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Title: THE DISTRIBUTION AND CHEMISTRY OF H{sub 2}CO IN THE DM TAU PROTOPLANETARY DISK

H{sub 2}CO ice on dust grains is an important precursor of complex organic molecules (COMs). H{sub 2}CO gas can be readily observed in protoplanetary disks and may be used to trace COM chemistry. However, its utility as a COM probe is currently limited by a lack of constraints on the relative contributions of two different formation pathways: on icy grain surfaces and in the gas phase. We use archival Atacama Large (sub-)Millimeter Array observations of the resolved distribution of H{sub 2}CO emission in the disk around the young low-mass star DM Tau to assess the relative importance of these formation routes. The observed H{sub 2}CO emission has a centrally peaked and radially broad brightness profile (extending out to 500 AU). We compare these observations with disk chemistry models with and without grain-surface formation reactions and find that both gas and grain-surface chemistry are necessary to explain the spatial distribution of the emission. Gas-phase H{sub 2}CO production is responsible for the observed central peak, while grain-surface chemistry is required to reproduce the emission exterior to the CO snow line (where H{sub 2}CO mainly forms through the hydrogenation of CO ice before being non-thermally desorbed). These observations demonstrate that both gas andmore » grain-surface pathways contribute to the observed H{sub 2}CO in disks and that their relative contributions depend strongly on distance from the host star.« less
Authors:
; ;  [1] ;  [2] ;  [3]
  1. Department of Astronomy, Harvard University, Cambridge, MA 02138 (United States)
  2. Department of Astronomy, University of Michigan, Ann Arbor, MI 48109 (United States)
  3. Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138 (United States)
Publication Date:
OSTI Identifier:
22518905
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal Letters; Journal Volume: 809; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; BRIGHTNESS; CARBON MONOXIDE; COMPARATIVE EVALUATIONS; COSMIC DUST; COSMOCHEMISTRY; EMISSION; HYDROGENATION; ICE; MASS; MOLECULES; PROTOPLANETS; SPATIAL DISTRIBUTION; STARS; SURFACES