MAXIMALLY STAR-FORMING GALACTIC DISKS. I. STARBURST REGULATION VIA FEEDBACK-DRIVEN TURBULENCE

By E. Ostriker, R. Shetty. 2011

209 citations recorded by the source corpus.

Star formation rates in the centers of disk galaxies often vastly exceed those at larger radii, whether measured by the surface density of star formation ΣSFR, by the star formation rate per unit gas mass, ΣSFR/Σ, or even by total output. In this paper, we investigate the idea that central starbursts are self-regulated systems in which the momentum flux injected to the interstellar medium (ISM) by star formation balances the gravitational force confining the ISM gas in the disk. For most starbursts, supernovae are the largest contributor to the momentum flux, and turbulence provides the main pressure support for the predominantly molecular ISM. If the momentum feedback per stellar mass formed is p*/m* ∼ 3000 km s−1, the predicted star formation rate is ΣSFR ∼ 2πGΣ2m*/p* ∼ 0.1 M☉ kpc−2 yr−1(Σ/100 M☉  pc−2)2 in regions where gas dominates the vertical gravity. We compare this prediction with numerical simulations of vertically resolved disks that model star formation including feedback, finding good agreement for gas surface densities in the range Σ ∼ 102–103 M☉  pc−2. We also compare to a compilation of star formation rates and gas contents from local and high-redshift galaxies (both mergers and normal galaxies), finding good agreement provided that the conversion factor XCO from integrated CO emission to H2 surface density decreases modestly as Σ and ΣSFR increase. Star formation rates in dense, turbulent gas are also expected to depend on the gravitational free-fall time at the corresponding mean ISM density ρ0; if the star formation efficiency per free-fall time is  εff(ρ0) ∼ 0.01, the turbulent velocity dispersion driven by feedback is expected to be vz = 0.4 εff(ρ0)p*/m* ∼ 10 km s−1, relatively independent of Σ or ΣSFR. Turbulence-regulated starbursts (controlled by kinetic momentum feedback) are part of the larger scheme of self-regulation; primarily atomic low-Σ outer disks may have star formation regulated by ultraviolet heating feedback, whereas regions at extremely high Σ may be regulated by feedback of stellar radiation that is reprocessed into trapped infrared.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/8eec58b6c6348be22fb9dd830ee873820bc7d089

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In Astronomy and Astrophysics

