Abstract
We perform a combined analysis of cosmic shear tomography, galaxy–galaxy lensing tomography, and redshift-space multipole power spectra (monopole and quadrupole) using 450 deg2 of imaging ...data by the Kilo Degree Survey (KiDS-450) overlapping with two spectroscopic surveys: the 2-degree Field Lensing Survey (2dFLenS) and the Baryon Oscillation Spectroscopic Survey (BOSS). We restrict the galaxy–galaxy lensing and multipole power spectrum measurements to the overlapping regions with KiDS, and self-consistently compute the full covariance between the different observables using a large suite of N-body simulations. We methodically analyse different combinations of the observables, finding that the galaxy–galaxy lensing measurements are particularly useful in improving the constraint on the intrinsic alignment amplitude, while the multipole power spectra are useful in tightening the constraints along the lensing degeneracy direction. The fully combined constraint on $S_8 \equiv \sigma _8 \sqrt{\Omega _{\rm m}/0.3}=0.742\pm 0.035$, which is an improvement by 20 per cent compared to KiDS alone, corresponds to a 2.6σ discordance with Planck, and is not significantly affected by fitting to a more conservative set of scales. Given the tightening of the parameter space, we are unable to resolve the discordance with an extended cosmology that is simultaneously favoured in a model selection sense, including the sum of neutrino masses, curvature, evolving dark energy and modified gravity. The complementarity of our observables allows for constraints on modified gravity degrees of freedom that are not simultaneously bounded with either probe alone, and up to a factor of three improvement in the S8 constraint in the extended cosmology compared to KiDS alone.
This paper describes a new publicly available codebase for modeling galaxy formation in a cosmological context, the "Semi-Analytic Galaxy Evolution" model, or sage for short. super(5) sage is a ...significant update to the 2006 model of Croton et al. and has been rebuilt to be modular and customizable. The model will run on any N-body simulation whose trees are organized in a supported format and contain a minimum set of basic halo properties. In this work, we present the baryonic prescriptions implemented in sage to describe the formation and evolution of galaxies, and their calibration for three N-body simulations: Millennium, Bolshoi, and GiggleZ. Updated physics include the following: gas accretion, ejection due to feedback, and reincorporation via the galactic fountain; a new gas cooling-radio mode active galactic nucleus (AGN) heating cycle; AGN feedback in the quasar mode; a new treatment of gas in satellite galaxies; and galaxy mergers, disruption, and the build-up of intra-cluster stars. Throughout, we show the results of a common default parameterization on each simulation, with a focus on the local galaxy population.
We present a detailed analysis of redshift-space distortions in the two-point correlation function of the 6dF Galaxy Survey (6dFGS). The K-band selected subsample which we employ in this study ...contains 81 971 galaxies distributed over 17 000 degree2 with an effective redshift z
eff= 0.067. By modelling the 2D galaxy correlation function,
, we measure the parameter combination f(z
eff)σ8(z
eff) = 0.423 ± 0.055, where
is the growth rate of cosmic structure and σ8 is the rms of matter fluctuations in 8 h
−1 Mpc spheres.
Alternatively, by assuming standard gravity we can break the degeneracy between σ8 and the galaxy bias parameter b. Combining our data with the Hubble constant prior from Riess et al., we measure σ8= 0.76 ± 0.11 and Ωm= 0.250 ± 0.022, consistent with constraints from other galaxy surveys and the cosmic microwave background data from Wilkinson Microwave Anisotropy Probe 7 (WMAP7).
Combining our measurement of fσ8 with WMAP7 allows us to test the cosmic growth history and the relationship between matter and gravity on cosmic scales by constraining the growth index of density fluctuations, γ. Using only 6dFGS and WMAP7 data we find γ= 0.547 ± 0.088, consistent with the prediction of General Relativity. We note that because of the low effective redshift of the 6dFGS our measurement of the growth rate is independent of the fiducial cosmological model (Alcock-Paczynski effect). We also show that our conclusions are not sensitive to the model adopted for non-linear redshift-space distortions.
