Probing the cosmic web in Ly$α$ emission over large scales: an Intensity Mapping forecast for DECaLS/BASS and DESI
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| Natura: | Preprint |
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2024
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| _version_ | 1866915108830052352 |
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| author | Renard, Pablo Spinoso, Daniele Sun, Zechang Zou, Hu Montero-Camacho, Paulo Cai, Zheng |
| author_facet | Renard, Pablo Spinoso, Daniele Sun, Zechang Zou, Hu Montero-Camacho, Paulo Cai, Zheng |
| contents | Being the most prominent HI line, Ly$α$ permeates the cosmic web in emission. Despite its potential as a cosmological probe, its detection on large scales remains elusive. We present a new methodology to perform Ly$α$ intensity mapping with broad-band optical images, by cross-correlating them with Ly$α$ forest data using a custom one-parameter estimator. We also develop an analytical large-scale Ly$α$ emission model with two parameters (average luminosity $\langle L_{\rm Lyα} \rangle$ and bias $b_{\rm e}$) that respects observational constraints from QSO luminosity functions. We compute a forecast for DECaLS/BASS $g$-band images cross-correlated with DESI Ly$α$ forest data, setting guidelines for reducing images into Ly$α$ intensity maps. Given the transversal scales of our cross-correlation (26.4 arcmin, $\sim$33 cMpc/h), our study effectively integrates Ly$α$ emission over all the cosmic volume inside the DESI footprint at $2.2 < z < 3.4$ (the $g$-band Ly$α$ redshift range). Over the parameter space ($\langle L_{\rm Lyα} \rangle$, $b_{\rm e}$) sampled by our forecast, we find a 3$σ$ of large-scale structure in Ly$α$ likely, with a probability of detection of 23.95\% for DESI-DECaLS/BASS, and 54.93\% for a hypothetical DESI phase II with twice as much Ly$α$ QSOs. Without a detection, we derive upper bounds on $\langle L_{\rm Lyα} \rangle$ competitive with optimistic literature estimates ($2.3 \pm 1 \cdot 10^{\rm 41}$ erg/s/cMpc$^3$ for DESI, and $\sim$35\% lower for its hypothetical phase II). Extrapolation to the DESI-Rubin overlap shows that a detection of large-scale structure with Ly$α$ intensity mapping using next-generation imaging surveys is certain. [abridged] |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2406_18775 |
| institution | arXiv |
| publishDate | 2024 |
| record_format | arxiv |
| spellingShingle | Probing the cosmic web in Ly$α$ emission over large scales: an Intensity Mapping forecast for DECaLS/BASS and DESI Renard, Pablo Spinoso, Daniele Sun, Zechang Zou, Hu Montero-Camacho, Paulo Cai, Zheng Cosmology and Nongalactic Astrophysics Being the most prominent HI line, Ly$α$ permeates the cosmic web in emission. Despite its potential as a cosmological probe, its detection on large scales remains elusive. We present a new methodology to perform Ly$α$ intensity mapping with broad-band optical images, by cross-correlating them with Ly$α$ forest data using a custom one-parameter estimator. We also develop an analytical large-scale Ly$α$ emission model with two parameters (average luminosity $\langle L_{\rm Lyα} \rangle$ and bias $b_{\rm e}$) that respects observational constraints from QSO luminosity functions. We compute a forecast for DECaLS/BASS $g$-band images cross-correlated with DESI Ly$α$ forest data, setting guidelines for reducing images into Ly$α$ intensity maps. Given the transversal scales of our cross-correlation (26.4 arcmin, $\sim$33 cMpc/h), our study effectively integrates Ly$α$ emission over all the cosmic volume inside the DESI footprint at $2.2 < z < 3.4$ (the $g$-band Ly$α$ redshift range). Over the parameter space ($\langle L_{\rm Lyα} \rangle$, $b_{\rm e}$) sampled by our forecast, we find a 3$σ$ of large-scale structure in Ly$α$ likely, with a probability of detection of 23.95\% for DESI-DECaLS/BASS, and 54.93\% for a hypothetical DESI phase II with twice as much Ly$α$ QSOs. Without a detection, we derive upper bounds on $\langle L_{\rm Lyα} \rangle$ competitive with optimistic literature estimates ($2.3 \pm 1 \cdot 10^{\rm 41}$ erg/s/cMpc$^3$ for DESI, and $\sim$35\% lower for its hypothetical phase II). Extrapolation to the DESI-Rubin overlap shows that a detection of large-scale structure with Ly$α$ intensity mapping using next-generation imaging surveys is certain. [abridged] |
| title | Probing the cosmic web in Ly$α$ emission over large scales: an Intensity Mapping forecast for DECaLS/BASS and DESI |
| topic | Cosmology and Nongalactic Astrophysics |
| url | https://arxiv.org/abs/2406.18775 |