arXiv subjects

Jean Kaplan

Publications and source records attributed to Jean Kaplan.

7 recordsLinked to original sources

arXiv2019

QUBIC: Exploring the primordial Universe with the Q\&U Bolometric Interferometer

In this paper we describe QUBIC, an experiment that will observe the polarized microwave sky with a novel approach, which combines the sensitivity of state-of-the art bolometric detectors with the systematic effects control typical of interferometers. QUBIC unique features are the so-called "self-calibration", a technique that allows us to clean the measured data from instrumental effects, and its spectral imaging power, i.e. the ability to separate the signal in various sub-bands within each frequency band. QUBIC will observe the sky in two main frequency bands: 150 GHz and 220 GHz. A technological demonstrator is currently under testing and will be deployed in Argentina during 2019, while the final instrument is expected to be installed during 2020.

astro-ph.IM↗

arXiv2009

QUBIC, a bolometric interferometer to measure the B modes of the CMB

Measuring the B modes of the CMB polarization fluctuations would provide very strong constraints on inflation. The main challenge in this measurement is the treatment of systematic effects. CMB observations with imagers and interferometers, subject to very different systematics, are complementary in this respect. Interferometry provides direct access to the Fourier transform of the sky signal. In bolometric interferometry, the interference pattern produced by the sky through a few hundred horns is imaged on a bolometer array. Several such modules are needed to achieve the required sensitivity. We will describe QUBIC, a merger of the US and European MBI and BRAIN collaborations. QUBIC is a polarized bolometric interferometer to be deployed in 2011-2012.

astro-ph.IM↗

arXiv2006

Beam mismatch effects in Cosmic Microwave Background polarization measurements

Measurement of cosmic microwave background polarization is today a major goal of observational cosmology. The level of the signal to measure, however, makes it very sensitive to various systematic effects. In the case of Planck, which measures polarization by combining data from various detectors, the beam asymmetry can induce a temperature leakage or a polarization mode mixing. In this paper, we investigate this effect using realistic simulated beams and propose a first-order method to correct the polarization power spectra for the induced systematic effect.

astro-ph↗

arXiv2001

Some sources of systematic errors on CMB polarized measurements with bolometers

Some sources of systematic errors, specific to polarized CMB measurements using bolometers, are examined. Although the evaluations we show have been made in the context of the Planck mission (and more specifically the Planck HFI), many of our conclusions are valid for other experiments as well.

astro-ph↗

arXiv1994

Microlensing by brown dwarfs: the case of dark clusters

Experiments are looking for diffuse brown dwarfs in the dark galactic halo through the gravitational lens effect. If brown dwarfs are clumped in dark clusters, the event rate is not changed, but events are spatially clustered, and stars nearby a micro-lensed one are likely to be micro-lensed in a near future. Therefore, an intensive survey of the region where a micro-lensing occurred should reveal many other events.

astro-ph↗

arXiv1993

Microlensing of Unresolved Stars as a Brown Dwarf Detection Method

We describe a project of brown dwarf detection in the dark halo of a galaxy using the microlensing effect. We argue that monitoring pixels instead of stars could provide an enhancement in the number of detectable events. We estimate the detection efficiency with a Monte-Carlo simulation. We expect a ten-fold increase with respect to current experiments. To assess the feasibility of this method we have determined the photometric precision of a pixel by comparing several pictures of a same field in the LMC. To be published in the Proceeding of the workshop 'The dark side of the universe...', Roma, Juin 1993,

astro-ph↗

arXiv1992

Detection of brown dwarfs by the micro-lensing of unresolved stars

The presence of brown dwarfs in the dark galactic halo could be detected through their gravitational lensing effect and experiments under way monitor about one million stars to observe a few lensing events per year. We show that if the photon flux from a galaxy is measured with a good precision, it is not necessary to resolve the stars and besides more events could be observed.

astro-ph↗