ESCAPE FRACTION OF IONIZING PHOTONS DURING REIONIZATION: EFFECTS DUE TO SUPERNOVA FEEDBACK AND RUNAWAY OB STARS

By T. Kimm, Renyue Cen. 2014

204 citations recorded by the source corpus.

The fraction of hydrogen ionizing photons escaping from galaxies into the intergalactic medium is a critical ingredient in the theory of reionization. We use two zoomed-in, high-resolution (4 pc), cosmological radiation hydrodynamic simulations with adaptive mesh refinement to investigate the impact of two physical mechanisms (supernova, SN, feedback, and runaway OB stars) on the escape fraction (fesc) at the epoch of reionization (z ⩾ 7). We implement a new, physically motivated SN feedback model that can approximate the Sedov solutions at all (from the free expansion to snowplow) stages. We find that there is a significant time delay of about ten million years between the peak of star formation and that of escape fraction, due to the time required for the build-up and subsequent destruction of the star-forming cloud by SN feedback. Consequently, the photon number-weighted mean escape fraction for dwarf galaxies in halos of mass 108–1010.5 M☉ is found to be , although instantaneous values of fesc > 20% are common when star formation is strongly modulated by the SN explosions. We find that the inclusion of runaway OB stars increases the mean escape fraction by 22% to . As SNe resulting from runaway OB stars tend to occur in less dense environments, the feedback effect is enhanced and star formation is further suppressed in halos with in the simulation with runaway OB stars compared with the model without them. While both our models produce enough ionizing photons to maintain a fully ionized universe at z ⩽ 7 as observed, a still higher amount of ionizing photons at z ⩾ 9 appears necessary to accommodate the high observed electron optical depth inferred from cosmic microwave background observations.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/366977259d234b5e4083adbdbb9f4bb0648a37b8

