@article{Connection:1954,
      recid = {1954},
      author = {Semenov, Vadim},
      title = {How Galaxies Form Stars: The Connection between Local and  Global Star Formation in Galaxies},
      publisher = {University of Chicago},
      school = {Ph.D.},
      address = {2019-08},
      pages = {193},
      abstract = {The fact that observed star-forming galaxies convert their  gas into stars inefficiently posits a long-standing  theoretical puzzle. Available gas in galaxies is depleted  on a timescale of several Gyrs which is orders of magnitude  longer than any timescale of the processes driving gas  evolution in galaxies. Many galaxy simulations can  reproduce observed long depletion times but the physical  mechanism controlling their values is not well understood.  In addition, some of the simulations show a rather  counter-intuitive behavior: global depletion times appear  to be almost insensitive to the assumptions about local  star formation in individual star-forming regions, a  phenomenon described as "self-regulation." Yet another part  of the puzzle is the observed tight and near-linear  correlation between star formation rates and the amount of  molecular gas on kiloparsec and larger scales. A linear  correlation implies that the depletion time of molecular  gas is almost independent of molecular gas density on  >kiloparsec scales, while a strong dependence is expected  if, e.g., star formation is controlled by molecular gas  self-gravity. We present an intuitive physical model that  explains the origin of long gas depletion times in galaxies  and the near-linear correlation between star formation  rates and molecular gas. Our model is based on mass  conservation of gas as the gas cycles between dense  star-forming and diffuse states in the interstellar medium.  We use simulations of an isolated L* galaxy to illustrate  our model and to explore the connection between global  depletion times and the timescales of processes driving gas  evolution on small scales. In particular, we show that our  model can explain the physics of self-regulation of star  formation in galaxies with efficient stellar feedback. We  also show that a linear correlation between star formation  rate and molecular gas emerges when feedback efficiently  regulates and stirs the evolution of dense, molecular gas.  Our model also provides insights into the likely origin of  this relation in real galaxies on different scales.},
      url = {http://knowledge.uchicago.edu/record/1954},
      doi = {https://doi.org/10.6082/uchicago.1954},
}