Cosmology from LOFAR Two-metre Sky Survey Data Release 2: Counts-in-Cells Statistics
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| Main Authors: | , , , , , , , |
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| Format: | Preprint |
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2025
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| _version_ | 1866910997663449088 |
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| author | Pashapour-Ahmadabadi, Morteza Böhme, Lukas Siewert, Thilo M. Schwarz, Dominik J. Hale, Catherine L. Heneka, Caroline Tiwari, Prabhakar Zheng, Jinglan |
| author_facet | Pashapour-Ahmadabadi, Morteza Böhme, Lukas Siewert, Thilo M. Schwarz, Dominik J. Hale, Catherine L. Heneka, Caroline Tiwari, Prabhakar Zheng, Jinglan |
| contents | We investigate the statistical distribution of source counts-in-cells in the second data release of the LOFAR Two-Metre Sky Survey (LoTSS-DR2) and we test a computationally cheap method based on the counts-in-cells to estimate the two-point correlation function. We compare three stochastic models for the counts-in-cells which result in a Poisson distribution, a compound Poisson distribution, and a negative binomial distribution. By analysing the variance of counts-in-cells for various cell sizes, we fit the reduced normalised variance to a single power-law model representing the angular two-point correlation function. Our analysis confirms that radio sources are not Poisson distributed, which is most likely due to multiple physical components of radio sources. Employing instead a Cox process, we show that there is strong evidence in favour of the negative binomial distribution above a flux density threshold of 2 mJy. Additionally, the mean number of radio components derived from the negative binomial distribution is in good agreement with corresponding estimates based on the value-added catalogue of LoTSS-DR2. The scaling of the counts-in-cells normalised variance with cell size is in good agreement with a power-law model for the angular two-point correlation. At a flux density threshold of 2 mJy and a signal-to-noise ratio of 7.5 for individual radio sources, we find that for a range of angular scales large enough to not be affected by the multi-component nature of radio sources, the value of the exponent of the power law ranges from -0.8 to -1.05. This closely aligns with findings from previous optical, infrared, and radio surveys of the large scale structure. The scaling of the counts-in-cells statistics with cell size provides a computationally efficient method to estimate the two-point correlation properties, offering a valuable tool for future large-scale structure studies. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2504_20723 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Cosmology from LOFAR Two-metre Sky Survey Data Release 2: Counts-in-Cells Statistics Pashapour-Ahmadabadi, Morteza Böhme, Lukas Siewert, Thilo M. Schwarz, Dominik J. Hale, Catherine L. Heneka, Caroline Tiwari, Prabhakar Zheng, Jinglan Cosmology and Nongalactic Astrophysics We investigate the statistical distribution of source counts-in-cells in the second data release of the LOFAR Two-Metre Sky Survey (LoTSS-DR2) and we test a computationally cheap method based on the counts-in-cells to estimate the two-point correlation function. We compare three stochastic models for the counts-in-cells which result in a Poisson distribution, a compound Poisson distribution, and a negative binomial distribution. By analysing the variance of counts-in-cells for various cell sizes, we fit the reduced normalised variance to a single power-law model representing the angular two-point correlation function. Our analysis confirms that radio sources are not Poisson distributed, which is most likely due to multiple physical components of radio sources. Employing instead a Cox process, we show that there is strong evidence in favour of the negative binomial distribution above a flux density threshold of 2 mJy. Additionally, the mean number of radio components derived from the negative binomial distribution is in good agreement with corresponding estimates based on the value-added catalogue of LoTSS-DR2. The scaling of the counts-in-cells normalised variance with cell size is in good agreement with a power-law model for the angular two-point correlation. At a flux density threshold of 2 mJy and a signal-to-noise ratio of 7.5 for individual radio sources, we find that for a range of angular scales large enough to not be affected by the multi-component nature of radio sources, the value of the exponent of the power law ranges from -0.8 to -1.05. This closely aligns with findings from previous optical, infrared, and radio surveys of the large scale structure. The scaling of the counts-in-cells statistics with cell size provides a computationally efficient method to estimate the two-point correlation properties, offering a valuable tool for future large-scale structure studies. |
| title | Cosmology from LOFAR Two-metre Sky Survey Data Release 2: Counts-in-Cells Statistics |
| topic | Cosmology and Nongalactic Astrophysics |
| url | https://arxiv.org/abs/2504.20723 |