Future constraints on halo thermodynamics from combined Sunyaev-Zel'dovich measurements

The improving sensitivity of measurements of the kinetic Sunyaev-Zel'dovich (SZ) effect opens a new window into the thermodynamic properties of the baryons in halos. We propose a methodology to constrain these thermodynamic properties by combining the kinetic SZ, which is an unbiased probe of the free electron density, and the thermal SZ, which probes their thermal pressure. We forecast that our method constrains the average thermodynamic processes that govern the energetics of galaxy evolution like energetic feedback across all redshift ranges where viable halos sample are available. Current Stage-3 cosmic microwave background (CMB) experiments like AdvACT and SPT-3G can measure the kSZ and tSZ to greater than 100$\sigma$ if combined with a DESI-like spectroscopic survey. Such measurements translate into percent-level constraints on the baryonic density and pressure profiles and on the feedback and non-thermal pressure support parameters for a given ICM model. This in turn will provide critical thermodynamic tests for sub-grid models of feedback in cosmological simulations of galaxy formation. The high fidelity measurements promised by the next generation CMB experiment, CMB-S4, allow one to further sub-divide these constraints beyond redshift into other classifications, like stellar mass or galaxy type.Comment: 11 pages, 3 figures, Accepted to JCA

A general existence result for the Toda system on compact surfaces

In this paper we consider the Toda system of equations on a compact surface, which is motivated by the study of models in non-abelian Chern-Simons theory. We prove a general existence result using variational methods. The same analysis applies to a mean field equation which arises in fluid dynamics.Comment: 28 pages, 1 figure, accepted on Advances in Mathematic

The Kinematic Sunyaev-Zel'dovich Effect with Projected Fields II: prospects, challenges, and comparison with simulations

The kinematic Sunyaev-Zel'dovich (kSZ) signal is a powerful probe of the cosmic baryon distribution. The kSZ signal is proportional to the integrated free electron momentum rather than the electron pressure (which sources the thermal SZ signal). Since velocities should be unbiased on large scales, the kSZ signal is an unbiased tracer of the large-scale electron distribution, and thus can be used to detect the "missing baryon" that evade most observational techniques. While most current methods for kSZ extraction rely on the availability of very accurate redshifts, we revisit a method that allows measurements even in the absence of redshift information for individual objects. It involves cross-correlating the square of an appropriately filtered cosmic microwave background (CMB) temperature map with a projected density map constructed from a sample of large-scale structure tracers. We show that this method will achieve high signal-to-noise when applied to the next generation of high-resolution CMB experiments, provided that component separation is sufficiently effective at removing foreground contamination. Considering statistical errors only, we forecast that this estimator can yield $S/N \approx$ 3, 120 and over 150 for Planck, Advanced ACTPol, and hypothetical Stage-IV CMB experiments, respectively, in combination with a galaxy catalog from WISE, and about 20% larger $S/N$ for a galaxy catalog from the proposed SPHEREx experiment. This work serves as a companion paper to the first kSZ measurement with this method, where we used CMB temperature maps constructed from Planck and WMAP data, together with galaxies from the WISE survey, to obtain a 3.8 - 4.5$\sigma$ detection of the kSZ$^2$ amplitude.Comment: 14 pages, 10 figures. Comments welcom

The Kinematic Sunyaev-Zel'dovich Effect with Projected Fields: A Novel Probe of the Baryon Distribution with Planck, WMAP, and WISE Data

The kinematic Sunyaev-Zel'dovich (kSZ) effect --- the Doppler boosting of cosmic microwave background (CMB) photons due to Compton-scattering off free electrons with non-zero bulk velocity --- probes the abundance and distribution of baryons in the Universe. All kSZ measurements to date have explicitly required spectroscopic redshifts. Here, we implement a novel estimator for the kSZ -- large-scale structure cross-correlation based on projected fields: it does not require redshift estimates for individual objects, allowing kSZ measurements from large-scale imaging surveys. We apply this estimator to cleaned CMB temperature maps constructed from Planck and Wilkinson Microwave Anisotropy Probe data and a galaxy sample from the Wide-field Infrared Survey Explorer (WISE). We measure the kSZ effect at 3.8-4.5$\sigma$ significance, depending on the use of additional WISE galaxy bias constraints. We verify that our measurements are robust to possible dust emission from the WISE galaxies. Assuming the standard $\Lambda$CDM cosmology, we directly constrain $( {f_{b}}/{0.158} ) ( {f_{\rm free}}/{1.0} ) = 1.48 \pm 0.19$ (statistical error only) at redshift $z \approx 0.4$, where $f_{b}$ is the fraction of matter in baryonic form and $f_{\rm free}$ is the free electron fraction. This is the tightest kSZ-derived constraint reported to date on these parameters. The consistency between the $f_{b}$ value found here and the values inferred from analyses of the primordial CMB and Big Bang nucleosynthesis verifies that baryons approximately trace the dark matter distribution down to $\sim$Mpc scales. While our projected-field estimator is already competitive with other kSZ approaches when applied to current datasets (because we are able to use the full-sky WISE photometric survey), it will yield enormous signal-to-noise when applied to upcoming high-resolution, multi-frequency CMB surveys.Comment: 5 pages + references, 2 figures; v2: matches PRL accepted version, results unchange

