29 research outputs found
The Atacama Cosmology Telescope: Millimeter Observations of a Population of Asteroids or: ACTeroids
We present fluxes and light curves for a population of asteroids at
millimeter (mm) wavelengths, detected by the Atacama Cosmology Telescope (ACT)
over 18, 000 deg2 of the sky using data from 2017 to 2021. We utilize high
cadence maps, which can be used in searching for moving objects such as
asteroids and trans-Neptunian Objects (TNOs), as well as for studying
transients. We detect 160 asteroids with a signal-to-noise of at least 5 in at
least one of the ACT observing bands, which are centered near 90, 150, and 220
GHz. For each asteroid, we compare the ACT measured flux to predicted fluxes
from the Near Earth Asteroid Thermal Model (NEATM) fit to WISE data. We confirm
previous results that detected a deficit of flux at millimeter wavelengths.
Moreover, we report a spectral characteristic to this deficit, such that the
flux is relatively lower at 150 and 220 GHz than at 90 GHz. Additionally, we
find that the deficit in flux is greater for S-type asteroids than for C-type.Comment: 15 pages, 9 Figures, 4 Table
Exploring Cosmic Origins with CORE: Cosmological Parameters
We forecast the main cosmological parameter constraints achievable with theCORE space mission which is dedicated to mapping the polarisation of the CosmicMicrowave Background (CMB). CORE was recently submitted in response to ESA'sfifth call for medium-sized mission proposals (M5). Here we report the resultsfrom our pre-submission study of the impact of various instrumental options, inparticular the telescope size and sensitivity level, and review the great,transformative potential of the mission as proposed. Specifically, we assessthe impact on a broad range of fundamental parameters of our Universe as afunction of the expected CMB characteristics, with other papers in the seriesfocusing on controlling astrophysical and instrumental residual systematics. Inthis paper, we assume that only a few central CORE frequency channels areusable for our purpose, all others being devoted to the cleaning ofastrophysical contaminants. On the theoretical side, we assume LCDM as ourgeneral framework and quantify the improvement provided by CORE over thecurrent constraints from the Planck 2015 release. We also study the jointsensitivity of CORE and of future Baryon Acoustic Oscillation and Large ScaleStructure experiments like DESI and Euclid. Specific constraints on the physicsof inflation are presented in another paper of the series. In addition to thesix parameters of the base LCDM, which describe the matter content of aspatially flat universe with adiabatic and scalar primordial fluctuations frominflation, we derive the precision achievable on parameters like thosedescribing curvature, neutrino physics, extra light relics, primordial heliumabundance, dark matter annihilation, recombination physics, variation offundamental constants, dark energy, modified gravity, reionization and cosmicbirefringence. (ABRIDGED
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, , 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 at greater than , or, in the
absence of a detection, of reaching an upper limit of at CL.Comment: 24 pages, 8 figures, 9 tables, submitted to ApJ. arXiv admin note:
text overlap with arXiv:1907.0447
CMB-S4: Forecasting Constraints on Primordial Gravitational Waves
Abstract: CMB-S4âthe next-generation ground-based cosmic microwave background (CMB) experimentâis 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 2â3 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 5Ï, or in the absence of a detection, of reaching an upper limit of r < 0.001 at 95% CL
Impact of modelling foreground uncertainties on future CMB polarization satellite experiments
We present an analysis of errors on the tensor-to-scalar ratio due to
residual diffuse foregrounds. We use simulated observations of a CMB
polarization satellite, the Cosmic Origins Explorer, using the specifications
of the version proposed to ESA in 2010 (COrE). We construct a full pipeline
from microwave sky maps to likelihood, using two models of diffuse Galactic
foregrounds with different complexity, and assuming component separation with
varying degrees of accuracy. Our pipeline uses a linear mixture (Generalized
Least Squares) solution for component separation, and a hybrid approach for
power spectrum estimation, with a Quadratic Maximum Likelihood estimator at low
s and a pseudo- deconvolution at high s. In the
likelihood for , we explore modelling foreground residuals as nuisance
parameters. Our analysis aims at measuring the bias introduced in by
mismodelling the foregrounds, and to determine what error is tolerable while
still successfully detecting . We find that can be measured
successfully even for a complex sky model and in the presence of foreground
parameters error. However, the detection of is a lot more
challenging, as inaccurate modelling of the foreground spectral properties may
result in a biased measurement of . Once biases are eliminated, the total
error on allows setting an upper limit rather than a detection, unless the
uncertainties on the foreground spectral indices are very small, i.e. equal or
better than 0.5\% error for both dust and synchrotron. This emphasizes the need
for pursuing research on component separation and foreground characterization
in view of next-generation CMB polarization experiments.Comment: 13 pages, 11 figures and 4 tables. Accepted for publication by MNRA