Feedback from Galaxy Formation: Production and Photodissociation of Primordial H2

By M. Ricotti, Y. Gnedin, J. Michael Shull. 2000

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We use one-dimensional radiative transfer simulations to study the evolution of H2 gas-phase (H- catalyzed) formation and photodissociation regions in the primordial universe. We find a new positive feedback mechanism capable of producing shells of H2 in the intergalactic medium (IGM), which are optically thick in some Lyman-Werner bands. While these shells exist, this feedback effect is important in reducing the H2 dissociating background flux and the size of photodissociation spheres around each luminous object. The maximum background opacity of the IGM in the H2 Lyman-Werner bands is τ ≈ 1-2 for a relic molecular fraction x = 2 × 10-6, about 6 times greater than that found by Haiman, Abel, & Rees. Therefore, the relic molecular hydrogen can decrease the photodissociation rate by about an order of magnitude. The problem is relevant to the formation of small primordial galaxies with masses MDM ≲ 108 M☉ that rely on molecular hydrogen cooling to collapse. Alternatively, the universe may have remained dark for several hundred million years after the birth of the first stars, until galaxies with virial temperature Tvir ≳ 104 K formed.

Subfields: Astronomy and Astrophysics, Plant Science

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Citations in the corpus

Fluctuations in the high-redshift Lyman–Werner background: close halo pairs as the origin of supermassive black holes (2008, background): “Additionally, a trace fraction of molecular hydrogen in the IGM (xH2 ∼ 2 × 10−6) is sufficient to produce an effective optical depth in the LW lines of τH2 ∼ 1 − 2 (Ricotti et al. 2001).”
Galaxy formation theory (2010, background): “…cooling are more complicated than those of atomic cooling: in addition to uncertainties in the molecular chemistry (Glover and Abel 2008), in many cases equilibrium is not reached and the photon background can lead to both negative (W s and Abel 2007a) and positive (Ricotti et al. 2001) feedbacks.”
Resolving the Formation of Protogalaxies. III. Feedback from the First Stars (2007, background): “…but the multiple sites of star formation are caused by H2 and Lyα cooling in central protogalactic shocks (Shapiro & Kang 1987) and aided by additional H2 cooling in ionization fronts (Ricotti et al. 2001; Ahn & Shapiro 2007; Whalen et al. 2008), not from residual cores from a recent major merger.”
FORMATION RATES OF POPULATION III STARS AND CHEMICAL ENRICHMENT OF HALOS DURING THE REIONIZATION ERA (2009, methodology): “In our model, we do not include positive radiative feedback that can promote H2 formation in the neighborhood of a first star (Ricotti et al. 2001).”
The First Billion Years project: the impact of stellar radiation on the co-evolution of Populations II and III (2012, background): “…the propagation of LW photons in which we assume that all LW photons generated by stars escape their host haloes, although it is likely that some fraction of LW photons are absorbed before escaping into the intergalactic medium (IGM) (see e.g. Kitayama et al. 2004; also Ricotti et al. 2001).”
The Fate of the First Galaxies. II. Effects of Radiative Feedback (2001, background): “In Ricotti et al. (2001) we emphasized the importance of PFRs in reducing the dissociating background.”
The first galaxies : assembly, cooling and the onset of turbulence (2008, methodology): “…medium (IGM) via radiation in the Lyman– Werner (LW) bands, which readily destroys molecular hydrogen (Glover & Brand 2001; Machacek et al. 2001; Ricotti et al. 2001; Omukai & Yoshii 2003; Greif & Bromm 2006; Mesinger et al. 2006; O’Shea & Norman 2008; Johnson et al. 2007b; Wise & Abel 2007d),…”
The Fate of the First Galaxies. I. Self-consistent Cosmological Simulations with Radiative Transfer (2001, methodology): “Based on the results of simple onedimensional radiative transfer simulations presented in Ricotti et al. (2001), we choose a0 ¼ 0:01 and a1 ¼ 10 when we use the Population III SED and a0 ¼ 0:1 and a1 ¼ 10 when we use the Population II SED.”
Signatures of X-rays in the early Universe (2012, background): “…halos was likely inefficient (with a handful of stars per halo), and was likely suppressed by heating and feedback processes (Haiman et al. 2000; Ricotti et al. 2001; Mesinger et al. 2006; Haiman & Bryan 2006; Tseliakhovich & Hirata 2010; O’Leary & McQuinn 2012; though Ahn et al. 2012 suggest…”
Early Cosmological H II/He III Regions and Their Impact on Second-Generation Star Formation (2006, background): “Oh&Haiman (2003) estimate that the gas 3 The primordial gas at very high redshift is not optically thin, because there is a trace amount of H2 molecules left over in the postrecombination epoch (e.g., Ricotti et al. 2001).”
Ubiquitous seeding of supermassive black holes by direct collapse (2012, unknown): “Previous studies , (Ricotti et al. 2001; Kitayama et al. 2004) have found that the minimum escape fraction for LW photons can be0.”
Effect of Primordial Black Holes on the Cosmic Microwave Background and Cosmological Parameter Estimates (2007, methodology): “The 1D radiative transfer code used to produce the temperature plots is described in detail in Ricotti et al. (2001).”
21CMMC: an MCMC analysis tool enabling astrophysical parameter studies of the cosmic 21 cm signal (2015, background): “…these haloes is likely inefficient (a few stars per halo) and can be quickly (z > 20) suppressed by Lyman–Werner or other feedback processes well before the EoR (Haiman et al. 2000; Ricotti et al. 2001; Haiman & Bryan 2006; Mesinger et al. 2006; Holzbauer & Furlanetto 2012; Fialkov et al. 2013).”