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PDFchem: A new fast method to determine ISM properties and infer environmental parameters using probability distributions
PDFchem: A new fast method to determine ISM properties and infer environmental parameters using probability distributions by Thomas G. Bisbas et al. on Friday 25 November
Determining the atomic and molecular content of the interstellar medium (ISM)
as a function of environmental parameters is of fundamental importance to
understand the star-formation process across the epochs. Although there exist
various three-dimensional hydro-chemical codes modelling the ISM at different
scales and redshifts, they are computationally expensive and inefficient for
studies over a large parameter space. Building on our earlier approach, we
present PDFchem, a novel algorithm that models the cold ISM at moderate and
large scales using functions connecting the quantities of the local ($A_{\rm
V,eff}$) and the observed ($A_{\rm V,obs}$) visual extinctions, and the local
number density, $n_{\rm H}$, with probability density functions (PDF) of
$A_{\rm V,obs}$ on cloud scales typically tens-to-hundreds of pc as an input.
For any given $A_{\rm V,obs}$-PDF, sampled with thousands of clouds, the
algorithm instantly computes the average abundances of the most important
species (HI, H$_2$, CII, CI, CO, OH, OH$^+$, H$_2$O$^+$, CH, HCO$^+$) and
performs radiative transfer calculations to estimate the average emission of
the most commonly observed lines ([CII]~$158\mu$m, both [CI] fine-structure
lines and the first five rotational transitions of $^{12}$CO). We examine two
$A_{\rm V,obs}$-PDFs corresponding to a non star-forming and a star-forming ISM
region, under a variety of environmental parameters combinations. These cover
FUV intensities in the range of $\chi/\chi_0=10^{-1}-10^3$, cosmic-ray
ionization rates in the range of $\zeta_{\rm CR}=10^{-17}-10^{-13}\,{\rm
s}^{-1}$ and metallicities in the range of $Z=0.1-2\,{\rm Z}_{\odot}$. PDFchem
is fast, easy to use, reproduces the PDR quantities of the time-consuming
hydrodynamical models and can be used directly with observed data to understand
the evolution of the cold ISM chemistry.
arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2211.12974v1
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By Corentin CadiouPDFchem: A new fast method to determine ISM properties and infer environmental parameters using probability distributions by Thomas G. Bisbas et al. on Friday 25 November
Determining the atomic and molecular content of the interstellar medium (ISM)
as a function of environmental parameters is of fundamental importance to
understand the star-formation process across the epochs. Although there exist
various three-dimensional hydro-chemical codes modelling the ISM at different
scales and redshifts, they are computationally expensive and inefficient for
studies over a large parameter space. Building on our earlier approach, we
present PDFchem, a novel algorithm that models the cold ISM at moderate and
large scales using functions connecting the quantities of the local ($A_{\rm
V,eff}$) and the observed ($A_{\rm V,obs}$) visual extinctions, and the local
number density, $n_{\rm H}$, with probability density functions (PDF) of
$A_{\rm V,obs}$ on cloud scales typically tens-to-hundreds of pc as an input.
For any given $A_{\rm V,obs}$-PDF, sampled with thousands of clouds, the
algorithm instantly computes the average abundances of the most important
species (HI, H$_2$, CII, CI, CO, OH, OH$^+$, H$_2$O$^+$, CH, HCO$^+$) and
performs radiative transfer calculations to estimate the average emission of
the most commonly observed lines ([CII]~$158\mu$m, both [CI] fine-structure
lines and the first five rotational transitions of $^{12}$CO). We examine two
$A_{\rm V,obs}$-PDFs corresponding to a non star-forming and a star-forming ISM
region, under a variety of environmental parameters combinations. These cover
FUV intensities in the range of $\chi/\chi_0=10^{-1}-10^3$, cosmic-ray
ionization rates in the range of $\zeta_{\rm CR}=10^{-17}-10^{-13}\,{\rm
s}^{-1}$ and metallicities in the range of $Z=0.1-2\,{\rm Z}_{\odot}$. PDFchem
is fast, easy to use, reproduces the PDR quantities of the time-consuming
hydrodynamical models and can be used directly with observed data to understand
the evolution of the cold ISM chemistry.
arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2211.12974v1