Taking the Universe's Temperature with Spectral Distortions of the Cosmic Microwave Background

The cosmic microwave background (CMB) energy spectrum is a near-perfect blackbody. The standard model of cosmology predicts small spectral distortions to this form, but no such distortion of the sky-averaged CMB spectrum has yet been measured. We calculate the largest expected distortion, which arises from the inverse Compton scattering of CMB photons off hot, free electrons, known as the thermal Sunyaev-Zel'dovich (tSZ) effect. We show that the predicted signal is roughly one order of magnitude below the current bound from the COBE-FIRAS experiment, but can be detected at enormous significance ($\gtrsim 1000\sigma$) by the proposed Primordial Inflation Explorer (PIXIE). Although cosmic variance reduces the effective signal-to-noise to $230\sigma$, this measurement will still yield a sub-percent constraint on the total thermal energy of electrons in the observable universe. Furthermore, we show that PIXIE can detect subtle relativistic effects in the sky-averaged tSZ signal at $30\sigma$, which directly probe moments of the optical depth-weighted intracluster medium electron temperature distribution. These effects break the degeneracy between the electron density and temperature in the mean tSZ signal, allowing a direct inference of the mean baryon density at low redshift. Future spectral distortion probes will thus determine the global thermodynamic properties of ionized gas in the universe with unprecedented precision. These measurements will impose a fundamental "integral constraint" on models of galaxy formation and the injection of feedback energy over cosmic time.Comment: 4.5 pages + references, 2 figures, comments welcome; v2: references updated; v3: matches PRL accepted versio

On the Assembly Bias of Cool Core Clusters Traced by Hα\alpha Nebulae

Do cool-core (CC) and noncool-core (NCC) clusters live in different environments? We make novel use of H$\alpha$ emission lines in the central galaxies of redMaPPer clusters as proxies to construct large (1,000's) samples of CC and NCC clusters, and measure their relative assembly bias using both clustering and weak lensing. We increase the statistical significance of the bias measurements from clustering by cross-correlating the clusters with an external galaxy redshift catalog from the Sloan Digital Sky Survey III, the LOWZ sample. Our cross-correlations can constrain assembly bias up to a statistical uncertainty of 6%. Given our H$\alpha$ criteria for CC and NCC, we find no significant differences in their clustering amplitude. Interpreting this difference as the absence of halo assembly bias, our results rule out the possibility of having different large-scale (tens of Mpc) environments as the source of diversity observed in cluster cores. Combined with recent observations of the overall mild evolution of CC and NCC properties, such as central density and CC fraction, this would suggest that either the cooling properties of the cluster core are determined early on solely by the local (<200 kpc) gas properties at formation or that local merging leads to stochastic CC relaxation and disruption in a periodic way, preserving the average population properties over time. Studying the small-scale clustering in clusters at high redshift would help shed light on the exact scenario.Comment: 17 pages, 9 figures, 2 tables, to be submitted to ApJ; comments welcom

Spin dynamics and level structure of quantum-dot quantum wells

We have characterized CdS/CdSe/CdS quantum-dot quantum wells using time-resolved Faraday rotation (TRFR). The spin dynamics show that the electron g-factor varies as a function of quantum well width and the transverse spin lifetime of several nano-seconds is robust up to room temperature. As a function of probe energy, the amplitude of the TRFR signal shows pronounced resonances, which allow one to identify individual exciton transitions. While the TRFR data are inconsistent with the conduction and valence band level scheme of spherical quantum-dot quantum wells, a model in which broken spherical symmetry is taken into account captures the essential features.Comment: 5 pages, 3 figure