WEAK TURBULENCE IN THE HD 163296 PROTOPLANETARY DISK REVEALED BY ALMA CO OBSERVATIONS

By K. Flaherty, A. Hughes, K. Rosenfeld, S. Andrews, E. Chiang, Jacob B. Simon, Skylar G. Kerzner, D. Wilner. 2015

163 citations recorded by the source corpus.

Turbulence can transport angular momentum in protoplanetary disks and influence the growth and evolution of planets. With spatially and spectrally resolved molecular emission line measurements provided by (sub)millimeter interferometric observations, it is possible to directly measure non-thermal motions in the disk gas that can be attributed to this turbulence. We report a new constraint on the turbulence in the disk around HD 163296, a nearby young A star, determined from Atacama Large Millimeter/submillimeter Array Science Verification observations of four CO emission lines (the CO(3-2), CO(2-1), 13CO(2-1), and C18O(2-1) transitions). The different optical depths for these lines permit probes of non-thermal line-widths at a range of physical conditions (temperature and density) and depths into the disk interior. We derive stringent limits on the non-thermal motions in the upper layers of the outer disk such that any contribution to the line-widths from turbulence is <3% of the local sound speed. These limits are approximately an order of magnitude lower than theoretical predictions for full-blown magnetohydrodynamic turbulence driven by the magnetorotational instability, potentially suggesting that this mechanism is less efficient in the outer (R ≳ 30 AU) disk than has been previously considered.

Subfields: Astronomy and Astrophysics, Spectroscopy

View Paper: https://www.semanticscholar.org/paper/d0d9ee5953b679ec32495dc573a94af4c904ba7b

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Citations in the corpus

Turbulence in the TW Hya Disk (2018, methodology): “Previous efforts to measure turbulence (Carr et al. 2004; Hughes et al. 2011; Guilloteau et al. 2012; Flaherty et al. 2015; Teague et al. 2016; Flaherty et al. 2017), utilize, at minimum, the full spectral line profile in searching for non-thermal motion and can rely on differences in e.g. the line…”
A Kinematical Detection of Two Embedded Jupiter-mass Planets in HD 163296 (2018, methodology): “Relative residuals from a Keplerian curve assuming 2.3 Msun and i = 47.7 ◦, appropriate for HD 163296 (Flaherty et al. 2015, 2017) are shown for the three transitions in the top row of Fig.”
Multiple Disk Gaps and Rings Generated by a Single Super-Earth (2017, background): “Not even in disk surface layers has turbulence been detected (Flaherty et al. 2015; Flaherty et al. 2017, in prep.).”
Accretion onto Pre-Main-Sequence Stars (2016, background): “Nonthermal ionization by stellar and accretion-driven X-rays and FUV radiation, and possibly also cosmic rays, may also allow an active MRI to develop at radii of 30 AU, although a recent ALMA study suggests that any turbulence in the outer disk may be quite weak (Flaherty et al. 2015).”
Kinematic Evidence for an Embedded Protoplanet in a Circumstellar Disk (2018, methodology): “HD 163296 has a mass of 1.9 M (e.g. Flaherty et al. 2015), a luminosity of 25 L (Natta et al. 2004), and an A1Ve spectral type, with effective temperature 9300 K. Observations with the Hubble Space Telescope (HST) revealed a disc in scattered light that extends as far out as 375 au (Grady et al.…”
Planetesimal formation starts at the snow line (2017, background): “Recent estimates range from αt < 10−3 for the outer parts of the disk around HD 163296 (Flaherty et al. 2015) to αt ≈ 10−2 in the outer parts of the TW Hya disk (Teague et al. 2016).”
Direct mapping of the temperature and velocity gradients in discs Imaging the vertical CO snow line around IM Lupi (2017, background): “…can provide an estimate of the vertical temperature structure of the disc (Dartois et al. 2003), indicate freeze-out of the gas phase molecules onto dust grains in the cold midplane (e.g. Qi et al. 2011; Zhang et al. 2017), and suggest a very low level of turbulence (e.g. Flaherty et al. 2015).”
ALMA Survey of Lupus Protoplanetary Disks. II. Gas Disk Radii (2018, unknown): “10−3 (Hughes et al. 2011; Flaherty et al. 2015; Teague et al. 2016).”
Measuring turbulence in TW Hydrae with ALMA: methods and limitations (2016, methodology): “…was accounted for in the more recent measurement of DM Tau by Guilloteau et al. (2012) using the heavier molecule CS, who found vturb ' 0.3− 0.4 cs More recently Flaherty et al. (2015) used parametric modeling of multiple CO isotopologue transitions to infer vturb <∼ 0.04 cs in HD 163296.”
The Disk Substructures at High Angular Resolution Project (DSHARP). I. Motivation, Sample, Calibration, and Overview (2018, unknown): “…et al. (2015), 2 = Cleeves et al. (2017), 3 = Pinte et al. (2018), 4 = Salyk et al. (2014), 5 = Dipierro et al. (2018), 6 = Pérez et al. (2016), 7 = Huang et al. (2016), 8 = Fedele et al. (2018), 9 = Flaherty et al. (2015), 10 = Isella et al. (2016). fore or after 2017 November, respectively.”
The Disk Substructures at High Angular Resolution Project (DSHARP). II. Characteristics of Annular Substructures (2018, background): “Studies of turbulence via molecular line observations may also help to characterize the overall disk gas dynamics, including the extent of the dead zone, but degeneracies with the thermal profile still pose a major challenge (e.g., Flaherty et al. 2015; Teague et al. 2018b).”
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).”
A Three-dimensional View of Turbulence: Constraints on Turbulent Motions in the HD 163296 Protoplanetary Disk Using DCO+ (2017, methodology): “We do not anticipate that this spectral binning will substantially limit our ability to constrain turbulence; we found similar constraints on turbulence based on CO(3-2) emission when using either a 0.1 km s−1 resolution spectrum (<0.04cs) or a 0.3 km s −1 spectrum (<0.06cs; Flaherty et al. 2015).”
Volatile carbon locking and release in protoplanetary disks. A study of TW Hya and HD 100546 (2016, methodology): “Direct measurements of the level of turbulence with ALMA show promise for remedying this (e.g. Hughes et al. 2011; Guilloteau et al. 2012; Flaherty et al. 2015).”