skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Kiloparsec-scale Simulations of Star Formation in Disk Galaxies. IV. Regulation of Galactic Star Formation Rates by Stellar Feedback

Abstract

Star formation from the interstellar medium of galactic disks is a basic process controlling the evolution of galaxies. Understanding the star formation rate (SFR) in a local patch of a disk with a given gas mass is thus an important challenge for theoretical models. Here we simulate a kiloparsec region of a disk, following the evolution of self-gravitating molecular clouds down to subparsec scales, as they form stars that then inject feedback energy by dissociating and ionizing UV photons and supernova explosions. We assess the relative importance of each feedback mechanism. We find that H{sub 2}-dissociating feedback results in the largest absolute reduction in star formation compared to the run with no feedback. Subsequently adding photoionization feedback produces a more modest reduction. Our fiducial models that combine all three feedback mechanisms yield, without fine-tuning, SFRs that are in excellent agreement with observations, with H{sub 2}-dissociating photons playing a crucial role. Models that only include supernova feedback—a common method in galaxy evolution simulations—settle to similar SFRs, but with very different temperatures and chemical states of the gas, and with very different spatial distributions of young stars.

Authors:
 [1];  [2]; ;  [3];  [4];  [5]
  1. Max Planck Institute for Astronomy, Königstuhl 17, D-69117 Heidelberg (Germany)
  2. Departments of Astronomy and Physics, University of Florida, Gainesville, FL 32611 (United States)
  3. Institute for Computational Science, University of Zurich, 8049 Zurich (Switzerland)
  4. Leiden Observatory, Leiden University, P.O. Box 9513, NL-2300 RA Leiden (Netherlands)
  5. School of Physics and Astronomy, University of Leeds, Leeds LS2 9JT (United Kingdom)
Publication Date:
OSTI Identifier:
22663563
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 841; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; COMPARATIVE EVALUATIONS; EXPLOSIONS; FEEDBACK; GALAXIES; HYDROGEN; MASS; PHOTOIONIZATION; PHOTONS; RADIANT HEAT TRANSFER; REDUCTION; REGULATIONS; SIMULATION; SPATIAL DISTRIBUTION; STARS

