IONIZING PHOTON ESCAPE FRACTIONS FROM HIGH-REDSHIFT DWARF GALAXIES

By John H. Wise, Renyue Cen. 2008

224 citations recorded by the source corpus.

It has been argued that low-luminosity dwarf galaxies are the dominant source of ionizing radiation during cosmological reionization. The fraction of ionizing radiation that escapes into the intergalactic medium from dwarf galaxies with masses less than ∼109.5 solar masses plays a critical role during this epoch. Using an extensive suite of very high resolution (0.1 pc), adaptive mesh refinement, radiation hydrodynamical simulations of idealized and cosmological dwarf galaxies, we characterize the behavior of the escape fraction in galaxies between 3 × 106 and 3 × 109 solar masses with different spin parameters, amounts of turbulence, and baryon mass fractions. For a given halo mass, escape fractions can vary up to a factor of two, depending on the initial setup of the idealized halo. In a cosmological setting, we find that the time-averaged photon escape fraction always exceeds 25% and reaches up to 80% in halos with masses above 108 solar masses with a top-heavy initial mass function (IMF). The instantaneous escape fraction can vary up to an order of magnitude in a few million years and tends to be positively correlated with star formation rate. We find that the mean of the star formation efficiency times ionizing photon escape fraction, averaged over all atomic cooling (Tvir ⩾ 8000 K) galaxies, ranges from 0.02 for a normal IMF to 0.03 for a top-heavy IMF, whereas smaller, molecular cooling galaxies in minihalos do not make a significant contribution to reionizing the universe due to much lower star formation rates. These results provide the physical basis for cosmological reionization by stellar sources, predominately atomic cooling dwarf galaxies.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/3242e2905cae54795ebee6fb5b5f5256a1f7157b

