FROM PRESTELLAR TO PROTOSTELLAR CORES. II. TIME DEPENDENCE AND DEUTERIUM FRACTIONATION

Journal Article · Tue Nov 20 04:00:00 EST 2012 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/760/1/40· OSTI ID:22086317

Aikawa, Y ^[1]; Wakelam, V; Hersant, F ^[2]; Garrod, R T ^[3]; Herbst, E ^[4]

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1. Department of Earth and Planetary Sciences, Kobe University, 657-8501 Kobe (Japan)
2. CNRS and Universite de Bordeaux, Observatoire Aquitain des Sciences de l'Univers, 2 rue de l'Observatoire, B.P. 89, F-33271 Floirac (France)
3. Department of Astronomy, Cornell University, Ithaca, NY 14853 (United States)
4. Departments of Chemistry, Astronomy, and Physics, University of Virginia, Charlottesville, VA 22904 (United States)

We investigate the molecular evolution and D/H abundance ratios that develop as star formation proceeds from a dense molecular cloud core to a protostellar core, by solving a gas-grain reaction network applied to a one-dimensional radiative hydrodynamic model with infalling fluid parcels. Spatial distributions of gas and ice-mantle species are calculated at the first-core stage, and at times after the birth of a protostar. Gas-phase methanol and methane are more abundant than CO at radii r {approx}< 100 AU in the first-core stage, but gradually decrease with time, while abundances of larger organic species increase. The warm-up phase, when complex organic molecules are efficiently formed, is longer-lived for those fluid parcels infalling at later stages. The formation of unsaturated carbon chains (warm carbon-chain chemistry) is also more effective in later stages; C{sup +}, which reacts with CH{sub 4} to form carbon chains, increases in abundance as the envelope density decreases. The large organic molecules and carbon chains are strongly deuterated, mainly due to high D/H ratios in the parent molecules, determined in the cold phase. We also extend our model to simulate simply the chemistry in circumstellar disks, by suspending the one-dimensional infall of a fluid parcel at constant disk radii. The species CH{sub 3}OCH{sub 3} and HCOOCH{sub 3} increase in abundance in 10{sup 4}-10{sup 5} yr at the fixed warm temperature; both also have high D/H ratios.

• OSTI ID: 22086317
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 1 Vol. 760; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
ASTRONOMY
ASTROPHYSICS
CARBON
CARBON IONS
CARBON MONOXIDE
DENSITY
DEUTERIUM
ELEMENT ABUNDANCE
FRACTIONATION
HYDRODYNAMICS
ICE
METHANE
METHANOL
MOLECULES
SPATIAL DISTRIBUTION
STARS
TIME DEPENDENCE