Primordial Star Formation under Far-Ultraviolet Radiation

By K. Omukai. 2000

224 citations recorded by the source corpus.

Thermal and chemical evolution of primordial gas clouds irradiated with far-ultraviolet (FUV; hν < 13.6 eV) radiation is investigated. In clouds irradiated by intense FUV radiation, sufficient hydrogen molecules to be important for cooling are never formed. However, even without molecular hydrogen, if the clouds are massive enough, they start collapsing via atomic hydrogen line cooling. Such clouds continue to collapse almost isothermally owing to successive cooling by H- free-bound emission up to the number density of 1016 cm-3. Inside the clouds, the Jeans mass eventually falls well below a solar mass. This indicates that hydrogen molecules are dispensable for low-mass primordial star formation, provided that fragmentation of the clouds occurs at sufficiently high density.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/34ca73d4d679b0771b43bdf20088f7c843791292

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In Astronomy and Astrophysics

1. S. Glover
2. Volker Bromm
3. Ralf Klessen
4. L. Hernquist
5. Tom Abel
6. P. Hopkins
7. A. Ferrara
8. Christoph Federrath

Citations in the corpus

• The First Cosmic Structures and Their Effects (2004, background): “Omukai (2001) argues that, in the absence of molecular hydrogen (which can be easily disso- review.tex; 15/06/2008; 8:20; p.25 26 ciated by feedback effects, Sec.”
• The First Billion Years project: the impact of stellar radiation on the co-evolution of Populations II and III (2012, background): “Shang et al. (2010; see also Omukai 2001; WolcottGreen et al. 2011) find that the ‘critical’ value J21,crit of the 9 Direct comparison with Ahn et al. (2009) is also difficult, due to our different choices of simulation volume and resolution.”
• Titans of the early Universe: The Prato statement on the origin of the first supermassive black holes (2018, methodology): “The earliest studies (Omukai 2001; Bromm&Loeb 2003) found that extremely high values of Jcrit were required, but Shang et al. (2010) later showed that this was a consequence of the simplified treatment of H2 collisional dissociation adopted in these studies, and that simulations with a more…”
• Supermassive black hole formation by direct collapse: keeping protogalactic gas H2 free in dark matter haloes with virial temperatures Tvir > rsim 104 K (2009, background): “The critical intensity Jcrit21 in larger halos, with virial temperatures Tvir > 10 4 K, however, is much higher (Omukai 2001, hereafter OM01; OH02; BL03).”
• FORMATION OF PRIMORDIAL SUPERMASSIVE STARS BY RAPID MASS ACCRETION (2013, background): “A number of processes preventing H2 formation have been proposed, e.g., photodissociation by strong UV background (Omukai 2001; Oh & Haiman 2002; Wise et al. 2008; Shang et al. 2010; Wolcott-Green et al. 2011; Inayoshi & Omukai 2011; Agarwal et al. 2012), and collisional dissociation in dense…”
• Simulations of Early Structure Formation: Primordial Gas Clouds (2003, methodology): “Omukai (2001) argues that both the density and temperature of gas clouds in the regime before they start to undergo run-away collapse become higher for a stronger radiation field and the characteristic Jeans mass becomes smaller.”
• Photodissociation of H2 in protogalaxies: modelling self‐shielding in three‐dimensional simulations (2011, background): “In one-zone models, NH2 must be specified from only “local” properties of the gas, by definition (Omukai & Nishi 1999; Omukai 2001; Omukai et al. 2008; Safranek-Shrader et al. 2010; Wolcott-Green & Haiman 2011).”
• Formation of the First Stars by Accretion (2003, background): “However, the formation of fragments of lower mass, down to d1 M , is also possible (e.g., Yoshii & Saio 1986; Uehara et al. 1996; Nakamura & Umemura 1999, 2001, 2002; Uehara & Inutsuka 2000; Omukai 2001).”
• First Stars, Very Massive Black Holes, and Metals (2001, methodology): “These results are based on the model of Omukai (2001).”
• Formation of Supermassive Black Hole Seeds (2016, methodology): “One of the main constraints for the formation of DCBHs via isothermal direct collapse is the suppression of molecular hydrogen formation which requires the presence of a strong LW flux (Omukai 2001; Omukai et al. 2008; Shang et al. 2010; Petri et al. 2012; Latif et al. 2013a).”
• Ubiquitous seeding of supermassive black holes by direct collapse (2012, background): “5) which is very close to the expected value during the reionization era4 (Omukai 2001; Bromm & Loeb 2003).”
• Can Supermassive Black Holes Form in Metal-enriched High-Redshift Protogalaxies? (2008, background): “The critical flux required to keep the gas H2-free as it collapses by several orders of magnitude therefore increases significantly; for halos with Tvir 104 K the value has been found to be J 21 103Y105, depending on the assumed spectral shape (Omukai 2001, hereafter O01; BL03).”
• Black hole formation in the early Universe (2013, background): “…flux ≥103 in units of J21 is required to photodissociate H2 molecules in haloes with virial temperatures >104 K for a radiation temperature of 105 K (Omukai 2001; Johnson & Bromm 2007; Dijkstra et al. 2008; Schleicher et al. 2010; Latif et al. 2011b; Wolcott-Green et al. 2011; Safranek-Shrader et…”
• Population III Star Formation in a ΛCDM Universe. II. Effects of a Photodissociating Background (2007, background): “Finally, Omukai (2001) and Omukai & Yoshii (2003) study the IMF of stars that form in Tvir k104 K metal-free protogalaxies in the presence of an H2 photodissociating background.”
• Second-Generation Objects in the Universe: Radiative Cooling and Collapse of Halos with Virial Temperatures above 104 K (2001, background): “3H, is unimportant in this regime, contrary to previous assumptions (e.g., Omukai 2001).”
• Primordial star formation under the influence of far ultraviolet radiation: 1540 cosmological haloes and the stellar mass distribution (2015, background): “In general, for the larger J21, the gas temperature in the accretion envelope is higher (e.g., Omukai 2001; O’Shea & Norman 2008), causing higher accretion rates on to the protostar.”
• Thermal and Fragmentation Properties of Star-forming Clouds in Low-Metallicity Environments (2005, background): “The former effect is included in calculating the level population of atomic and molecular species as in Omukai (2001).”
• The First Stars (2003, background): “The gas may then be able to collapse, albeit at higher temperatures, to increasingly large densities (see also Omukai 2001).”
• Hyper-Eddington accretion flows on to massive black holes (2015, methodology): “We here neglect radiative cooling via other Lyman series and Balmer series photons since their total cooling rate is comparable or smaller than that of two-photon emission (Omukai 2001; Schleicher, Spaans & Glover 2010; Johnson et al. 2012).”