REGULATION OF STAR FORMATION RATES IN MULTIPHASE GALACTIC DISKS: A THERMAL/DYNAMICAL EQUILIBRIUM MODEL

By E. Ostriker, C. McKee, A. Leroy. 2010

243 citations recorded by the source corpus.

We develop a model for the regulation of galactic star formation rates ΣSFR in disk galaxies, in which interstellar medium (ISM) heating by stellar UV plays a key role. By requiring that thermal and (vertical) dynamical equilibrium are simultaneously satisfied within the diffuse gas, and that stars form at a rate proportional to the mass of the self-gravitating component, we obtain a prediction for ΣSFR as a function of the total gaseous surface density Σ and the midplane density of stars+dark matter ρsd. The physical basis of this relationship is that the thermal pressure in the diffuse ISM, which is proportional to the UV heating rate and therefore to ΣSFR, must adjust until it matches the midplane pressure value set by the vertical gravitational field. Our model applies to regions where Σ ≲ 100 M☉  pc−2. In low-ΣSFR (outer-galaxy) regions where diffuse gas dominates, the theory predicts that . The decrease of thermal equilibrium pressure when ΣSFR is low implies, consistent with observations, that star formation can extend (with declining efficiency) to large radii in galaxies, rather than having a sharp cutoff at a fixed value of Σ. The main parameters entering our model are the ratio of thermal pressure to total pressure in the diffuse ISM, the fraction of diffuse gas that is in the warm phase, and the star formation timescale in self-gravitating clouds; all of these are (at least in principle) direct observables. At low surface density, our model depends on the ratio of the mean midplane FUV intensity (or thermal pressure in the diffuse gas) to the star formation rate, which we set based on solar-neighborhood values. We compare our results to recent observations, showing good agreement overall for azimuthally averaged data in a set of spiral galaxies. For the large flocculent spiral galaxies NGC 7331 and NGC 5055, the correspondence between theory and observation is remarkably close.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/b11a3b56c5e3902018c8cf5f8f92cf59723c8493

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In Astronomy and Astrophysics

1. P. Hopkins
2. L. Hernquist
3. R. Somerville
4. Mark R. Krumholz
5. R. Dav'e
6. T. Naab
7. E. Quataert
8. D. Narayanan

Citations in the corpus

• THE STATE OF THE GAS AND THE RELATION BETWEEN GAS AND STAR FORMATION AT LOW METALLICITY: THE SMALL MAGELLANIC CLOUD (2011, background): “In the following sections we will focus on two recent theoretical models for the dependence of star formation and phase balance on local gas content and other galactic properties, those of Krumholz et al. (2009c), henceforth KMT09, and Ostriker et al. (2010), henceforth OML10.”
• The energy and momentum input of supernova explosions in structured and ionized molecular clouds (2014, background): “They can be an important regulator of the galactic star formation rate (Ostriker et al. 2010; Shetty & Ostriker 2012; Hopkins et al. 2 2012), eventually powering large scale galactic winds (Larson 1974; Veilleux et al. 2005; Joung & Mac Low 2006; Dubois & Teyssier 2008; Creasey et al. 2013), which…”
• MOMENTUM INJECTION BY SUPERNOVAE IN THE INTERSTELLAR MEDIUM (2014, background): “Among the successes of these models are reaching realistic turbulence levels in the diffuse ISM, and achieving states of self-regulated star formation with rates that are consistent with observations (see also Ostriker et al. 2010; Ostriker & Shetty 2011).”
• Star formation in semi-analytic galaxy formation models with multiphase gas (2015, background): “A somewhat different view has been presented by Ostriker et al. (2010), who propose that heating of the Interstellar Medium (ISM) by the stellar UV background plays a key role in regulating star formation.”
• How Stellar Feedback Simultaneously Regulates Star Formation and Drives Outflows (2015, methodology): “Various previous works have presented such models (e.g.Murray et al. 2005, 2011; Thompson et al. 2005; Ostriker et al. 2010; Ostriker & Shetty 2011; Shetty & Ostriker 2012; Faucher-Giguère et al. 2013).”
• Three-phase Interstellar Medium in Galaxies Resolving Evolution with Star Formation and Supernova Feedback (TIGRESS): Algorithms, Fiducial Model, and Convergence (2016, background): “Here, Ptwo is characteristic of the midplane thermal pressure in the warm/cold atomic ISM when star formation is in a self-regulated state (Ostriker et al. 2010; Kim et al. 2011, 2013).”
• THE ARECIBO LEGACY FAST ALFA SURVEY: THE GALAXY POPULATION DETECTED BY ALFALFA (2012, background): “Meanwhile, the low stellar surface density found in gas-rich systems results in a weaker gravitational field, and, by extension, a lower mid plane gas pressure and a higher fraction of diffuse HI gas (Ostriker et al. 2010).”
• Cloud-scale Molecular Gas Properties in 15 Nearby Galaxies (2018, background): “Moreover, the ambient pressure is expected to vary as a function of location in the galaxy in response to the distribution of gas and the potential of the galaxy (e.g., Elmegreen 1989; Wolfire et al. 2003; Ostriker et al. 2010; Herrera-Camus et al. 2017; Meidt et al. 2018).”
• The CO-H2 Conversion Factor in Disc Galaxies and Mergers (2011, background): “Beyond this, more sophisticatedphysical models may provide reasonable prescriptions for star formation in galaxy evolution models (e.g. Tan 2000; Krumholz et al. 2009b; Ostriker et al. 2010).”
• MOLECULAR GAS AND STAR FORMATION IN NEARBY DISK GALAXIES (2013, background): “They advocated a scenario for star formation in disk galaxies in which star formation in isolated giant molecular clouds is a fairly universal process while the formation of these clouds out of the atomic gas reservoir depends sensitively on environment (see also, Wong 2009; Ostriker et al. 2010).”