Unclustered tracers remain unclustered: the lack of primordial non-Gaussianity response of bias-zero tracers
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| Formato: | Preprint |
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2026
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| author | Merino, Celia Avila, Santiago Adame, A. G. Anguren, A. Gonzalez-Perez, V. Meneses-Rizo, J. |
| author_facet | Merino, Celia Avila, Santiago Adame, A. G. Anguren, A. Gonzalez-Perez, V. Meneses-Rizo, J. |
| contents | Constraining primordial non-Gaussianities (PNG) is one of the main goals of new-generation large-scale galaxy surveys. It had been proposed that unclustered tracers (with bias $b_1=0$) could be optimal for PNG studies, and that these could be found by selecting galaxies in bins of their local density. Here, we test this hypothesis in state-of-the-art simulations from the PNG-UNITsim suite with local $f_{\rm NL}=100$ and $f_{\rm NL}=-20$. We consider different parent tracer catalogues: all halos together, halos in large mass bins, and HOD models for LRGs and QSO. We then classify these tracers by their local density ($δ_{t,R}$) and measure the linear bias ($b_1$) and PNG-response ($b_ϕ$). Most $δ_{t,R}$ bins show a PNG-response compatible with $b_ϕ=0$ for all halos or the low-mass bin (log$M<11$). For high-mass halos (log$M>$12), QSO or LRG, we recover a trend closer to the universality relation ($b_ϕ= 2 δ_{\rm crit}(b_1-1)$) for $b_1>1$, but the $b_ϕ(b_1)$ curve flattens to 0 below $\vert b_1\lvert<1$. Hence, we find $b_ϕ\approx0$ for all bias-zero tracers considered. The complex $δ_{t,R}$-based selection causes their clustering to strongly deviate from simple assumptions, namely the universality relation and Poisson shot noise, hindering their capability to constrain PNG. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2602_04698 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | Unclustered tracers remain unclustered: the lack of primordial non-Gaussianity response of bias-zero tracers Merino, Celia Avila, Santiago Adame, A. G. Anguren, A. Gonzalez-Perez, V. Meneses-Rizo, J. Cosmology and Nongalactic Astrophysics Constraining primordial non-Gaussianities (PNG) is one of the main goals of new-generation large-scale galaxy surveys. It had been proposed that unclustered tracers (with bias $b_1=0$) could be optimal for PNG studies, and that these could be found by selecting galaxies in bins of their local density. Here, we test this hypothesis in state-of-the-art simulations from the PNG-UNITsim suite with local $f_{\rm NL}=100$ and $f_{\rm NL}=-20$. We consider different parent tracer catalogues: all halos together, halos in large mass bins, and HOD models for LRGs and QSO. We then classify these tracers by their local density ($δ_{t,R}$) and measure the linear bias ($b_1$) and PNG-response ($b_ϕ$). Most $δ_{t,R}$ bins show a PNG-response compatible with $b_ϕ=0$ for all halos or the low-mass bin (log$M<11$). For high-mass halos (log$M>$12), QSO or LRG, we recover a trend closer to the universality relation ($b_ϕ= 2 δ_{\rm crit}(b_1-1)$) for $b_1>1$, but the $b_ϕ(b_1)$ curve flattens to 0 below $\vert b_1\lvert<1$. Hence, we find $b_ϕ\approx0$ for all bias-zero tracers considered. The complex $δ_{t,R}$-based selection causes their clustering to strongly deviate from simple assumptions, namely the universality relation and Poisson shot noise, hindering their capability to constrain PNG. |
| title | Unclustered tracers remain unclustered: the lack of primordial non-Gaussianity response of bias-zero tracers |
| topic | Cosmology and Nongalactic Astrophysics |
| url | https://arxiv.org/abs/2602.04698 |