Local Radiative Feedback in the Formation of the First Protogalaxies

Johnson, Jarrett L.; Greif, Thomas H.; Bromm, Volker

doi:10.1086/519212

Cited by 145 publications

(194 citation statements)

References 68 publications

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“…Finally, we note that while our chemical enrichment model accommodates the important contribution of metals ejected by the supernovae from Population III stars formed in minihalos, with masses less than 10 8 M (see Greif et al 2007), this contribution is neglected in Salvadori et al (2007) based on the assumption that strong photodissociating radiation from the first stars quenches their formation. It appears likely, however, that this effect may not have substantially lowered the Population III star formation rate (e.g., Ricotti et al 2001;Johnson et al 2007;Wise & Abel 2007;O'Shea & Norman 2008; see also Yoshida et al 2003). Despite these differences, both models generate broadly similar MDFs.…”

Section: Discussion and Summarymentioning

confidence: 99%

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Uncovering the Chemical Signature of the First Stars in the Universe

Karlsson

Johnson

Bromm

2008

ApJ

Self Cite

131

156

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The chemical abundance patterns observed in metal-poor Galactic halo stars contain the signature of the first supernovae, and thus allow us to probe the first stars that formed in the universe. We construct a theoretical model for the early chemical enrichment history of the Milky Way, aiming in particular at the contribution from pair-instability supernovae (PISNe). These are a natural consequence of current theoretical models for primordial star formation at the highest masses. However, no metal-poor star displaying the distinct PISN signature has yet been observed. We here argue that this apparent absence of any PISN signature is due to an observational selection effect. Whereas most surveys traditionally focus on the most metal-poor stars, we predict that early PISN enrichment tends to ''overshoot,'' reaching enrichment levels of ½Ca/H ' À2:5 that would be missed by current searches. We utilize existing observational data to place constraints on the primordial initial mass function (IMF). The number fraction of PISNe in the primordial stellar population is estimated to be <0.07, or P40% by mass, assuming that metal-free stars have masses in excess of 10 M . We further predict, based on theoretical estimates for the relative number of PISNe, that the expected fraction of second-generation stars below ½Ca/H ¼ À2 with a dominant (i.e., >90%) contribution from PISNe is merely $10 À4 to 5 ; 10 À4 . The corresponding fraction of stars formed from gas exclusively enriched by PISNe is a factor of $4 smaller. With the advent of next-generation telescopes and new, deeper surveys, we should be able to test these predictions.

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Section: Discussion and Summarymentioning

confidence: 99%

“…The simulation is set up similarly to those conducted in Johnson et al (2007), employing a cosmological box of comoving length 660 kpc. We track the sites where the primordial gas is able to collapse to form Population III stars in this simulation (Fig.…”

Section: Star Formation Ratesmentioning

confidence: 99%

Uncovering the Chemical Signature of the First Stars in the Universe

Karlsson

Johnson

Bromm

2008

ApJ

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131

156

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“…Stellar feedback can have both a positive and negative impact on subsequent star formation. Some examples of positive feedback include enhanced H 2 formation in relic H ii regions (Ferrara 1998;O'Shea et al 2005;Johnson et al 2007) and dust and metal-line cooling (Glover 2003;Schneider et al 2006;Jappsen et al 2007a). Negative feedback may occur from baryonic expulsion from host halos ( Whalen et al 2004;Kitayama et al 2004;Yoshida et al 2007;Abel et al 2007) and halo photoevaporation (Susa & Umemura 2006;Whalen et al 2008).…”

Section: Desired Improvementsmentioning

confidence: 99%

Resolving the Formation of Protogalaxies. II. Central Gravitational Collapse

Wise

Turk

Abel

2008

ApJ

214

236

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Numerous cosmological hydrodynamic studies have addressed the formation of galaxies. Here we choose to study the first stages of galaxy formation, including nonequilibrium atomic primordial gas cooling, gravity, and hydrodynamics. Using initial conditions appropriate for the concordance cosmological model of structure formation, we perform two adaptive mesh refinement simulations of $10 8 M galaxies at high redshift. The calculations resolve the Jeans length at all times with more than 16 cells and capture over 14 orders of magnitude in length scales. In both cases, the dense, 10 5 solar mass, one parsec central regions are found to contract rapidly and have turbulent Mach numbers up to 4. Despite the ever decreasing Jeans length of the isothermal gas, we only find one site of fragmentation during the collapse. However, rotational secular bar instabilities transport angular momentum outward in the central parsec as the gas continues to collapse and lead to multiple nested unstable fragments with decreasing masses down to sub-Jupiter mass scales. Although these numerical experiments neglect star formation and feedback, they clearly highlight the physics of turbulence in gravitationally collapsing gas. The angular momentum segregation seen in our calculations plays an important role in theories that form supermassive black holes from gaseous collapse.

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“…These stars emit UV radiation, photoionize gas and photodissociate molecules. Consequently, they influence the subsequent formation of structure in the surrounding intergalactic medium (Johnson et al 2007;Johnson 2011;Maio et al 2011). It is likely that atomic cooling halos are polluted by trace amounts of metals through Pop III supernova explosions (Greif et al 2010).…”

Section: Introductionmentioning

confidence: 99%

The implications of dust for high-redshift protogalaxies and the formation of binary disks

Latif

Schleicher

Spaans

2012

A&A

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Numerical simulations suggest that the first galaxies are formed in protogalactic halos with virial temperatures ≥10 4 K. It is likely that such halos are polluted with trace amounts of metals produced by the first generation of stars. The presence of dust can significantly change the chemistry and dynamics of early galaxies. In this article, we aim to assess the role of dust on the thermal and dynamical evolution of the first galaxies in the presence of a background UV flux, and its implications for the observability of Lyman-α emitters and sub-mm sources. We have performed high resolution cosmological simulations using the adaptive mesh refinement code FLASH to accomplish this goal. We have developed a chemical network appropriate for these conditions and coupled it with the FLASH code. The main ingredients of our chemical model include the formation of molecules (both in the gas phase and on dust grains), a multi-level treatment of atomic hydrogen, line trapping of Ly-α photons and, photoionization and photodissociation processes in a UV background. We found that the formation of molecules (H 2 and HD) is significantly enhanced in the presence of dust grains as compared to only gas phase reactions by up to two orders of magnitude. The presence of dust may thus establish a molecular ISM in high-redshift galaxies. The presence of a background UV flux strongly influences the formation of molecules by photodissociating them. We explore the evolution after a major merger, leading to the formation of a binary disk. These disks have gas masses of ∼10 7 M at a redshift of 5.4. Each disk lies in a separate subhalo as a result of the merger event. The disks are supported by turbulent pressure due to the highly supersonic turbulence present in the halo. For values of J 21 = 1000 (internal flux), we find that fragmentation may be enhanced due to thermal instabilities in the hot gas. The presence of dust does not significantly reduce the Ly-α emission. The emission of Ly-α is extended and originates from the envelope of the halo due to line trapping effects. We also find that dust masses of a few ×10 8 M are required to observe the dust continuum emission from z ∼ 5 galaxies with ALMA.

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Local Radiative Feedback in the Formation of the First Protogalaxies

Cited by 145 publications

References 68 publications

Uncovering the Chemical Signature of the First Stars in the Universe

Uncovering the Chemical Signature of the First Stars in the Universe

Resolving the Formation of Protogalaxies. II. Central Gravitational Collapse

The implications of dust for high-redshift protogalaxies and the formation of binary disks

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