We present moderate-resolution ( R \sim 4000–5000 ) near-infrared integral field spectroscopy of the young ( 1–5 Myr ) 6–14 M _ { \mathrm { Jup } } companions ROXs 42B b and FW Tau b obtained with Keck/OSIRIS and Gemini-North/NIFS .
The spectrum of ROXs 42B b exhibits clear signs of low surface gravity common to young L dwarfs , confirming its extreme youth , cool temperature , and low mass .
Overall , it closely resembles the free-floating 4–7 M _ { \mathrm { Jup } } L-type Taurus member 2MASS J04373705+2331080 .
The companion to FW Tau AB is more enigmatic .
Our optical and near-infrared spectra show strong evidence of outflow activity and disk accretion in the form of line emission from [ S ii ] , [ O i ] , H \alpha , Ca II , [ Fe ii ] , Pa \beta , and H _ { 2 } .
The molecular hydrogen emission is spatially resolved as a single lobe that stretches \approx 0 \farcs 1 ( 15 AU ) .
Although the extended emission is not kinematically resolved in our data , its morphology resembles shock-excited H _ { 2 } jets primarily seen in young Class 0 and Class I sources .
The near-infrared continuum of FW Tau b is mostly flat and lacks the deep absorption features expected for a cool , late-type object .
This may be a result of accretion-induced veiling , especially in light of its strong and sustained H \alpha emission ( EW ( H \alpha ) \gtrsim 290 Å ) .
Alternatively , FW Tau b may be a slightly warmer ( M5-M8 ) accreting low-mass star or brown dwarf ( 0.03–0.15 M _ { \odot } ) with an edge-on disk .
Regardless , its young evolutionary stage is in stark contrast to its Class III host FW Tau AB , indicating a more rapid disk clearing timescale for the host binary system than for its wide companion .
Finally , we present near-infrared spectra of the young ( \sim 2–10 Myr ) low-mass ( 12–15 M _ { \mathrm { Jup } } ) companions GSC 6214-210 B and SR 12 C and find they best resemble low gravity M9.5 and M9 substellar templates .