Fossil H ii regions: self-limiting star formation at high redshift

By S. Oh, Zoltán Haiman. 2003

206 citations recorded by the source corpus.

Recent results from the Wilkinson Microwave Anisotropy Probe (WMAP) satellite suggest that the intergalactic medium (IGM) was significantly reionized at redshifts as high as z ∼ 17. At this early epoch, the first ionizingsources probably appeared in the shallow potential wells of mini-haloes with virial temperatures T v i r < 10 4 K. Once such an ionizing source turns off, its surrounding H II region Compton cools and recombines. None the less, we show that the 'fossil' H ii regions left behind remain at high adiabats, prohibiting gas accretion and cooling in subsequent generations of mini-haloes. This greatly amplifies feedback effects explored in previous studies, and early star formation is self-limiting. We quantify this effect to show that star formation in mini-haloes cannot account for the bulk of the electron scattering opacity measured by WMAP. which must be due to more massive objects. We argue that gas entropy, rather than IGM metallicity, regulates the evolution of the global ionizing emissivity and impedes full reionization until lower redshifts. We discuss several important consequences of this early entropy floor for reionization. It reduces gas clumping, curtailing the required photon budget for reionization. An entropy floor also prevents H 2 formation and cooling, due to reduced gas densities: it greatly enhances feedback from ultraviolet photodissociation of H 2 . An early X-ray background would also furnish an entropy floor to the entire IGM; thus, X-rays impede rather than enhance H 2 formation. Future 21-cm observations may probe the topology of fossil H II regions.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/44fc6bea369d7ff395dd56d68fefca77265bffe7

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In Astronomy and Astrophysics

1. L. Hernquist
2. M. McQuinn
3. S. Furlanetto
4. P. Hopkins
5. Volker Bromm
6. A. Mesinger
7. Tom Abel
8. Volker Springel

In Nuclear and High Energy Physics

1. S. Furlanetto
2. M. McQuinn
3. L. Hernquist
4. Abraham Loeb
5. A. Mesinger
6. M. Zaldarriaga
7. A. Ferrara
8. S. Oh

Citations in the corpus

• Early Cosmological H II/He III Regions and Their Impact on Second-Generation Star Formation (2006, background): “After the first star dies, some of the nearby halos are able to reform enough hydrogen molecules to meet the baryonic cooling criteria (Tegmark et al. 1997; Yoshida et al. 2003; Oh & Haiman 2003).”
• Radiation Hydrodynamic Evolution of Primordial H II Regions (2003, background): “Only three dimensional models of the first HII regions will allow us to address the detailed questions recently raised by Oh & Haiman (2003).”
• The First Cosmic Structures and Their Effects (2004, background): “Nonetheless, the “fossil” H II regions left behind remain at high adiabats, prohibiting gas accretion and cooling in subsequent generations of Pop III objects (Oh & Haiman 2003).”
• The aftermath of the first stars: massive black holes (2006, methodology): “We compute the timescale for the photodissociation of H2 and HD as c© 2006 RAS, MNRAS 000, 000–000 tdiss ∼ 10 8 yr ( Q21S 1045s−1 )−1 , (10) where we have taken R ∼ 500 pc and used tdiss ∼ 10 8 yr (JLW/10 −4)−1 (see Oh & Haiman 2003; Johnson & Bromm 2006).”
• Photoevaporation of cosmological minihaloes during reionization (2003, background): “…H2 in minihaloes may have been more negative than positive, however, if they raised the entropy floor of the IGM from which the minihaloes condensed (Oh & Haiman 2003). starlight with a 105 K black-body spectrum (hereafter, ‘BB 1e5’), as expected for massive Population III stars, and (3)…”
• Simulations and Analytic Calculations of Bubble Growth during Hydrogen Reionization (2006, background): “Oh & Haiman 2003), estimates show this effect is important only at the tail end of reionization, when xi,v & 0.77 (Furlanetto & Oh 2005), which we do not presently simulate.”
• The First Stars (2003, background): “Second, the free electrons in relic H II regions (Oh & Haiman 2003), or inside the outer boundary of a still-active one (Ricotti et al. 2001, 2002a,b), may accomplish the same.”
• Three-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Implications for Cosmology (2006, unknown): “…physics of reionization has been a subject of extensive theoretical study (Cen 2003; Ciardi et al. 2003; Haiman & Holder 2003; Madau et al. 2004; Oh & Haiman 2003; Venkatesan et al. 2003; Ricotti & Ostriker 2004; Sokasian et al. 2004; Somerville & Livio 2003; Wyithe & Loeb 2003; Iliev et al.…”
• Suppression of H2 Cooling in the Ultraviolet Background (2007, background): “— Baryonic expulsion from host halos (Whalen et al. 2004; Kitayama et al. 2004; Yoshida et al. 2007; Abel et al. 2007), photoevaporation (Susa & Umemura 2006), entropy floors (Oh & Haiman 2003).”