Star formation in galaxy mergers with realistic models of stellar feedback and the interstellar medium

By P. Hopkins, Thomas J. Cox, L. Hernquist, D. Narayanan, C. Hayward, N. Murray. 2012

212 citations recorded by the source corpus.

We use simulations with realistic models for stellar feedback to study galaxy mergers. These high resolution (1 pc) simulations follow formation and destruction of individual GMCs and star clusters. The final starburst is dominated by in situ star formation, fueled by gas which flows inwards due to global torques. The resulting high gas density results in rapid star formation. The gas is self gravitating, and forms massive (~10^10 M_sun) GMCs and subsequent super-starclusters (masses up to 10^8 M_sun). However, in contrast to some recent simulations, the bulk of new stars which eventually form the central bulge are not born in superclusters which then sink to the center of the galaxy, because feedback efficiently disperses GMCs after they turn several percent of their mass into stars. Most of the mass that reaches the nucleus does so in the form of gas. The Kennicutt-Schmidt law emerges naturally as a consequence of feedback balancing gravitational collapse, independent of the small-scale star formation microphysics. The same mechanisms that drive this relation in isolated galaxies, in particular radiation pressure from IR photons, extend over seven decades in SFR to regulate star formation in the most extreme starbursts (densities >10^4 M_sun/pc^2). Feedback also drives super-winds with large mass loss rates; but a significant fraction of the wind material falls back onto the disks at later times, leading to higher post-starburst SFRs in the presence of stellar feedback. Strong AGN feedback is required to explain sharp cutoffs in star formation rate. We compare the predicted relic structure, mass profile, morphology, and efficiency of disk survival to simulations which do not explicitly resolve GMCs or feedback. Global galaxy properties are similar, but sub-galactic properties and star formation rates can differ significantly.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/ae21dd029d06835a0c191c5c0e9d78508a0a43ab

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Citations in the corpus

A model for cosmological simulations of galaxy formation physics: multi-epoch validation (2013, background): “…for such an approach are significantly beyond what is currently feasible in large-scale cosmological simulations, hence this is applicable only in “zoom-in” simulations of individual galaxies of low to moderate mass or in idealised simulations of isolated galaxies (Hopkins et al. 2012a, 2013a,b).”
Bulge mass is king: the dominant role of the bulge in determining the fraction of passive galaxies in the Sloan Digital Sky Survey (2014, background): “Even if the disks reform (as argued for in Hopkins et al. 2013), these reformed disk would be actively forming stars, not passive as seen in many cases in this paper.”
Galaxies on FIRE (Feedback In Realistic Environments): stellar feedback explains cosmologically inefficient star formation (2013, methodology): “…only for particles with density above n > ncrit (generally ncrit = 100cm−3), which are also locally self-gravitating using the criteria developed in Hopkins et al. (2013d) (α ≡ δv2 δr/Gmgas(< δr) ≈ β (|∇ × v|2 + |∇·v|2)/Gρ < 1, with β ≈ 0.25), and which have a non-zero molecular fraction fmol > 0.”
THE SYSTEMATIC PROPERTIES OF THE WARM PHASE OF STARBURST-DRIVEN GALACTIC WINDS (2015, background): “…et al. 2015; Henriques et al. 2015; Mitra et al. 2015), high-resolution simulations of individual galaxies that are able to calculate ab initio more of the relevant physical processes are clearly needed (e.g. Cooper et al. 2008, 2009; Shen et al. 2013; Hopkins et al. 2013; Muratov et al. 2015).”
THE SCUBA-2 COSMOLOGY LEGACY SURVEY: ALMA RESOLVES THE REST-FRAME FAR-INFRARED EMISSION OF SUB-MILLIMETER GALAXIES (2014, background): “Hopkins et al. (2013) show that the major merger triggers an intense central starburst, with 50% of the star formation activity concentrated within a diameter of ∼ 2 kpc.”
Neutral hydrogen in galaxy haloes at the peak of the cosmic star formation history (2014, background): “…the structure of the ISM and the properties of giant molecular clouds (GMCs; Hopkins et al. 2012c), galactic winds driven by stellar feedback (Hopkins et al. 2012b), gas inflow in gas rich disks (Hopkins et al. 2012a) and during galaxy mergers (Hopkins et al. 2013a), and a range of other problems.”
Kiloparsec-scale outflows are prevalent among luminous AGN: outflows and feedback in the context of the overall AGN population (2014, background): “…Vecchia & Schaye 2008; Hopkins et al. 2013a), it is believed that AGN activityis required to drive the highest velocity outflows and are particularly important for the evolution of the most massive galaxies (e.g., Benson et al. 2003; McCarthy et al. 2011; Hopkins et al. 2013b; Zubovas & King 2014).”
Stellar and Quasar Feedback in Concert: Effects on AGN Accretion, Obscuration, and Outflows (2015, background): “As shown in Hopkins et al. (2013b) this is especially important for small scales around black holes, where any simple constant-density threshold for star formation fails to account for the radially-dependent tidal forces.”
The origin and evolution of the galaxy mass–metallicity relation (2015, background): “Star formation is allowed only in dense, molecular, and selfgravitating regions with hydrogen number density above some threshold nth = 10–100 cm−3 (Hopkins et al. 2013b).”
FIRE-2 simulations: physics versus numerics in galaxy formation (2017, methodology): “…the global efficiency of star formation (either on galaxy or GMC scales) is necessarily high – we find that it is self-regulated by feedback at ∼ 1−10% per free-fall time (see Hopkins et al. 2011, 2013e, 2014) even in gas with densities & 100cm−3, in agreement with observations (Lee et al. 2016).”
Dusty Star Forming Galaxies at High Redshift (2014, background): “The increase in turbulence driven by the accreted gas reduces the star formation efficiency, and allows gas fractions to rise accordingly (though see Hopkins et al., 2013b, for counter arguments).”
Galaxy and mass assembly (GAMA): End of survey report and data release 2 (2015, methodology): “…galaxies (e.g. De Lucia et al. 2006), morphological transformations (e.g. Toomre 1977; Cox et al. 2006; Hopkins et al. 2009), triggering (e.g. Hopkins et al. 2013a; Patton et al. 2013) and truncating (e.g. Hopkins et al. 2008) star formation, fuelling central supermassive black holes (e.g.…”