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S. Stanimirovic (Arecibo Observatory, NAIC/Cornell University)
Many observations in the past decade have challenged the traditional picture of the interstellar medium (ISM). Instead of a two-level hierarchical system, consisting of clouds uniformly dispersed in the intercloud medium, the ISM shows an astonishing inhomogeneity, with many levels of hierarchy. In order to consider real density functions in physical processes, a better understanding of the inventory and topology of the ISM is essential, as well as the processes responsible for their creation. Having an extremely gas-rich ISM, dwarf irregular galaxies are particularly suitable for such studies.
We hence here describe quantitatively, using the spatial power spectrum, the inventory of the ISM in the Small Magellanic Cloud (SMC) and point to several processes that may be involved in the sculpturing of its ISM. We find that the spatial power spectrum of HI and dust content in the SMC is extremely well fitted by a power law, with power law slopes being similar. This means that the hierarchical structure organization of the HI and dust content is present, with similar processes being involved. The HI spectrum appears to be modified by velocity fluctuations. After disentangling velocity from density fluctuations, the 3-D HI density spectrum has slope of -3.3. This is significantly shallower than for Kolmogorov turbulence.