Polarization Maps Research Articles

Characterization of extragalactic point-sources on E- and B-mode maps of the CMB polarization

Although interesting in themselves, extragalactic sources emitting in the microwave range (mainly radio-loud active galactic nuclei and dusty galaxies) are also considered a contaminant from the point of view of Cosmic Microwave Background (CMB) experiments. These sources appear as unresolved point-like objects in CMB measurements because of the limited resolution of CMB experiments. Amongst other issues, point-like sources are known to obstruct the reconstruction of the lensing potential, and can hinder the detection of the Primordial Gravitational Wave Background for low values of r. Therefore, extragalactic point-source detection and subtraction is a fundamental part of the component separation process necessary to achieve some of the science goals set for the next generation of CMB experiments. As a previous step to their removal, in this work we present a new filter based on steerable wavelets that allows the characterization of the emission of these extragalactic sources. Instead of the usual approach of working in polarization maps of the Stokes' Q and U parameters, the proposed filter operates on E- and B-mode polarization maps. In this way, it benefits from the lower intensity that, both, the CMB, and the galactic foreground emission, present in B-modes to improve its performance. To demonstrate its potential, we have applied the filter to simulations of the future PICO satellite, and we predict that, for the regions of fainter galactic foreground emission in the 30 GHz and 155 GHz bands of PICO, our filter will be able to characterize sources down to a minimum polarization intensity of, respectively, 125 pK and 14 pK. Adopting a Π=0.02 polarization degree, these values correspond to 169 mJy and 288 mJy intensities.

Direct Attenuation Correction Using Deep Learning for Cardiac SPECT: A Feasibility Study.

Dedicated cardiac SPECT scanners with cadmium-zinc-telluride cameras have shown capabilities for shortened scan times or reduced radiation doses, as well as improved image quality. Since most dedicated scanners do not have integrated CT, image quantification with attenuation correction (AC) is challenging and artifacts are routinely encountered in daily clinical practice. In this work, we demonstrated a direct AC technique using deep learning (DL) for myocardial perfusion imaging (MPI). Methods: In an institutional review board-approved retrospective study, 100 cardiac SPECT/CT datasets with 99mTc-tetrofosmin, obtained using a scanner specifically with a small field of view, were collected at the Yale New Haven Hospital. A convolutional neural network was used for generating DL-based attenuation-corrected SPECT (SPECTDL) directly from noncorrected SPECT (SPECTNC) without undergoing an additional image reconstruction step. The accuracy of SPECTDL was evaluated by voxelwise and segmentwise analyses against the reference, CT-based AC (SPECTCTAC), using the 17-segment myocardial model of the American Heart Association. Polar maps of representative (best, median, and worst) cases were visually compared to illustrate potential benefits and pitfalls of the DL approach. Results: The voxelwise correlations with SPECTCTAC were 92.2% ± 3.7% (slope, 0.87; R2 = 0.81) and 97.7% ± 1.8% (slope, 0.94; R2 = 0.91) for SPECTNC and SPECTDL, respectively. The segmental errors of SPECTNC scattered from -35% to 21% (P < 0.001), whereas the errors of SPECTDL stayed mostly within ±10% (P < 0.001). The average segmental errors (mean ± SD) were -6.11% ± 8.06% and 0.49% ± 4.35% for SPECTNC and SPECTDL, respectively. The average absolute segmental errors were 7.96% ± 6.23% and 3.31% ± 2.87% for SPECTNC and SPECTDL, respectively. Review of polar maps revealed successful reduction of attenuation artifacts; however, the performance of SPECTDL was not consistent for all subjects, likely because of different amounts of attenuation and different uptake patterns. Conclusion: We demonstrated the feasibility of direct AC using DL for SPECT MPI. Overall, our DL approach reduced attenuation artifacts substantially compared with SPECTNC, justifying further studies to establish safety and consistency for clinical applications in stand-alone SPECT systems suffering from attenuation artifacts.

