Abstract We present a systematic assessment of two major cloudy atmospheric model grids— SM08 and Sonora Diamondback —when applied to low-resolution, near-infrared (0.8–2.5 μ m) spectroscopy. Our analysis focuses on a uniform sample of 142 age-benchmark brown dwarfs and planetary-mass objects spanning late M, L, and T spectral types, with independently determined ages from 10 Myr to 10 Gyr. We perform forward-model spectral fitting for all benchmarks’ Infrared Telescope Facility/SpeX spectra ( R ∼ 80–250) using both SM08 and Sonora Diamondback atmospheric models to infer effective temperatures, surface gravities, metallicities, radii, and cloud sedimentation efficiencies. The two model grids yield broadly consistent results. Among L4–L9 dwarfs, we identify a statistically significant, population-level age dependence of the cloud parameter f sed , with young benchmarks ( log ( g ) and mass from spectral fitting for late M and L dwarfs. Finally, we show that including an interstellar-medium-like extinction term significantly improves the spectral fits, confirming and broadening previous findings and suggesting missing opacity sources in current cloudy models.
Mader et al. (Mon,) studied this question.