TY - JOUR
T1 - A New Look at T Tauri Star Forbidden Lines
T2 - MHD-driven Winds from the Inner Disk
AU - Fang, Min
AU - Pascucci, Ilaria
AU - Edwards, Suzan
AU - Gorti, Uma
AU - Banzatti, Andrea
AU - Flock, Mario
AU - Hartigan, Patrick
AU - Herczeg, Gregory J.
AU - Dupree, Andrea K.
N1 - Funding Information:
We thank Kelle Cruz and Scott Dahm for doing the observations with Keck/HIRES. I.P., U.G., and S.E. acknowledge support from a Collaborative NSF Astronomy & Astrophysics Research Grant (ID:1715022, ID:1713780, and ID:1714229). This material is based on work supported by the National Aeronautics and Space Administration under agreement no. NNX15AD94G for the program “Earths in Other Solar Systems.” The results reported herein benefited from collaborations and/or information exchange within the NASA Nexus for Exoplanet System Science (NExSS) research coordination network sponsored by NASA’s Science Mission Directorate. The data presented here were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Maunakea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain. This research has made use of the Keck Observatory Archive (KOA), which is operated by the W. M. Keck Observatory and the NASA Exoplanet Science Institute (NExScI), under contract with the National Aeronautics and Space Administration. Facility: Keck:I (HIRES).
Publisher Copyright:
© 2018. The American Astronomical Society. All rights reserved.
PY - 2018/11/20
Y1 - 2018/11/20
N2 - Magnetohydrodynamic (MHD) and photoevaporative winds are thought to play an important role in the evolution and dispersal of planet-forming disks. We report the first high-resolution (Δv ∼ 6 km s-1) analysis of [S ii] λ4068, [O i] λ5577, and [O i] λ6300 lines from a sample of 48 T Tauri stars. Following Simon et al. we decompose them into three kinematic components: a high-velocity component (HVC) associated with jets, and low-velocity narrow (LVC-NC) and broad (LVC-BC) components. We confirm previous findings that many LVCs are blueshifted by more than 1.5 km s-1 and thus most likely trace a slow disk wind. We further show that the profiles of individual components are similar in the three lines. We find that most LVC-NC and LVC-BC line ratios are explained by thermally excited gas with temperatures between 5000 and 10,000 K and electron densities of ∼107-108 cm-3. The HVC ratios are better reproduced by shock models with a pre-shock H number density of ∼106-107 cm-3. Using these physical properties, we estimate for the LVC and for the HVC. In agreement with previous work, the mass carried out in jets is modest compared to the accretion rate. With the likely assumption that the LVC-NC wind height is larger than the LVC-BC, the LVC-BC is found to be higher than the LVC-NC. These results suggest that most of the mass loss occurs close to the central star, within a few au, through an MHD-driven wind. Depending on the wind height, MHD winds might play a major role in the evolution of the disk mass.
AB - Magnetohydrodynamic (MHD) and photoevaporative winds are thought to play an important role in the evolution and dispersal of planet-forming disks. We report the first high-resolution (Δv ∼ 6 km s-1) analysis of [S ii] λ4068, [O i] λ5577, and [O i] λ6300 lines from a sample of 48 T Tauri stars. Following Simon et al. we decompose them into three kinematic components: a high-velocity component (HVC) associated with jets, and low-velocity narrow (LVC-NC) and broad (LVC-BC) components. We confirm previous findings that many LVCs are blueshifted by more than 1.5 km s-1 and thus most likely trace a slow disk wind. We further show that the profiles of individual components are similar in the three lines. We find that most LVC-NC and LVC-BC line ratios are explained by thermally excited gas with temperatures between 5000 and 10,000 K and electron densities of ∼107-108 cm-3. The HVC ratios are better reproduced by shock models with a pre-shock H number density of ∼106-107 cm-3. Using these physical properties, we estimate for the LVC and for the HVC. In agreement with previous work, the mass carried out in jets is modest compared to the accretion rate. With the likely assumption that the LVC-NC wind height is larger than the LVC-BC, the LVC-BC is found to be higher than the LVC-NC. These results suggest that most of the mass loss occurs close to the central star, within a few au, through an MHD-driven wind. Depending on the wind height, MHD winds might play a major role in the evolution of the disk mass.
KW - ISM: jets and outflows
KW - accretion, accretion disks
KW - magnetohydrodynamics (MHD)
KW - protoplanetary disks
KW - stars: pre-main sequence
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U2 - 10.3847/1538-4357/aae780
DO - 10.3847/1538-4357/aae780
M3 - Article
AN - SCOPUS:85057174984
VL - 868
JO - Astrophysical Journal
JF - Astrophysical Journal
SN - 0004-637X
IS - 1
M1 - 28
ER -