Growth and anisotropy of ionization fronts near high redshift quasars in the MassiveBlack simulation

Abstract

We use radiative transfer to study the growth of ionized regions around the brightest, z=8 quasars in a large cosmological hydrodynamic simulation that includes black hole growth and feedback (the MassiveBlack simulation). We find that in the presence of the quasar s the comoving HII bubble radii reach 10 Mpc/h after 20 My while with the stellar component alone the HII bubbles are smaller by at least an order of magnitude. Our calculations show that several features are not captured within an analytical growth model of Stromgren spheres. The X-ray photons from hard quasar spectra drive a smooth transition from fully neutral to partially neutral in the ionization front. However the transition from partially neutral to fully ionized is significantly more complex. We measure the distance to the edge of bubbles as a function of angle and use the standard deviation of these distances as a diagnostic of the isotropy of ionized regions. We find that the overlapping of nearby ionized regions from clustered halos not only increases the anisotropy, but also is the main mechanism which allows the outer radius to grow. We therefore predict that quasar ionized bubbles at this early stage in the reionization process should be both significantly larger and more irregularly shaped than bubbles around star forming galaxies. Before the star formation rate increases and the Universe fully reionizes, quasar bubbles will form the most striking and recognizable features in 21cm maps.

11 pages, 10 figures. Updated after referee report

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Cited by in corpus (7)

• Reionization on Large Scales I: A Parametric Model Constructed from Radiation-Hydrodynamic Simulations
• Probing the end of reionization with the near-zones of z > 6 QSOs
• The Concerted Impact of Galaxies and QSOs on the Ionization and Thermal State of the Intergalactic Medium
• The formation and evolution of star clusters in interacting galaxies
• A novel probe of bubble size statistics and time scales of the epoch of reionization using the contour Minkowski Tensor
• Bayesian approach to constraining the properties of ionized bubbles during reionization
• Observing the redshifted 21 cm signal around a bright QSO at $z\sim 10$