to an objects surface gravity; therefore at younger ages, hence lower gravities, the $H-$band spectrum is peaked (@Luhman04 and Figure 6 from @Rice11).

An equally important indicator for brown dwarf members of young groups is a strong deviation in near-infrared color (significantly redder J-K$_{s}$) from the mean of a given spectral subtype. The clearest example is 2MASS J12073346$-$3932539 (2M1207b), a late-L dwarf member of the TW Hydrae association with $J-K$=3.05, $\sim$0.5 mag redder than any other known L dwarf (@Chauvin04; @Mohanty07). Similar to the spectral deviations of young brown dwarfs, the photometric peculiarities can be explained as a consequence of lower surface gravity. At lower values–hence lower pressure at a given temperature in the photosphere–, H$_{2}$ collision induced absorption (CIA) is reduced leading to a reduction of the strongest absorption feature at 2.5 $\mu$m (less absorption at $K$ band relative to $J$ band) and a red $J-K$ color (@Kirkpatrick06). An evolutionary model comparison of a large collection of low-surface gravity or young companion brown dwarfs to tracks with differing cloud, metallicity and gravity properties demonstrates that the change in near-IR color is attributed to changes in CIA H$_{2}$ affected by lower-surface gravities (see @Faherty12 and references there-in).

Additionally, the kinematics 