1. P. Hopkins
2. L. Hernquist
3. E. Quataert
4. T. Naab
5. R. Dav'e
6. R. Somerville
7. C. Faucher-Giguére
8. A. Dekel

Citations in the corpus

• COMBINED CO AND DUST SCALING RELATIONS OF DEPLETION TIME AND MOLECULAR GAS FRACTIONS WITH COSMIC TIME, SPECIFIC STAR-FORMATION RATE, AND STELLAR MASS (2014, unknown): “However, this approach has since come under criticism (e.g. Ostriker & Shetty 2011, Kennicutt & Evans 2012, Krumholz, Dekel & McKee 2012) on the grounds that the resulting smaller depletion time scales then immediately introduce a bi-modal, and thus probably unphysical gas-star formation relation.”
• A general model for the CO–H2 conversion factor in galaxies with applications to the star formation law (2011, methodology): “…regions where supernova-driven turbulence controls the SFR and gas dominates the vertical gravity, the SFR surface density should be proportional to the gas surface density squared: log( SFR) = 2 × log( mol) − 5.0 [adopting fiducial parameters in equation (13) of Ostriker & Shetty (2011)].”
• SHORT-LIVED STAR-FORMING GIANT CLUMPS IN COSMOLOGICAL SIMULATIONS OF z ≈ 2 DISKS (2010, background): “Ostriker & Shetty (2011), however, estimate the specific momentum available from supernovae to be≈ 3000 kms−1.”
• Cool Gas in High-Redshift Galaxies (2013, background): “…a function of local ISM conditions, including pressure, gas dynamics, and metallicity, and remains an active area of research for nearby galaxies (Ostriker & Shetty 2011; Narayanan et al. 2012; Narayanan & Hopkin 2012; Papadopoulos et al. 2012, Leroy et al. 2013, Schruba et al. 2012, Sandstrom…”
• Supernova feedback in an inhomogeneous interstellar medium (2014, methodology): “…of individual SNRs, we also present initial results on the effects of multiple SNRs interacting selfconsistently in a periodic box (for previous work in this direction, see Joung et al. 2009; Kim, Kim & Ostriker 2011; Ostriker & Shetty 2011; Creasey, Theuns & Bower 2013; Hennebelle & Iffrig 2014).”
• How Stellar Feedback Simultaneously Regulates Star Formation and Drives Outflows (2015, methodology): “…virtually all previous models for how momentum deposition drives turbulence (e.g.Krumholz & McKee 2005; Krumholz et al. 2009b; Murray et al. 2010; Ostriker & Shetty 2011; FQH13) and generates outflows (e.g.Murray et al. 2005, 2011; Thompson et al. 2005) have considered only the mean gas surface…”
• Star Formation in the Milky Way and Nearby Galaxies (2012, background): “Recent work by Ostriker et al. (2010) and Ostriker & Shetty (2011) provides a theoretical explanation for these relations.”
• The physics of galactic winds driven by active galactic nuclei (2012, background): “Such momentum boosts have a large effect on the efficiency of stellar feedback in galaxies (e.g., Ostriker & Shetty 2011; Hopkins et al. 2012).”
• Dusty Star Forming Galaxies at High Redshift (2014, methodology): “After applying their models for a continuously varying CO–H2 conversion factor, both Ostriker and Shetty (2011) and Narayanan et al. (2012b) found that the bimodal KS relation reduces to a tight, unimodal relation, with index roughly 2.”
• A UNIVERSAL, LOCAL STAR FORMATION LAW IN GALACTIC CLOUDS, NEARBY GALAXIES, HIGH-REDSHIFT DISKS, AND STARBURSTS (2011, unknown): “…starburst galaxies typically have SFR surface densities that are a factor of ∼ 10 higher than disk galaxies at equal gas surface density (however, as Ostriker & Shetty 2011 and Narayanan et al. 2011a point out, the disk starburst distinction is significantly enhanced by the use of single,…”
• The CO-H2 Conversion Factor in Disc Galaxies and Mergers (2011, background): “Both observation l (Bigiel et al. 2008) and theoretical (Krumholz et al. 2009b;Ostriker & Shetty 2011) evidence suggest that a KS index> 1 may describe high-surface density systems.”
• PHYSICAL PROPERTIES OF MOLECULAR CLOUDS FOR THE ENTIRE MILKY WAY DISK (2016, background): “Estimates for the first three forms of feedback give v∗ ≈ 300 km s−1, while supernovae provide v∗ ≈ 3000 km s−1 (e.g., Ostriker & Shetty 2011).”
• FIRE-2 simulations: physics versus numerics in galaxy formation (2017, result): “Recently, similar implementations to ours have also found consistent results on large scales (Semenov et al. 2016; Agertz & Kravtsov 2016), consistent with analytic expectations (Ostriker & Shetty 2011; Faucher-Giguère et al. 2013).”
• Ionized gas outflows and global kinematics of low-z luminous star-forming galaxies (2014, methodology): “…massive star formation and/or feeding of central black holes would expel the surrounding interstellar medium as a consequence of the mechanical and radiative energy liberated, generating strong outflows (di Matteo et al. 2005;Hopkins et al. 2012; Murray et al. 2011; Ostriker & Shetty 2011).”
• MOMENTUM INJECTION BY SUPERNOVAE IN THE INTERSTELLAR MEDIUM (2014, background): “The momentum, which is transferred to the warm and cold gas, determines the amplitude of turbulence in the volume-filling ISM, and also enters inversely in determining the large-scale star formation rate (e.g., Kim et al. 2011; Ostriker & Shetty 2011).”
• The difficulty of getting high escape fractions of ionizing photons from high-redshift galaxies: A view from the FIRE cosmological simulations (2015, background): “This is because the galaxyaveraged star formation efficiency is regulated by stellar feedback (1–2% per dynamical time, e.g. Hopkins et al. 2011; Ostriker & Shetty 2011; Agertz et al. 2013; Faucher-Giguère et al. 2013), not the SF criteria (Hopkins et al. 2013).”
• Gusty, gaseous flows of FIRE: Galactic winds in cosmological simulations with explicit stellar feedback (2015, background): “Feedback from star formation contributes to the stability of this disc by stirring turbulence (Thompson, Quataert & Murray 2005; Ostriker & Shetty 2011; Faucher-Giguère, Quataert & Hopkins 2013; Hopkins, Kereš & Murray 2013).”