Direct mapping of the temperature and velocity gradients in discs Imaging the vertical CO snow line around IM Lupi

By C. Pinte, F. Ménard, G. Duchêne, T. Hill, W. Dent, Peter Woitke, S. Maret, G. V. D. Plas, A. Hales, I. Kamp and 7 more. 2017

142 citations recorded by the source corpus.

Accurate measurements of the physical structure of protoplanetary discs are critical inputs for planet formation models. These constraints are traditionally established via complex modelling of continuum and line observations. Instead, we present an empirical framework to locate the CO isotopologue emitting surfaces from high spectral and spatial resolution ALMA observations. We apply this framework to the disc surrounding IM Lupi, where we report the first direct, i.e. model independent, measurements of the radial and vertical gradients of temperature and velocity in a protoplanetary disc. The measured disc structure is consistent with an irradiated self-similar disc structure, where the temperature increases and the velocity decreases towards the disc surface. We also directly map the vertical CO snow line, which is located at about one gas scale height at radii between 150 and 300 au, with a CO freeze-out temperature of 21 ± 2 K. In the outer disc (>300 au), where the gas surface density transitions from a power law to an exponential taper, the velocity rotation field becomes significantly sub-Keplerian, in agreement with the expected steeper pressure gradient. The sub-Keplerian velocities should result in a very efficient inward migration of large dust grains, explaining the lack of millimetre continuum emission outside of 300 au. The sub-Keplerian motions may also be the signature of the base of an externally irradiated photo-evaporative wind. In the same outer region, the measured CO temperature above the snow line decreases to ≈15 K because of the reduced gas density, which can result in a lower CO freeze-out temperature, photo-desorption, or deviations from local thermodynamic equilibrium.

Subfields: Astronomy and Astrophysics, Spectroscopy

View Paper: https://www.semanticscholar.org/paper/433935a2354683b754c77d9ecccadae04ad26776

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In Astronomy and Astrophysics

1. D. Wilner
2. T. Birnstiel
3. S. Andrews
4. A. Hughes
5. Matthew R. Bate
6. E. Bergin
7. Xue-Ning Bai
8. C. Qi

In Spectroscopy

1. D. Wilner
2. T. Birnstiel
3. S. Andrews
4. A. Hughes
5. C. Qi
6. E. Bergin
7. K. Oberg
8. C. Walsh

Citations in the corpus

• Kinematic Evidence for an Embedded Protoplanet in a Circumstellar Disk (2018, methodology): “In a recent paper (Pinte et al. 2018) we showed how to reconstruct the position and velocity of each of the CO layers, for discs at intermediate inclination, by simple geometrical arguments based on the emission in each channel map.”
• The Disk Substructures at High Angular Resolution Project (DSHARP). I. Motivation, Sample, Calibration, and Overview (2018, unknown): “References—1 = Öberg 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…”
• Molecules with ALMA at Planet-forming Scales (MAPS). I. Program Overview and Highlights (2021, methodology): “…spatially and spectrally resolved lines can be used to identify chemical, and kinematic signatures of planets in the making (e.g., Kanagawa et al. 2015; Perez et al. 2015; Cleeves et al. 2015; Pinte et al. 2018a; Teague et al. 2018a; Dong et al. 2019; Tsukagoshi et al. 2019; Nomura et al. 2021).”
• A Kinematical Detection of Two Embedded Jupiter-mass Planets in HD 163296 (2018, methodology): “For this we follow the method presented in Pinte et al. (2018), using a position angle of 132◦ which we obtained from fitting a Keplerian rotation pattern to the first moment map and is consistent with previous determinations (Flaherty et al. 2015, 2017).”
• Turbulence in the TW Hya Disk (2018, background): “…the molecular emission layers above and below the midplane (Rosenfeld et al. 2013; de Gregorio-Monsalvo et al. 2013; van der Plas et al. 2017; Pinte et al. 2018; Dutrey et al. 2017) provides a geometric constraint on the midplane temperature, which influences the puffiness of the disk and…”