CMB-S4: Forecasting Constraints on Primordial Gravitational Waves

CMB-S4---the next-generation ground-based cosmic microwave background (CMB) experiment---is set to significantly advance the sensitivity of CMB measurements and enhance our understanding of the origin and evolution of the Universe, from the highest energies at the dawn of time through the growth of structure to the present day. Among the science cases pursued with CMB-S4, the quest for detecting primordial gravitational waves is a central driver of the experimental design. This work details the development of a forecasting framework that includes a power-spectrum-based semi-analytic projection tool, targeted explicitly towards optimizing constraints on the tensor-to-scalar ratio, $r$, in the presence of Galactic foregrounds and gravitational lensing of the CMB. This framework is unique in its direct use of information from the achieved performance of current Stage 2--3 CMB experiments to robustly forecast the science reach of upcoming CMB-polarization endeavors. The methodology allows for rapid iteration over experimental configurations and offers a flexible way to optimize the design of future experiments given a desired scientific goal. To form a closed-loop process, we couple this semi-analytic tool with map-based validation studies, which allow for the injection of additional complexity and verification of our forecasts with several independent analysis methods. We document multiple rounds of forecasts for CMB-S4 using this process and the resulting establishment of the current reference design of the primordial gravitational-wave component of the Stage-4 experiment, optimized to achieve our science goals of detecting primordial gravitational waves for $r > 0.003$ at greater than $5\sigma$, or, in the absence of a detection, of reaching an upper limit of $r < 0.001$ at $95\%$ CL.Comment: 24 pages, 8 figures, 9 tables, submitted to ApJ. arXiv admin note: text overlap with arXiv:1907.0447

CMB-S4

We describe the stage 4 cosmic microwave background ground-based experiment CMB-S4

CMB-S4: Forecasting Constraints on Primordial Gravitational Waves

Abstract: CMB-S4—the next-generation ground-based cosmic microwave background (CMB) experiment—is set to significantly advance the sensitivity of CMB measurements and enhance our understanding of the origin and evolution of the universe. Among the science cases pursued with CMB-S4, the quest for detecting primordial gravitational waves is a central driver of the experimental design. This work details the development of a forecasting framework that includes a power-spectrum-based semianalytic projection tool, targeted explicitly toward optimizing constraints on the tensor-to-scalar ratio, r, in the presence of Galactic foregrounds and gravitational lensing of the CMB. This framework is unique in its direct use of information from the achieved performance of current Stage 2–3 CMB experiments to robustly forecast the science reach of upcoming CMB-polarization endeavors. The methodology allows for rapid iteration over experimental configurations and offers a flexible way to optimize the design of future experiments, given a desired scientific goal. To form a closed-loop process, we couple this semianalytic tool with map-based validation studies, which allow for the injection of additional complexity and verification of our forecasts with several independent analysis methods. We document multiple rounds of forecasts for CMB-S4 using this process and the resulting establishment of the current reference design of the primordial gravitational-wave component of the Stage-4 experiment, optimized to achieve our science goals of detecting primordial gravitational waves for r > 0.003 at greater than 5σ, or in the absence of a detection, of reaching an upper limit of r < 0.001 at 95% CL

The dynamic properties of intermediate filaments during organelle transport

Intermediate filament (IF) dynamics during organelle transport and their role in organelle movement were studied using Xenopus laevis melanophores. In these cells, pigment granules (melanosomes) move along microtubules and microfilaments, toward and away from the cell periphery in response to α-melanocyte stimulating hormone (α-MSH) and melatonin, respectively. In this study we show that melanophores possess a complex network of vimentin IFs which interact with melanosomes. IFs form an intricate, honeycomb-like network that form cages surrounding individual and small clusters of melanosomes, both when they are aggregated and dispersed. Purified melanosome preparations contain a substantial amount of vimentin, suggesting that melanosomes bind to IFs. Analyses of individual melanosome movements in cells with disrupted IF networks show increased movement of granules in both anterograde and retrograde directions, further supporting the notion of a melanosome-IF interaction. Live imaging reveals that IFs, in turn, become highly flexible as melanosomes disperse in response to α-MSH. During the height of dispersion there is a marked increase in the rate of fluorescence recovery after photobleaching of GFP-vimentin IFs and an increase in vimentin solubility. These results reveal a dynamic interaction between membrane bound pigment granules and IFs and suggest a role for IFs as modulators of granule movement