Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userAMR Simulations of the Cosmological Light Cone: SZE Surveys of the Synthetic Universe
50
0
0.0
(
0
)
Authors
Eric J. Hallman
Ask ChatGPT about the research
No Arabic abstract
We present preliminary results from simulated large sky coverage (~100 square degrees) Sunyaev-Zeldovich effect (SZE) cluster surveys using the cosmological adaptive mesh refinement N-body/hydro code Enzo. We have generated simulated light cones to match the resolution and sensitivity of current and future SZE instruments. These simulations are the most advanced calculations of their kind. The simulated sky surveys allow a direct comparison of large N-body/hydro cosmological simulations to current and pending sky surveys. Our synthetic surveys provide an indispensable guide for observers in the interpretation of large area sky surveys, and will develop the tools necessary to discriminate between models for cluster baryonic physics, and to accurately determine cosmological parameters.
rate research
Read More
Detection of the Warm-Hot Intergalactic Medium (WHIM) using Sunyaev-Zeldovich effect (SZE) surveys is an intriguing possibility, and one that may allow observers to quantify the amount of missing baryons in the WHIM phase. We estimate the necessary sensitivity for detecting low density WHIM gas with the South Pole Telescope (SPT) and Planck Surveyor for a synthetic 100 square degree sky survey. This survey is generated from a very large, high dynamic range adaptive mesh refinement cosmological simulation performed with the Enzo code. We find that for a modest increase in the SPT survey sensitivity (a factor of 2-4), the WHIM gas makes a detectable contribution to the integrated sky signal. For a Planck-like satellite, similar detections are possible with a more significant increase in sensitivity (a factor of 8-10). We point out that for the WHIM gas, the kinematic SZE signal can sometimes dominate the thermal SZE where the thermal SZE decrement is maximal (150 GHz), and that using the combination of the two increases the chance of WHIM detection using SZE surveys. However, we find no evidence of unique features in the thermal SZE angular power spectrum that may aid in its detection. Interestingly, there are differences in the power spectrum of the kinematic SZE, which may not allow us to detect the WHIM directly, but could be an important contaminant in cosmological analyses of the kSZE-derived velocity field. Corrections derived from numerical simulations may be necessary to account for this contamination.
With Gaia Data Release 2, the astronomical community is entering a new era of multidimensional surveys of the Milky Way. This new phase-space view of our Galaxy demands new tools for comparing observations to simulations of Milky-Way-mass galaxies in a cosmological context, to test the physics of both dark matter and galaxy formation. We present ananke, a framework for generating synthetic phase-space surveys from high-resolution baryonic simulations, and use it to generate a suite of synthetic surveys resembling Gaia DR2 in data structure, magnitude limits, and observational errors. We use three cosmological simulations of Milky-Way-mass galaxies from the Latte suite of the Feedback In Realistic Environments (FIRE) project, which feature self-consistent clustering of star formation in dense molecular clouds and thin stellar/gaseous disks in live cosmological halos with satellite dwarf galaxies and stellar halos. We select three solar viewpoints from each simulation to generate nine synthetic Gaia-like surveys. We sample synthetic stars by assuming each star particle (of mass 7070 $M_{odot}$) represents a single stellar population. At each viewpoint, we compute dust extinction from the simulated gas metallicity distribution and apply a simple error model to produce a synthetic Gaia-like survey that includes both observational properties and a pointer to the generating star particle. We provide the complete simulation snapshot at $z = 0$ for each simulated galaxy. We describe data access points, the data model, and plans for future upgrades. These synthetic surveys provide a tool for the scientific community to test analysis methods and interpret Gaia data.
In studying temperature fluctuations in the cosmic microwave background Weinberg has noted that some ease of calculation and insight can be achieved by looking at the structure of the perturbed light cone on which the perturbed photons propagate. In his approach Weinberg worked in a specific gauge and specialized to fluctuations around the standard Robertson-Walker cosmological model with vanishing spatial three-curvature. In this paper we generalize this analysis by providing a gauge invariant treatment in which no choice of gauge is made, and by considering geometries with non-vanishing spatial three-curvature. By using the scalar, vector, tensor fluctuation basis we find that the relevant gauge invariant combinations that appear in the light cone temperature fluctuations have no explicit dependence on the spatial curvature even if the spatial curvature of the background geometry is nonvanishing. We find that a not previously considered, albeit not too consequential, temperature fluctuation at the observer has to be included in order to enforce gauge invariance. As well as working with comoving time we also work with conformal time in which a background metric of any given spatial three-curvature can be written as a time-dependent conformal factor (the comoving time expansion radius as written in conformal time) times a static Robertson-Walker geometry of the same spatial three-curvature. For temperature fluctuations on the light cone this conformal factor drops out identically. Thus the gauge invariant combinations that appear in the photon temperature fluctuations have no explicit dependence on either the conformal factor or the spatial three-curvature at all.
Using self-consistent cosmological simulations of disc galaxy formation, we analyse the 1.4 GHz radio flux from high-redshift progenitors of present-day normal spirals within the context of present-day and planned next-generation observational facilities. We demonstrate that while current radio facilities such as the Very Large Array (VLA) are unlikely to trace these progenitors beyond redshifts z<0.2, future facilities such as the Square Kilometer Array (SKA) will readily probe their characteristics to redshifts z<2, and are likely to provide detections beyond z~3. We also demonstrate that the progenitors of present-day cD galaxies can emit in excess of 10 uJy of flux at redshifts z>1, and may be a non-negligible contributor to the micro-Jansky source counts derived from current deep VLA cm-wave surveys.
Theoretical descriptions of observable quantities in cosmological perturbation theory should be independent of coordinate systems. This statement is often referred to as gauge-invariance of observable quantities, and the sanity of their theoretical description is verified by checking its gauge-invariance. We argue that cosmological observables are invariant scalars under diffeomorphisms and as a consequence their theoretical description is gauge-invariant, only at linear order in perturbations. Beyond linear order, they are usually not gauge-invariant, and we provide the general law for the gauge-transformation that the perturbation part of an observable does obey. We apply this finding to derive the second-order expression for the observational light-cone average in cosmology and demonstrate that our expression is indeed invariant under diffeomorphisms.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
