Mock halo catalogs: assigning unresolved halo properties using correlations with local halo environment

Abstract

Large-scale sky surveys require companion large volume simulated mock catalogs. To ensure precision cosmology studies are unbiased, the correlations in these mocks between galaxy properties and their large-scale environments must be realistic. Since galaxies are embedded in dark matter halos, an important first step is to include such correlations -- sometimes called assembly bias -- for dark matter halos. However, galaxy properties correlate with smaller scale physics in halos which large simulations struggle to resolve. We describe an algorithm which addresses and largely mitigates this problem. Our algorithm exploits the fact that halo assembly bias is unchanged as long as correlations between halo property $c$ and the intermediate-scale tidal environment $\alpha$ are preserved. Therefore, knowledge of $\alpha$ is sufficient to assign small-scale, otherwise unresolved properties to a halo in a way which preserves its large-scale assembly bias accurately. We demonstrate this explicitly for halo internal properties like formation history (concentration $c_{200b}$), shape $c/a$, dynamics $c_v/a_v$, velocity anisotropy $\beta$ and angular momentum (spin $\lambda$). Our algorithm increases a simulation's reach in halo mass and number density by an order of magnitude, with improvements in the bias signal as large as 45% for 30-particle halos, thus significantly reducing the cost of mocks for future weak lensing and redshift space distortion studies.

13 pages, 10 figures, minor revisions, accepted in MNRAS

References in corpus (7)

• The spin and shape of dark matter haloes in the Millennium simulation of a LambdaCDM universe
• A universal model for halo concentrations
• Halo assembly bias and its effects on galaxy clustering
• A Halo Model of Galaxy Colors and Clustering in the SDSS
• Spatial Clustering of Dark Matter Halos: Secondary Bias, Neighbor Bias, and the Influence of Massive Neighbors on Halo Properties
• Universality of dark matter haloes shape over six decades in mass: Insights from the Millennium XXL and SBARBINE simulations
• Separate Universe calibration of the dependence of halo bias on cosmic web anisotropy

Cited by in corpus (2)

• Multi-wavelength mock galaxy catalogs of the low-redshift Universe
• Accurate Analytic Mass-Scale Relations for Dark Matter Haloes of all Masses and Redshifts