Polarimetric and photometric observations of CB54, with analysis of four other dark clouds

ABSTRACTWe present the results of our BVR-band photometric and R-band polarimetric observations of ∼40 stars in the periphery of the dark cloud CB54. From different photometric data, we estimate E(B − V) and E(J − H). After involving data from other sources, we discuss the extinction variations towards CB54. We reveal two main dust layers: a foreground, E(B − V) ≈ 0.1 mag, at ∼200 pc and an extended layer, $E(B-V) \gtrsim 0.3$ mag, at ∼1.5 kpc. CB54 belongs to the latter. Based on these results, we consider the reason for the random polarization map that we have observed for CB54. We find that the foreground is characterized by low polarization ($P \lesssim 0.5$ per cent) and a magnetic field parallel to the Galactic plane. The extended layer shows high polarization (P up to 5–7 per cent). We suggest that the field in this layer is nearly perpendicular to the Galactic plane and both layers are essentially inhomogeneous. This allows us to explain the randomness of polarization vectors around CB54 generally. The data – primarily observed by us in this work for CB54, by A. K. Sen and colleagues in previous works for three dark clouds CB3, CB25 and CB39, and by other authors for a region including the B1 cloud – are analysed to explore any correlation between polarization, the near-infrared, E(J − H), and optical, E(B − V), excesses, and the distance to the background stars. If polarization and extinction are caused by the same set of dust particles, we should expect good correlations. However, we find that, for all the clouds, the correlations are not strong.

Quantitative analysis of myocardial metabolic heterogeneity is superior to visual assessment for the detection of active cardiac sarcoidosis by F-18 FDG PET-CT imaging

Abstract Funding Acknowledgements Type of funding sources: None. Background Myocardial inflammation may occur in the context of a multisystem disease such as sarcoidosis, adversely affecting prognosis. A definitive diagnosis of cardiac sarcoidosis (CS) is essential to implementing life-saving treatment but this is complicated by the invasive nature of endomyocardial biopsy (EMB) and its low accuracy. Positron emission tomography (PET) assists in diagnosis, which relies on visual interpretation of myocardial F-18 FDG uptake. The value of quantitative analysis and its application to clinical practice remain uncertain. Purpose To investigate the power of quantitative F-18 FDG PET-CT imaging analysis for detecting CS in patients with suspected disease. Methods All patients underwent F-18 FDG PET-CT after a 24-hour low-carbohydrate diet and 15-hour fasting as part of their diagnostic work-up for suspected cardiac inflammation. Cardiovascular magnetic resonance acted as gatekeeper to PET-CT in 8 of every 10 scans. Myocardial F-18 FDG uptake was assessed qualitatively and quantitatively using both manually drawn regions of interest and automatic polar maps to measure global and segmental standardised F-18 FDG uptake values (SUV). The coefficient of variation (CoV) was calculated to determine uptake heterogeneity. To confirm diagnosis, follow-up data regarding disease progression, further testing and treatment were collected. To allow for sufficient follow-up time, the first 40 consecutive patients from a prospective registry (n= 214; Sep 2017-Jun 2020) were included. Results A comprehensive clinical picture was obtained successfully in 37 patients (median [IQR], 17 [13.5] months) and a final diagnosis of CS reached in 7 (disease prevalence, 19%). EMB was performed in 2 patients only while 3 underwent PPM/ICD implantation. Significant predictors of CS were fulfilment of Japanese Ministry of Health and Welfare criteria (Wald, 6.44; p = 0.01) and left ventricular dysfunction (Wald 6.72; p = 0.01). Qualitative F-18 FDG PET-CT had a high negative (95%) but low positive (45%) predictive value for CS (sensitivity, 83%; specificity, 77%). F-18 FDG SUV CoV was the strongest imaging predictor (Wald, 6.77; p = 0.009) and was significantly higher in CS than non-CS (CoV median [quartiles], 0.26 [0.21, 0.36] and 0.12 [0.11, 0.14] respectively; p = 0.004). As per ROC curve analysis (AUC, 0.84), a CoV threshold of 0.20 was highly specific (93%) and sensitive (86%) for CS. Conclusion In a referring population with a low prevalence of cardiac sarcoidosis, F-18 FDG PET-CT imaging is sensitive for the detection of myocardial inflammation with active disease unlikely in patients with a negative scan. Quantitative evaluation of metabolic heterogeneity within the myocardium provides a strong, independent marker of active disease and should be considered alongside visual assessment.

