Spectroscopy of young planetary mass candidates with disks

It is now well established that many young brown dwarfs exhibit characteristics similar to classical T Tauri stars, including infrared excess from disks and emission lines related to accretion. Whether the same holds true for even lower mass objects, namely, those near and below the Deuterium-burning limit, is an important question. Here we present optical spectra of six isolated planetary mass candidates in Chamaeleon II, Lupus I, and Ophiuchus star-forming regions, recently identified by Allers and collaborators to harbor substantial mid-infrared excesses. Our spectra, from ESO's Very Large Telescope and New Technology Telescope, show that four of the targets have spectral types in the similar to M9-L1 range, and three of those also exhibit Ha. Their luminosities are consistent with masses of similar to 5M(J)-15M(J) according to models of Baraffe and coworkers, thus placing these four objects among M M the lowest mass brown dwarfs known to be surrounded by circum-substellar disks. Our findings bolster the idea that free-floating planetary mass objects could have infancies remarkably similar to those of Sun-like stars and suggest the intriguing possibility of planet formation around primaries whose masses are comparable to those of extrasolar giant planets. Another target appears to be a brown dwarf (similar to M8) with prominent H alpha emission, possibly arising from accretion. The sixth candidate is likely a background source, underlining the need for spectroscopic confirmation.