The Sunyaev-Zeldovich MITO Project

Compton scattering of the cosmic microwave background radiation by electrons in the hot gas in clusters of galaxies - the Sunyaev-Zeldovich effect - has long been recognized as a uniquely important feature, rich in cosmological and astrophysical information. We briefly describe the effect, and emphasize the need for detailed S-Z and X-ray measurements of nearby clusters in order to use the effect as a precise cosmological probe. This is the goal of the MITO project, whose first stage consisted of observations of the S-Z effect in the Coma cluster. We report the results of these observations.Comment: To appear in Proceedings of `Understanding our Universe at the close of XXth century', School held Apr 25 - May 6 2000, Cargese, 16 pages LaTeX, 2 figures ps (using elsart.sty & elsart.cls), text minor revisio

Far infrared polarimeter with very low instrumental polarization

After a short analysis of the main problems involved in the construction of a Far Infrared polarimeter with very low instrumental noise, we describe the instrument that will be employed at MITO telescope to search for calibration sources and investigate polarization near the CMB anisotropy peaks in the next campaign (Winter 2002-03).Comment: 9 pages, 5 figures, to appear in SPIE conference proceedings "Astronomical telescopes and instrumentation

End-to-end instrument performance simulation system (EIPS) framework: application to satellite microwave atmospheric sounding systems

This article presents a generic flexible framework for an End-to-end Instrument Performance Simulation System (EIPS) for satellite atmospheric remote sensing instruments. A systematic process for developing an end-to-end simulation system based on Rodgers’ atmospheric observing system design process has been visualised. The EIPS has been developed to support the quantitative evaluation of new satellite instrument concepts in terms of performance simulations, design optimisation, and trade-off analysis. Important features of this framework include: fast radiative transfer simulation capabilities (fast computation and line-by-line like simulations), applicability across the whole electromagnetic (EM) spectrum and a number of integrated retrieval diagnostics. Because of its applicability across the whole EM spectrum, the framework can be usefully applied to synergistic atmospheric retrieval studies. The framework is continually developing and evolving, and finding applications to support and evaluate emerging instrument and mission concepts. To demonstrate the framework’s flexibility in relation to advanced sensor technologies in the microwave range, a novel superconducting transition edge sensor (TES) -based multi-spectral microwave instrument has been presented as an example. As a case study, the performance of existing multi-spectral-type microwave instruments and a TES-technology-based multi-spectral microwave instrument has been simulated and compared using the developed end-to-end simulation framework

MITO measurements of the Sunyaev-Zeldovich Effect in the Coma cluster of galaxies

We have measured the Sunyaev-Zeldovich effect towards the Coma cluster (A1656) with the MITO experiment, a 2.6-m telescope equipped with a 4-channel 17 arcminute (FWHM) photometer. Measurements at frequency bands 143+/-15, 214+/-15, 272+/-16 and 353+/-13 GHz, were made during 120 drift scans of Coma. We describe the observations and data analysis that involved extraction of the S-Z signal by employing a spatial and spectral de-correlation scheme to remove a dominant atmospheric component. The deduced values of the thermal S-Z effect in the first three bands are DT_{0} = -179+/-38,-33+/-81,170+/-35 microKelvin in the cluster center. The corresponding optical depth, tau=(4.1+/-0.9) 10^{-3}, is consistent (within errors) with both the value from a previous low frequency S-Z measurement, and the value predicted from the X-ray deduced gas parameters.Comment: Ap.J.Letters accepted, 4 pages, 2 figure

Information content analysis for a novel TES-based hyperspectral microwave atmospheric sounding instrument

In context of numerical weather prediction (NWP), increased usage of satellites radiance observations from passive microwave sensors have brought significant improvements in the forecast skills. In the infrared spectral region, hyperspectral sounder instruments such as IASI have already benefitted the NWP assimilation systems, but they are useful only under clear sky conditions. Currently, microwave instruments are providing wealth of information on clouds, precipitation and surface etc., but only with limited number of channels. Furthermore, due to limited number of channels and with poor signal-to-noise ratio, existing passive microwave sensors have very poor resolution and accuracy. We are currently developing a new microwave instrument concept, based on superconducting filterbank spectrometers, which will enable high spectral resolution observations of atmospheric temperature and humidity profiles across the microwave/sub-millimeter wavelength region with photon-noise-limited sensitivity. This study aims at investigating the information content on temperature and water-vapour that could be provided by such a hyperspectral microwave instrument under clear sky-conditions. Here, we present a new concept of Transition Edge Sensors (TESs)-based hyperspectral microwave instrument for atmospheric sounding applications. In this study, for assessing the impact of hyperspectral sampling in microwave spectral region in clear sky-conditions, we have estimated the information content as standard figure of merit called as degrees of freedom for signal (DFS). The DFS for a set of temperature and humidity sounding channels (50-60 GHz, 118GHz and 183 GHz) have been analyzed under the linear optimal estimation theory framework

