Strömgren Sphere

Joachim Köppen Kiel May 2016

This script computes the size and mass of an HII region that a star with given temperature and radius produces in an uniform medium of given density and (electron) temperature, by ionizing the surrounding gas with its hydrogen-ionizing photons (i.e. with energies above 13.6 eV). In the ionization bounded case the medium extends as far as to absorb all the photons produced by the star.

In the density bounded mode, one specifies the number of ionizing photons. Hence one can indirectly determine how many photons are necessary to ionize the medium to some radius, or its mass. This number is equal to the number of recombinations in the HII region.

Light green fields contain the necessary input parameters. Hit the Enter key to recompute with the new values.

Electron density [1/cm³]
Electron temperature [K]
Stellar temperature [K]
Stellar radius [Rsun]
Stellar luminosity [Lsun]
Ionizing photons/sec

Radius [pc]
Mass [Msun]

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