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Max Planck

Bio: Max Planck is an academic researcher. The author has contributed to research in topics: Galaxy formation and evolution & Halo. The author has an hindex of 1, co-authored 1 publications receiving 9 citations.

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01 Jan 2007
TL;DR: In this article, the authors used the Millennium Simulation to measure the cross-correlation between halo centres and mass in a CDM cosmology and found that the results are surprisingly well fit by approximating the inner region by a density profile of NFW or Einasto form, the outer region by biased version of the lin- ear mass autocorrelation function, and by adopting the maximum of the two where they are comparable.
Abstract: We use the Millennium Simulation to measure the cross-correlation between halo centres and mass (or equivalently the average density profiles of dark haloes) in aCDM cosmology. We present results for radii in the range 10 h −1 kpc < r < 30 h −1 Mpc for halo masses in the range 4 × 10 10 h −1 M⊙ < M200 < 4×10 14 h −1 M⊙. Both at z = 0 and at z = 0.76 these cross-correlations are surprisingly well fit by approximating the inner region by a density profile of NFW or Einasto form, the outer region by a biased version of the lin- ear mass autocorrelation function, and by adopting the maximum of the two where they are comparable. We use a simulation of the formation of galaxies within the Millennium Simulation to explore how these results are reflected in cross-correlations between galaxies and mass. These are directly observ- able through galaxy-galaxy lensing. Here also we find that simple models can represent the simulation results remarkably well, typically to � 10%. Such models can be used to extend our results to other redshifts, to cosmologies with other parameters, and to other assumptions about how galaxies populate dark haloes. The characteristic features predicted in the galaxy-galaxy lensing signal should provide a strong test of theCDM cosmology as well as a route to understanding how galaxies form within it.

10 citations


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Journal ArticleDOI
TL;DR: In this article, a new parametrisation of halo profiles based on gas, stellar, and dark matter density components is presented to modify outputs of gravity-only N-body simulations in order to mimic baryonic effects on the matter density field.
Abstract: Feedback processes from baryons are expected to strongly affect weak-lensing observables of current and future cosmological surveys. In this paper we present a new parametrisation of halo profiles based on gas, stellar, and dark matter density components. This parametrisation is used to modify outputs of gravity-only N-body simulations (following the prescription of [1]) in order to mimic baryonic effects on the matter density field. The resulting baryonic correction model relies on a few well motivated physical parameters and is able to reproduce the redshift zero clustering signal of hydrodynamical simulations at two percent accuracy below k~10 h/Mpc. A detailed study of the baryon suppression effects on the matter power spectrum and the weak lensing shear correlation reveals that the signal is dominated by two parameters describing the slope of the gas profile in haloes and the maximum radius of gas ejection. We show that these parameters can be constrained with the observed gas fraction of galaxy groups and clusters from X-ray data. Based on these observations we predict a beyond percent effect on the power spectrum above k=0.2–1.0 h/Mpc with a maximum suppression of 15–25 percent around k~ 10 h/Mpc. As a result, the weak lensing angular shear power spectrum is suppressed by 15–25 percent at scales beyond l~ 100–600 and the shear correlations ξ+ and ξ− are affected at the 10–25 percent level below 5 and 50 arc-minutes, respectively. The relatively large uncertainties of these predictions are a result of the poorly known hydrostatic mass bias of current X-ray observations as well as the generic difficulty to observe the low density gas outside of haloes.

111 citations

Journal ArticleDOI
TL;DR: In this article, the authors employ the hydrodynamical simulation IllustrisTNG-300-1 to explore the halo occupation distribution and environmental dependence of luminous star-forming emission-line galaxies (ELGs) at $z \sim 1$.
Abstract: We employ the hydrodynamical simulation IllustrisTNG-300-1 to explore the halo occupation distribution (HOD) and environmental dependence of luminous star-forming emission-line galaxies (ELGs) at $z \sim 1$. Such galaxies are key targets for current and upcoming cosmological surveys. We select model galaxies through cuts in colour-colour space allowing for a direct comparison with the Extended Baryon Oscillation Spectroscopic Survey and the Dark Energy Spectroscopic Instrument (DESI) surveys and then compare them with galaxies selected based on specific star-formation rate (sSFR) and stellar mass. We demonstrate that the ELG populations are twice more likely to reside in lower-density regions (sheets) compared with the mass-selected populations and twice less likely to occupy the densest regions of the cosmic web (knots). We also show that the colour-selected and sSFR-selected ELGs exhibit very similar occupation and clustering statistics, finding that the agreement is best for lower redshifts. In contrast with the mass-selected sample, the occupation of haloes by a central ELG peaks at $\sim$20\%. We furthermore explore the dependence of the HOD and the auto-correlation on environment, noticing that at fixed halo mass, galaxies in high-density regions cluster about 10 times more strongly than low-density ones. This result suggests that we should model carefully the galaxy-halo relation and implement assembly bias effects into our models (estimated at $\sim$4\% of the clustering of the DESI colour-selected sample at $z = 0.8$). Finally, we apply a simple mock recipe to recover the clustering on large scales ($r \gtrsim 1 \ {\rm Mpc}/h$) to within 1\% by augmenting the HOD model with an environment dependence, demonstrating the power of adopting flexible population models.

