and log g ). We used cross-sections of relevant gases to identify the species that are present in each atmosphere. Of particular interest is the silicate absorption feature at 8–11 μm, which provides insight into the complex cloud structure of brown dwarfs. We examined this silicate absorption feature in detail and tested whether a latitudinal dependence exists in the silicate absorption feature within a coeval sample of brown dwarfs. Results . Various molecular absorption bands are visible in our spectra, including H 2 O, CH 4 , CO, and CO 2 . The shape of the silicate absorption feature varies within our sample, and we find that four out of five of our L type objects agree with previously observed trends, namely, that objects viewed equator-on have deeper silicate absorption. We highlight W1741–46 as an outlier in our sample with an unusually strong silicate absorption given its near pole-on orientation. We also present a tentative correlation between the wavelength of peak silicate absorption and inclination, which may suggest variations in cloud chemical composition or physical properties. Conclusions . We found an unexpected spectral diversity within our sample, which motivates future studies on these objects through atmospheric retrievals, which will determine the silicate cloud composition and reveal whether there exists a trend with inclination.