# Chemistry as a diagnostic of prestellar core geometry

Source: [Chemistry as a diagnostic of prestellar core geometry](<https://www.sota2.com/research/paper/68fa33021e209131ce88c9a5>)

Collection index: [llms.txt](<https://www.sota2.com/research/llms.txt>)

Data updated: 2025-10-24T19:49:26.893Z

Authors: A. Tritsis, K. Tassis, K. Willacy

Published: 2016-02-09T21:00:04.000Z

## Abstract

We present a new method for assessing the intrinsic 3D shape of prestellar cores from molecular column densities. We have employed hydrodynamic simulations of contracting, isothermal cores considering three intrinsic geometries: spherical, cylindrical/filamentary and disk-like. We have coupled our hydrodynamic simulations with non-equilibrium chemistry. We find that a) when cores are observed very elongated (i.e. for aspect ratios $\\le$ 0.15) the intrinsic 3D geometry can be probed by their 2D molecular emission maps, since these exhibit significant qualitative morphological differences between cylindrical and disk-like cores. Specifically, if a disk-like core is observed as a filamentary object in dust emission, then it will be observed as two parallel filaments in $\\rm{N\_2H^{+}}$; b) for cores with higher aspect ratios (i.e. 0.15 $\\sim$ 0.9) we define a metric $\\Delta$ that quantifies whether a molecular column density profile is centrally peaked, depressed or flat. We have identified one molecule ($\\rm{CN}$) for which $\\Delta$ as a function of the aspect ratio probes the 3D geometry of the core; and c) for cores with almost circular projections (i.e. for aspect ratios $\\sim$ 1), we have identified three molecules ($\\rm{OH}$, $\\rm{CO}$ and $\\rm{H\_2CO}$) that can be used to probe the intrinsic 3D shape by close inspection of their molecular column density radial profiles. We alter the temperature and the cosmic-ray ionization rate and demonstrate that our method is robust against the choice of parameters.

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## Original sources and implementation

[Original paper](<https://arxiv.org/abs/1602.03187>)

[PDF](<https://arxiv.org/pdf/1602.03187.pdf>)