The QUaD Galactic Plane Survey. I. Maps and Analysis of Diffuse Emission

We present a survey of ~800 deg$^{2}$ of the galactic plane observed with the QUaD telescope. The primary products of the survey are maps of Stokes I, Q, and U parameters at 100 and 150 GHz, with spatial resolution of 5' and 3'.5, respectively. Two regions are covered, spanning approximately 245°-295° and 315°-5° in the galactic longitude l and –4° < b < +4° in the galactic latitude b. At 0°.02 square pixel size, the median sensitivity is 74 and 107 kJy sr$^{–1}$ at 100 GHz and 150 GHz respectively in I, and 98 and 120 kJy sr$^{–1}$ for Q and U. In total intensity, we find an average spectral index of α = 2.35 ± 0.01(stat) ± 0.02(sys) for |b| ≤ 1°, indicative of emission components other than thermal dust. A comparison to published dust, synchrotron, and free-free models implies an excess of emission in the 100 GHz QUaD band, while better agreement is found at 150 GHz. A smaller excess is observed when comparing QUaD 100 GHz data to the WMAP five-year W band; in this case, the excess is likely due to the wider bandwidth of QUaD. Combining the QUaD and WMAP data, a two-component spectral fit to the inner galactic plane (|b| ≤ 1°) yields mean spectral indices of α s = –0.32 ± 0.03 and α$_{d}$ = 2.84 ± 0.03; the former is interpreted as a combination of the spectral indices of synchrotron, free-free, and dust, while the second is largely attributed to the thermal dust continuum. In the same galactic latitude range, the polarization data show a high degree of alignment perpendicular to the expected galactic magnetic field direction, and exhibit mean polarization fraction 1.38 ± 0.08(stat) ± 0.1(sys)% at 100 GHz and 1.70 ± 0.06(stat) ± 0.1(sys)% at 150 GHz. We find agreement in polarization fraction between QUaD 100 GHz and the WMAP W band, the latter giving 1.1% ± 0.4%.Astronom

Parameter Estimation From Improved Measurements of the Cosmic Microwave Background From QUaD

We evaluate the contribution of cosmic microwave background (CMB) polarization spectra to cosmological parameter constraints. We produce cosmological parameters using high-quality CMB polarization data from the ground-based QUaD experiment and demonstrate for the majority of parameters that there is significant improvement on the constraints obtained from satellite CMB polarization data. We split a multi-experiment CMB data set into temperature and polarization subsets and show that the best-fit confidence regions for the ΛCDM six-parameter cosmological model are consistent with each other, and that polarization data reduces the confidence regions on all parameters. We provide the best limits on parameters from QUaD EE/BB polarization data and we find best-fit parameters from the multi-experiment CMB data set using the optimal pivot scale of k$_{p}$ = 0.013 Mpc$^{–1}$ to be {h$^{2}$Ω$_{c}$, h$^{2}$Ω$_{b}$, H$_{0}$, A$_{s}$, n$_{s}$, τ} = {0.113, 0.0224, 70.6, 2.29 × 10$^{-9}$, 0.960, 0.086}.Astronom

Observing the Evolution of the Universe

How did the universe evolve? The fine angular scale (l>1000) temperature and polarization anisotropies in the CMB are a Rosetta stone for understanding the evolution of the universe. Through detailed measurements one may address everything from the physics of the birth of the universe to the history of star formation and the process by which galaxies formed. One may in addition track the evolution of the dark energy and discover the net neutrino mass. We are at the dawn of a new era in which hundreds of square degrees of sky can be mapped with arcminute resolution and sensitivities measured in microKelvin. Acquiring these data requires the use of special purpose telescopes such as the Atacama Cosmology Telescope (ACT), located in Chile, and the South Pole Telescope (SPT). These new telescopes are outfitted with a new generation of custom mm-wave kilo-pixel arrays. Additional instruments are in the planning stages.Comment: Science White Paper submitted to the US Astro2010 Decadal Survey. Full list of 177 author available at http://cmbpol.uchicago.ed

Research Data supporting "First Characterization of a Superconducting Filter-bank Spectrometer for Hyper-spectral Microwave Atmospheric Sounding with Transition Edge Sensor Readout."

Data Set collected and modelled during Hymas Programme 2018-2019. Data measured at cryogenic temperatures.Funded by UK CEOI under Grant number RP61060435A07

Calibration strategy for the SPICA/SAFARI instrument

SPICA is a mid to far infra-red space mission to explore the processes that form galaxies, stars and planets. SPICA/SAFARI is the far infrared spectrometer that provides near-background limited observations between 34 and 230 micrometers. The core of SAFARI consists of 4 grating modules, dispersing light onto 5 arrays of TES detectors per module. The grating modules provide low resolution (250) instantaneous spectra over the entire wavelength range. The high resolution (1500 to 12000) mode is accomplished by placing a Fourier Transform Spectrometer (FTS) in front of the gratings. Each grating module detector sees an interferogram from which the high resolution spectrum can be constructed. SAFARI data will be a convolution of complex spectral, temporal and spatial information. Along with spectral calibration accuracy of <1%, a relative flux calibration of 1% and an absolute flux calibration accuracy of 10% are required. This paper will discuss the calibration strategy and its impact on the instrument design of SAFAR