The Star Formation Laws of Eddington-Limited Star-Forming Disks
Abstract
Two important avenues into understanding the formation and evolution of galaxies are the Kennicutt-Schmidt (KS) and Elmegreen-Silk (ES) laws. These relations connect the surface densities of gas and star formation (σgas\ and σstar, respectively) in a galaxy. To elucidate the KS and ES laws for disks where σgas >~ 104 Msun pc-2, we compute 132 Eddington-limited star-forming disk models with radii spanning tens to hundreds of parsecs. The theoretically expected slopes (approx. 1 for the KS law and approx. 0.5 for the ES relation) are relatively robust to spatial averaging over the disks. However, the star formation laws exhibit a strong dependence on opacity that separates the models by the dust-to-gas ratio that may lead to the appearance of a erroneously large slope. The total infrared luminosity (LTIR) and multiple carbon monoxide (CO) line intensities were computed for each model. While LTIR can yield an estimate of the average σstar\ that is correct to within a factor of 2, the velocity-integrated CO line intensity is a poor proxy for the average σgas\ for these warm and dense disks, making the CO conversion factor (αCO) all but useless. Thus, observationally derived KS and ES laws at these values of σgas\ that uses any transition of CO will provide a poor measurement of the underlying star formation relation. Studies of the star formation laws of Eddington-limited disks will require a high-J transition of a high density molecular tracer, as well as a sample of galaxies with known metallicity estimates.
Turn this paper into a lesson
ArcXiv compiles a structured reading guide from this paper's metadata: plain-English importance, contributions, prerequisite concepts, which sections to read first, flashcards, and a quiz. Grounded in the abstract, never invented.