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courses:ast403:gunn-peterson-test [2026/03/24 10:03] – shuvocourses:ast403:gunn-peterson-test [2026/03/28 01:37] (current) – [Implications and Sensitivity] shuvo
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 **The Reionization "Wall":** For many years, astronomers observed the "Lyman-alpha Forest" (thin lines of absorption), indicating a highly ionized IGM. However, when quasars at $z > 6$ were discovered (most notably by the Sloan Digital Sky Survey), the flux suddenly dropped to zero, signaling that we had reached the era when the Universe was still substantially neutral. **The Reionization "Wall":** For many years, astronomers observed the "Lyman-alpha Forest" (thin lines of absorption), indicating a highly ionized IGM. However, when quasars at $z > 6$ were discovered (most notably by the Sloan Digital Sky Survey), the flux suddenly dropped to zero, signaling that we had reached the era when the Universe was still substantially neutral.
  
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 +[{{ :courses:ast403:iniozation_model.jpeg?600 | Fig 3: Cosmic ionnizaton history.}}]
 ===== Comparison: LLS vs. Gunn-Peterson ===== ===== Comparison: LLS vs. Gunn-Peterson =====
 While the Lyman-limit systems (LLSs) mentioned previously represent discrete, dense clouds (optically thick at $912 \text{ Å}$), the Gunn-Peterson effect represents the global, diffuse state of the IGM (optically thick at $1216 \text{ Å}$).  While the Lyman-limit systems (LLSs) mentioned previously represent discrete, dense clouds (optically thick at $912 \text{ Å}$), the Gunn-Peterson effect represents the global, diffuse state of the IGM (optically thick at $1216 \text{ Å}$). 
courses/ast403/gunn-peterson-test.1774368230.txt.gz · Last modified: by shuvo
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