THE SCALING RELATIONS AND STAR FORMATION LAWS OF MINI-STARBURST COMPLEXES

The scaling relations and star formation laws for molecular cloud complexes (MCCs) in the Milky Way are investigated. MCCs are mostly large (R> 50 pc), massive (similar to 106 M circle dot) gravitationally unbound cloud structures. We compare their masses M-gas, mass surface densities Sigma(Mgas), radii R, velocity dispersions sigma, star formation rates (SFRs), and SFR densities Sigma(SFR) with those of structures ranging from cores, clumps, and giant molecular clouds, to MCCs, and galaxies, spanning eight orders of magnitudes in size and 13 orders of magnitudes in mass. This results in the following universal relations: sigma similar to R-0.5, M-gas similar to R-2, Sigma(SFR) similar to Sigma(1.5)(Mgas) , SFR similar to M-gas(0.9) , and SFR similar to sigma(2.7) Variations in the slopes and coefficients of these relations are found at individual scales, signifying different physics acting at different scales. Additionally, there are breaks at the MCC scale in the sigma-R relation and between starburst and normal star-forming objects in the SFR-M-gas and Sigma(SFR)-Sigma(Mgas) gas relations. Therefore, we propose to use the Schmidt-Kennicutt diagram to distinguish starburst from normal star-forming structures by applying a SMgas threshold of similar to 100M circle dot pc (2) and a Sigma(SFR) threshold of 1M circle dot yr (1) kpc (2). Mini-starburst complexes are gravitationally unbound MCCs that have enhanced Sigma(SFR) (> 1M circle dot yr(-1) kpc(-2)), probably caused by dynamic events such as radiation pressure, colliding flows, or spiral arm gravitational instability. Because of dynamical evolution, gravitational boundedness does not play a significant role in regulating the star formation activity of MCCs, especially the mini-starburst complexes, which leads to the dynamical formation of massive stars and clusters. We emphasize the importance of understanding mini-starbursts in investigating the physics of starburst galaxies.