Searcharxiv⌕ Search

arXiv subjects

F. Boulanger

Publications and source records attributed to F. Boulanger.

At least 19 recordsLinked to original sources
arXiv2026

Proof of concept of the COSMOCal project at the IRAM 30m telescope

This work reports on a test campaign conducted at the IRAM 30m telescope to validate the COSMOCal instrument, a novel concept for absolute calibration of polarization angle, beam properties, and instrumental efficiency. The development is motivated by the stringent calibration requirements of current and next-generation Cosmic Microwave Background (CMB) experiments, whose goal is the precise measurement of CMB polarization. Such measurements are essential to probe fundamental physics, including the possible imprint of primordial inflation. The COSMOCal concept is designed as a space-borne calibration reference intended to provide a stable and absolute polarized signal observable simultaneously by multiple large-aperture ground-based observatories. Prior to any space deployment, a terrestrial prototype was developed and characterized in the laboratory, as reported in Ritacco et al. 2024. The results presented here describe the first validation of the system coupled to an antenna, carried out at the IRAM 30m telescope in September 2024. This campaign aimed at assessing the performance of the full instrument under realistic observational conditions, including its ability to reconstruct polarization observables and interface with a state-of-the-art millimeter-wave polarimeter.

astro-ph.IM↗
arXiv2026

LiteBIRD Mission Overview after Mission Reformation

LiteBIRD is a JAXA-led space mission designed to produce all-sky microwave polarization maps. Its primary science goal is to test representative inflationary models by measuring the cosmic microwave background $B$-mode polarization generated by primordial gravitational waves, while also providing new insights into cosmology, particle physics, and astrophysics. The mission concept has been updated following the reformation activities initiated after the Mission Definition Review in 2024. The current concept preserves the central scientific objectives, while simplifying the payload configuration: a single telescope covers 12 frequency bands with band centers spanning 40 to 402~GHz, corresponding to an optical coverage of 34--448~GHz. The telescope is a cross-Dragone reflector with a 500~mm aperture diameter, cooled to approximately 5~K and coupled to transition-edge-sensor bolometer arrays operated at 0.1~K. LiteBIRD will observe from a Lissajous orbit around the Sun--Earth L2 point during a nominal 3-year survey. More specifically, the primary scientific objective is to achieve total uncertainty in the tensor-to-scalar ratio of $\delta r < 0.002$ (68\% C.L.), including contributions from foreground residuals, statistical uncertainties, instrumental systematics, and margin contingency. The corresponding map-noise requirements are specified separately for the low-, mid-, and high-frequency ranges over the reionization and recombination multipole ranges. This sensitivity makes LiteBIRD unique not only for inflationary science but also for a broad range of scientific investigations probing the history of both the early and late Universe, as well as for astrophysical processes, including Galactic science. This paper summarizes the scientific objectives, updated payload and instrument concepts, observation strategy, and ground segment plans.

astro-ph.IM↗
arXiv2026

Status of the COSmological Microwave Observations CALibrator

As the sensitivity of CMB telescopes increases, the need for precise calibration becomes critical. Started in 2022, the COSMOCal project aims to place an artificial polarized source in geostationary orbit, which will serve as a reference for CMB telescopes. This source will emit at 90, 150 and 270 GHz and will be linearly polarized with a highly precise orientation smaller than 0.1 deg. This proceeding presents the scientific motivations for the project, the current status of the development of the instrument and the results of a calibration campaign performed in March 2026 at the Institut d'Astrophysique Spatiale.

astro-ph.IM↗
arXiv2026

JWST imaging of the Pleiades: anisotropy of turbulence in the cold neutral medium

Interstellar medium studies rely on magnetohydrodynamic (MHD) turbulence as a framework for interpretation. In this context, the statistical characterization of interstellar observations is of prime importance. We open a new perspective on diffuse interstellar matter by analyzing James Webb Space Telescope (JWST) observations of the Pleiades nebula with NIRCam. These observations are remarkable in that they provide a microscope view at the cold neutral medium (CNM) with a spatial resolution of 0.2 mpc (40 au). A two-dimensional Fourier analysis is used to characterize the structure of PAH emission in regions near and far from the Pleiades star Merope. To produce maps of the interstellar emission, stars and galaxies are filtered out. The final step in the data cleaning involves subtracting a component, in Fourier space, which we infer to be a residual of the near-infrared cosmic background. The PAH emission power spectra are highly anisotropic. They are well fitted with a break-free power-law, suggesting that we do not observe a specific scale for energy dissipation. Power-law indices are -3.5 near Merope and -3 in the more distant field. The magnetic field orientation, as derived from the Planck dust polarization data, aligns with the PAH anisotropy. The power anisotropy is constant across scales. These findings are discussed in relation to interstellar turbulence that may be driven by the Pleiades stars. The JWST observations of the Pleiades offer a new viewpoint for comparing observations and theoretical models, as they examine physical scales at which turbulence in the CNM is subsonic and decoupled from the thermal instability. The observations may indicate that the turbulent energy cascade in the CNM is anisotropic.

