ALMA Survey of Lupus Protoplanetary Disks. II. Gas Disk Radii
By M. Ansdell, Jonathan P. Williams, L. Trapman, S. V. Terwisga, S. Facchini, C. Manara, N. Marel, A. Miotello, M. Tazzari, M. Hogerheijde and 3 more. 2018
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We present Atacama Large Millimeter/Sub-Millimeter Array (ALMA) Band 6 observations of a complete sample of protoplanetary disks in the young (∼1–3 Myr) Lupus star-forming region, covering the 1.33 mm continuum and the 12CO, 13CO, and C18O J = 2–1 lines. The spatial resolution is ∼0.″25 with a medium 3σ continuum sensitivity of 0.30 mJy, corresponding to Mdust ∼ 0.2 M⊕. We apply Keplerian masking to enhance the signal-to-noise ratios of our 12CO zero-moment maps, enabling measurements of gas disk radii for 22 Lupus disks; we find that gas disks are universally larger than millimeter dust disks by a factor of two on average, likely due to a combination of the optically thick gas emission and the growth and inward drift of the dust. Using the gas disk radii, we calculate the dimensionless viscosity parameter, αvisc, finding a broad distribution and no correlations with other disk or stellar parameters, suggesting that viscous processes have not yet established quasi-steady states in Lupus disks. By combining our 1.33 mm continuum fluxes with our previous 890 μm continuum observations, we also calculate the millimeter spectral index, αmm, for 70 Lupus disks; we find an anticorrelation between αmm and millimeter flux for low-mass disks (Mdust ≲ 5), followed by a flattening as disks approach αmm ≈ 2, which could indicate faster grain growth in higher-mass disks, but may also reflect their larger optically thick components. In sum, this work demonstrates the continuous stream of new insights into disk evolution and planet formation that can be gleaned from unbiased ALMA disk surveys.
Subfields: Astronomy and Astrophysics, Instrumentation
View Paper: https://www.semanticscholar.org/paper/2b04e93c73d7e9bd70ac1f810d15d8fcb2cd11d5
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Citations in the corpus
- Why do protoplanetary disks appear not massive enough to form the known exoplanet population? (2018, background): “It has been shown that Article number, page 3 of 8 some dust mass can be confined into optically thick inner regions of disks (Tripathi et al. 2017; Ansdell et al. 2018) and that the opacity of disks and their temperature is still debatable (e.g., Andrews et al. 2013; Pascucci et al. 2016).”
- Gaps and Rings in an ALMA Survey of Disks in the Taurus Star-forming Region (2018, background): “This explanation should be valid if Rgas/Rdust is higher in smaller disks, for which dust inward migration is very efficient without “traps” formed at larger radii, though this is not seen in Ansdell et al. (2018).”
- The Disk Substructures at High Angular Resolution Project (DSHARP). II. Characteristics of Annular Substructures (2018, result): “This is consistent with the finding from Ansdell et al. (2018) that most of the disks observed in the Lupus star-forming region have cores that are optically thick at millimeter wavelengths.”
- The Disk Substructures at High Angular Resolution Project (DSHARP). I. Motivation, Sample, Calibration, and Overview (2018, background): “…line emission have led to suggestions that the mass ratio of solids relative to gas also varies with radius (higher closer to the star; Panić et al. 2009; Andrews et al. 2012; de Gregorio-Monsalvo et al. 2013; Rosenfeld et al. 2013; Zhang et al. 2014; Facchini et al. 2017; Ansdell et al. 2018).”
- The Close Binary Fraction of Solar-type Stars Is Strongly Anticorrelated with Metallicity (2018, background): “For the parameters chosen in their models, low-mass solar-metallicity stars have disk radii of order ≈1000 au, which is large compared to our best observational constraints of ≈100–300 au (Ansdell et al. 2018).”