EVIDENCE OF FAST PEBBLE GROWTH NEAR CONDENSATION FRONTS IN THE HL TAU PROTOPLANETARY DISK

By Ke Zhang, G. Blake, E. Bergin. 2015

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Water and simple organic molecular ices dominate the mass of solid materials available for planetesimal and planet formation beyond the water snow line. Here we analyze ALMA long baseline 2.9, 1.3 and 0.87 mm continuum images of the young star HL Tau, and suggest that the emission dips observed are due to rapid pebble growth around the condensation fronts of abundant volatile species. Specifically, we show that the prominent innermost dip at 13 AU is spatially resolved in the 0.87 mm image, and its center radius is coincident with the expected mid-plane condensation front of water ice. In addition, two other prominent dips, at distances of 32 and 63 AU, cover the mid-plane condensation fronts of pure ammonia or ammonia hydrates and clathrate hydrates (especially with CO and N2) formed from amorphous water ice. The spectral index map of HL Tau between 1.3 and 0.87 mm shows that the flux ratios inside the dips are statistically larger than those of nearby regions in the disk. This variation can be explained by a model with two dust populations, where most of the solid mass resides in a component that has grown to decimeter size scales inside the dips. Such growth is in accord with recent numerical simulations of volatile condensation, dust coagulation, and settling.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/06cb7ee3554a8d632c5cdb54deb6e4f051619fa2

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Citations in the corpus

The Disk Substructures at High Angular Resolution Project (DSHARP). VII. The Planet–Disk Interactions Interpretation (2018, background): “…to explain gaps with young planets, we want to point out that there are many other possible mechanisms to produce gaps and rings, such as ice lines (Zhang et al. 2015; Okuzumi et al. 2016), the dead zone transition (Pinilla et al. 2016), MHD zonal flows (Flock et al. 2015; Ruge et al. 2016), the…”
ALMA unveils rings and gaps in the protoplanetary system HD 169142: signatures of two giant protoplanets (2017, background): “…& Lin 1984), magneto-rotational instability that creates dead-zones (Flock et al. 2015), dust grain growth corresponding to condensation fronts (Zhang et al. 2015), fusing of dust grains at temperatures below the sublimation point (dust sintering, Okuzumi et al. 2016), and photoevaporation…”
ALMA continuum observations of the protoplanetary disk AS 209. Evidence of multiple gaps opened by a single planet (2017, background): “…formation of gaps and rings in disks can be due to several mechanisms such as: planet formation (e.g., Papaloizou & Lin 1984); magneto-rotational instability (Flock et al. 2015); condensation fronts (Zhang et al. 2015); dust sintering (Okuzumi et al. 2016); photoevaporation (Ercolano et al. 2017).”
Dust Evolution and the Formation of Planetesimals (2016, background): “Other proposed explanations include pressure bumps formed due to magnetised turbulence (Johansen et al. 2009; Dittrich et al. 2013; Flock et al. 2015) or condensation fronts (Cuzzi & Zahnle 2004; Ros & Johansen 2013; Zhang et al. 2015; Okuzumi et al. 2015).”
Gaps and Rings in an ALMA Survey of Disks in the Taurus Star-forming Region (2018, methodology): “…zones where gas accretion is regulated by spatial variations of the ionization level (Flock et al. 2015), grain growth around condensation fronts (Zhang et al. 2015), ambipolar diffusion-assisted reconnection in magnetically coupled disk wind systems in the presence of a poloidal magnetic field…”
The Disk Substructures at High Angular Resolution Project (DSHARP). II. Characteristics of Annular Substructures (2018, background): “Snowlines Previously detected substructures in the HL Tau, TW Hya, and HD 163296 disks have been hypothesized to be due to volatile freezeout altering the coagulation and fragmentation properties of dust grains (e.g., Zhang et al. 2015; Okuzumi et al. 2016; Pinilla et al. 2017).”
Kinematic Evidence for an Embedded Protoplanet in a Circumstellar Disk (2018, background): “This excludes, for example, ice lines (Zhang et al. 2015), self-induced dust traps (Gonzalez et al. 2015), instabilities (Takahashi & Inutsuka 2014; Lorén-Aguilar & Bate 2015) and zonal flows (Flock et al. 2015).”
A Kinematical Detection of Two Embedded Jupiter-mass Planets in HD 163296 (2018, background): “…able to excite spiral waves which open up secondary and tertiary gaps (Bae, et al. 2017; Fedele et al. 2018), while grain growth around ice lines (Zhang et al. 2015) and the shepherding of dust by (magneto-)hydrodynamic instabilities have also been shown to produce ring like structure in the…”
DUST AND GAS IN THE DISK OF HL TAURI: SURFACE DENSITY, DUST SETTLING, AND DUST-TO-GAS RATIO (2015, background): “The high optical depth of the disk in our model also means that the temperature in the gaps is significantly lower than what was assumed by Zhang et al. (2015) and that the gaps do not seem to be coincident with molecular condensation fronts.”
Three Radial Gaps in the Disk of TW Hydrae Imaged with SPHERE (2016, background): “Dust evolution (Birnstiel et al. 2015), increased coagulation efficiency after ice condensation fronts (Zhang et al. 2015), and a sintering-induced change of agglomeration state (Okuzumi et al. 2016) may all lead to ringed structures in disks.”
On planet formation in HL Tau (2015, background): “This begs the question of whether the gaps seen in HL Tau are genuine signatures of planet formation, or due to some oth r phenomena such as clumping (Lyra & Kuchner 2013), magnetic or Rossby-wave instabilities (Pinilla et al. 2012) or condensation fronts (Zhang et al. 2015).”