On the Observed Diversity of Star Formation Efficiencies in Giant Molecular Clouds
Monthly Notices of the Royal Astronomical Society Oxford University Press (OUP) 468:4 (2019) 5482-5491
Abstract:
Observations find a median star formation efficiency per free-fall time in Milky Way Giant Molecular Clouds (GMCs) on the order of $\epsilon_{\rm ff}\sim 1\%$ with dispersions of $\sim0.5\,{\rm dex}$. The origin of this scatter in $\epsilon_{\rm ff}$ is still debated and difficult to reproduce with analytical models. We track the formation, evolution and destruction of GMCs in a hydrodynamical simulation of a Milky Way-like galaxy and by deriving cloud properties in an observationally motivated way, measure the distribution of star formation efficiencies which are in excellent agreement with observations. We find no significant link between $\epsilon_{\rm ff}$ and any measured global property of GMCs (e.g. gas mass, velocity dispersion). Instead, a wide range of efficiencies exist in the entire parameter space. From the cloud evolutionary tracks, we find that each cloud follow a \emph{unique} evolutionary path which gives rise to wide diversity in all properties. We argue that it is this diversity in cloud properties, above all else, that results in the dispersion of $\epsilon_{\rm ff}$.Physical properties and scaling relations of molecular clouds: the effect of stellar feedback
Monthly Notices of the Royal Astronomical Society (2018)
The impact of stellar feedback on the density and velocity structure of the interstellar medium
Monthly Notices of the Royal Astronomical Society 466:1 (2017) 1093-1110
Abstract:
© 2016 The Authors. We study the impact of stellar feedback in shaping the density and velocity structure of neutral hydrogen (H I) in disc galaxies. For our analysis, we carry out ~4.6 pc resolution N-body+adaptive mesh refinement hydrodynamic simulations of isolated galaxies, set up to mimic a Milky Way and a Large and Small Magellanic Cloud. We quantify the density and velocity structure of the interstellar medium using power spectra and compare the simulated galaxies to observedHI in local spiral galaxies from THINGS (TheHI Nearby Galaxy Survey). Our models with stellar feedback give an excellent match to the observed THINGS HI density power spectra. We find that kinetic energy power spectra in feedback-regulated galaxies, regardless of galaxy mass and size, show scalings in excellent agreement with supersonic turbulence (E(k) ∝ k -2 ) on scales below the thickness of the HI layer. We show that feedback influences the gas density field, and drives gas turbulence, up to large (kpc) scales. This is in stark contrast to density fields generated by large-scale gravity-only driven turbulence. We conclude that the neutral gas content of galaxies carries signatures of stellar feedback on all scales.Characterizing gravitational instability in turbulent multicomponent galactic discs
Monthly Notices of the Royal Astronomical Society Oxford University Press (OUP) 449:2 (2015) 2156-2166