Resolving the Formation of Protogalaxies. I. Virialization

By John H. Wise, Tom Abel. 2007

151 citations recorded by the source corpus.

Galaxies form in hierarchically assembling dark matter halos. With cosmological three-dimensional adaptive mesh refinement simulations, we explore in detail the virialization of baryons in the concordance cosmology, including optically thin primordial gas cooling. We focus on early protogalaxies with virial temperatures of 104 K and their progenitors. Without cooling, virial heating occurs in shocks close to the virial radius for material falling in from voids. Material in dense filaments penetrates deeper to about half that radius. With cooling, the virial shock position shrinks, and the filaments reach scales as small as a third the virial radius. The temperatures in protogalaxies found in adiabatic simulations decrease by a factor of 2 from the center and show flat entropy cores. In cooling halos, the gas reaches virial equilibrium with the dark matter potential through its turbulent velocities. We observe turbulent Mach numbers ranging from 1 to 3 in the cooling cases. This turbulence is driven by the large scale merging and, interestingly, remains supersonic in the centers of these early galaxies, even in the absence of any feedback processes. The virial theorem is shown to approximately hold over 3 orders of magnitude in length scale, with the turbulent pressure prevailing over the thermal energy. The turbulent velocity distributions are Maxwellian and by far dominate the small rotation velocities associated with the total angular momentum of the galaxies. Decomposing the velocity field using the Cauchy-Stokes theorem, we show that ample amounts of vorticity are present around shocks even at the very centers of these objects. In the cold flow regime of galaxy formation for halo masses below 1012 M☉, this dominant role of virialization-driven turbulence should play an important role in star formation, as well as the build up of early magnetic fields.

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Citations in the corpus

Gravitational quenching in massive galaxies and clusters by clumpy accretion (2007, result): “This crude estimate is on the same order of magnitude as results of hydrodynamical simulations (Wise & Abel 2007; Faltenbacher et al. 2007), perhaps indicating that clumpy accretion may play a non-negligible role in driving turbulence in these simulations.”
Tracing the dark matter sheet in phase space (2011, methodology): “The global distribution has been measured from simulations many times (see e.g. Hoeft et al. 2004; Wise & Abel 2007; Navarro et al. 2010; Vogelsberger et al. 2009) but, to the best of our knowledge, this was never done at individual points in the simulations.”
Suppression of H2 Cooling in the Ultraviolet Background (2007, background): “The initial conditions are the same as in Wise & Abel (2007).”
The first galaxies : assembly, cooling and the onset of turbulence (2008, background): “Even a single SN from a massive Pop III star would already suffice to reach levels above the critical metallicity, at least on average (Bromm et al. 2003; Greif et al. 2007; Wise & Abel 2007c).”
Galaxy formation theory (2010, background): “…et al. 2008; O’Shea and Norman 2007, 2008; Harris et al. 2007; Stacy and Bromm 2007) may be crucialfor understanding how this population of galaxies grows (Tegmark et al. 1997; Ricotti et al. 2001; Wise and Abel 2007a,b; Greif et al. 2008; Wise and Abel 2008b; Wise et al. 2008; Bromm et al. 2009).”
LIMITING ACCRETION ONTO MASSIVE STARS BY FRAGMENTATION-INDUCED STARVATION (2010, background): “The situation is very different in atomic cooling halos (Wise & Abel 2007; Greif et al. 2009).”
THE BIRTH OF A GALAXY: PRIMORDIAL METAL ENRICHMENT AND STELLAR POPULATIONS (2010, background): “We expect a uniform H2 dissociating radiation background to further delay them (Machacek et al. 2001; Wise & Abel 2007; O’Shea & Norman 2008).”
CLASH: THREE STRONGLY LENSED IMAGES OF A CANDIDATE z ≈ 11 GALAXY (2012, background): “470 million years old (Wise & Abel 2007; Wise et al. 2008; Greif et al. 2008, 2010; and for recent reviews, see Bromm & Yoshida 2011 and Dunlop 2012).”
Near-Field Cosmology with Extremely Metal-Poor Stars (2015, background): “Detailed numerical simulations of star formation in atomic cooling halos have already suggested where these pathways may occur, although details so far remain unclear (Wise & Abel 2007, Greif et al. 2008, Ritter et al. 2012).”
Resolving the Formation of Protogalaxies. II. Central Gravitational Collapse (2007, background): “We repeat that this isothermal collapse occurs through atomic hydrogen cooling only, but in reality, H2 cooling is important even in the presence of a ultraviolet background (e.g., Machacek et al. 2001; Wise & Abel 2007b; O’Shea & Norman 2008).”
Hyper-Eddington accretion flows on to massive black holes (2015, background): “According to cosmological simulations of high-z protogalaxies, a gas density profile following ∝ r−2 develops due to efficient radiative cooling (e.g. Wise & Abel 2007).”
Evolution of magnetic fields in galaxies and future observational tests with the Square Kilometre Array (2008, methodology): “The turbulence became supersonic with Mach numbers ranging from 1 to 3 (Wise & Abel 2007).”
A NEW JEANS RESOLUTION CRITERION FOR (M)HD SIMULATIONS OF SELF-GRAVITATING GAS: APPLICATION TO MAGNETIC FIELD AMPLIFICATION BY GRAVITY-DRIVEN TURBULENCE (2011, background): “…it became clear that primordial gas becomes highly turbulent during the formation of the first galaxies and stars as well (e.g., Abel et al. 2002; O’Shea & Norman 2007; Wise & Abel 2007; Clark et al. 2008; Greif et al. 2008), which has far-reaching consequences for all cosmic structure formation.”
The birth of a galaxy – II. The role of radiation pressure (2012, background): “For example, virial shocks and internal weak shocks have been found to drive turbulence during halo virialization (Wise & Abel 2007a; Greif et al. 2008).”
Resolving the Formation of Protogalaxies. III. Feedback from the First Stars (2007, background): “We have verified that nothing atypical occurs during the assembly of the halos studied here (see Wise & Abel 2007, hereafter Paper I).”
Small-scale dynamo action during the formation of the first stars and galaxies - I. The ideal MHD limit (2010, methodology): “Radial profiles of the turbulent velocity in the first galaxies indicate that there are some random fluctuations, but the orderof-magnitude of the turbulent velocity does not change during the collapse (Wise & Abel 2007; Greif et al. 2008; Wise et al. 2008).”