The Near Zone Sizes of High-Redshift Quasars as a Probe of the Epoch of Reionization

Abstract

This paper presents a review and further development of the current methodology for measuring the near zone sizes of high redshift quasars. I assess the near zone size measurement methods used by three key papers in the field, Fan et al. (2006), Eilers et. al (2017), and Ishimoto et al. (2020), and discuss their derived results. The work of these three papers has greatly progressed our knowledge of near zone sizes and the Epoch of Reionization, but the issue of noisy spectra still hinders our research from reaching further. Here I present an improved methodology for measuring near zone sizes, one that offers a more robust and stable measurement when dealing with low signal-to-noise ratio data. In addition, using data provided by high-redshift quasar surveys such as The Sloan Digital Sky Survey, The Dark Energy Survey, VISTA Hemisphere Survey, Wide-field Infrared Survey Explorer, Pan-STARRS, and SHELLQs, I present a collection of 282 high redshift (5.68 ≤ z ≤ 7.07) quasars (after initial data cuts) and their near zone sizes as calculated by my new methodology. Using this large sample of quasars, I then compare my dataset to the key results of the three prior papers, taking special note of how the near zone size evolves with redshift. I find that my results agree broadly with those of the three papers, but a new fit for the near zone size dependence on redshift may need to be calculated in the future. Finally, I evaluate the robustness of my methodology by degrading the spectra to different noise levels and determining when the calculation breaks down. By determining the signal to noise ratio at which my method breaks down, I can further inform future telescope proposals by quantifying a noise threshold after which we can no longer do reliable science. While my analysis does not yet give us an exact signal to noise ratio where the methodology breaks down, I am optimistic about finding this value in future work.