astro-ph.GA↗
arXiv2024

Bird's-eye View of Molecular Gas across Stephan's Quintet Galaxy Group and Intra-group Medium

We present the large-scale distribution and kinematics of cold molecular gas across the compact galaxy group Stephan's Quintet, based on CO(2-1) observations performed with the Atacama Compact Array (ACA) and CO(1-0) data from the Combined Array for Research in Millimeter-wave Astronomy (CARMA). We find coherent structures of molecular gas associated with the galaxies and intra-group medium, which follow the distribution of warm H$_{2}$ previously seen with the James Webb Space Telescope (JWST). CO is associated with a ridge of shocked gas that crosses the galaxy group, and with a spiral arm of the intruding galaxy NGC7318b, which interacts with the intra-group medium along the ridge. Although the ridge contains widespread shocks, turbulent gas, and warm H$_{2}$, the CO lines are narrower than elsewhere in Stephan's Quintet (FWHM~25-65 km/s), indicative of settled cold gas. At a distinctly different velocity, CO is found in the active galaxy NGC7319 and Northern star-forming region SQ-A. A bridge of turbulent molecular gas connects NGC7319 with the ridge, covering a gap of ~700 km/s between these structures. The gas excitation ranges from $L'_{\rm CO(2-1)}$/$L'_{\rm CO(1-0)}$ ~ 0.3 in the bridge and SQ-A, to ~0.5 along the ridge, to near unity in the center of NGC7319. We also detect either a molecular outflow or turbulent molecular gas associated with the radio source in NGC7319. These ACA data are part of a program with the Atacama Large Millimeter/submillimeter Array (ALMA) and JWST to study molecular gas physics from the largest to the smallest scales across the intra-group medium of Stephan's Quintet.

astro-ph.GA↗
arXiv2024

Absolute reference for microwave polarization experiments -- The COSMOCal project and its proof of concept

The cosmic microwave background (CMB), a remnant of the Big Bang, provides unparalleled insights into the primordial universe, its energy content, and the origin of cosmic structures. The success of forthcoming terrestrial and space experiments hinges on meticulously calibrated data. Specifically, the ability to achieve an absolute calibration of the polarization angles with a precision of < 0.1 deg is crucial to identify the signatures of primordial gravitational waves and cosmic birefringence within the CMB polarization. We introduce the COSMOCal project, designed to deploy a polarized source in space for calibrating microwave frequency observations. The project aims to integrate microwave polarization observations from small and large telescopes, ground-based and in space, into a unified scale, enhancing the effectiveness of each observatory and allowing robust combination of data. To demonstrate the feasibility and confirm the observational approach of our project, we developed a prototype instrument that operates in the atmospheric window centered at 260 GHz, specifically tailored for use with the NIKA2 camera at the IRAM 30 m telescope. We present the instrument components and their laboratory characterization. The results of tests performed with the fully assembled prototype using a KIDs-based instrument, similar concept of NIKA2, are also reported. This study paves the way for an observing campaign using the IRAM 30m telescope and contributes to the development of a space-based instrument.

astro-ph.CO↗
arXiv2024

Associating LOFAR Galactic Faraday structures with the warm neutral medium

Faraday tomography observations with the Low Frequency Array (LOFAR) have unveiled a remarkable network of structures in polarized synchrotron emission at high Galactic latitudes. The observed correlation between LOFAR structures, dust polarization, and HI emission suggests a connection to the neutral interstellar medium (ISM). We investigated this relationship by estimating the rotation measure (RM) of the warm neutral (partially ionized) medium (WNM) in the local ISM. Our work combines UV spectroscopy from FUSE and dust polarization observations from \Planck\ with LOFAR data. We derived electron column densities from UV absorption spectra toward nine background stars, within the field of published data from the LOFAR two-meter sky survey. The associated RMs were estimated using a local magnetic field model fitted to the dust polarization data of \Planck. A comparison with Faraday spectra at the position of the stars suggests that LOFAR structures delineate a slab of magnetized WNM and synchrotron emission, located ahead of the bulk of the warm ionized medium. This conclusion establishes an astrophysical framework for exploring the link between Faraday structures and the dynamics of the magnetized multiphase ISM. It will be possible to test it on a larger sample of stars when maps from the full northern sky survey of LOFAR become available.

