SimLine

SimLine is a FORTRAN code for computing molecular transition line profiles in spherically symmetric clouds with arbitrary density, temperature and velocity structure. Turbulence and clumping are treated in a local statistical approximation with a radial dependence of the correlation parameters.

The code solves two coupled problems:

1. Self-consistent level populations via accelerated lambda iteration
2. Emergent line profiles convolved with a finite Gaussian telescope beam

All numerical grids are fully adaptive; the user has direct control over all accuracy thresholds. Optical depths at line centre may range from approximately −5 (moderate masering) to +5000.

Features

• Spherically symmetric radiative transfer in an arbitrary number of molecular transitions
• Adaptive radial, frequency and displacement grids
• Accelerated lambda iteration for fast convergence
• Local statistical treatment of turbulence and clumping (effective absorption coefficients)
• Optional central H II region (free-free continuum source)
• Sobolev approximation available as initial guess
• FITS and ASCII output formats
• Reads molecular data in native format or LAMDA/RADEX format
• Interactive or fully file-driven operation

Building

The code requires the cfitsio library.

cd src
make linux        # default Linux build (gfortran)
make mclarge      # large memory model for molecules with >100 levels
make debug        # debug build with runtime checks

Other targets: aix, osf, hp-ux, absoft, sun-os. Always run make clean before switching targets.

Quick start

cd src
make linux
./simline

The program runs interactively by default. Pass -fileinput to read all parameters from files, and -numdefaults to skip numerical parameter prompts. Example input files are in examples/.

Documentation

Document	Description
Introduction	Overview of the code
Installation	System requirements and compilation
Usage	Command-line options, input parameters, file formats, error messages
Theory	Radiative transfer equations, turbulence model, Sobolev approximation
Implementation	Source code structure and routine descriptions
Limitations	Known limitations and caveats
Future plans	Planned features
References	Literature references and acknowledgements
Changelog	Version history

The original LaTeX manual is preserved as docs/simline.tex (and compiled PDF docs/simline.pdf).

Repository layout

simline/
├── README.md
├── docs/               # Documentation
├── src/                # FORTRAN source code and Makefile
│   ├── ltr.f           # Main program and core routines
│   ├── ltrio.f         # I/O routines
│   ├── initial.f       # Grid initialization and adjustment
│   ├── stpdiff.f       # Radiative transfer (all lines)
│   ├── stpline.f       # Radiative transfer (single line)
│   ├── matrix.f        # Balance equations and lambda iteration
│   ├── sobolev.f       # Sobolev approximation
│   ├── einstein.f      # Molecular constants
│   ├── collrate.f      # Collision rate input
│   ├── ltrinteg.f      # Intensity integration routines
│   ├── fitsadd.f       # FITS I/O helpers
│   ├── cline.f         # Auxiliary: extract zero-offset line profile
│   ├── trapfpe.c       # Optional: floating-point exception trap (Linux/glibc, debug use)
│   ├── fsizes_normal.inc
│   └── fsizes_large.inc
├── analyze/
│   └── testcloud.f     # Auxiliary: analyse level population files
├── special_cases/      # Special-case reference programs
└── examples/           # Example input files

Author

Dr. V. Ossenkopf-Okada
I. Physikalisches Institut, Universität zu Köln
ossk@ph1.uni-koeln.de

License

SimLine is released under the GNU General Public License v3.0 (GPL-3.0-or-later).

Copyright © Dr. V. Ossenkopf-Okada, I. Physikalisches Institut, Universität zu Köln.