34 citations

Journal ArticleDOI
TL;DR: This paper proposed a new definition of the halo boundary that lies at the ''by-eye'' transition radius from the one--halo to the two-halo term in the Halo-mass correlation function.
Abstract: We present a model for the halo--mass correlation function that explicitly incorporates halo exclusion We assume that halos trace mass in a way that can be described using a single scale-independent bias parameter However, our model exhibits scale dependent biasing due to the impact of halo-exclusion, the use of a ``soft'' (ie not infinitely sharp) halo boundary, and differences in the one halo term contributions to $\xi_{\rm hm}$ and $\xi_{\rm mm}$ These features naturally lead us to a redefinition of the halo boundary that lies at the ``by eye'' transition radius from the one--halo to the two--halo term in the halo--mass correlation function When adopting our proposed definition, our model succeeds in describing the halo--mass correlation function with $\approx 2\%$ residuals over the radial range $01\ h^{-1}{\rm Mpc} < r < 80\ h^{-1}{\rm Mpc}$, and for halo masses in the range $10^{13}\ h^{-1}{\rm M}_{\odot} < M < 10^{15}\ h^{-1}{\rm M}_{\odot}$ Our proposed halo boundary is related to the splashback radius by a roughly constant multiplicative factor Taking the 87-percentile as reference we find $r_{\rm t}/R_{\rm sp} \approx 13$ Surprisingly, our proposed definition results in halo abundances that are well described by the Press-Schechter mass function with $\delta_{\rm sc}=1449\pm 0004$ The clustering bias parameter is offset from the standard background-split prediction by $\approx 10\%-15\%$ This level of agreement is comparable to that achieved with more standard halo definitions

27 citations

Journal ArticleDOI
TL;DR: Mead et al. as mentioned in this paper derived a simple prescription for including beyond-linear halo bias within the standard, analytical halo-model power spectrum calculation, which results in a corrective term that is added to the usual two-halo term.
Abstract: We derive a simple prescription for including beyond-linear halo bias within the standard, analytical halo-model power spectrum calculation. This results in a corrective term that is added to the usual two-halo term. We measure this correction using data from $N$-body simulations and demonstrate that it can boost power in the two-halo term by a factor of $\sim2$ at scales $k\sim0.7\,h Mpc^{-1}$, with the exact magnitude of the boost determined by the specific pair of fields in the two-point function. How this translates to the full power spectrum depends on the relative strength of the one-halo term, which can mask the importance of this correction to a greater or lesser degree, again depending on the fields. Generally we find that our correction is more important for signals that arise from lower-mass haloes. When comparing our calculation to simulated data we find that the under-prediction of power in the transition region between the two- and one-halo terms, which typically plagues halo-model calculations, is almost completely eliminated when including the full non-linear halo bias. We show improved results for the auto and cross spectra of galaxies, haloes and matter. In the specific case of matter-matter or matter-halo power we note that a large fraction of the improvement comes from the non-linear biasing between low- and high-mass haloes. We envisage our model being useful in the analytical modelling of cross correlation signals. Our non-linear bias halo-model code is available at https://github.com/alexander-mead/BNL

24 citations

Journal ArticleDOI
TL;DR: In this paper , the authors revisited cosmological constraints on the sum of neutrino masses from a combination of full-shape BOSS galaxy clustering [$P(k)$] data and measurements of the cross-correlation between Planck Cosmic Microwave Background (CMB) lensing convergence and bOSS galaxy overdensity maps [C^{\kappa \text{g}}_{\ell}$], using a simple but theoretically motivated model for the scale-dependent galaxy bias in auto-and cross correlation measurements.

23 citations