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@astrojohannes astrojohannes released this 31 Mar 16:20
· 17 commits to master since this release
v1.2
cf13efe

Dense Gas Toolbox

Aim

Calculate density and temperature from observed molecular lines.

Method

Minimize observed line ratios against radiative transfer models. Our models assume that the molecular emission lines emerge from a multi-density medium rather than from a single density alone.

Results

Using an ascii table of observed molecular intensities [K km/s], the results (mass-weighted mean density, temperature and width of the density distribution) are saved in an output ascii file. Furthermore, diagnostic plots are created to assess the quality of the fit/derived parameters.

VERSION HISTORY

  • Mar 31, 2020 | Version 1.2 (major update):

    • New: An online version is now available at:

             http://www.densegastoolbox.com

    • New: The models can be explored using an interactive application at:

             http://www.densegastoolbox.com/explorer

    • Update: Model fit parameters are: density (mass-weighted), temperature and width
      of the distribution. The temperature and NOW ALSO WIDTH can be fixed.

    • Update: Re-calculation of models, now including the following transitions:
      12CO (up to J=3), 13CO (up to J=3), C18O (up to J=3), C17O (up to J=3),
      HCN (up to J=3), HCO+ (up to J=3) and HNC (up to J=3)

    • Update: The one-zone model grids are now more extended with H_2 densities
      between 10^-2 and 10^8 cm^-3.

    • Update: Diagnosis plots improved: (n,T) vs. chi2 and (n,width) vs. chi2

    • See "example.py" for how to use the Dense Gas Toolbox. It's easy!

    • Still needs Python 2.7 (will be upgraded to 3.X).

  • Feb 25, 2020 | Version 1.0:

    • http://doi.org/10.5281/zenodo.3686330

    • The initial release contains models for the following lines:
      12CO (1-0), 12CO (2-1), 12CO (3-2), 13CO (1-0), HCN (1-0), HNC (1-0) and
      HCO+ (1-0)

    • abundances and optical depths are fixed based on observations of the
      EMPIRE survey

    • Two density distributions (PDFs) are available: lognorm and lognorm+power law

    • Model fit parameters are: density (mass-weighted), temperature and width
      of the distribution. The temperature can be fixed.

    • Emissivities per density bin are calculated using RADEX, i.e. LVG method
      for an expanding sphere. These one-zone model grids are limited to H_2
      densities between 10 and 10^8 cm^-3.

    • The total line intensity is found from summation of the emissivities per H_2
      molecule along the gas density distribution (and multiplication with
      column per linewidth and abundance). For some models, at the very low and
      very high density ends, the extent of the PDF exceeds the one-zone density grid
      limits (10-10^8 cm^-3). In these regimes (where emissivities are very low anyway
      for the molecules under consideration), the emissivities are set constant to
      the grid limit value.

    • See "example.py" for how to use the Dense Gas Toolbox. It's easy!

    • Needs Python 2.7 (will be upgraded to 3.X).

    • Depends on the following Python packages:
      numpy, matplotlib, pylab, scipy

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