scholarly journals The importance of magnetic fields for the initial mass function of the first stars

2020 ◽  
Vol 497 (1) ◽  
pp. 336-351 ◽  
Author(s):  
Piyush Sharda ◽  
Christoph Federrath ◽  
Mark R Krumholz
Keyword(s):  
Magnetic Fields ◽  
Initial Conditions ◽  
High Redshift ◽  
Three Dimensional ◽  
Mass Function ◽  
Initial Mass Function ◽  
Initial Mass ◽  
Dynamo Theory ◽  
First Stars ◽  
High Redshift Galaxies

ABSTRACT Magnetic fields play an important role for the formation of stars in both local and high-redshift galaxies. Recent studies of dynamo amplification in the first dark matter haloes suggest that significant magnetic fields were likely present during the formation of the first stars in the Universe at redshifts of 15 and above. In this work, we study how these magnetic fields potentially impact the initial mass function (IMF) of the first stars. We perform 200 high-resolution, three-dimensional (3D), magnetohydrodynamic (MHD) simulations of the collapse of primordial clouds with different initial turbulent magnetic field strengths as predicted from turbulent dynamo theory in the early Universe, forming more than 1100 first stars in total. We detect a strong statistical signature of suppressed fragmentation in the presence of strong magnetic fields, leading to a dramatic reduction in the number of first stars with masses low enough that they might be expected to survive to the present-day. Additionally, strong fields shift the transition point where stars go from being mostly single to mostly multiple to higher masses. However, irrespective of the field strength, individual simulations are highly chaotic, show different levels of fragmentation and clustering, and the outcome depends on the exact realization of the turbulence in the primordial clouds. While these are still idealized simulations that do not start from cosmological initial conditions, our work shows that magnetic fields play a key role for the primordial IMF, potentially even more so than for the present-day IMF.

scholarly journals The importance of initial conditions and metallicity for the fragmentation of protogalactic gas

2009 ◽  
Vol 5 (S265) ◽  
pp. 65-66
Author(s):  
Anne-Katharina Jappsen ◽  
Simon C. O. Glover ◽  
Mordecai-Mark Mac Low ◽  
Ralf S. Klessen
Keyword(s):  
Initial Conditions ◽  
Three Dimensional ◽  
Mass Function ◽  
Initial Mass Function ◽  
Ionized Gas ◽  
First Stars ◽  
Particle Hydrodynamics ◽  
Order Of Magnitude ◽  
Smoothed Particle ◽  
Metal Abundances

AbstractThe formation of the first stars out of metal-free gas appears to result in stars at least an order of magnitude more massive than in the present-day case. We here consider what controls the transition from a primordial to a modern initial mass function. We study the influence of low levels of metal enrichment and different initial conditions on the cooling and collapse of initially ionized gas in small protogalactic halos using three-dimensional, smoothed particle hydrodynamics simulations. We argue that fragmentation at moderate density depends on the initial conditions for star formation more than on the metal abundances present.

scholarly journals The influence of a top-heavy integrated galactic IMF and dust on the chemical evolution of high-redshift starbursts

2020 ◽  
Vol 494 (2) ◽  
pp. 2355-2373 ◽  
Author(s):  
M Palla ◽  
F Calura ◽  
F Matteucci ◽  
X L Fan ◽  
F Vincenzo ◽  
...  
Keyword(s):  
Star Formation ◽  
Chemical Evolution ◽  
Chemical Elements ◽  
High Redshift ◽  
Mass Function ◽  
Initial Mass Function ◽  
Initial Mass ◽  
Strong Impact ◽  
Star Forming ◽  
Abundance Patterns

ABSTRACT We study the effects of the integrated galactic initial mass function (IGIMF) and dust evolution on the abundance patterns of high redshift starburst galaxies. In our chemical models, the rapid collapse of gas clouds triggers an intense and rapid star formation episode, which lasts until the onset of a galactic wind, powered by the thermal energy injected by stellar winds and supernova explosions. Our models follow the evolution of several chemical elements (C, N, α-elements, and Fe) both in the gas and dust phases. We test different values of β, the slope of the embedded cluster mass function for the IGIMF, where lower β values imply a more top-heavy initial mass function (IMF). The computed abundances are compared to high-quality abundance measurements obtained in lensed galaxies and from composite spectra in large samples of star-forming galaxies in the redshift range 2 ≲ z ≲ 3. The adoption of the IGIMF causes a sensible increase of the rate of star formation with respect to a standard Salpeter IMF, with a strong impact on chemical evolution. We find that in order to reproduce the observed abundance patterns in these galaxies, either we need a very top-heavy IGIMF (β < 2) or large amounts of dust. In particular, if dust is important, the IGIMF should have β ≥ 2, which means an IMF slightly more top-heavy than the Salpeter one. The evolution of the dust mass with time for galaxies of different mass and IMF is also computed, highlighting that the dust amount increases with a top-heavier IGIMF.

scholarly journals Constraints on the initial mass function of the first stars

2006 ◽  
Vol 369 (2) ◽  
pp. 825-834 ◽  
Author(s):  
Raffaella Schneider ◽  
Ruben Salvaterra ◽  
Andrea Ferrara ◽  
Benedetta Ciardi
Keyword(s):  
Mass Function ◽  
Initial Mass Function ◽  
Initial Mass ◽  
First Stars

scholarly journals Generic Spectrum and Ionization Efficiency of a Heavy Initial Mass Function for the First Stars

2001 ◽  
Vol 552 (2) ◽  
pp. 464-472 ◽  
Author(s):  
Volker Bromm ◽  
Rolf P. Kudritzki ◽  
Abraham Loeb
Keyword(s):  
Mass Function ◽  
Initial Mass Function ◽  
Ionization Efficiency ◽  
Initial Mass ◽  
First Stars

scholarly journals Population III.1 stars: formation, feedback and evolution of the IMF

2008 ◽  
Vol 4 (S255) ◽  
pp. 24-32 ◽  
Author(s):  
Jonathan C. Tan
Keyword(s):  
Dark Matter ◽  
Initial Conditions ◽  
Mass Function ◽  
Initial Mass Function ◽  
Dark Matter Annihilation ◽  
Subsequent Evolution ◽  
First Stars ◽  
Field Amplification ◽  
Accretion Rates ◽  
Stars Formation

AbstractI discuss current theoretical expectations of how primordial, Pop III.1 stars form. Lack of direct observational constraints makes this a challenging task. In particular predicting the mass of these stars requires solving a series of problems, which all affect, perhaps drastically, the final outcome. While there is general agreement on the initial conditions, H2-cooled gas at the center of dark matter minihalos, the subsequent evolution is more uncertain. In particular, I describe the potential effects of dark matter annihilation heating, fragmentation within the minihalo, magnetic field amplification, and protostellar ionizing feedback. After these considerations, one expects that the first stars are massive ≳100M⊙, with dark matter annihilation heating having the potential to raise this scale by large factors. Higher accretion rates in later-forming minihalos may cause the Pop III.1 initial mass function to evolve to higher masses.

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