Measuring and unbiasing the BAO shift in the Lyman-Alpha forest with AbacusSummit
Fuente:
arXiv
Saved in:
| Main Authors: | , , , , , , |
|---|---|
| Format: | Preprint |
| Published: |
2025
|
| Subjects: | |
| Online Access: | |
| Tags: |
Add Tag
No Tags, Be the first to tag this record!
|
| _version_ | 1866915202051604480 |
|---|---|
| author | Hadzhiyska, Boryana de Belsunce, Roger Cuceu, Andrei Guy, Julien Ivanov, Mikhail M. Coquinot, Henri Font-Ribera, Andreu |
| author_facet | Hadzhiyska, Boryana de Belsunce, Roger Cuceu, Andrei Guy, Julien Ivanov, Mikhail M. Coquinot, Henri Font-Ribera, Andreu |
| contents | The currently observing Dark Energy Spectroscopic Instrument (DESI) places sub-percent constraints on the Baryon Acoustic Oscillations (BAO) scaling parameters from the Lyman-$α$ (Ly-$α$) forest. However, no systematic error budget stemming from non-linearities in the 3D clustering of the Ly-$α$ forest is included in the DESI-Ly-$α$ analysis. In this work, we measure the size of the shift of the BAO peak using large Ly-$α$ forest mocks produced on the $N$-body simulation suite \textsc{AbacusSummit}. Specifically, we measure the Ly-$α$ auto-correlation and the Ly-$α$-quasar cross-correlation functions. We use the DESI Ly-$α$ forest fitting pipeline, \textsc{Vega}, with the publicly available covariance matrix from eBOSS DR16. To mitigate the noise, we adopt a linear control variates (LCV) technique, reducing the error bars by a factor of up to $\sim \sqrt{50}$ on large scales. From the auto-correlation, we detect a small positive shift in radial direction of $Δα_\parallel = 0.35\%$ at the 3$σ$ level and virtually no shift in the transverse direction, $α_\perp$. From the cross-correlation, we see a similar shift to $Δα_\parallel$, albeit with larger error bars, and a small negative shift, $Δα_\perp=\sim$0.25\%, at the 2$σ$ level. We also make a connection with the Ly-$α$ forest effective field theory (EFT) framework and find that the one-loop EFT power spectrum yields unbiased measurements of the BAO shift parameters in radial and transverse direction for Ly-$α$ auto and the Ly-$α$-quasar cross-correlation measurements. When using the one-loop EFT framework, we find that we can recover the BAO parameters without a shift, which has important implications for future Ly-$α$ forest analyses based on EFT. This work paves the way for the full-shape analysis of DESI and future surveys. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2503_13442 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Measuring and unbiasing the BAO shift in the Lyman-Alpha forest with AbacusSummit Hadzhiyska, Boryana de Belsunce, Roger Cuceu, Andrei Guy, Julien Ivanov, Mikhail M. Coquinot, Henri Font-Ribera, Andreu Cosmology and Nongalactic Astrophysics Astrophysics of Galaxies The currently observing Dark Energy Spectroscopic Instrument (DESI) places sub-percent constraints on the Baryon Acoustic Oscillations (BAO) scaling parameters from the Lyman-$α$ (Ly-$α$) forest. However, no systematic error budget stemming from non-linearities in the 3D clustering of the Ly-$α$ forest is included in the DESI-Ly-$α$ analysis. In this work, we measure the size of the shift of the BAO peak using large Ly-$α$ forest mocks produced on the $N$-body simulation suite \textsc{AbacusSummit}. Specifically, we measure the Ly-$α$ auto-correlation and the Ly-$α$-quasar cross-correlation functions. We use the DESI Ly-$α$ forest fitting pipeline, \textsc{Vega}, with the publicly available covariance matrix from eBOSS DR16. To mitigate the noise, we adopt a linear control variates (LCV) technique, reducing the error bars by a factor of up to $\sim \sqrt{50}$ on large scales. From the auto-correlation, we detect a small positive shift in radial direction of $Δα_\parallel = 0.35\%$ at the 3$σ$ level and virtually no shift in the transverse direction, $α_\perp$. From the cross-correlation, we see a similar shift to $Δα_\parallel$, albeit with larger error bars, and a small negative shift, $Δα_\perp=\sim$0.25\%, at the 2$σ$ level. We also make a connection with the Ly-$α$ forest effective field theory (EFT) framework and find that the one-loop EFT power spectrum yields unbiased measurements of the BAO shift parameters in radial and transverse direction for Ly-$α$ auto and the Ly-$α$-quasar cross-correlation measurements. When using the one-loop EFT framework, we find that we can recover the BAO parameters without a shift, which has important implications for future Ly-$α$ forest analyses based on EFT. This work paves the way for the full-shape analysis of DESI and future surveys. |
| title | Measuring and unbiasing the BAO shift in the Lyman-Alpha forest with AbacusSummit |
| topic | Cosmology and Nongalactic Astrophysics Astrophysics of Galaxies |
| url | https://arxiv.org/abs/2503.13442 |