Exploring the $S_8$ Tension: Insights from the CatNorth 1.5-Million Quasar Candidates
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arXiv
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| Natura: | Preprint |
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2026
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| author | Qin, Jin Wu, Xue-Bing Fu, Yuming Xu, Haojie Pang, Yuxuan Zhang, Yun-Hao Zhang, Pengjie |
| author_facet | Qin, Jin Wu, Xue-Bing Fu, Yuming Xu, Haojie Pang, Yuxuan Zhang, Yun-Hao Zhang, Pengjie |
| contents | The parameter $S_8$, a key probe of cosmic structure growth, exhibits a persistent $\sim3σ$ tension between high-redshift measurements from cosmic microwave background (CMB) anisotropies and low-redshift weak gravitational lensing observations. This discrepancy may indicate either unaccounted systematic effects or new physics beyond the standard $Λ$CDM cosmology. In this work, we constrain $S_8$ using the high purity CatNorth 1.5 million quasar candidate catalog and the {\it Planck} DR4 CMB lensing data across the broad redshift ranges through auto-correlation and cross-correlation analyses. To address the spatial incompleteness, we develop a machine-learning-based selection function that effectively suppresses the systematics-induced power spectrum excess on large scales. Our robust low-redshift measurements at $z<1.5$ yield $S_8 = 0.844^{+0.058}_{-0.056}$, consistent with the {\it Planck} 2018 CMB anisotropies constraints of $S_8=0.834\pm0.016$ but lower than the $0.879^{+0.055}_{-0.055}$ reported by a previous work using the Quaia quasar candidate catalog. However, for high-redshift faint quasars at $z>1.5$, we find a lower value of $S_8=0.724^{+0.058}_{-0.054}$, likely due to the sample incompleteness and/or the foreground contamination. Further tests on the volume-limited samples exhibit a consistent trend: $S_8 = 0.835^{+0.053}_{-0.049}$ for $z < 2$, $0.824^{+0.061}_{-0.062}$ for $0.4 < z < 1.5$, and a lower value of $0.789^{+0.062}_{-0.062}$ for the higher redshift range of $1.5 < z < 2.5$. While future data may refine these results, our current measurements based on a large sample of quasar candidates show less evidence of the $S_8$ tension. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2603_09457 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | Exploring the $S_8$ Tension: Insights from the CatNorth 1.5-Million Quasar Candidates Qin, Jin Wu, Xue-Bing Fu, Yuming Xu, Haojie Pang, Yuxuan Zhang, Yun-Hao Zhang, Pengjie Cosmology and Nongalactic Astrophysics The parameter $S_8$, a key probe of cosmic structure growth, exhibits a persistent $\sim3σ$ tension between high-redshift measurements from cosmic microwave background (CMB) anisotropies and low-redshift weak gravitational lensing observations. This discrepancy may indicate either unaccounted systematic effects or new physics beyond the standard $Λ$CDM cosmology. In this work, we constrain $S_8$ using the high purity CatNorth 1.5 million quasar candidate catalog and the {\it Planck} DR4 CMB lensing data across the broad redshift ranges through auto-correlation and cross-correlation analyses. To address the spatial incompleteness, we develop a machine-learning-based selection function that effectively suppresses the systematics-induced power spectrum excess on large scales. Our robust low-redshift measurements at $z<1.5$ yield $S_8 = 0.844^{+0.058}_{-0.056}$, consistent with the {\it Planck} 2018 CMB anisotropies constraints of $S_8=0.834\pm0.016$ but lower than the $0.879^{+0.055}_{-0.055}$ reported by a previous work using the Quaia quasar candidate catalog. However, for high-redshift faint quasars at $z>1.5$, we find a lower value of $S_8=0.724^{+0.058}_{-0.054}$, likely due to the sample incompleteness and/or the foreground contamination. Further tests on the volume-limited samples exhibit a consistent trend: $S_8 = 0.835^{+0.053}_{-0.049}$ for $z < 2$, $0.824^{+0.061}_{-0.062}$ for $0.4 < z < 1.5$, and a lower value of $0.789^{+0.062}_{-0.062}$ for the higher redshift range of $1.5 < z < 2.5$. While future data may refine these results, our current measurements based on a large sample of quasar candidates show less evidence of the $S_8$ tension. |
| title | Exploring the $S_8$ Tension: Insights from the CatNorth 1.5-Million Quasar Candidates |
| topic | Cosmology and Nongalactic Astrophysics |
| url | https://arxiv.org/abs/2603.09457 |