astro-ph.GA↗
arXiv2023

All We Are Is Dust In The WIM: Constraints on Dust Properties in the Milky Way's Warm Ionized Medium

We present a comparison of the presence and properties of dust in two distinct phases of the Milky Way's interstellar medium: the warm neutral medium (WNM) and the warm ionized medium (WIM). Using distant pulsars at high Galactic latitudes and vertical distance ($|b| > 40°$, $D \sin|b| > 2 \mathrm{\,\, kpc}$) as probes, we measure their dispersion measures and the neutral hydrogen component of the warm neutral medium ($\text{WNM}_\text{HI}$) using HI column density. Together with dust intensity along these same sightlines, we separate the respective dust contributions of each ISM phase in order to determine whether the ionized component contributes to the dust signal. We measure the temperature ($T$), spectral index ($β$), and dust opacity ($τ/N_{H}$) in both phases. We find $T~{\text{(WNM}_\text{HI})}=20^{+3}_{-2}$~K, $β~{\text{(WNM}_\text{HI})} = 1.5\pm{0.4}$, and $τ_{\text{353}}/N_{H}~{\text{(WNM}_\text{HI})}=(1.0\pm0.1)\times 10^{-26}$~cm$^2$. Assuming that the temperature and spectral index are the same in both the WNM$_\text{HI}$ and WIM, and given our simple model that widely separated lines-of-sight can be fit together, we find evidence that there is a dust signal associated with the ionized gas and $τ_{\text{353}}/N_{H}~\text{(WIM)}=(0.3\pm0.3)\times 10^{-26}$, which is about three times smaller than $τ_{\text{353}}/N_{H}~{\text{(WNM}_\text{HI})}$. We are 80% confident that $τ_{\text{353}}/N_{H}~\text{(WIM)}$ is at least two times smaller than $τ_{\text{353}}/N_{H}~{\text{(WNM}_\text{HI})}$.

astro-ph.GA↗
arXiv2023

Polarization angle accuracy for future CMB experiments. The COSMOCal project and its prototype in the 1mm band

The Cosmic Microwave Background (CMB) radiation offers a unique window into the early Universe, facilitating precise examinations of fundamental cosmological theories. However, the quest for detecting B-modes in the CMB, predicted by theoretical models of inflation, faces substantial challenges in terms of calibration and foreground modeling. The COSMOCal (COsmic Survey of Millimeter wavelengths Objects for CMB experiments Calibration) project aims at enhancing the accuracy of the absolute calibration of the polarization angle $ψ$ of current and future CMB experiments. The concept includes the build of a very well known artificial source emitting in the frequency range [20-350] GHz that would act as an absolute calibrator for several polarization facilities on Earth. A feasibility study to place the artificial source in geostationary orbit, in the far field for all the telescopes on Earth, is ongoing. In the meanwhile ongoing hardware work is dedicated to build a prototype to test the technology, the precision and the stability of the polarization recovering in the 1 mm band (220-300 GHz). High-resolution experiments as the NIKA2 camera at the IRAM 30m telescope will be deployed for such use. Once carefully calibrated ($Δψ$ < 0.1 degrees) it will be used to observe astrophysical sources such as the Crab nebula, which is the best candidate in the sky for the absolute calibration of CMB experiments.

astro-ph.IM↗
arXiv2023

Multi-phase gas interactions on subarcsec scales in the shocked IGM of Stephan's Quintet with JWST and ALMA

