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SUMMARY:The effect of inhomogeneous reionisation on the Lyman-𝛼 forest 
 - Margherita Molaro (Nottingham) 
DTSTART:20211001T103000Z
DTEND:20211001T113000Z
UID:TALK161644@talks.cam.ac.uk
CONTACT:Martin Haehnelt
DESCRIPTION:Lyman-alpha absorption features in the spectra of bright\, hig
 h-redshift quasars contain a wealth of information on the evolution of the
  intergalactic medium (IGM) during and soon after the final stages of reio
 nisation. By comparing observations with simulations of these absorption f
 eatures in different reionisation scenarios we are therefore able to obtai
 n information on how this process unfolded.\nOne of the most significant c
 hallenges on the simulation side of this effort remains the implementation
  of photo-ionisation and -heating of the IGM by UV photons. Homogeneous UV
  background approximations are widely used to keep computational costs dow
 n\, however it is believed they might miss crucial fluctuations in the ion
 isation and temperature fields\, and therefore artificially alter the simu
 lated Lyman alpha features. It is therefore important to establish whether
  constraints obtained from such models might be affected by biases.\nIn th
 is talk\, I will review a recent work directly comparing a homogeneous UVB
  approximation with an hybrid-RT prescription in the Sherwood-Relics suite
  of IGM simulations. This study has indeed confirmed that the different tr
 eatment of the UV radiation field leads to significant differences in the 
 1D Lyman alpha power spectrum\, at both small and large scales. More impor
 tantly\, it has highlighted that inhomogeneous reionisation effects should
  be accounted for in analyses of forthcoming high precision measurements o
 f high redshift quasars if systematic biases are to be avoided. Convenient
 ly\, the same study also allowed us to develop a correction term to accoun
 t for these effects that can be easily applied to existing simulations rel
 ying on homogeneous UV background approximations.
LOCATION:via zoom 
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