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arXiv · 2305.01266

Impact of tidal environment on galaxy clustering in GAMA

Shadab Alam·Aseem Paranjape·John A. Peacock
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Abstract

We constrain models of the galaxy distribution in the cosmic web using data from the Galaxy and Mass Assembly (GAMA) survey. We model the redshift-space behaviour of the 2-point correlation function (2pcf) and the recently proposed Voronoi volume function (VVF) -- which includes information beyond 2-point statistics. We extend the standard halo model using extra satellite degrees of freedom and two assembly bias parameters, $α_{\rm cen}$ and $α_{\rm sat}$, which respectively correlate the occupation numbers of central and satellite galaxies with their host halo's tidal environment. We measure $α_{\rm sat}=1.44^{+0.25}_{-0.43}$ and $α_{\rm cen}=-0.79^{+0.29}_{-0.11}$ using a combination of 2pcf and VVF measurements, representing a detection of assembly bias at the 3.3$σ$ (2.4$σ$) significance level for satellite (central) galaxies. This result remains robust to possible anisotropies in the halo-centric distribution of satellites as well as technicalities of estimating the data covariance. We show that the growth rate ($fσ_8$) deduced using models with assembly bias is about 7\% (i.e. $1.5σ$) lower than if assembly bias is ignored. When projected onto the $Ω_m$-$σ_8$ plane, the model constraints without assembly bias overlap with Planck expectations, while allowing assembly bias introduces significant tension with Planck, preferring either a lower $Ω_m$ or a lower $σ_8$. Finally, we find that the all-galaxy weak lensing signal is unaffected by assembly bias, but the central and satellite sub-populations individually show significantly different signals in the presence of assembly bias. Our results illustrate the importance of accurately modelling galaxy formation for cosmological inference from future surveys.

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Shadab Alam, Aseem Paranjape, John A. Peacock. 2023-12-05. Impact of tidal environment on galaxy clustering in GAMA. https://doi.org/10.1093/mnras%2Fstad3423

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