Reionization in Technicolor

Abstract

We present the Technicolor Dawn simulations, a suite of cosmological radiationhydrodynamic simulations of the first 1.2 billion years. By modeling a spatiallyinhomogeneous UVB on-the-fly with 24 frequencies and resolving dark matter halos down to 10 8 M ⊙ within 12h −1 Mpc volumes, our simulations unify observations of the intergalactic and circumgalactic media, galaxies, and reionization into a common framework. The only empirically-tuned parameter, the fraction f esc,gal (z) of ionizing photons that escape the interstellar medium, is adjusted to match observations of the Lyman-α forest and the cosmic microwave background. With this single calibration, our simulations reproduce the history of reionization; the stellar mass-star formation rate relation of galaxies; the number density and metallicity of damped Lyman-α absorbers (DLAs) at z ∼ 5; the abundance of weak metal absorbers; the ultraviolet background (UVB) amplitude; and the Lyman-α flux power spectrum at z = 5.4. The galaxy stellar mass and UV luminosity functions are underproduced by ≤ 2×, suggesting an overly vigorous feedback model. The mean transmission in the Lyman-α forest is underproduced at z < 6, indicating tension between measurements of the UVB amplitude and Lyman-α transmission. The observed Si IV column density distribution is reasonably well-reproduced (∼ 1σ low). By contrast, C IV remains significantly underproduced despite being boosted by an intense > 4 Ryd UVB. Solving this problem by increasing metal yields would overproduce both weak absorbers and DLA metallicities. Instead, the observed strength of high-ionization emission from high-redshift galaxies and absorption from their environments suggest that the ionizing flux from conventional stellar population models is too soft.

The z ∼ 6 Luminosity Function Fainter than −15 mag from the Hubble Frontier Fields: The Impact of Magnification Uncertainties

“…The impact of radiative feedback is less important in the CROC simulations than in CoDa. Finlator et al (2015Finlator et al ( , 2016Finlator et al ( , 2017: the Finlator et al (2015Finlator et al ( , 2016Finlator et al ( , 2017 LF results are based on a cosmological simulation of galaxy formation in a h 7.5 1 3 -( ) Mpc 3 volume of the universe including both gravity and hydrodynamics as implemented in the GADGET-3 code (Springel 2005). To this code, gas cooling is added through collisional excitation of hydrogen and helium as in Katz et al (1996), and metal line cooling is implemented using the collisional ionization equilibrium tables of Sutherland & Dopita (1993).…”

“…Star formation is added using the Kennicutt-Schmidt law, with supernovae feedback included following the "ezw" prescription from Davé et al (2013) and metal enrichment from supernovae as implemented as in Oppenheimer & Davé (2008). Flattening in the Finlator et al (2015Finlator et al ( , 2016Finlator et al ( , 2017 LFs occurs mostly due to less efficient gas cooling at lower halo masses.…”

“…8 In addition to the clear scientific importance of the faint-end slope α for computing the total ionizing emissivity from faint galaxies, the observations also allow us to test for a possible flattening or turn-over of the UV LF at low luminosities. Many cosmological hydrodynamic simulations of galaxy formation predict a flattening in the UV LF at approximately−13 or approximately−15magdue to less efficient atomic and molecular hydrogen cooling, respectively (Muñoz & Loeb 2011;Krumholz & Dekel 2012;Jaacks et al 2013;Kuhlen et al 2013;Wise et al 2014;Finlator et al 2016;Gnedin 2016;Liu et al 2016), while other simulations predict a flattening in the rangeapproximately−16 to approximately−13 magdue to the impact of radiative feedback (O'Shea et al 2015;Ocvirk et al 2016). Meanwhile, by combining abundance matching and detailed studies of the color-magnitude diagram of lowluminosity dwarfs in the local universe, evidence for a lowmass turn-over in the LF has been reported at −13 mag (Boylan-Kolchin et al 2015 see also Boylan-Kolchin et al 2014).…”

Contribution from stars stripped in binaries to cosmic reionization of hydrogen and helium

“…Numerical and analytical models of the early Universe (e.g., Gnedin & Ostriker 1997;McQuinn et al 2007;Robertson et al 2010;Haardt & Madau 2012;Finlator et al 2018;Katz et al 2019) reproduce the observed completion of hydrogen reionization around a redshift, z, of ∼ 6 (Fan et al 2006b). However, to achieve this, the models require that a large fraction of the produced ionizing photons escape the host galaxies and reach the IGM.…”

Metal-enriched galaxies in the first ∼1 billion years: evidence of a smooth metallicity evolution at z ∼ 5

“…z < 4.5 DLAs n512RT64 simulation at z = 5(Finlator et al 2018) volatile elements at z < 4.5 volatile elements at z > 4.5 N HI -weighted mean metallicity for median z=4.83 Metallicity evolution with redshift. The red dots with blue error bars are the binned N H I -weighted mean metallicities of DLAs at z < 4.5 using volatile elements from the literature, with each bin containing 16 or 17 DLAs and the solid blue line showing the corresponding best fit.…”