[Astro] Lunch talk

[Michael Anderson Jennings]

Hi everyone,

This week's lunch talk will be given by Fiona, on Thursday at 1pm in A113. Title and abstract are below:

How probable is the Ly-𝛼 damping wing in the spectrum of the redshift z = 5.9896 quasar ULAS J0148+0600?

At the end of the Epoch of Reionisation we expect most of the IGM to be ionized, interspersed with patches of fully neutral hydrogen. The first direct measurement of an island of neutral hydrogen at the end stages of reionisation, z~6, was from the damping wing of the quasar ULAS J0148+0600 (J0148) by Becker et al. 2024. Here we use simulations from Sherwood Relics to assess the expected incidence of quasars with Ly-𝛼 and Ly-𝛽 absorption similar to the observed J0148 spectrum for different quasar properties and reionisation histories. We find a late end to reionisation at 𝑧 = 5.3 is a necessary requirement for reproducing a Ly-𝛼 damping wing consistent with J0148, but it is still rare, with our fiducial model producing an observation similar to J0148 in only ~3 per cent of lines of sight. We speculate this is because the ionising emission from J0148 is variable on timescales 𝑡 < 10^5 yr, or alternatively that the Ly-𝛼 transmission in the J0148 near zone is impacted by the transverse proximity effect from nearby star-forming galaxies or undetected quasars. We also assess the efficacy of the method used to find the neutral island in Becker 24, finding that an observation such as J0148 is very likely due to a neutral island, however many neutral islands are also missed with this analysis of the quasar damping wing.

Thanks,
Mikey

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