Precision era of the kinetic Sunyaev-Zeldovich effect: simulations, analytical models and observations and the power to constrain reionization

The kinetic SZ effect, which is the dominant CMB source at arc-minute scales and $\nu \sim 217$ Ghz, probes the ionized gas peculiar momentum up to the epoch of reionization and is a sensitive measure of the reionization history. We ran high resolution self-similar and $\Lambda$CDM hydro simulations and built an analytical model to study this effect. Our model reproduces the $\Lambda$CDM simulation results to several percent accuracy, passes various tests against self-similar simulations, and shows a wider range of applicability than previous analytical models. Our model in its continuous version is free of simulation limitations such as finite simulation box and finite resolution and allows an accurate prediction of the kinetic SZ power spectrum $C_l$. For the WMAP cosmology, we find $l^2C_l/(2\pi)\simeq 0.91 \times 10^{-12} [(1+z_{\rm reion})/10]^{0.34}(l/5000)^{0.23-0.015(z_{\rm reion}-9)}$ for the reionization redshift $6<z_{\rm reion}<20$ and $3000<l<9000$. The corresponding temperature fluctuation is several $\mu$K at these ranges. The dependence of $C_l$ on the reionization history allows an accurate measurement of the reionization epoch. For the Atacama cosmology telescope experiment, $C_l$ can be measured with $\sim 1$ accuracy. $C_l$ scales as $(\Omega_b h)^2 \sigma_8^{4\sim 6}$. Given cosmological parameters, ACT would be able to constrain $z_{\rm reion}$ with several percent accuracy. Some multi-reionization scenarios degenerate in the primary CMB temperature and TE measurement can be distinguished with $\sim 10 \sigma$ confidence.Comment: 14 pages, 7 figures. Accepted by MNRAS. We corrected the primary CMB power spectrum we used. We added discussions about the effects of lensing and relativistic SZ correctio. We withdraw a claim about the patchy reionizatio

Risk of Arrhythmia and Mortality from Macrolide Antibiotic Prescription: A Population-Based Cohort Study

Many respiratory tract infections are treated with macrolide antibiotics. Regulatory agencies warn that these antibiotics increase the risk of ventricular arrhythmia. This population-based retrospective cohort study examined the 30-day risk of a hospital encounter with ventricular arrhythmia and all-cause mortality in 503,612 matched pairs of older adults who received a new outpatient prescription for an oral macrolide antibiotic and those prescribed referent antibiotics from 2002 to 2013 in Ontario. Conditional logistic regression was used to measure the association between macrolide exposure and outcomes. Macrolide antibiotics compared with referent antibiotics were not associated with a higher 30-day risk of ventricular arrhythmia (0.03% vs. 0.03%, relative risk [RR] 1.06, 95% confidence interval [CI] 0.83- 1.36), and were associated with a lower risk of 30-day all-cause mortality (0.62% vs. 0.76%, RR 0.82, 95% CI 0.78-0.86). These findings suggest that current warnings from Health Canada and the U.S. Food and Drug Administration may be overstated

Optimized Multi-Frequency Spectra for Applications in Radiative Feedback and Cosmological Reionization

The recent implementation of radiative transfer algorithms in numerous hydrodynamics codes has led to a dramatic improvement in studies of feedback in various astrophysical environments. However, because of methodological limitations and computational expense, the spectra of radiation sources are generally sampled at only a few evenly-spaced discrete emission frequencies. Using one-dimensional radiative transfer calculations, we investigate the discrepancies in gas properties surrounding model stars and accreting black holes that arise solely due to spectral discretization. We find that even in the idealized case of a static and uniform density field, commonly used discretization schemes induce errors in the neutral fraction and temperature by factors of two to three on average, and by over an order of magnitude in certain column density regimes. The consequences are most severe for radiative feedback operating on large scales, dense clumps of gas, and media consisting of multiple chemical species. We have developed a method for optimally constructing discrete spectra, and show that for two test cases of interest, carefully chosen four-bin spectra can eliminate errors associated with frequency resolution to high precision. Applying these findings to a fully three-dimensional radiation-hydrodynamic simulation of the early universe, we find that the HII region around a primordial star is substantially altered in both size and morphology, corroborating the one-dimensional prediction that discrete spectral energy distributions can lead to sizable inaccuracies in the physical properties of a medium, and as a result, the subsequent evolution and observable signatures of objects embedded within it.Comment: 15 pages, 13 figures, 2 tables, accepted for publication in the Astrophysical Journa

Dynamical Mass Measurements of Contaminated Galaxy Clusters Using Machine Learning

We study dynamical mass measurements of galaxy clusters contaminated by interlopers and show that a modern machine learning (ML) algorithm can predict masses by better than a factor of two compared to a standard scaling relation approach. We create two mock catalogs from Multidark's publicly available $N$-body MDPL1 simulation, one with perfect galaxy cluster membership information and the other where a simple cylindrical cut around the cluster center allows interlopers to contaminate the clusters. In the standard approach, we use a power-law scaling relation to infer cluster mass from galaxy line-of-sight (LOS) velocity dispersion. Assuming perfect membership knowledge, this unrealistic case produces a wide fractional mass error distribution, with a width of $\Delta\epsilon\approx0.87$. Interlopers introduce additional scatter, significantly widening the error distribution further ($\Delta\epsilon\approx2.13$). We employ the support distribution machine (SDM) class of algorithms to learn from distributions of data to predict single values. Applied to distributions of galaxy observables such as LOS velocity and projected distance from the cluster center, SDM yields better than a factor-of-two improvement ($\Delta\epsilon\approx0.67$) for the contaminated case. Remarkably, SDM applied to contaminated clusters is better able to recover masses than even the scaling relation approach applied to uncontaminated clusters. We show that the SDM method more accurately reproduces the cluster mass function, making it a valuable tool for employing cluster observations to evaluate cosmological models.Comment: 18 pages, 12 figures, accepted for publication at Ap

Radiative transfer simulations of cosmic reionization I: methodology and initial results

We present a new hybrid code for large volume, high resolution simulations of cosmic reionization, which utilizes a N-body algorithm for dark matter, physically motivated prescriptions for baryons and star formation, and an adaptive ray tracing algorithm for radiative transfer of ionizing photons. Two test simulations each with 3 billion particles and 400 million rays in a 50 Mpc/h box have been run to give initial results. Halos are resolved down to virial temperatures of 10^4 K for the redshift range of interest in order to robustly model star formation and clumping factors. This is essential to correctly account for ionization and recombination processes. We find that the halos and sources are strongly biased with respect to the underlying dark matter, re-enforcing the requirement of large simulation boxes to minimize cosmic variance and to obtain a qualitatively correct picture of reionization. We model the stellar initial mass function (IMF), by following the spatially dependent gas metallicity evolution, and distinguish between the first generation, Population III (PopIII) stars and the second generation, Population II (PopII) stars. The PopIII stars with a top-heavy IMF produce an order of magnitude more ionizing photons at high redshifts z>10, resulting in a more extended reionization. In our simulations, complete overlap of HII regions occurrs at z~6.5 and the computed mass and volume weighted residual HI fractions at 5<z<6.5 are both in good agreement with high redshift quasar absorption measurements from SDSS. The values for the Thomson optical depth are consistent within 1-sigma of the current best-fit value from third-year WMAP.Comment: 15 pages, 13 figures; accepted by ApJ; higher resolution figures can be found at http://www.astro.princeton.edu/~htrac/reionization.htm