SPECTROSCOPIC CONFIRMATION OF YOUNG PLANETARY-MASS COMPANIONS ON WIDE ORBITS

We present moderate-resolution (R ~ 4000-5000) near-infrared integral field spectroscopy of the young (1-5 Myr) 6-14 M sub(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 sub(jup) L-type Taurus member 2MASS J04373705+2331080. 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 ) [gap] 290 A). Finally, we present near-infrared spectra of the young (~2-10 Myr) low-mass (12-15 M sub(jup)) companions GSC 6214-210 B and SR 12 C and find they best resemble low-gravity M9.5 and M9 substellar templates.