Velocity Reconstruction from KSZ: Measuring $f_{NL}$ with ACT and DESILS
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| Format: | Preprint |
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2025
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| _version_ | 1866913914759938048 |
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| author | Hotinli, Selim C. Smith, Kendrick M. Ferraro, Simone |
| author_facet | Hotinli, Selim C. Smith, Kendrick M. Ferraro, Simone |
| contents | The kinetic Sunyaev-Zel'dovich (kSZ) effect offers an indirect way to reconstruct large-scale cosmic velocities, by correlating high-resolution CMB temperature maps with galaxy surveys. In this work, we present the first three-dimensional reconstruction of the large-scale velocity field using a photometric galaxy survey, using data from the DESI Legacy Imaging Surveys (DESILS) and the Atacama Cosmology Telescope (ACT) DR5. We detect an $11.7σ$ correlation between our velocity reconstruction and the galaxy field, using only DESILS LRGs in the northern Galactic hemisphere. We find that the overall amplitude of the kSZ-induced correlation is low relative to a halo model prediction ($b_v = 0.45^{+0.06}_{-0.05}$), in agreement with previous results which find high feedback and smoothed gas profiles near massive galaxies. We use this measurement to place new constraints on local-type primordial non-Gaussianity (PNG), obtaining $f_{\rm NL}\!=\!-39^{+40}_{-33}$. This represents the most stringent $f_{\rm NL}$ constraint from kSZ velocity-based analyses to date. We validate our findings through extensive null tests, including tests for CMB foregrounds based on comparing 90 and 150 GHz CMB data. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2506_21657 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Velocity Reconstruction from KSZ: Measuring $f_{NL}$ with ACT and DESILS Hotinli, Selim C. Smith, Kendrick M. Ferraro, Simone Cosmology and Nongalactic Astrophysics The kinetic Sunyaev-Zel'dovich (kSZ) effect offers an indirect way to reconstruct large-scale cosmic velocities, by correlating high-resolution CMB temperature maps with galaxy surveys. In this work, we present the first three-dimensional reconstruction of the large-scale velocity field using a photometric galaxy survey, using data from the DESI Legacy Imaging Surveys (DESILS) and the Atacama Cosmology Telescope (ACT) DR5. We detect an $11.7σ$ correlation between our velocity reconstruction and the galaxy field, using only DESILS LRGs in the northern Galactic hemisphere. We find that the overall amplitude of the kSZ-induced correlation is low relative to a halo model prediction ($b_v = 0.45^{+0.06}_{-0.05}$), in agreement with previous results which find high feedback and smoothed gas profiles near massive galaxies. We use this measurement to place new constraints on local-type primordial non-Gaussianity (PNG), obtaining $f_{\rm NL}\!=\!-39^{+40}_{-33}$. This represents the most stringent $f_{\rm NL}$ constraint from kSZ velocity-based analyses to date. We validate our findings through extensive null tests, including tests for CMB foregrounds based on comparing 90 and 150 GHz CMB data. |
| title | Velocity Reconstruction from KSZ: Measuring $f_{NL}$ with ACT and DESILS |
| topic | Cosmology and Nongalactic Astrophysics |
| url | https://arxiv.org/abs/2506.21657 |