Vectorial Holograms with Spatially Continuous Polarization Distributions.

Metasurface-based holography presents opportunities for applications that include optical displays, data storage, and optical encryption. Holograms that control polarization are sometimes referred to as vectorial holograms. Most studies on this topic have concerned devices that display different images when illuminated with different polarization states. Fewer studies have demonstrated holographic images whose polarization varies spatially, i.e., as a function of the position within the image. Here, we experimentally demonstrate a vectorial hologram that produces an image with a spatially continuous distribution of polarization states, for the first time to our knowledge. An unlimited number of polarization states can be achieved within the image. Furthermore, the holographic image and its polarization map (polarization vs position in image) are independent. The same image can be thus encoded with different polarization maps. As far as we know, our approach is conceptually new. We anticipate that it could broaden the application scope of metasurface holography.

Symmetry of the Underlying Lattice in (K,Na)NbO3-Based Relaxor Ferroelectrics with Large Electromechanical Response.

The piezoelectric constant (d33) and converse piezoelectric coefficient (d33*) of a piezoelectric material are critically important parameters for sensors and actuators. Here, we simultaneously achieve a high d33 of 595 ± 10 pC/N and a large d33* of ∼776 ± 20 pm/V in (K,Na)NbO3 (KNN)-based ceramics, which exceed those of PZT5H and PZT4 ceramics, presenting good potential for practical piezoelectric applications. Moreover, the ceramic exhibits a relaxor-like and diffuse dielectric behavior due to the occurrence of local heterogeneity. According to the experiments and atomic resolution polarization mapping by Z-contrast imaging, hierarchical architecture of nanodomains and even smaller polar nanoregions with multiphase coexistence caused by compositional modification is the structural origin of the enhanced piezoelectric properties in this work. This work would pave a practical way to future applications of lead-free KNN-based ceramics.

Optimization of Resonant PZT MEMS Mirrors by Inverse Design and Electrode Segmentation

This paper presents a systematic approach to transduction optimization of resonant piezo-based MEMS devices. The method is based on inverse design approach using direct piezoelectric effect and exploits mechanical action of desired mode to calculate the polarization map of the piezoelectric ceramics. Optimal transduction is achieved by matching the excited electric field distribution to the inversely retrieved polarization map using the electrode segmentation and topology optimization technique. The proposed method was applied to improve the design of existing state-of-the-art piezoelectric MEMS mirrors. The optimized devices feature 70% increase in the optical scan angle ( $\theta _{\mathrm {opt}}$ ) as well as 47 % reduction in power consumption compared to original design. At the same optical scan angle, the optimized devices required 2.28-fold less driving voltage amplitude. [2020-0342]

Speckle Tracking Echocardiography: Early Predictor of Diagnosis and Prognosis in Coronary Artery Disease.

Echocardiography represents a first level technique for the evaluation of coronary artery disease (CAD) which supports clinicians in the diagnostic and prognostic workup of these syndromes. However, visual estimation of wall motion abnormalities sometimes fails in detecting less clear or transient myocardial ischemia and in providing accurate differential diagnosis. Speckle tracking echocardiography (STE) is a widely available noninvasive tool that could easily and quickly provide additive information over basic echocardiography, since it is able to identify subtle myocardial damage and to localize ischemic territories in accordance to the coronary lesions, obtaining a clear visualization with a “polar map” useful for differential diagnosis and management. Therefore, it has increasingly been applied in acute and chronic coronary syndromes using rest and stress echocardiography, showing good results in terms of prediction of CAD, clinical outcome, left ventricular remodeling, presence, and quantification of new/residual ischemia. The aim of this review is to illustrate the current available evidence on STE usefulness for the assessment and follow-up of CAD, discussing the main findings on bidimensional and tridimensional strain parameters and their potential application in clinical practice.