Using a Fisher matrix analysis we report predictions for constraints on fσ8 for the Wide-field Australian SKA Pathfinder telescope L-band Legacy All-sky Blind surveY (WALLABY) and the proposed Transforming Astronomical Imaging surveys through Polychromatic Analysis of Nebulae (TAIPAN) survey. The WALLABY survey will be able to measure fσ8 with a precision of 4-10 per cent, depending on the modelling of non-linear structure formation. This is comparable to the predicted precision for the best redshift bins of the Baryon Oscillation Spectroscopic Survey, demonstrating that low-redshift surveys have a significant role to play in future tests of dark energy and modified gravity.
We present precise measurements of the growth rate of cosmic structure for the redshift range 0.1 < z < 0.9, using redshift-space distortions in the galaxy power spectrum of the WiggleZ Dark Energy ...Survey. Our results, which have a precision of around 10 per cent in four independent redshift bins, are well fitted by a flat Λ cold dark matter (ΛCDM) cosmological model with matter density parameter Ωm= 0.27. Our analysis hence indicates that this model provides a self-consistent description of the growth of cosmic structure through large-scale perturbations and the homogeneous cosmic expansion mapped by supernovae and baryon acoustic oscillations. We achieve robust results by systematically comparing our data with several different models of the quasi-linear growth of structure including empirical models, fitting formulae calibrated to N-body simulations, and perturbation theory techniques. We extract the first measurements of the power spectrum of the velocity divergence field, P
θθ(k), as a function of redshift (under the assumption that
, where g is the galaxy overdensity field), and demonstrate that the WiggleZ galaxy-mass cross-correlation is consistent with a deterministic (rather than stochastic) scale-independent bias model for WiggleZ galaxies for scales k < 0.3 h Mpc−1. Measurements of the cosmic growth rate from the WiggleZ Survey and other current and future observations offer a powerful test of the physical nature of dark energy that is complementary to distance-redshift measures such as supernovae and baryon acoustic oscillations.
We introduce meraxes, a new, purpose-built semi-analytic galaxy formation model designed for studying galaxy growth during reionization. meraxes is the first model of its type to include a temporally ...and spatially coupled treatment of reionization and is built upon a custom (100 Mpc)3
N-body simulation with high temporal and mass resolution, allowing us to resolve the galaxy and star formation physics relevant to early galaxy formation. Our fiducial model with supernova feedback reproduces the observed optical depth to electron scattering and evolution of the galaxy stellar mass function between z = 5 and 7, predicting that a broad range of halo masses contribute to reionization. Using a constant escape fraction and global recombination rate, our model is unable to simultaneously match the observed ionizing emissivity at z ≲ 6. However, the use of an evolving escape fraction of 0.05–0.1 at z ∼ 6, increasing towards higher redshift, is able to satisfy these three constraints. We also demonstrate that photoionization suppression of low-mass galaxy formation during reionization has only a small effect on the ionization history of the intergalactic medium. This lack of ‘self-regulation’ arises due to the already efficient quenching of star formation by supernova feedback. It is only in models with gas supply-limited star formation that reionization feedback is effective at regulating galaxy growth. We similarly find that reionization has only a small effect on the stellar mass function, with no observationally detectable imprint at M
* > 107.5 M⊙. However, patchy reionization has significant effects on individual galaxy masses, with variations of factors of 2–3 at z = 5 that correlate with environment.