We combine JWST and HST imaging with ALMA~CO(2-1) spectroscopy to study the highly turbulent multi-phase intergalactic medium (IGM) in Stephan's Quintet on 25-150 pc scales. Previous Spitzer observations revealed luminous H$_2$ line cooling across a 45 kpc-long filament, created by a giant shock-wave, following the collision with an intruder galaxy NGC~7318b. We demonstrate that the MIRI/F1000W/F770W filters are dominated by 0-0~S(3)~H$_2$ and a combination of PAH and 0-0~S(5)~H$_2$ emission. They reveal the dissipation of kinetic energy as massive clouds experience collisions, interactions and likely destruction/re-cycling within different phases of the IGM. In one kpc-scaled structure, warm H$_2$ formed a triangular-shaped head and tail of compressed and stripped gas behind a narrow shell of cold H$_2$. In another region, two cold molecular clumps with very different velocities are connected by an arrow-shaped stream of warm, probably shocked, H$_2$ suggesting a cloud-cloud collision is occurring. In both regions, a high warm-to-cold molecular gas fraction indicates that the cold clouds are being disrupted and converted into warm gas. We also map gas associated with an apparently forming dwarf galaxy. We suggest that the primary mechanism for exciting strong mid-IR H$_2$ lines throughout Stephan's Quintet is through a fog of warm gas created by the shattering of denser cold molecular clouds and mixing/recycling in the post-shocked gas. A full picture of the diverse kinematics and excitation of the warm H$_2$ will require future JWST mid-IR spectroscopy. The current observations reveal the rich variety of ways that different gas phases can interact with one another.

astro-ph.GA↗
arXiv2023

Probing Cosmic Inflation with the LiteBIRD Cosmic Microwave Background Polarization Survey

LiteBIRD, the Lite (Light) satellite for the study of B-mode polarization and Inflation from cosmic background Radiation Detection, is a space mission for primordial cosmology and fundamental physics. The Japan Aerospace Exploration Agency (JAXA) selected LiteBIRD in May 2019 as a strategic large-class (L-class) mission, with an expected launch in the late 2020s using JAXA's H3 rocket. LiteBIRD is planned to orbit the Sun-Earth Lagrangian point L2, where it will map the cosmic microwave background (CMB) polarization over the entire sky for three years, with three telescopes in 15 frequency bands between 34 and 448 GHz, to achieve an unprecedented total sensitivity of 2.2$μ$K-arcmin, with a typical angular resolution of 0.5$^\circ$ at 100 GHz. The primary scientific objective of LiteBIRD is to search for the signal from cosmic inflation, either making a discovery or ruling out well-motivated inflationary models. The measurements of LiteBIRD will also provide us with insight into the quantum nature of gravity and other new physics beyond the standard models of particle physics and cosmology. We provide an overview of the LiteBIRD project, including scientific objectives, mission and system requirements, operation concept, spacecraft and payload module design, expected scientific outcomes, potential design extensions and synergies with other projects.

astro-ph.IM↗
arXiv2022

Non-Gaussian modelling and statistical denoising of Planck dust polarization full-sky maps using scattering transforms

Scattering transforms have been successfully used to describe dust polarization for flat-sky images. This paper expands this framework to noisy observations on the sphere with the aim of obtaining denoised Stokes Q and U all-sky maps at 353GHz, as well as a non-Gaussian model of dust polarization, from the Planck data. To achieve this goal, we extend the computation of scattering coefficients to the Healpix pixelation and introduce cross-statistics that allow us to make use of half-mission maps as well as the correlation between dust temperature and polarization. Introducing a general framework, we develop an algorithm that uses the scattering statistics to separate dust polarization from data noise. The separation is validated on mock data, before being applied to the SRoll2 Planck maps at N_side = 256. The validation shows that the statistics of the dust emission, including its non-Gaussian properties, are recovered until l < 700, where, at high Galactic latitudes, the dust power is smaller than that of the dust by two orders of magnitude. On scales where the dust power is lower than one tenth of that of the noise, structures in the output maps have comparable statistics but are not spatially coincident with those of the input maps. Our results on \Planck\ data are significant milestones opening new perspectives for statistical studies of dust polarization and for the simulation of Galactic polarized foregrounds. The Planck denoised maps is available (see http://sroll20.ias.u-psud.fr/sroll40_353_data.html) together with results from our validation on mock data, which may be used to quantify uncertainties.

astro-ph.CO↗
arXiv2022

Moment expansion of polarized dust SED: a new path towards capturing the CMB $B$-modes with $\textit{LiteBIRD}$