Towards ending the partial sky E-B ambiguity in CMB observations

A crucial problem for partial sky analysis of CMB polarization is the E-B leakage problem. Such leakage arises from the presence of `ambiguous' modes that satisfy properties of both E and B modes. Solving this problem is critical for primordial polarization B mode detection in partial sky CMB polarization experiments. In this work we introduce a new method for reducing the leakage. We demonstrate that if we complement the E-mode information outside the observation patch with ancillary data from full-sky CMB observations, we can reduce and even effectively remove the E-to-B leakage. For this objective, we produce E-mode Stokes QU maps from Wiener filtered full-sky intensity and polarization CMB observations. We use these maps to fill the sky region that is not observed by the ground-based experiment of interest, and thus complement the partial sky Stokes QU maps. Since the E-mode information is now available on the full sky we see a significant reduction in the E-to-B leakage. We evaluate on simulated data sets the performance of our method for a `shallow' fsky = 8%, and a `deep' fsky = 2% northern hemisphere sky patch, with AliCPT-like properties, and a LSPE-like fsky = 30% sky patch, by combining those observations with Planck-like full sky polarization maps. We find that our method outperforms the standard and the pure-B method pseudo-Cℓ estimators for all of our simulations. Our new method gives unbiased estimates of the B-mode power spectrum through-out the entire multipole range with near-optimal pseudo-Cℓ errors for ℓ > 20. We also study the application of our method to the CMB-S4 experiment combined with LiteBIRD-like full sky data, and show that using signal-dominated full sky E-mode data we can eliminate the E-to-B leakage problem.

Growth and Atomically Resolved Polarization Mapping of Ferroelectric Bi2WO6 Thin Films

Aurivillius ferroelectric $Bi_2WO_6$ (BWO) encompasses a broad range of functionalities, including robust fatigue-free ferroelectricity, high photocatalytic activity, and ionic conductivity. Despite these promising characteristics, an in-depth study on the growth of BWO thin films and ferroelectric characterization, especially at the atomic scale, is still lacking. Here, we report pulsed laser deposition (PLD) of BWO thin films on (001) $SrTiO_3$ substrates and characterization of ferroelectricity using the scanning transmission electron microscopy (STEM) and piezoresponse force microscopy (PFM) techniques. We show that the background oxygen gas pressure used during PLD growth mainly determines the phase stability of BWO films, whereas the influence of growth temperature is comparatively minor. Atomically resolved STEM study of a fully strained BWO film revealed collective in-plane polar off-centering displacement of W atoms. We estimated the spontaneous polarization value based on polar displacement mapping to be about 54 $\pm$ 4 ${\mu}C cm^{-2}$, which is in good agreement with the bulk polarization value. Furthermore, we found that pristine film is composed of type-I and type-II domains, with mutually orthogonal polar axes. Complementary PFM measurements further elucidated that the coexisting type-I and type-II domains formed a multidomain state that consisted of 90$\deg$ domain walls (DWs) alongside multiple head-to-head and tail-to-tail 180$\deg$ DWs. Application of an electrical bias led to in-plane 180$\deg$ polarization switching and 90$\deg$ polarization rotation, highlighting a unique aspect of domain switching, which is immune to substrate-induced strain.

