Baffling and shielding system for a mm-wave balloon-borne telescope

We describe a balloon borne telescope devoted to millimeter observations of diffuse sky radiation and optimized with a custom set of baffles and shields. The basic idea of the shield design is to shape the surfaces as roof mirrors to redirect the stray radiation in the opposite direction of incidence. The baffles are used to stop radiation close to the field of view. In this way we are able to avoid most of the unwanted radiation. We successfully operated this telescope (ARGO) during two flights, in 1989 and 1993, while detecting the faint structures of the cosmic microwave background at degree scale. (C) 1998 Optical Society of America

The Three Hundred project: Contrasting clusters galaxy density in hydrodynamical and dark matter only simulations

International audienceCluster number count is a major cosmological probe for the next generation of cosmological large scale-structure surveys like the one expected from the Euclid satellite mission. Cosmological constraints will be mainly limited by the understanding of the selection function (SF), which characterize the probability of detecting a cluster of a given mass and redshift. The SF can be estimated by injecting realistic simulated clusters into the survey and re-applying the detection procedure. For this purpose we intend to use The Three Hundreds project, a 324 cluster sample simulated with full-physics hydrodynamical re-simulations. In this paper we concentrate on the study of the distribution of member galaxies in the cluster sample. First, we study possible resolution effects by comparing low and high resolution simulations. Finally, accounting for the latter we derive the density profiles of the member galaxies and discuss their evolution with cluster mass and redshift

Preliminary results on the instrumental polarization of NIKA2-Pol at the IRAM 30m telescope

International audienceClarifying the role of magnetic fields in the star formation process is crucial. Observations have already shown that magnetic fields play an important role in the early stages of star formation. The high spatial resolution (∼0.01 to 0.05 pc) provided by NIKA2-Pol 1.2 mm imaging polarimetry of nearby clouds will help us clarify the geometry of the B-field within dense cores and molecular filaments as part of the IRAM 30m large program B-FUN. There are numerous challenging issues in the validation of NIKA2-Pol such as the calibration of instrumental polarization. The commissioning phase of NIKA2-Pol is underway and is helping us characterize the intensity-to-polarization “leakage” pattern of the instrument. We present a preliminary analysis of the leakage pattern and its dependence with elevation. We also present the current leakage correction made possible by the NIKA2 pipeline in polarization mode based on the NIKA2-Pol commissioning data taken in December 2018. Based on reduced Stokes I, Q, U data we find that the leakage pattern of NIKA2-Pol depends on elevation and is sensitive to the focus of the telescope

Dust Emission in Galaxies at Millimeter Wavelengths: Cooling of star forming regions in NGC6946

International audienceInterstellar dust plays an important role in the formation of molecular gas and the heating and cooling of the interstellar medium. The spatial distribution of the mm-wavelength dust emission from galaxies is largely unexplored. The NIKA2 Guaranteed Time Project IMEGIN (Interpreting the Millimeter Emission of Galaxies with IRAM and NIKA2) has recently mapped the mm emission in the grand design spiral galaxy NGC6946. By subtracting the contributions from the free-free, synchrotron, and CO line emission, we map the distribution of the pure dust emission at 1:15mm and 2mm. Separating the arm/interarm regions, we find a dominant 2mm emission from interarms indicating the significant role of the general interstellar radiation field in heating the cold dust. Finally, we present maps of the dust mass, temperature, and emissivity index using the Bayesian MCMC modeling of the spectral energy distribution in NGC6946

QUBIC – The Q & U Bolometric Interferometer for Cosmology

International audienceThis In this paper we briefly describe QUBIC, the Q & U Bolometric Interferometer for Cosmology, a novel ground-based instrument designed to measure the extremely faint polarization anisotropy of the cosmic microwave background at intermediate angular scales. In particular we will describe simulations of the optical combiner and feedhorn array used to generate synthesized beam patterns for each detector on our focal plane. A QUBIC technical demonstrator has been built and is being installed in the observing site at Alto Chorrillos, Argentina with first light expected in 2022

QUBIC: the Q and U bolometric interferometer for cosmology

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Detection chain and electronic readout of the QUBIC instrument

International audienceThe Q and U Bolometric Interferometer for Cosmology (QUBIC) Technical Demonstrator (TD) aiming to shows the feasibility of the combination of interferometry and bolometric detection. The electronic readout system is based on an array of 128 NbSi Transition Edge Sensors cooled at 350mK readout with 128 SQUIDs at 1K controlled and amplified by an Application Specific Integrated Circuit at 40K. This readout design allows a 128:1 Time Domain Multiplexing. We report the design and the performance of the detection chain in this paper. The technological demonstrator unwent a campaign of test in the lab. Evaluation of the QUBIC bolometers and readout electronics includes the measurement of I-V curves, time constant and the Noise Equivalent Power. Currently the mean Noise Equivalent Power is ~ 2 x 10-16W= p √H