Characterizing the polarized dust emission from our Galaxy will be decisive for the quest for the Cosmic Microwave Background (CMB) primordial $B$-modes. The incomplete modelling of its potentially complex spectral properties could lead to biases in the CMB polarization analyses and to a spurious detection of the tensor-to-scalar ratio $r$. It is crucial for future surveys like the $LiteBIRD$ satellite, which aims at constraining the primordial signal leftover by Inflation with an accuracy on $r$ of the order 1e-3. Variations of the dust properties along and between lines of sight lead to distortions of the spectral energy distribution (SED) that can not be easily anticipated by standard component separation methods. This issue can be tackled with a moment expansion of the dust SED, an innovative parametrization method imposing minimal assumptions on the sky complexity. In this paper, we apply this formalism to the $B$-mode cross-angular power spectra computed from simulated $LiteBIRD$ polarization data at frequencies between 100 and 402 GHz, containing CMB, dust and instrumental noise. The spatial variation of the dust spectral parameters (spectral index $β$ and temperature $T$) in our simulations, lead to significant biases on $r$ if not properly taken into account. Performing the moment expansion in $β$, reduces the bias but do not lead to reliable enough estimates of $r$. We introduce for the first time the expansion of the cross-angular power spectra SED in $β$ and $T$, showing that, at the $LiteBIRD$ sensitivity, it is required to take into account the SED complexity due to temperature variations to prevent analysis biases on $r$. Thanks to this expansion and despite the existing correlations between some of the dust moments and the CMB signal, responsible for a rise of the error on $r$, we can measure an unbiased value of $r$ with an uncertainty of $σ(r)$=8.8e-4.

astro-ph.CO↗
arXiv2022

The CO emission in the Taffy Galaxies (UGC 12914/5) at 60pc resolution-I: The battle for star formation in the turbulent Taffy Bridge

We present ALMA observations at a spatial resolution of 0.2 arcsec (60 pc) of CO emission from the Taffy galaxies (UGC 12914/5). The observations are compared with narrow-band Pa$α$, mid-IR, radio continuum and X-ray imaging, plus optical spectroscopy. The galaxies have undergone a recent head-on collision, creating a massive gaseous bridge which is known to be highly turbulent. The bridge contains a complex web of narrow molecular filaments and clumps. The majority of the filaments are devoid of star formation, and fall significantly below the Kennicutt-Schmidt relationship for normal galaxies, especially for the numerous regions undetected in Pa$α$ emission. Within the loosely connected filaments and clumps of gas we find regions of high velocity dispersion which appear gravitationally unbound for a wide range of likely values of $X_{\rm CO}$. Like the "Firecracker" region in the Antennae system, they would require extremely high external dynamical or thermal pressure to stop them dissipating rapidly on short crossing timescales of 2-5~Myrs. We suggest that the clouds may be transient structures within a highly turbulent multi-phase medium which is strongly suppressing star formation. Despite the overall turbulence in the system, stars seem to have formed in compact hotspots within a kpc-sized extragalactic HII region, where the molecular gas has a lower velocity dispersion than elsewhere, and shows evidence for a collision with an ionized gas cloud. Like the shocked gas in the Stephan's Quintet group, the conditions in the Taffy bridge shows how difficult it is to form stars within a turbulent, multi-phase, gas.

astro-ph.GA↗
arXiv2022

Contribution to the 2022 Cosmology session of the 56th Rencontres de Moriond: Moment expansion of polarized dust SED: A new path towards capturing the CMB $B$-modes with LiteBIRD

Characterizing accurately the polarized dust emission from our Galaxy will be decisive for the quest for the Cosmic Microwave Background (CMB) primordial $B$-modes. The incomplete modeling of its potentially complex spectral properties could lead to biases in the CMB polarization analyses and to a spurious detection of the tensor-to-scalar ratio $r$. Variations of the dust properties along and between lines of sight lead to unavoidable distortions of the spectral energy distribution (SED) that can not be easily anticipated by standard component separation methods. This issue can be tackled using a moment expansion of the dust SED, an innovative parametrization method imposing minimal assumptions on the sky complexity. In the recent work [Vacher \emph{et al.} (2022)]\cite{Vacher_2022}, we apply this formalism to the $B$-mode cross-angular power spectra computed from simulated \lb{} polarization data at frequencies between 100 and 402\,GHz, containing CMB, dust and instrumental noise. Thanks to the moment expansion, we can measure an unbiased value of the tensor-to-scalar ratio with a dispersion compatible with the target values aimed by the instrument.

astro-ph.CO↗
arXiv2021

Extremely broad Lyman-alpha line emission from the molecular intra-group medium in Stephan's Quintet: evidence for a turbulent cascade in a highly clumpy multi-phase medium?

