Evolution of Chemistry and Molecular Line Profiles during Protostellar Collapse

By Jeong-Eun Lee, E. Bergin, N. Evans II. 2004

161 citations recorded by the source corpus.

Understanding the chemical evolution in star-forming cores is a necessary precondition to correctly assessing physical conditions when using molecular emission. We follow the evolution of chemistry and molecular line profiles through the entire star formation process, including a self-consistent treatment of dynamics, dust continuum radiative transfer, gas energetics, chemistry, molecular excitation, and line radiative transfer. In particular, the chemical code follows a gas parcel as it falls toward the center, passing through regimes of density, dust temperature, and gas temperature that are changing because of both the motion of the parcel and the evolving luminosity of the central source. We combine a sequence of Bonnor-Ebert spheres and the inside-out collapse model to describe dynamics from the pre-protostellar stage to later stages. The overall structures of abundance profiles show complex behavior that can be understood as interactions between freezeout and evaporation of molecules. We find that the presence or absence of gas-phase CO has a tremendous effect on the less abundant species. In addition, the ambient radiation field and the grain properties have important effects on the chemical evolution, and the variations in abundance have strong effects on the predicted emission-line profiles. Multitransition and multiposition observations are necessary to constrain the parameters and interpret observations correctly in terms of physical conditions. Good spatial and spectral resolution is also important in distinguishing evolutionary stages.

Subfields: Astronomy and Astrophysics, Spectroscopy

View Paper: https://www.semanticscholar.org/paper/8943501b8782996d25de4876dfea587376488917

How researchers see this paper

The researchers whose trusted networks rank it highest, strongest advocate first. Every researcher gets a different order.

In Astronomy and Astrophysics

1. R. Garrod
2. E. Dishoeck
3. E. Bergin
4. K. Oberg
5. E. Herbst
6. V. Wakelam
7. P. Caselli
8. M. Tafalla

In Spectroscopy

1. R. Garrod
2. E. Dishoeck
3. K. Oberg
4. V. Wakelam
5. E. Herbst
6. E. Bergin
7. S. Doty
8. C. Dullemond

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).”
• CHEMISTRY IN INFRARED DARK CLOUD CLUMPS: A MOLECULAR LINE SURVEY AT 3 mm (2011, background): “(18) Chemical models of low-mass star-forming regions (e.g., Lee et al. 2004; Jørgensen et al. 2004) and one of a massive star-forming region (Kim et al. 2006) show that the N2H +/HCO+ ratio is high in early stages due to HCO+ depletion (because most of the CO is frozen out) and is low in later…”
• Cold Dark Clouds: The Initial Conditions for Star Formation (2007, background): “Moreover, the combination of chemical/dynamical models with radiative transfer (see Lee et al. 2004, as an example) offers the best opportunity to take these models to the next level and truly begin to test star formation theory.”
• Molecular Evolution and Star Formation: From Prestellar Cores to Protostellar Cores (2007, methodology): “First, the inside-out core model, which is adopted in Lee et al. (2004), yields lower temperatures than our core model, as discussed above.”
• Water in Star-forming Regions with the Herschel Space Observatory (WISH). I. Overview of Key Program and First Results (2010, unknown): “…as the cloud collapses and the luminosity 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 &…”
• Desorption rates and sticking coefficients for CO and N2 interstellar ices (2006, background): “This heating rate was chosen because it matches the timescale over which a newly-formed protostar increases the temperature in its surrounding envelope from<10 K to 20 K (Lee et al. 2004).”