Few-layer tin sulfide (SnS): Controlled synthesis, thickness dependent vibrational properties, and ferroelectricity

• Consistently ultrathin SnS was synthesized on SnS 2 van der Waals substrates. • Real-time microscopy establishes underlying growth processes. • Experiment and calculations identify thickness-dependent vibrational properties. • First high-quality PFM maps of SnS ferroelectric polarization and domains. • Non-equilibrium stacking provides net polarization independent of thickness. Group IV monochalcogenides, anisotropic van der Waals crystals (and black phosphorus analogues), are attracting increasing interest due to a number of exceptional properties including anisotropic optoelectronics and multiferroicity predicted and in part realized in the ultrathin limit. Due to their enhanced chemical reactivity, both exfoliation and synthesis of monolayer and few-layer crystals pose challenges not found in other 2D/layered materials, such as the transition metal dichalcogenides. Here, we show that SnS synthesis on SnS 2 van der Waals substrates can address these challenges and consistently produces few-layer flakes, a capability that is explained via analysis of real-time microscopy of the growth process. Raman spectroscopy combined with efficient computations of the Raman-active modes across an extended thickness range enables a comprehensive understanding of the evolution of the vibrational properties of SnS with number of layers. Lateral piezoresponse force microscopy provides unprecedented insight into the stacking-dependent polarization and ferroelectric domain structures in large few-layer SnS flakes. The combined results establish a basis for further fundamental studies and applications of SnS and other group IV monochalcogenides in the few-layer regime.

Experimental Mueller matrix polarimetry with full Poincaré beams and a CCD camera

Recently, the use of full Poincaré beams for extracting the Mueller matrix of a sample has been proposed. These beams present all possible polarization states across their transverse section. By placing a CCD camera behind a simple polarization analyzer formed by a quarter wave phase plate and a linear polarizer, a polarization map of the beam cross section can be obtained. This polarization map is modified when a sample is inserted before the polarization state analyzer. Comparison of these two polarization maps allows to obtain the Mueller matrix of the sample. An overdetermined system of linear equations (thousands of equations) can be written from this comparison. Standard mathematical methods are used to find optimum solution of this overdetermined system of equations. Some experimental results will be presented to check the performance of the proposed polarimetric method.

Polar Coded Modulation Operated With Physical Network Coding

This letter proposes a polarization mapping (PM) for polar coded modulation with physical network coding (PM-PNC) over two-way relay channels (TWRC). The achievable information rates (AIRs) of the mapped bits within a XOR symbol from bit-wise XOR of two user symbols are significantly different, since the users adopt non-uniform PAM modulation to avoid mapping ambiguity. In the polar-coded PM-PNC, the original channels associated with the split information bit channel are mapped to the XOR bit stream with a larger AIR. In this way, the achieved rate of the split information channels can be maximized and is illustrated in distribution of split bit channel AIRs. Simulation results show that the proposed PM-PNC can achieve significant performance gains of more than 0.5 dB as compared to the bit-interleaved coded modulation (BICM) and multilevel coded (MLC) PNC systems over Gaussian and block fading channels.

Constraining the magnetic field properties of Bok globule B335 using SOFIA/HAWC+

Thanks to their well-defined shape and mostly isolated locations, Bok globules are suitable objects for studying the physics of low-mass star formation. To study the magnetic field of the prototypical Bok globule B335, we obtained a spatially resolved polarization map with SOFIA/HAWC+ at a wavelength of 214 μm. For the first time, these observations reveal that polarization holes in Bok globules, that is, the decrease in polarization degree towards their dense centers, also occur in the far-infrared wavelength regime. The observed polarization pattern is uniform with a mean polarization angle of 48° ± 26° and a magnetic field strength of ~142 μG. Moreover, we use complementary polarimetic data for B335 obtained at near-infrared to millimeter wavelengths to analyze and constrain the magnetic field across different scales. By applying the 3D Monte-Carlo radiative transfer code POLARIS, we developed a model for the density and magnetic field structure as well as for the dust properties of this globule. We conclude that the column density towards the center of B335 is too low to cause the observed polarization hole in B335 via dichroic absorption. Furthermore, we conclude that the effect of self-scattering has no significant impact on the observed polarization. Adopting dust-grain alignment via the radiative torque mechanism, a combination of the interstellar radiation field and the central star as radiation sources is consistent with the decrease in polarization degree at the outer regions of B335 (≈104 au from the core). However, the model fails to explain the low polarization degree within the inner 5000 au.

