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Arxiv: Mapping reionization bubbles in the JWST era II: inferring the position and characteristic size of individual bubbles Published: 1/14/2025 11:58:47 AM Updated: 1/14/2025 11:58:47 AM

Paper abstract: The James Webb Space Telescope (JWST) is discovering an increasing number ofgalaxies well into the early stages of the Epoch of Reionization (EoR). Many ofthese galaxies are clustered with strong Lyman alpha (Ly\alpha) emission,motivating the presence of surrounding cosmic HII regions that would facilitateLy\alpha transmission through the intergalactic medium (IGM). Detecting theseHII "bubbles" would allow us to connect their growth to the properties of thegalaxies inside them. Here we develop a new forward-modeling framework toestimate the local HII region size and location from Ly\alpha spectra ofgalaxy groups in the early stages of the EoR. Our model takes advantage of thecomplementary information provided by neighboring sightlines through the IGM.Our forward models sample the main sources of uncertainty, including: (i) theglobal neutral fraction; (ii) EoR morphology; (iii) emergent Ly\alphaemission; and (iv) NIRSpec instrument noise. Depending on the availability ofcomplementary nebular lines, ~ 0.006 \unicode{x2013} 0.01 galaxies percMpc^3, are required to be \gtrsim95\% confident that the HII bubblelocation and size recovered by our method is accurate to within ~ 1comoving Mpc. This corresponds roughly to tens of galaxies atz~7\unicode{x2013}8 in ~2x2 tiled pointing with JWST NIRSpec. Such asample is achievable with a targeted survey with completeness down to M_{\rmUV}^{\rm min}<~ -19 \unicode{x2013} -17, depending on the over-densityof the field. We test our method on 3D EoR simulations as well as misspecifiedequivalent width distributions, in both cases accurately recovering the HIIregion surrounding targeted galaxy groups.