Molecular Evolution and Star Formation: From Prestellar Cores to Protostellar Cores

By Y. Aikawa, V. Wakelam, R. Garrod, E. Herbst. 2007

204 citations recorded by the source corpus.

We investigate molecular evolution in a star-forming core that is initially a hydrostatic starless core and collapses to form a low-mass protostar. The results of a one-dimensional radiation-hydrodynamics calculation are adopted as a physical model of the core. We first derive radii at which CO and large organic species sublimate. CO sublimation in the central region starts shortly before the formation of the first hydrostatic core. When the protostar is born, the CO sublimation radius extends to 100 AU, and the region inside ≲10 AU is hotter than 100 K, at which temperature some large organic species evaporate. We calculate the temporal variation of physical parameters in infalling shells, in which the molecular evolution is solved using an updated gas-grain chemical model to derive the spatial distribution of molecules in a protostellar core. The shells pass through the warm region of 10-100 K in several × 104 yr, and fall into the central star ~100 yr after they enter the region where T≳ 100 K. We find that large organic species are formed mainly via grain-surface reactions at temperatures of 20-40 K and then desorbed into the gas phase at their sublimation temperatures. Carbon-chain species can be formed by a combination of gas-phase reactions and grain-surface reactions following the sublimation of CH4. Our model also predicts that CO2 is more abundant in isolated cores, while gas-phase large organic species are more abundant in cores embedded in ambient clouds.

Subfields: Astronomy and Astrophysics, Atomic and Molecular Physics, and Optics, Spectroscopy

View Paper: https://www.semanticscholar.org/paper/e7acf964255085ee2944aa6b6a869be1da3aac11

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Citations in the corpus

The chemical history of molecules in circumstellar disks - I. Ices (2009, methodology): “Ceccarelli et al. (1996) modelled the chemistry in the collapse phase, and others have done so more recently (Rodgers & Charnley 2003; Doty et al. 2004; Lee et al. 2004; Garrod & Herbst 2006; Aikawa et al. 2008; Garrod et al. 2008).”
Dust coagulation and fragmentation in molecular clouds. I. How collisions between dust aggregates alter the dust size distribution (2009, background): “Moreover, surface chemistry provides a driving force towards molecular complexity (Charnley et al. 1992; Aikawa et al. 2008).”
Water in Star-forming Regions with the Herschel Space Observatory (WISH). I. Overview of Key Program and First Results (2010, methodology): “…evolves have been made by Ceccarelli et al. (1996), Viti & Williams (1999), Rodgers & Charnley (2003), Lee et al. (2004), Doty et al. (2006), and Aikawa et al. (2008) in 1D and by Visser et al. (2009) in 2D. Grids of 1D C-type shock models by Kaufman & Neufeld (1996) and bow-shock models by…”
Physical Processes in the Interstellar Medium (2014, background): “At the same time, chemical models of prestellar cores predict that molecules in the envelope of the core are destroyed by the interstellar UV field (Pavlyuchenkov et al. 2006; Aikawa et al. 2008).”
Our astrochemical heritage (2012, background): “[7]; [170]; [210]; [120]; [86]; [411]; [410]).”