Local C–V mapping for ferroelectrics using scanning nonlinear dielectric microscopy

Detailed analysis of local polarization switching will promote the further development of a wide range of applications using ferroelectrics. Here, we propose a local C–V mapping technique using scanning nonlinear dielectric microscopy (SNDM) that enables visualization of dynamic ferroelectric switching behavior in real space. Using this method, C–V butterfly curves characteristic of ferroelectrics can be measured on a scanning probe microscopy platform with nanoscale resolution by virtue of the high capacitance-detection sensitivity of SNDM. This provides real-space mapping of the net switchable polarization, the switching voltage, and the local imprint with a short measurement time (e.g., 10 min or less for 256×256 pixels). Furthermore, the proposed method will be useful for study of the electric-field response of domain walls. In this paper, we present some examples of experiments with LiTaO3 single crystals and HfO2-based ferroelectric thin films and give an overview of what kind of evaluation is possible with the local C–V mapping technique.

An accurate reconstruction of CMB E-mode signal over large angular scales using prior information of CMB covariance matrix in ILC algorithm

ABSTRACT Recently, the internal-linear-combination (ILC) method was investigated extensively in the context of reconstruction of Cosmic Microwave Background (CMB) temperature anisotropy signal using observations obtained by WMAP and Planck satellite missions. In this article, we, for the first time, apply the ILC method to reconstruct the large-scale CMB E mode polarization signal, which could probe the ionization history, using simulated observations of 15 frequency CMB polarization maps of future generation Cosmic Origin Explorer (COrE) satellite mission. We find that the clean power spectra, from the usual ILC, are strongly biased due to non-zero CMB-foregrounds chance correlations. In order to address the issues of bias and errors we extend and improve the usual ILC method for CMB E-mode reconstruction by incorporating prior information of theoretical E-mode angular power spectrum while estimating the weights for linear combination of input maps (Sudevan &amp; Saha 2018b). Using the E-mode covariance matrix effectively suppresses the CMB-foreground chance correlation power leading to an accurate reconstruction of cleaned CMB E-mode map and its angular power spectrum. We compare the performance of the usual ILC and the new method over large angular scales and show that the later produces significantly statistically improved results than the former. The new E-mode CMB angular power spectrum contains neither any significant negative bias at the low multipoles nor any positive foreground bias at relatively higher mutltipoles. The error estimates of the cleaned spectrum agree very well with the cosmic variance induced error.

Atomic-Scale Domain Mediation in Nd-Doped BiFeO3 Film

A large number of applications involving ferroelectric materials are substantially influenced by domain walls (DWs). Especially, charged DWs (CDWs) show great potentials in controlling the switching mechanism and the electric and piezoelectric properties of ferroelectric materials. In the present 5% Nd-doped BiFeO3 film, besides the uniformly downward polarization in the film matrix, special domain configurations including 71° CDW and the adjacent inserting nanodomain as well as the resulting DW junction near the film surface have been quantitatively resolved by aberration-corrected scanning transmission electron microscopy. Direct polarization mapping of DWs combined with the unit-cell-wise strain map at an atomic scale demonstrate the accumulation of Nd at the CDWs. The favorable formation of the observed local domain configurations depends on the minimization of the total DW energy and the screening of bound charges accumulated at the local surface of the film.

