Turbulence in the TW Hya Disk
By K. Flaherty, A. Hughes, R. Teague, Jacob B. Simon, S. Andrews, D. Wilner. 2018
142 citations recorded by the source corpus.
Turbulence is a fundamental parameter in models of grain growth during the early stages of planet formation. As such, observational constraints on its magnitude are crucial. Here we self-consistently analyze ALMA CO(2–1), SMA CO(3–2), and SMA CO(6–5) observations of the disk around TW Hya and find an upper limit on the turbulent broadening of <0.08cs (α < 0.007 for α defined only within 2–3 pressure scale heights above the midplane), lower than the tentative detection previously found from an analysis of the CO(2–1) data. We examine in detail the challenges of image plane fitting versus directly fitting the visibilities, while also considering the role of the vertical temperature gradient, systematic uncertainty in the amplitude calibration, and assumptions about the CO abundance, as potential sources of the discrepancy in the turbulence measurements. These tests result in variations of the turbulence limit between <0.04cs and <0.13cs, consistently lower than the 0.2–0.4cs found previously. Having ruled out numerous factors, we restrict the source of the discrepancy to our assumed coupling between temperature and density through hydrostatic equilibrium in the presence of a vertical temperature gradient and/or the confinement of CO to a thin molecular layer above the midplane, although further work is needed to quantify the influence of these prescriptions. Assumptions about hydrostatic equilibrium and the CO distribution are physically motivated, and may have a small influence on measuring the kinematics of the gas, but they become important when constraining small effects such as the strength of the turbulence within a protoplanetary disk.
Subfields: Astronomy and Astrophysics, Atmospheric Science, Spectroscopy
View Paper: https://www.semanticscholar.org/paper/bb90cafec0ca42f1e86f661f7e590c0fb843c9f8
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Citations in the corpus
- The Disk Substructures at High Angular Resolution Project (DSHARP). VI. Dust Trapping in Thin-ringed Protoplanetary Disks (2018, result): “These low values of αturb are consistent with the low values or upper limits reported recently (Pinte et al. 2016; Flaherty et al. 2018).”
- The Disk Substructures at High Angular Resolution Project (DSHARP). VII. The Planet–Disk Interactions Interpretation (2018, background): “While a moderate α∼10−2 is preferred to explain the disk accretion (Hartmann et al. 1998), recent works suggest that a low turbulence level (α< 10−2) is needed to explain molecular line widths in TW Hya (Flaherty et al. 2018) and dust settling in HL Tau (Pinte et al. 2016).”
- The Disk Substructures at High Angular Resolution Project (DSHARP). II. Characteristics of Annular Substructures (2018, background): “Few estimates exist for disk turbulence, but the turbulent line broadening upper limits derived for HD 163296 and TW Hya are less than a tenth of the sound speed, which is considered weak (e.g., Flaherty et al. 2015, 2018).”
- Gaps and Rings in an ALMA Survey of Disks in the Taurus Star-forming Region (2018, methodology): “When the turbulence parameter (Shakura & Sunyaev 1973) is assumed to be α=10−4, a value consistent with recent turbulence constraints by Flaherty et al. (2015) and Flaherty et al. (2018), the diagnostic of 0.25 corresponds to a planet mass of ∼15M⊕ (0.05MJ).”