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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): “Previous groups (Wise & Cen 2009; Kimm & Cen 2014; Wise et al. 2014) have found a correlation between the SFR and fesc with some delay as the ionization front propagates beyond the virial radius.”
The stellar mass-halo mass relation of isolated field dwarfs : a critical test of ΛCDM at the edge of galaxy formation (2016, background): “In particular, Kimm & Cen (2014) found, using high resolution simulations of galaxies forming in haloes with virial masses ∼108 − 1010M at z & 7, that fesc fluctuates by orders of magnitude over a dynamical time due to stellar feedback (and see also Trebitsch et al. 2015).”
MOMENTUM INJECTION BY SUPERNOVAE IN THE INTERSTELLAR MEDIUM (2014, methodology): “In their AMR simulations, Kimm & Cen (2014) apply either the initial ejecta momentum or a “final” (post-ST) momentum to zones depending on whether the mass in a given feedback sector is greater or less than an SNR would have at the “transition” time of Blondin et al. (1998).”
Cosmic Dawn (CoDa): the first radiation-hydrodynamics simulation of reionization and galaxy formation in the Local Universe (2015, background): “• the very high resolution regime, which is closer to resolving the interstellar medium and star forming molecular clouds, such as Kim et al. (2013); Kimm & Cen (2014); Rosdahl et al. (2015), where the cell can be as small as dx∼ 1 pc in the most refined regions.”
Large Ly α opacity fluctuations and low CMB τ in models of late reionization with large islands of neutral hydrogen extending to z < 5.5 (2018, background): “…to the evolution of the escape fraction of ionizing photons from galaxies, possibly due to changes in morphology, stellar populations, and dust con- tent of these galaxies (Rosdahl et al. 2018; Trebitsch et al. 2017; Kimm et al. 2017; Paardekooper et al. 2015; Kimm & Cen 2014; Yajima et al. 2011).”
Detection of high Lyman continuum leakage from four low-redshift compact star-forming galaxies (2016, background): “According to Kimm & Cen (2014) and Trebitsch, Blaizot & Rosdahl (2015) simulations, the escape fraction of ionizing photons from low-mass galaxies is probably also strongly variable with time, due to the very bursty star formation histories in their low mass halos.”
ARE ULTRA-FAINT GALAXIES AT z = 6–8 RESPONSIBLE FOR COSMIC REIONIZATION? COMBINED CONSTRAINTS FROM THE HUBBLE FRONTIER FIELDS CLUSTERS AND PARALLELS (2015, background): “While cosmological simulations point to a halo mass limit of 106M⊙ for early galaxy formation (Jaacks et al. 2012; Kimm & Cen 2014; Wise et al. 2014), the depth of current observations however limits the exploration of the LF to galaxies brighter than ∼0.1L⋆.”
FIRE-2 simulations: physics versus numerics in galaxy formation (2017, methodology): “Similar aspects of that algorithm – in particular the treatment of SNe momentum accounting for the terminal momentum – have been recently developed for other codes by Kimm & Cen (2014), Martizzi et al. (2015), and Rosdahl et al. (2017).”
The difficulty of getting high escape fractions of ionizing photons from high-redshift galaxies: A view from the FIRE cosmological simulations (2015, background): “…simulations with “sub-grid” ISM, star formation, and feedback models (e.g. Razoumov & Sommer-Larsen 2010; Yajima et al. 2011), but our results are more consistent with many recent simulations with state-of-art ISM and feedback models (e.g. Kim et al. 2013; Wise et al. 2014; Kimm & Cen 2014).”
The First Billion Years project: the escape fraction of ionizing photons in the epoch of reionization (2015, result): “Our results refine the study of Kimm & Cen (2014), who found that in galaxies of low escape fraction the optical depth in a radius of 100 pc is ∼ 2 − 4, large enough to absorb the majority of produced ionising photons.”
Fluctuating feedback-regulated escape fraction of ionizing radiation in low-mass, high-redshift galaxies (2017, methodology): “studies (e.g. Kimm & Cen 2014; Wise et al. 2014; Ma et al. 2015), we must tread carefully in that direction, and not take this number at face value: this is the direct result of our subgrid recipe for supernovae, which explode 10 Myr after the birth of the star particle.”
Three-phase Interstellar Medium in Galaxies Resolving Evolution with Star Formation and Supernova Feedback (TIGRESS): Algorithms, Fiducial Model, and Convergence (2016, methodology): “The SN feedback prescriptions described in Kimm & Cen (2014) and Hopkins et al. (2014) use an EJ-transitioning-to-MC approach.”
Massive runaway and walkaway stars (2018, background): “…galaxies (more efficient mixing of nuclear yields), on the ionization of their surroundings (enhanced escape fraction, e.g. Conroy & Kratter 2012; Kimm & Cen 2014; Ma et al. 2016), but it might possibly decrease the efficiency of their mechanical feedback because of the lower density of the…”
PARSEC evolutionary tracks of massive stars up to 350 M ☉ at metallicities 0.0001 ≤ Z ≤ 0.04 (2015, background): “They are the most important stellar sources of ionizing and dissociation photons (Schaerer et al. 2011; Kimm & Cen 2014; Dale, Ercolano & Bonnell 2012; Cai et al. 2014; Hollenbach & Tielens 1999; Yu, Wang & Li 2015).”
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 SPHINX Cosmological Simulations of the First Billion Years: the Impact of Binary Stars on Reionization★ (2018, methodology): “The sources of reionization, however, form and emit radiation on relatively tiny, subpc scales, and even if subpc scales are not represented, predicting the transfer and escape of ionizing radiation through the ISM requires at least a few pc resolution (e.g. Kimm & Cen 2014; Xu et al. 2016).”
Feedback-regulated star formation and escape of LyC photons from mini-haloes during reionization (2016, methodology): “We adopt the mechanical feedback scheme introduced by Kimm & Cen (2014) and Kimm et al. (2015) to model the explosion of massive (M ≥ 8 M ) Pop II stars.”