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Author Kalvans, J.
Source United States Department of Energy Office of Scientific and Technical Information
Content type Text
Language English
Subject Keyword INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY ♦ ASTROPHYSICS, COSMOLOGY AND ASTRONOMY ♦ AMMONIA ♦ CARBON DIOXIDE ♦ CARBON MONOXIDE ♦ CLOUDS ♦ COMPARATIVE EVALUATIONS ♦ COSMOCHEMISTRY ♦ DESORPTION ♦ FORMATES ♦ HYDROGEN PEROXIDE ♦ HYDROGENATION ♦ ICE ♦ INTERSTELLAR SPACE ♦ MASS ♦ MOLECULES ♦ NITROGEN ♦ OXYGEN ♦ SULFUR ♦ TURBULENCE ♦ WATER
Abstract Starless molecular cores are natural laboratories for interstellar molecular chemistry research. The chemistry of ices in such objects was investigated with a three-phase (gas, surface, and mantle) model. We considered the center part of five starless cores, with their physical conditions derived from observations. The ice chemistry of oxygen, nitrogen, sulfur, and complex organic molecules (COMs) was analyzed. We found that an ice-depth dimension, measured, e.g., in monolayers, is essential for modeling of chemistry in interstellar ices. Particularly, the H{sub 2}O:CO:CO{sub 2}:N{sub 2}:NH{sub 3} ice abundance ratio regulates the production and destruction of minor species. It is suggested that photodesorption during the core-collapse period is responsible for the high abundance of interstellar H{sub 2}O{sub 2} and O{sub 2}H and other species synthesized on the surface. The calculated abundances of COMs in ice were compared to observed gas-phase values. Smaller activation barriers for CO and H{sub 2}CO hydrogenation may help explain the production of a number of COMs. The observed abundance of methyl formate HCOOCH{sub 3} could be reproduced with a 1 kyr, 20 K temperature spike. Possible desorption mechanisms, relevant for COMs, are gas turbulence (ice exposure to interstellar photons) or a weak shock within the cloud core (grain collisions). To reproduce the observed COM abundances with the present 0D model, 1%–10% of ice mass needs to be sublimated. We estimate that the lifetime for starless cores likely does not exceed 1 Myr. Taurus cores are likely to be younger than their counterparts in most other clouds.
ISSN 0004637X
Educational Use Research
Learning Resource Type Article
Publisher Date 2015-06-20
Publisher Place United States
Journal Astrophysical Journal
Volume Number 806
Issue Number 2


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