Cloud busting: enstatite and quartz clouds in the atmosphere of 2M2224-0158

ABSTRACT We present the most detailed data-driven exploration of cloud opacity in a substellar object to-date. have tested over 60 combinations composition and structure, particle-size distribution, scattering model, gas phase assumptions against archival 1–15 ?m spectroscopy for unusually red L4.5 dwarf 2MASSW J2224438-015852 using Brewster retrieval framework. find that, within our framework, model that includes enstatite quartz layers at shallow pressures, combined with deep iron deck fits data best. This assumes Hansen distribution particle sizes each cloud, Mie scattering. retrieved effective radii $\log _{10} {\rm (\mu m)} = -1.41^{+0.18}_{-0.17}$ enstatite, $-0.44^{+0.04}_{-0.20}$ quartz, $-0.77^{+0.05}_{-0.06}$ iron. Our inferred column densities suggest ${\rm (Mg/Si)} 0.69^{+0.06}_{-0.08}$ if there are no other sinks magnesium or silicon. Models include forsterite alongside, place of, these species strongly rejected favour above combination. estimate radius 0.75 ± 0.02 RJup, which is considerably smaller than predicted by evolutionary models field age luminosity 2M2224-0158. assume vertically constant fractions consistently preferred thermochemical equilibrium. From fractions, we infer [M/H]} +0.38^{+0.07}_{-0.06}$ C/O} 0.83^{+0.06}_{-0.07}$. Both values towards upper end stellar Solar neighbourhood, mutually consistent this context. A extremes local target being an outlier ultracool population.