The probability distribution functions (PDF) of density of the interstellar medium (ISM) in galactic disks and global star formation rate (SFR) are discussed. 3-D hydrodynamic simulations show that the PDFs in globally stable, inhomogeneous ISM in galactic disks are well fitted by a single log-normal function over a wide density range. The dispersion of the log-normal PDF (LN-PDF) is larger for more gas-rich systems, whereas the characteristic density of LN-PDF, for which the volume fraction becomes the maximum, is not sensitive for the gas mass. Using the LN-PDF, we give a generalized version of Schmidt-Kennicutt law, i.e. SFR as a function of average gas density, a critical local density for star formation, and star formation efficiency. We find that the observed SFR in normal and starburst galaxies are well-fitted by the theoretical SFR in a wide range of the global gas density (10 –104 M⊙pc–2). Star formation efficiency (SFE) for high density gas (n>103 cm–3) may be intrinsically different between starburst and normal galaxies.
Keywords
- Probability Distribution Function
- Star Formation
- Star Formation Rate
- Galactic Disk
- Characteristic Density
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Wada, K., Norman, C.A. (2008). Numerical Modeling of the ISM in the Galactic Center and Disks. In: Wada, K., Combes, F. (eds) Mapping the Galaxy and Nearby Galaxies. Astrophysics and Space Science Proceedings. Springer, New York, NY. https://doi.org/10.1007/978-0-387-72768-4_11
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DOI: https://doi.org/10.1007/978-0-387-72768-4_11
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