Light from the FIRE: CO, CII and H alpha Emission in Cosmological Simulations

In order to understand how close to the "ground truth" observational star formation relations are, I am forward modeling observables in the FIRE simulations. By predicting molecular gas and star formation rate tracers, we can get a handle on just how good a job we are doing with various observational conversion factors. This can be summed up with the questions: How much molecular gas is there actually? What fraction of all the gas is that? and, How much star formation is really occuring?

Do Galaxy Disks Breathe?

In the feedback-regulated model of star formation, the dissipation of supersonic turbulence (ostensibly the primary support of galaxy disks) balances the injection of stellar feedback momentum from ionizing radiation and supernovae. This is generally thought of in a "static equilibrium" sense. However, the injection of supernova feedback is inherently bursty, and lags relative to star formation itself. As a result, galaxy disks may be expected to "breathe" to some extent. How much do typical disk galaxies breathe?

What FIREs Up Star formation? Kennicutt-Schmidt on FIRE

Cosmological simulations have given us a unique ability to understand how scaling relations in star formation emerge on kpc scales in galaxies. We are investigated the Kennicutt-Schmidt relation in the FIRE simulations- specifically, looking at how and at what spatial and temporal scales the relation breaks down, and its dependencies on redshift, metallicity, and gas surface density and star formation rate tracers. As well, we inquired about what sets the extent of the star forming disks in our galaxies, finding that they were circumscribed by the limits of gravitational fragmentation in hot, ionized gas. See the paper here: Orr et al. 2018, MNRAS 478, 3, 3653-3673

Stacking is Hacking

High-redshift observations of galaxies are difficult, and have low signal-to-noise. As a result, observers often stack many spatially-resolved observations of similar galaxies to get a result. How does stacking affect inferred average star formation rate profiles? Turns out, quite a bit. High-redshift galaxies are very bursty in their star formation, and as a result stacking can bias our inferences of how those galaxies and their star formation rate profiles evolve. See the letter here: Orr et al. 2017, ApJ 849:L2