Citation Formats

Butler, Michael J., Tan, Jonathan C., Teyssier, Romain, Nickerson, Sarah, Rosdahl, Joakim, and Van Loo, Sven. Kiloparsec-scale Simulations of Star Formation in Disk Galaxies. IV. Regulation of Galactic Star Formation Rates by Stellar Feedback. United States: N. p., 2017. Web. doi:10.3847/1538-4357/AA7054.
Butler, Michael J., Tan, Jonathan C., Teyssier, Romain, Nickerson, Sarah, Rosdahl, Joakim, & Van Loo, Sven. Kiloparsec-scale Simulations of Star Formation in Disk Galaxies. IV. Regulation of Galactic Star Formation Rates by Stellar Feedback. United States. doi:10.3847/1538-4357/AA7054.
Butler, Michael J., Tan, Jonathan C., Teyssier, Romain, Nickerson, Sarah, Rosdahl, Joakim, and Van Loo, Sven. Thu . "Kiloparsec-scale Simulations of Star Formation in Disk Galaxies. IV. Regulation of Galactic Star Formation Rates by Stellar Feedback". United States. doi:10.3847/1538-4357/AA7054.
@article{osti_22663563,
title = {Kiloparsec-scale Simulations of Star Formation in Disk Galaxies. IV. Regulation of Galactic Star Formation Rates by Stellar Feedback},
author = {Butler, Michael J. and Tan, Jonathan C. and Teyssier, Romain and Nickerson, Sarah and Rosdahl, Joakim and Van Loo, Sven},
abstractNote = {Star formation from the interstellar medium of galactic disks is a basic process controlling the evolution of galaxies. Understanding the star formation rate (SFR) in a local patch of a disk with a given gas mass is thus an important challenge for theoretical models. Here we simulate a kiloparsec region of a disk, following the evolution of self-gravitating molecular clouds down to subparsec scales, as they form stars that then inject feedback energy by dissociating and ionizing UV photons and supernova explosions. We assess the relative importance of each feedback mechanism. We find that H{sub 2}-dissociating feedback results in the largest absolute reduction in star formation compared to the run with no feedback. Subsequently adding photoionization feedback produces a more modest reduction. Our fiducial models that combine all three feedback mechanisms yield, without fine-tuning, SFRs that are in excellent agreement with observations, with H{sub 2}-dissociating photons playing a crucial role. Models that only include supernova feedback—a common method in galaxy evolution simulations—settle to similar SFRs, but with very different temperatures and chemical states of the gas, and with very different spatial distributions of young stars.},
doi = {10.3847/1538-4357/AA7054},
journal = {Astrophysical Journal},
number = 2,
volume = 841,
place = {United States},
year = {Thu Jun 01 00:00:00 EDT 2017},
month = {Thu Jun 01 00:00:00 EDT 2017}
}
  • We present hydrodynamic simulations of the evolution of self-gravitating dense gas on scales of 1 kpc down to {approx}< parsec in a galactic disk, designed to study dense clump formation from giant molecular clouds (GMCs). These structures are expected to be the precursors to star clusters and this process may be the rate limiting step controlling star formation rates in galactic systems as described by the Kennicutt-Schmidt relation. We follow the thermal evolution of the gas down to {approx}5 K using extinction-dependent heating and cooling functions. We do not yet include magnetic fields or localized stellar feedback, so the evolutionmore » of the GMCs and clumps is determined solely by self-gravity balanced by thermal and turbulent pressure support and the large-scale galactic shear. While cloud structures and densities change significantly during the simulation, GMC virial parameters remain mostly above unity for timescales exceeding the free-fall time of GMCs indicating that energy from galactic shear and large-scale cloud motions continuously cascades down to and within the GMCs. We implement star formation at a slow, inefficient rate of 2% per local free-fall time, but even this yields global star formation rates that are about two orders of magnitude larger than the observed Kennicutt-Schmidt relation due to overproduction of dense gas clumps. We expect a combination of magnetic support and localized stellar feedback is required to inhibit dense clump formation to {approx}1% of the rate that results from the nonmagnetic, zero-feedback limit.« less
  • The energy and momentum feedback from young stars has a profound impact on the interstellar medium (ISM), including heating and driving turbulence in the neutral gas that fuels future star formation. Recent theory has argued that this leads to a quasi-equilibrium self-regulated state, and for outer atomic-dominated disks results in the surface density of star formation Σ{sub SFR} varying approximately linearly with the weight of the ISM (or midplane turbulent + thermal pressure). We use three-dimensional numerical hydrodynamic simulations to test the theoretical predictions for thermal, turbulent, and vertical dynamical equilibrium, and the implied functional dependence of Σ{sub SFR} onmore » local disk properties. Our models demonstrate that all equilibria are established rapidly, and that the expected proportionalities between mean thermal and turbulent pressures and Σ{sub SFR} apply. For outer disk regions, this results in Σ{sub SFR}∝Σ√(ρ{sub sd}), where Σ is the total gas surface density and ρ{sub sd} is the midplane density of the stellar disk (plus dark matter). This scaling law arises because ρ{sub sd} sets the vertical dynamical time in our models (and outer disk regions generally). The coefficient in the star formation law varies inversely with the specific energy and momentum yield from massive stars. We find proportions of warm and cold atomic gas, turbulent-to-thermal pressure, and mean velocity dispersions that are consistent with solar-neighborhood and other outer disk observations. This study confirms the conclusions of a previous set of simulations, which incorporated the same physics treatment but was restricted to radial-vertical slices through the ISM.« less
  • Stellar feedback, star formation, and gravitational interactions are major controlling forces in the evolution of giant molecular clouds (GMCs). To explore their relative roles, we examine the properties and evolution of GMCs forming in an isolated galactic disk simulation that includes both localized thermal feedback and photoelectric heating. The results are compared with the three previous simulations in this series, which consists of a model with no star formation, star formation but no form of feedback, and star formation with photoelectric heating in a set with steadily increasing physical effects. We find that the addition of localized thermal feedback greatlymore » suppresses star formation but does not destroy the surrounding GMC, giving cloud properties closely resembling the run in which no stellar physics is included. The outflows from the feedback reduce the mass of the cloud but do not destroy it, allowing the cloud to survive its stellar children. This suggests that weak thermal feedback such as the lower bound expected for a supernova may play a relatively minor role in the galactic structure of quiescent Milky-Way-type galaxies, compared to gravitational interactions and disk shear.« less
  • VLA images at 6 cm of eight nearby galaxies show extended emission on kpc scales. Optical data reveal that six of the host galaxies are likely to be genuine ellipticals or lenticulars, and two are possibly ellipticals or lenticulars. All eight galaxies have substantial FIR luminosities. One or more gas-rich companions are identified for each of seven galaxies. 45 references.
  • Using two volume-limited main galaxy samples of the Sloan Digital Sky Survey Data Release 8 (SDSS DR8), we explore the environmental dependence of the star formation rate (SFR), specific star formation rate (SSFR), and the presence of active galactic nuclei (AGNs) for high stellar mass (HSM) and low stellar mass (LSM) galaxies. It is found that the environmental dependence of the SFR and SSFR for luminous HSM galaxies and faint LSM ones remains very strong: galaxies in the lowest density regime preferentially have higher SFR and SSFR than galaxies in the densest regime, while the environmental dependence of the SFRmore » and SSFR for luminous LSM galaxies is substantially reduced. Our result also shows that the fraction of AGNs in HSM galaxies decreases as a function of density, while the one in LSM galaxies depends very little on local density. In the faint LSM galaxy sample, the SFR and SSFR of galaxies strongly decrease with increasing density, but the fraction of AGNs depends very little on local density. Such a result can rule out that AGNs are fueled by the cold gas in the disk component of galaxies that is also driving the star formation of those galaxies.« less