We present Hubble Space Telescope Cosmic Origin Spectrograph (COS) UV line spectroscopy and integral-field unit (IFU) observations of the intra-group medium in Stephan's Quintet (SQ). SQ hosts a 30 kpc long shocked ridge triggered by a galaxy collision at a relative velocity of 1000 km/s, where large amounts of molecular gas coexist with a hot, X-ray emitting, plasma. COS spectroscopy at five positions sampling the diverse environments of the SQ intra-group medium reveals very broad (2000 km/s) Ly$α$ line emission with complex line shapes. The Ly$α$ line profiles are similar to or much broader than those of H$β$, [CII]$\lambda157.7μ$m and CO~(1-0) emission. The extreme breadth of the Ly$α$ emission, compared with H$β$, implies resonance scattering within the observed structure. Scattering indicates that the neutral gas of the intra-group medium is clumpy, with a significant surface covering factor. We observe significant variations in the Ly$α$/H$β$ flux ratio between positions and velocity components. From the mean line ratio averaged over positions and velocities, we estimate the effective escape fraction of Ly$α$ photons to be 10-30%. Remarkably, over more than four orders of magnitude in temperature, the powers radiated by X-rays, Ly$α$, H$_2$, [CII] are comparable within a factor of a few, assuming that the ratio of the Ly$α$ to H$_2$ fluxes over the whole shocked intra-group medium stay in line with those observed at those five positions. Both shocks and mixing layers could contribute to the energy dissipation associated with a turbulent energy cascade. Our results may be relevant for the cooling of gas at high redshifts, where the metal content is lower than in this local system, and a high amplitude of turbulence is more common.

astro-ph.GA↗
arXiv2021

Planck 2018 results. VI. Cosmological parameters

We present cosmological parameter results from the final full-mission Planck measurements of the CMB anisotropies. We find good consistency with the standard spatially-flat 6-parameter $Λ$CDM cosmology having a power-law spectrum of adiabatic scalar perturbations (denoted "base $Λ$CDM" in this paper), from polarization, temperature, and lensing, separately and in combination. A combined analysis gives dark matter density $Ω_c h^2 = 0.120\pm 0.001$, baryon density $Ω_b h^2 = 0.0224\pm 0.0001$, scalar spectral index $n_s = 0.965\pm 0.004$, and optical depth $τ= 0.054\pm 0.007$ (in this abstract we quote $68\,\%$ confidence regions on measured parameters and $95\,\%$ on upper limits). The angular acoustic scale is measured to $0.03\,\%$ precision, with $100θ_*=1.0411\pm 0.0003$. These results are only weakly dependent on the cosmological model and remain stable, with somewhat increased errors, in many commonly considered extensions. Assuming the base-$Λ$CDM cosmology, the inferred late-Universe parameters are: Hubble constant $H_0 = (67.4\pm 0.5)$km/s/Mpc; matter density parameter $Ω_m = 0.315\pm 0.007$; and matter fluctuation amplitude $σ_8 = 0.811\pm 0.006$. We find no compelling evidence for extensions to the base-$Λ$CDM model. Combining with BAO we constrain the effective extra relativistic degrees of freedom to be $N_{\rm eff} = 2.99\pm 0.17$, and the neutrino mass is tightly constrained to $\sum m_ν< 0.12$eV. The CMB spectra continue to prefer higher lensing amplitudes than predicted in base -$Λ$CDM at over $2\,σ$, which pulls some parameters that affect the lensing amplitude away from the base-$Λ$CDM model; however, this is not supported by the lensing reconstruction or (in models that also change the background geometry) BAO data. (Abridged)

astro-ph.CO↗
arXiv2021

Overview of the Medium and High Frequency Telescopes of the LiteBIRD satellite mission

LiteBIRD is a JAXA-led Strategic Large-Class mission designed to search for the existence of the primordial gravitational waves produced during the inflationary phase of the Universe, through the measurements of their imprint onto the polarization of the cosmic microwave background (CMB). These measurements, requiring unprecedented sensitivity, will be performed over the full sky, at large angular scales, and over 15 frequency bands from 34GHz to 448GHz. The LiteBIRD instruments consist of three telescopes, namely the Low-, Medium- and High-Frequency Telescope (respectively LFT, MFT and HFT). We present in this paper an overview of the design of the Medium-Frequency Telescope (89-224GHz) and the High-Frequency Telescope (166-448GHz), the so-called MHFT, under European responsibility, which are two cryogenic refractive telescopes cooled down to 5K. They include a continuous rotating half-wave plate as the first optical element, two high-density polyethylene (HDPE) lenses and more than three thousand transition-edge sensor (TES) detectors cooled to 100mK. We provide an overview of the concept design and the remaining specific challenges that we have to face in order to achieve the scientific goals of LiteBIRD.

astro-ph.IM↗