Inpainting Galactic Foreground Intensity and Polarization Maps Using Convolutional Neural Networks

Abstract The Deep Convolutional Neural Networks (DCNNs) have been a popular tool for image generation and restoration. In this work, we applied DCNNs to the problem of inpainting non-Gaussian astrophysical signal, in the context of Galactic diffuse emissions at the millimetric and submillimetric regimes, specifically Synchrotron and Thermal Dust emissions. Both signals are affected by contamination at small angular scales due to extragalactic radio sources (the former) and dusty star-forming galaxies (the latter). We compare the performance of the standard diffusive inpainting with that of two novel methodologies relying on DCNNs, namely Generative Adversarial Networks and Deep-Prior. We show that the methods based on the DCNNs are able to reproduce the statistical properties of the ground-truth signal more consistently with a higher confidence level. The Python Inpainter for Cosmological and AStrophysical SOurces (PICASSO) is a package encoding a suite of inpainting methods described in this work and has been made publicly available at http://giuspugl.github.io/picasso/.

A novel analytical model of the magnetic field configuration in the Galactic center

Context. Cosmic-ray propagation is strongly dependent on the large-scale configuration of the Galactic magnetic field. In particular, the Galactic center region provides highly interesting cosmic-ray data from gamma-ray maps and it is clear that a large fraction of the cosmic rays detected at Earth originate in this region of the Galaxy. Yet because of confusion from line-of-sight integration, the magnetic field structure in the Galactic center is not well known and no large-scale magnetic field model exists at present. Aims. In this paper, we develop a magnetic field model, derived from observational data on the diffuse gas, nonthermal radio filaments, and molecular clouds. Methods. We derive an analytical description of the magnetic field structure in the central molecular zone by combining observational data with the theoretical modeling of the basic properties of magnetic fields. Results. We provide a first description of the large-scale magnetic field in the Galactic center region. We present first test simulations of cosmic-ray propagation and the impact of the magnetic field structure on the cosmic-ray distribution in the three dimensions. Conclusions. Our magnetic field model is able to describe the main features of polarization maps; it is particularly important to note that they are significantly better than standard global Galactic magnetic field models. It can also be used to model cosmic-ray propagation in the Galactic center region more accurately.

Formation of the Musca filament: evidence for asymmetries in the accretion flow due to a cloud–cloud collision

Context.Dense molecular filaments are ubiquituous in the interstellar medium, yet their internal physical conditions and the role of gravity, turbulence, the magnetic field, radiation, and the ambient cloud during their evolution remain debated.Aims.We study the kinematics and physical conditions in the Musca filament, the ambient cloud, and the Chamaeleon-Musca complex to constrain the physics of filament formation.Methods.We produced CO(2–1) isotopologue maps with the APEX telescope that cut through the Musca filament. We further study a NANTEN212CO(1–0) map of the full Musca cloud, H Iemission of the Chamaeleon-Musca complex, aPlanckpolarisation map, line radiative transfer models,Gaiadata, and synthetic observations from filament formation simulations.Results.The Musca cloud, with a size of ~3–6 pc, contains multiple velocity components. Radiative transfer modelling of the CO emission indicates that the Musca filament consists of a cold (~10 K), dense (nH2∼ 104cm−3) crest, which is best described with a cylindrical geometry. Connected to the crest, a separate gas component atT~ 15 K andnH2∼ 103cm−3is found, the so-called strands. The velocity-coherent filament crest has an organised transverse velocity gradient that is linked to the kinematics of the nearby ambient cloud. This velocity gradient has an angle ≥30° with respect to the local magnetic field orientation derived fromPlanck, and the magnitude of the velocity gradient is similar to the transonic linewidth of the filament crest. Studying the large scale kinematics, we find coherence of the asymmetric kinematics from the 50 pc H Icloud down to the Musca filament. We also report a strong [C18O]/[13CO] abundance drop by an order of magnitude from the filament crest to the strands over a distance &lt;0.2 pc in a weak ambient far-ultraviolet (FUV) field.Conclusions.The dense Musca filament crest is a long-lived (several crossing times), dynamic structure that can form stars in the near future because of continuous mass accretion replenishing the filament. This mass accretion on the filament appears to be triggered by a H Icloud–cloud collision, which bends the magnetic field around dense filaments. This bending of the magnetic field is then responsible for the observed asymmetric accretion scenario of the Musca filament, which is, for instance, seen as a V-shape in the position–velocity (PV) diagram.