30 research outputs found
Stellar Property Statistics of Massive Halos from Cosmological Hydrodynamics Simulations: Common Kernel Shapes
We study stellar property statistics, including satellite galaxy occupation, of massive halo populations realized by three cosmological hydrodynamics simulations: BAHAMAS + MACSIS, TNG300 of the IllustrisTNG suite, and Magneticum Pathfinder. The simulations incorporate independent sub-grid methods for astrophysical processes with spatial resolutions ranging from to kpc, and each generates samples of or more halos with at redshift . Applying localized, linear regression (LLR), we extract halo mass-conditioned statistics (normalizations, slopes, and intrinsic covariance) for a three-element stellar property vector consisting of: i) , the number of satellite galaxies with stellar mass, within radius of the halo; ii) , the total stellar mass within that radius, and; iii) , the gravitationally-bound stellar mass of the central galaxy within a radius. Scaling parameters for the three properties with halo mass show mild differences among the simulations, in part due to numerical resolution, but there is qualitative agreement on property correlations, with halos having smaller than average central galaxies tending to also have smaller total stellar mass and a larger number of satellite galaxies. Marginalizing over total halo mass, we find the satellite galaxy kernel, to be consistently skewed left, with skewness parameter , while that of is closer to log-normal, in all three simulations. The highest resolution simulations find for the shape of and also that the fractional scatter in total stellar mass is below in halos more massive than
Galaxy velocity bias in cosmological simulations: towards per cent-level calibration
Galaxy cluster masses, rich with cosmological information, can be estimated from internal dark matter (DM) velocity dispersions, which in turn can be observationally inferred from satellite galaxy velocities. However, galaxies are biased tracers of the DM, and the bias can vary over host halo and galaxy properties as well as time. We precisely calibrate the velocity bias, bv – defined as the ratio of galaxy and DM velocity dispersions – as a function of redshift, host halo mass, and galaxy stellar mass threshold (M ,sat), for massive haloes (M200c > 1013.5 M ) from five cosmological simulations: IllustrisTNG, Magneticum, Bahamas + Macsis, The Three Hundred Project, and MultiDark Planck-2. We first compare scaling relations for galaxy and DM velocity dispersion across simulations; the former is estimated using a new ensemble velocity likelihood method that is unbiased for low galaxy counts per halo, while the latter uses a local linear regression. The simulations show consistent trends of bv increasing with M200c and decreasing with redshift and M ,sat. The ensemble-estimated theoretical uncertainty in bv is 2–3 per cent, but becomes percent-level when considering only the three highest resolution simulations. We update the mass–richness normalization for an SDSS redMaPPer cluster sample, and find our improved bv estimates reduce the normalization uncertainty from 22 to 8 per cent, demonstrating that dynamical mass estimation is competitive with weak lensing mass estimation. We discuss necessary steps for further improving this precision. Our estimates for bv (M200c, M ,sat, z) are made publicly available
The Three Hundred Project: the gizmo-simba run
We introduce gizmo-simba, a new suite of galaxy cluster simulations within The Three Hundred project. The Three Hundred consists of zoom re-simulations of 324 clusters with M 200≳ 1014.8, M ⊙ drawn from the MultiDark-Planck N-body simulation, run using several hydrodynamic and semi-analytical codes. The gizmo-simba suite adds a state-of-the-art galaxy formation model based on the highly successful Simba simulation, mildly re-calibrated to match z = 0 cluster stellar properties. Comparing to The Three Hundred zooms run with gadget-x, we find intrinsic differences in the evolution of the stellar and gas mass fractions, BCG ages, and galaxy colour-magnitude diagrams, with gizmo-simba generally providing a good match to available data at z ≈ 0. gizmo-simba's unique black hole growth and feedback model yields agreement with the observed BH scaling relations at the intermediate-mass range and predicts a slightly different slope at high masses where few observations currently lie. Gizmo-Simba provides a new and novel platform to elucidate the co-evolution of galaxies, gas, and black holes within the densest cosmic environments
Shocks in the Stacked Sunyaev-Zel'dovich Profiles of Clusters II: Measurements from SPT-SZ + Planck Compton-y Map
We search for the signature of cosmological shocks in stacked gas pressure
profiles of galaxy clusters using data from the South Pole Telescope (SPT).