Abstract
There are at present
(
100
)
gravitational-wave candidates from compact binary mergers reported in the astronomical literature. As detector sensitivities are improved, the catalog will ...swell in size: first to
(
1000
)
events in the A+ era and then to
(
10
6
)
events in the era of third-generation observatories like Cosmic Explorer and the Einstein Telescope. Each event is analyzed using Bayesian inference to determine properties of the source including component masses, spins, tidal parameters, and the distance to the source. These inference products are the fodder for some of the most exciting gravitational-wave science, enabling us to measure the expansion of the universe with standard sirens, to characterize the neutron-star equation of state, and to unveil how and where gravitational-wave sources are assembled. In order to maximize the science from the coming deluge of detections, we introduce GW
Cloud
, a searchable repository for the creation and curation of gravitational-wave inference products. It is designed with five pillars in mind: uniformity of results, reproducibility of results, stability of results, access to the astronomical community, and efficient use of computing resources. We describe how to use GW
Cloud
with examples, which readers can replicate using the companion code to this paper. We describe our long-term vision for GW
Cloud
.
Using a suite of cosmology simulations of a sample of >120 galaxy clusters with log (M sub( DM, vir)) less than or equal to 14.5. We compare clusters that form in purely dark matter (DM) run and ...their counterparts in hydro-runs and investigate four independent parameters that are normally used to classify dynamical state. We find that the virial ratio ... in hydro-dynamical runs is ~10 per cent lower than in the DM run, and there is no clear separation between the relaxed and unrelaxed clusters for any parameter. Further, using the velocity dispersion deviation parameter ..., which is defined as the ratio between cluster velocity dispersion ... and the theoretical prediction ..., we find that there is a linear correlation between the virial ratio ... and this ... parameter. We propose to use this ... parameter, which can be easily derived from observed galaxy clusters, as a substitute of the ... parameter to quantify the cluster dynamical state. (ProQuest: ... denotes formulae/symbols omitted.)
Peculiar velocity surveys, which measure galaxy velocities directly from standard candles in addition to redshifts, can provide strong constraints on the growth rate of structure at low redshift. The ...improvement originates from the physical relationship between galaxy density and peculiar velocity, which substantially reduces cosmic variance. We use Fisher matrix forecasts to show that peculiar velocity data can improve the growth rate constraints by about a factor of 2 compared to density alone for surveys with galaxy number density of 10−2 (h
−1 Mpc)−3, if we can use all the information for wavenumber k ≤ 0.2 h Mpc−1. In the absence of accurate theoretical models at k = 0.2 h Mpc− 1, the improvement over redshift-only surveys is even larger – around a factor of 5 for k ≤ 0.1 h Mpc−1. Future peculiar velocity surveys, Transforming Astronomical Imaging surveys through Polychromatic Analysis of Nebulae (TAIPAN), and the all-sky H i surveys, Widefield ASKAP L-band Legacy All-sky Blind Survey (WALLABY) and Westerbork Northern Sky H i Survey (WNSHS), can measure the growth rate to 3 per cent at z ∼ 0.025. Although the velocity subsample is about an order of magnitude smaller than the redshift sample from the same survey, it improves the constraint by 40 per cent compared to the same survey without velocity measurements. Peculiar velocity surveys can also measure the growth rate as a function of wavenumber with 15–30 per cent uncertainties in bins with widths Δk = 0.01 h Mpc−1 in the range k ≤ 0.1 h Mpc−1, which is a large improvement over galaxy density only. Such measurements on very large scales can detect signatures of modified gravity or non-Gaussianity through scale-dependent growth rate or galaxy bias. We test our modelling in detail using N-body simulations.
We introduce a simple model to self-consistently connect the growth of galaxies to the formation history of their host dark matter haloes. Our model is defined by two simple functions: the 'baryonic ...growth function' which controls the rate at which new baryonic material is made available for star formation, and the 'physics function' which controls the efficiency with which this material is converted into stars. Using simple, phenomenologically motivated forms for both functions that depend only on a single halo property, we demonstrate the model's ability to reproduce the z = 0 red and blue stellar mass functions. Furthermore, by adding redshift as a second input variable to the physics function we show that the reproduction of the global stellar mass function out to z = 3 is improved. We conclude by discussing the general utility of our new model, highlighting its usefulness for creating mock galaxy samples which have a number of key advantages over those generated by other techniques.
PDF
