Escaping Lyman continuum photons from galaxies likely reionized the intergalactic medium at redshifts z ≳ 6. However, the Lyman continuum is not directly observable at these redshifts and secondary indicators of Lyman continuum escape must be used to estimate the budget of ionizing photons. Observationally, at redshifts z ∼ 2–3 where the Lyman continuum is observationally accessible, surveys have established that many objects that show appreciable Lyman continuum escape fractions f esc also show enhanced [O iii]/[O ii] (O32) emission line ratios. Here, we use radiative transfer analyses of cosmological zoom-in simulations of galaxy formation to study the physical connection between f esc and O32. Like the observations, we find that the largest f esc values occur at elevated O32 ∼ 3–10 and that the combination of high f esc and low O32 is extremely rare. While high f esc and O32 often are observable concurrently, the timescales of the physical origin for the processes are very different. Large O32 values fluctuate on short (∼1 Myr) timescales during the Wolf–Rayet-powered phase after the formation of star clusters, while channels of low absorption are established over tens of megayears by collections of supernovae. We find that while there is no direct causal relation between f esc and O32, high f esc most often occurs after continuous input from star formation-related feedback events that have corresponding excursions to large O32 emission. These calculations are in agreement with interpretations of observations that large f esc tends to occur when O32 is large, but large O32 does not necessarily imply efficient Lyman continuum escape.

We present synthetic observations for the first generations of galaxies in the Universe and make predictions for future deep field observations for redshifts greater than 6. Due to the strong impact of nebular emission lines and the relatively compact scale of H ii regions, high resolution cosmological simulations and a robust suite of analysis tools are required to properly simulate spectra. We created a software pipeline consisting of FSPS, Hyperion, Cloudy and our own tools to generate synthetic IR observations from a fully three-dimensional arrangement of gas, dust, and stars. Our prescription allows us to include emission lines for a complete chemical network and tackle the effect of dust extinction and scattering in the various lines of sight. We provide spectra, 2-D binned photon imagery for both HST and JWST IR filters, luminosity relationships, and emission line strengths for a large sample of high redshift galaxies in the Renaissance Simulations. Our resulting synthetic spectra show high variability between galactic halos with a strong dependence on stellar mass, metallicity, gas mass fraction, and formation history. haloes with the lowest stellar mass have the greatest variability in [O iii]/Hβ, [O iii] and C iii] while haloes with higher masses are seen to show consistency in their spectra and [O iii] equivalent widths (EW) between 1Å and 10Å. Viewing angle accounted for three-fold difference in flux due to the presence of ionized gas channels in a halo. Furthermore, JWST colour plots show a discernible relationship between redshift, colour, and mean stellar age.

We study a simulation of a nascent massive, so-called direct-collapse, black hole that induces a wave of nearby massive metal-free star formation, unique to this seeding scenario and to very high redshifts. We implement a dynamic, fully-three dimensional prescription for black hole radiative feedback, star formation, and radiative transfer to explore the observational signatures of the massive black hole hosting galaxy. We find a series of distinct colors and emission line strengths, dependent on the relative strength of star formation and black hole accretion. We predict that the forthcoming James Webb Space Telescope might be able to detect and distinguish a young galaxy that hosts a direct-collapse black hole in this configuration at redshift 15 with as little as a 20,000-second total exposure time across four filters, critical for constraining supermassive black hole seeding mechanisms and early growth rates. We also find that a massive seed black hole produces strong, H 2 -dissociating Lyman-Werner radiation. 1 arXiv:1809.03526v1 [astro-ph.GA] 10 Sep 2018The existence of quasars when the Universe was less than a billion years old 1-5 implies that their progenitors are seeded at very early times and grow rapidly. However, black hole growth rates 6,7 are limited by their own radiation feedback, requiring models to either demonstrate high accretion rates or a massive black hole seed 8,9 . In the presense of a Lyman-Werner (LW; 11.2 -13.6 eV) background, the formation of molecular hydrogen (H 2 ) in a primordial, star-less halo is suppressed and the gas can only cool atomically 10, 11 . After reaching a virial temperature of ∼ 10 4 K, these "atomic cooling" halos collapse isothermally to hydrogen number densities of 10 6 cm −3 without fragmenting 12 . After which, the gas becomes optically thick to Ly-α, and we expect the medium to begin a runaway collapse that eventually leads to the formation of a massive (10 3 − 10 5 M ) direct collapse black hole (DCBH) [13][14][15] .We simulate the evolution of a DCBH-hosting halo using the radiation hydrodynamics ENZO 16 code. In our simulation, star formation is suppressed by the dissociation of molecular hydrogen (H 2 ) due to an isotropic, strong (10 3 J 21 * ), and constant LW background, which we apply from z = 30 until the end of the simulation. Prior to the introduction of the black hole at z = 15, our host halo has a virial temperature of ∼ 10 4 K, is hydrodynamically collapsing, is metal-free, and hosts no prior star formation, which is physically conincident with the conditions preceeding DCBH formation. Chon et al. (2016) 17 suggest a peak in the frequency of DCBH formation around z ≈ 15 and we focus on this value for our analysis in light of observational evidence of * J 21 ≡ 10 −21 erg s −1 cm −2 Hz −1 sr −1