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Hi all,</div>
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Reminder of today's lunch talk!</div>
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Thanks,</div>
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Rhys</div>
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<div id="divRplyFwdMsg" dir="ltr"><font face="Calibri, sans-serif" style="font-size:11pt" color="#000000"><b>From:</b> Astro <astro-bounces@lists.nottingham.ac.uk> on behalf of Rhys Jordan <rhys.jordan@nottingham.ac.uk><br>
<b>Sent:</b> 09 March 2026 10:21<br>
<b>To:</b> Nottingham Astro Group <astro@nottingham.ac.uk><br>
<b>Subject:</b> [Astro] Lunch Talk - 12/03/2026</font>
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Hi all,</div>
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This week’s lunch talk will be given by Ke Ma on Thursday, the 12th of March, at 1 PM in A113. Title and abstract below.</div>
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<b>Title</b>: Constraining the silicon abundance in the IGM by modelling the Lyá – Si III correlations</div>
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<b>Abstract</b>:<br>
The one-dimensional Lyman-á Forest power spectrum (P1D) serves as an important probe of the IGM and cosmological parameters. However, contamination from Si III absorption lines embedded within the Lyá forest introduces a significant systematic uncertainty in
P1D measurements. To better model and mitigate this effect, we performed a detailed analysis of Si III absorption and its impact on the P1D using the Sherwood-Relics hydrodynamical simulation suite. We identify several effects that were not captured in earlier
studies, largely due to limitations in spectral resolution at the time. These effects are also present in the more recent DESI measurements. To address them, we develop a new analytical fitting function that incorporates previously neglected physical ingredients.
The model is validated against multiple simulated datasets across redshifts 2.2 < z < 5.0 and wavenumbers k < 0.2 s/km (See arXiv:2509.08613). Applying this model to eBOSS and DESI observations reveals a Si III signal stronger than expected from forward modelling
based on published Si abundance constraints. This might point to a new way to constrain the metal abundance in the IGM.</div>
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Thanks,</div>
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Rhys</div>
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