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

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 N{sub 2}) 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 growthmore » is in accord with recent numerical simulations of volatile condensation, dust coagulation, and settling.« less
Authors:
 [1] ;  [2] ;  [3]
  1. Division of Physics, Mathematics and Astronomy, MC 249-17, California Institute of Technology, Pasadena, CA 91125 (United States)
  2. Division of Geological and Planetary Sciences, MC 150-21, California Institute of Technology, Pasadena, CA 91125 (United States)
  3. Department of Astronomy, University of Michigan, 500 Church Street, Ann Arbor, Michigan 48109 (United States)
Publication Date:
OSTI Identifier:
22518962
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal Letters; Journal Volume: 806; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; AMMONIA; CARBON MONOXIDE; CLATHRATES; COMPUTERIZED SIMULATION; COSMIC DUST; HYDRATES; ICE; IMAGES; MASS; NITROGEN; PLANETS; PROTOPLANETS; SATELLITES; STARS; WATER