The effects of projection on measuring the splashback feature
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arXiv
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| Main Authors: | , , , |
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| Format: | Preprint |
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2025
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| _version_ | 1866918102332080128 |
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| author | Sun, Xiaoqing O'Neil, Stephanie Shen, Xuejian Vogelsberger, Mark |
| author_facet | Sun, Xiaoqing O'Neil, Stephanie Shen, Xuejian Vogelsberger, Mark |
| contents | The splashback radius $R_{\rm sp}$ is a boundary of a halo that separates infalling and accreted matter. This results in a steep drop in the density profile at $R_{\rm st}$, which is a commonly adopted proxy for $R_{\rm sp}$. Observationally, $R_{\rm st}$ can be measured through fitting the projected galaxy number density profile of the halo, but there has been some discrepancy between the observed and expected $R_{\rm st}$. Therefore, we investigate whether the projection of the density profile onto the plane of the sky could lead to any systematic bias in determining $R_{\rm st}$, by studying the true 3-dimensional and projected halo density profiles from the IllustrisTNG simulation. We investigate a range of projection lengths, and find that $R^p_{\rm st}$ obtained from projected profiles is close to the true $R^*_{\rm st}$, but has a slight decreasing trend with increasing projection length. We also quantify the prominence of the splashback feature and find how the feature shape changes with projection length. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2503_04882 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | The effects of projection on measuring the splashback feature Sun, Xiaoqing O'Neil, Stephanie Shen, Xuejian Vogelsberger, Mark Astrophysics of Galaxies Cosmology and Nongalactic Astrophysics The splashback radius $R_{\rm sp}$ is a boundary of a halo that separates infalling and accreted matter. This results in a steep drop in the density profile at $R_{\rm st}$, which is a commonly adopted proxy for $R_{\rm sp}$. Observationally, $R_{\rm st}$ can be measured through fitting the projected galaxy number density profile of the halo, but there has been some discrepancy between the observed and expected $R_{\rm st}$. Therefore, we investigate whether the projection of the density profile onto the plane of the sky could lead to any systematic bias in determining $R_{\rm st}$, by studying the true 3-dimensional and projected halo density profiles from the IllustrisTNG simulation. We investigate a range of projection lengths, and find that $R^p_{\rm st}$ obtained from projected profiles is close to the true $R^*_{\rm st}$, but has a slight decreasing trend with increasing projection length. We also quantify the prominence of the splashback feature and find how the feature shape changes with projection length. |
| title | The effects of projection on measuring the splashback feature |
| topic | Astrophysics of Galaxies Cosmology and Nongalactic Astrophysics |
| url | https://arxiv.org/abs/2503.04882 |