Specifically, we stack the latest Compton-y maps from the 2500 deg^2 SPT-SZ
survey on the locations of clusters identified in that same dataset. The sample
contains 516 clusters with mean mass = 1e14.9 msol and redshift =
0.55. We analyze in parallel a set of zoom-in hydrodynamical simulations from
The Three Hundred project. The SPT-SZ data show two features: (i) a pressure
deficit at R/R200m = , measured at significance and
not observed in the simulations, and; (ii) a sharp decrease in pressure at
R/R200m = at significance. The pressure deficit is
qualitatively consistent with a shock-induced thermal non-equilibrium between
electrons and ions, and the second feature is consistent with accretion shocks
seen in previous studies. We split the cluster sample by redshift and mass, and
find both features exist in all cases. There are also no significant
differences in features along and across the cluster major axis, whose
orientation roughly points towards filamentary structure. As a consistency
test, we also analyze clusters from the Planck and Atacama Cosmology Telescope
Polarimeter surveys and find quantitatively similar features in the pressure
profiles. Finally, we compare the accretion shock radius (Rsh_acc) with
existing measurements of the splashback radius (Rsp) for SPT-SZ and constrain
the lower limit of the ratio, Rsh_acc/Rsp > .Comment: [v1]: 8 Figures, 16 Pages in Main text. [v2]: Added text to
discussion. Version accepted in MNRA
Shocks in the stacked Sunyaev-Zel'dovich profiles of clusters II: Measurements from SPT-SZ + Planck Compton-y map
We search for the signature of cosmological shocks in stacked gas pressure profiles of galaxy clusters using data from the South Pole Telescope (SPT). Specifically, we stack the latest Compton-y maps from the 2500 deg2 SPT-SZ survey on the locations of clusters identified in that same data set. The sample contains 516 clusters with mean mass 〈 M 200m〉 = 1014.9\, M⊙ and redshift z= 0.55. We analyse in parallel a set of zoom-in hydrodynamical simulations from the three hundred project. The SPT-SZ data show two features: (i) a pressure deficit at R/R200m = 1.08 ± 0.09, measured at 3.1σ significance and not observed in the simulations, and; (ii) a sharp decrease in pressure at R/R200m = 4.58 ± 1.24 at 2.0σ significance. The pressure deficit is qualitatively consistent with a shock-induced thermal non-equilibrium between electrons and ions, and the second feature is consistent with accretion shocks seen in previous studies. We split the cluster sample by redshift and mass, and find both features exist in all cases. There are also no significant differences in features along and across the cluster major axis, whose orientation roughly points towards filamentary structure. As a consistency test, we also analyse clusters from the Planck and Atacama Cosmology Telescope Polarimeter surveys and find quantitatively similar features in the pressure profiles. Finally, we compare the accretion shock radius (R sh,\, acc) with existing measurements of the splashback radius (Rsp) for SPT-SZ and constrain the lower limit of the ratio, R sh,\, acc/R sp\> 2.16\± 0.59
Beyond the 3rd moment: A practical study of using lensing convergence CDFs for cosmology with DES Y3
Widefield surveys of the sky probe many clustered scalar fields -- such as
galaxy counts, lensing potential, gas pressure, etc. -- that are sensitive to
different cosmological and astrophysical processes. Our ability to constrain
such processes from these fields depends crucially on the statistics chosen to
summarize the field. In this work, we explore the cumulative distribution
function (CDF) at multiple scales as a summary of the galaxy lensing
convergence field. Using a suite of N-body lightcone simulations, we show the
CDFs' constraining power is modestly better than that of the 2nd and 3rd
moments of the field, as they approximately capture the information from all
moments of the field in a concise data vector. We then study the practical
aspects of applying the CDFs to observational data, using the first three years
of the Dark Energy Survey (DES Y3) data as an example, and compute the impact
of different systematics on the CDFs. The contributions from the point spread
function are 2-3 orders of magnitude below the cosmological signal, while those
from reduced shear approximation contribute to the signal.
Source clustering effects and baryon imprints contribute . Enforcing
scale cuts to limit systematics-driven biases in parameter constraints degrades
these constraints a noticeable amount, and this degradation is similar for the
CDFs and the moments. We also detect correlations between the observed
convergence field and the shape noise field at . We find that the
non-Gaussian correlations in the noise field must be modeled accurately to use
the CDFs, or other statistics sensitive to all moments, as a rigorous cosmology
tool.Comment: 21 pages, 12 figure
Cosmological shocks around galaxy clusters: A coherent investigation with DES, SPT & ACT
We search for signatures of cosmological shocks in gas pressure profiles of
galaxy clusters using the cluster catalogs from three surveys: the Dark Energy
Survey (DES) Year 3, the South Pole Telescope (SPT) SZ survey, and the Atacama
Cosmology Telescope (ACT) data releases 4, 5, and 6, and using thermal
Sunyaev-Zeldovich (SZ) maps from SPT and ACT. The combined cluster sample
contains around clusters with mass and redshift ranges and , and the total sky coverage
of the maps is . We find a clear pressure
deficit at in SZ profiles around both ACT and SPT
clusters, estimated at significance, which is qualitatively
consistent with a shock-induced thermal non-equilibrium between electrons and
ions. The feature is not as clearly determined in profiles around DES clusters.
We verify that measurements using SPT or ACT maps are consistent across all
scales, including in the deficit feature. The SZ profiles of optically selected
and SZ-selected clusters are also consistent for higher mass clusters. Those of
less massive, optically selected clusters are suppressed on small scales by
factors of 2-5 compared to predictions, and we discuss possible interpretations
of this behavior. An oriented stacking of clusters -- where the orientation is
inferred from the SZ image, the brightest cluster galaxy, or the surrounding
large-scale structure measured using galaxy catalogs -- shows the normalization
of the one-halo and two-halo terms vary with orientation. Finally, the location
of the pressure deficit feature is statistically consistent with existing
estimates of the splashback radius.Comment: [v2]: Version accepted to MNRA