• DOI:10.1088/0004-637X/779/2/178
• Corpus ID: 119001471

THE ATOMIC AND MOLECULAR CONTENT OF DISKS AROUND VERY LOW-MASS STARS AND BROWN DWARFS

@article{Pascucci2013THEAA,
  title={THE ATOMIC AND MOLECULAR CONTENT OF DISKS AROUND VERY LOW-MASS STARS AND BROWN DWARFS},
  author={I. Pascucci and Gregory J. Herczeg and John S. Carr and Simon Bruderer},
  journal={The Astrophysical Journal},
  year={2013},
  volume={779}
}

• I. Pascucci, G. Herczeg, +1 author S. Bruderer
• Published 5 November 2013
• Physics, Geology
• The Astrophysical Journal

There is growing observational evidence that disk evolution is stellar-mass-dependent. Here, we show that these dependencies extend to the atomic and molecular content of disk atmospheres. We analyze a unique dataset of high-resolution Spitzer/IRS spectra from eight very low mass star and brown dwarf disks. We report the first detections of Ne+, H2, CO2, and tentative detections of H2O toward these faint and low-mass disks. Two of our [Ne ii] 12.81 μm emission lines likely trace the hot (⩾5000 K) disk surface irradiated by X-ray photons from the central stellar/sub-stellar object. The H2 S(2) and S(1) fluxes are consistent with arising below the fully or partially ionized surface traced by the [Ne ii] emission in gas at ∼600 K. We confirm the higher C2H2/HCN flux and column density ratio in brown dwarf disks previously noted from low-resolution IRS spectra. Our high-resolution spectra also show that the HCN/H2O fluxes of brown dwarf disks are on average higher than those of T Tauri disks. Our LTE modeling hints that this difference extends to column density ratios if H2O lines trace warm ⩾600 K disk gas. These trends suggest that the inner regions of brown dwarf disks have a lower O/C ratio than those of T Tauri disks, which may result from a more efficient formation of non-migrating icy planetesimals. An O/C = 1, as inferred from our analysis, would have profound implications on the bulk composition of rocky planets that can form around very low mass stars and brown dwarfs.