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Citations in the corpus

GALAXY PROPERTIES AND UV ESCAPE FRACTIONS DURING THE EPOCH OF REIONIZATION: RESULTS FROM THE RENAISSANCE SIMULATIONS (2016, background): “…factor in determining the photon budget in reionization models and has attracted much attention from numerical studies (e.g., Gnedin et al. 2008; Wise & Cen 2009; Razoumov & Sommer-Larsen 2010; Yajima et al. 2011; Ferrara & Loeb 2013; Paardekooper et al. 2013; Kimm & Cen 2014; Wise et al. 2014;…”
Fluctuating feedback-regulated escape fraction of ionizing radiation in low-mass, high-redshift galaxies (2017, methodology): “This is in line with the more recent findings of Gnedin et al. (2008), Wise & Cen (2009), Kim et al. (2013) and Paardekooper et al. (2015) who showed that the ionizing radiation escapes anisotropically, favouring low column density regions resulting from such outflows.”
Escape fraction of ionizing photons from high-redshift galaxies in cosmological SPH simulations (2010, background): “…(2010) further examined the fesc of star-forming galaxies in a wide mass range (Mh = 107.8−1011.5M⊙) at z = 4−10, and found that fesc decreases steeply as the halo mass increases in their cosmological SPH simulations, in contrast to the work by Gnedin et al. (2008) and Wise & Cen (2009).”
A DEEP HUBBLE SPACE TELESCOPE SEARCH FOR ESCAPING LYMAN CONTINUUM FLUX AT z ∼ 1.3: EVIDENCE FOR AN EVOLVING IONIZING EMISSIVITY (2010, background): “However, Gnedin et al. (2008) suggest that the smaller gas-to-stellar scale height ratios in high mass disks results in a higher probability of young stars being exposed to low column LOSs (see also Wise & Cen 2009, for high redshift dwarf galaxy results).”
The birth of a galaxy – III. Propelling reionization with the faintest galaxies (2014, methodology): “Examples of such feedback include photoevaporation, H2 dissociation, and gas blowout from H II regions and SN, which all depend on halo mass (e.g. Gnedin 2000; Wise & Cen 2009; Hopkins et al. 2013; Stinson et al. 2013).”
Galaxies–intergalactic medium interaction calculation – I. Galaxy formation as a function of large-scale environment (2009, background): “If the escape fraction of ionizing radiation from the small haloes that dominate ρ̇ at these epochs is high, say ∼(25–80) per cent as suggested by Wise & Cen (2009), then these galaxies will be the dominant contributors to the UV background at high redshift, and thus may have been the main sources…”
Predicted UV properties of very metal-poor starburst galaxies (2010, background): “In certain circumstances, especially in high redshift galaxies, a fraction of the Lyman continuum photons are expected to escape (see e.g. Gnedin et al. 2008; Wise & Cen 2009; Razoumov & Sommer-Larsen 2009).”
The difficulty of getting high escape fractions of ionizing photons from high-redshift galaxies: A view from the FIRE cosmological simulations (2015, background): “At lower masses, Wise & Cen (2009) found fesc ∼ 5%–40% and fesc ∼ 25%–80% by invoking a normal initial mass function (IMF) and a top-heavy IMF, respectively, for galaxies of halo mass in 106.5–109.5 M ; whereas Paardekooper et al. (2011) reported lower escape fraction of 10−5–0.1 in their…”
PHYSICAL CONDITIONS IN A YOUNG, UNREDDENED, LOW-METALLICITY GALAXY AT HIGH REDSHIFT (2010, background): “…indeed similar to typical galaxies at higher redshifts, the implication is that the escape fraction may significantly increase with increasing redshift, as already shown between z ∼ 1 and z ∼ 3 (Siana et al. 2010) and predicted at higher redshifts (Wise & Cen 2009; Razoumov & Sommer-Larsen 2010).”
Ubiquitous seeding of supermassive black holes by direct collapse (2012, background): “Recent studies (Wise & Cen 2009; Yajima et al. 2011; Paardekooper et al. 2011) have shown that that the escape fraction for UV photons could vary with the parent halo mass, however, the precise values of LW escape fractions from haloes is still unclear.”
The First Billion Years project: the escape fraction of ionizing photons in the epoch of reionization (2015, background): “…simulations find ranges between fesc < 10% (Razoumov & Sommer-Larsen 2006, 2007; Gnedin et al. 2008; Paardekooper et al. 2011; Kim et al. 2013) and fesc > 80% (Wise & Cen 2009; Razoumov & Sommer-Larsen 2010), with likely a strong mass and redshift dependence (Yajima et al. 2010; Wise et al. 2014).”
ESCAPE FRACTION OF IONIZING PHOTONS DURING REIONIZATION: EFFECTS DUE TO SUPERNOVA FEEDBACK AND RUNAWAY OB STARS (2014, background): “Wise & Cen (2009) performed cosmological radiation hydrodynamic simulations employing very high resolution (0.1 pc), and found that the neutral hydrogen column density varies over the solid angles fromNHI ∼ 1016cm−2 to 1022cm−2 with the aid of SN explosions and photo-ionization.”
Extended Lyman-alpha emission from cold accretion streams (2011, methodology): “Second, the inside-out method would require finely tuned star formation rates and UV escape fractions for simulated galaxies to produce a ‘correct’ UV background, and this is a subject onto itself (see e.g. Wise & Cen 2009; Aubert & Teyssier 2010).”
EXTREME FEEDBACK AND THE EPOCH OF REIONIZATION: CLUES IN THE LOCAL UNIVERSE (2011, background): “Such processes have been extensively studied from a theoretical perspective ovre the past decade (e.g. Dove et al. 2000; Clarke & Oey 2002; Fujita et al. 2003; Gnedin & Kravtsov 2008; Wise & Cen 2009; Razoumov & Somer-Larson 2010; Yajima et al. 2010).”
The Evolution of the Intergalactic Medium (2015, methodology): “…problem of calculating fesc (which requires the daunting task of resolving the multiphase ISM), but with answers essentially ranging from zero to one (Gnedin, Kravtsov & Chen 2008; Wise & Cen 2009) with some recent simulations finding average values of fesc ∼ 10% (Kimm & Cen 2014; Ma et al. 2015).”
THE BIRTH OF A GALAXY: PRIMORDIAL METAL ENRICHMENT AND STELLAR POPULATIONS (2010, methodology): “This discrepancy could be caused by undetected satellite dwarf galaxies, such ones presented here, that contribute to local radiation field, or an ionizing radiation escape fraction near unity (Wise & Cen 2009; Razoumov & Sommer-Larsen 2010; Paardekooper et al. 2011; Yajima et al. 2011).”
Using Lyman-α to detect galaxies that leak Lyman continuum (2014, background): “…from LBGs. Theorists have repeatedly shown that LyC leakage generally increases at lower galaxy masses (e.g. Ferrara & Loeb 2013; Yajima et al. 2011; Wise & Cen 2009), which superficially seems to be consitent with the stronger LyC leakage found from Article published by EDP Sciences A7, page 1…”
Galaxy formation theory (2010, background): “…distribution of mass and ionized regions in the IGM and about the ionizing photon escape probability from high redshift galaxies (Dove et al. 2000; Ricotti and Shull 2000; Razoumov and Sommer-Larsen 2006; Gnedin et al. 2008; Yajima et al. 2009; Wise and Cen 2009) which are still poorly understood.”