The Planck collaboration has made public its third data release, alongisde a series of eight "legacy" papers. Vincent Guillet and I have led one of these papers, "Planck 2018 results. XII. Galactic astrophysics using polarized dust emission", which has been accepted for publication in Astronomy & Astrophysics. In this paper, we present full-sky maps of the polarization properties of Galactic dust thermal emission at 353 GHz, and provide a statistical analysis of these maps, showing that the observed inverse behaviour between the polarization fraction and the dispersion of polarization angles is consistent with models of the polarized sky that include effects from only the topology of the turbulent Galactic magnetic field. Thus, the statistical polarization properties mostly reflect the structure of the magnetic field. Potential signatures of varying grain alignment and dust properties are weak. A comparison of Planck data with starlight polarization in the visible at high latitudes yields strong constraints for models of Galactic dust in diffuse gas. The preprint for the paper is available here.

The Planck collaboration has made public its third data release, alongisde a series of eight "legacy" papers. Vincent Guillet and I have led one of these papers, "Planck 2018 results. XII. Galactic astrophysics using polarized dust emission", which has been submitted for publication in Astronomy & Astrophysics. In this paper, we present full-sky maps of the polarization properties of Galactic dust thermal emission at 353 GHz, and provide a statistical analysis of these maps, showing that the observed inverse behaviour between the polarization fraction and the dispersion of polarization angles is consistent with models of the polarized sky that include effects from only the topology of the turbulent Galactic magnetic field. Thus, the statistical polarization properties mostly reflect the structure of the magnetic field. Potential signatures of varying grain alignment and dust properties are weak. A comparison of Planck data with starlight polarization in the visible at high latitudes yields strong constraints for models of Galactic dust in diffuse gas. The preprint for the paper is available here.

The paper "On the statistics of the polarized submillimetre emission maps from thermal dust in the turbulent, magnetized, diffuse ISM" has been accepted for publication in Astronomy & Astrophysics. It presents an analysis framework which is based on simulating polarized thermal dust emission maps using model dust density (proportional to gas density) and magnetic field cubes, integrated along the line of sight, and comparing these statistically to actual data. The model fields are derived from fBm processes, which allow a precise control of their one- and two-point statistics. We explore the nine-dimensional parameter space of these models through a MCMC analysis, which yields best-fitting parameters and associated uncertainties. We apply that framework to Planck maps of the Polaris Flare molecular cloud. The preprint for the paper is available here.

The project "Molecules, Magnetic fields and Intermittency in Cosmic Turbulence - Following the energy trail" (MIST), led by E. Falgarone and of which I am part, has been selected for an "Advanced Grant" by the European Resarch Council, for the period 2017-2022. It will focus on the physics of the dissipation of magnetized astrophysical turbulence, with an emphasis on the connection with the emergence of molecular species. The 2.5 M€ of the grant will in particular fund three PhD students and three postdoc fellows.
Because when it rains, it pours, the project "Interstellar B-fields crossing inflation B-modes" (BxB), led by F. Boulanger and of which I am also part as a work package coordinator, has been selected for the 2017 call "Projet de recherche collaborative" by the Agence Nationale de la Recherche (ANR). It will focus on the cross-fertilization between Galactic and cosmological studies, with an emphasis on the distenganglement between polarized submillimetre emission from Galactic dust and primordial polarization signals in the Cosmic Microwave Background (CMB). The 500 k€ of the grant will in particular fund three postdoc fellows for two years each.

The ORION-B ("Outstanding Radio-Imaging of OrionN B") project, of which I am part, has issued a press release in conjunction with the publication of its first three papers, led by J. Pety, P. Gratier, and J. Orkisz. Using the IRAM 30 meter radio-telescope in Sierra Nevada (Spain), we have achieved the most complete observations in the radio domain of the Orion B giant molecular cloud (GMC), a huge reservoir of interstellar matter in the Orion nebula, containing about 70,000 times the mass of the Sun in gas and dust. The dataset amounts to about 160,000 images of 325 x 435 pixels, enough to make a movie of 1h50m at 24 frames per second. However, only 1% of these frames -1 minute of the movie- deliver a clear signal, including emission from molecules such as carbon monoxide, carbon monosulfide, cyanides, methanol, small hydrocarbons, and the like. Detecting these molecules is crucial, since molecular hydrogen, which makes up about 75% of interstellar gas, is invisible in cold molecular clouds. Molecular emission thus enables a radiography of clouds that are otherwise invisible to the unaided eye. The press release is available here, the three associated papers and data sets are available through the project's website.

The paper "The anatomy of the Orion B Giant Molecular Cloud: A local template for studies of nearby galaxies", by Pety et al., has been accepted for publication in Astronomy & Astrophysics. It presents wide-band 3mm (84-116 GHz) observations of almost 1 square degree in the Orion B Giant Molecular Cloud (GMC), at high spectral and spatial resolutions. We exhibit relations between molecular spectral line intensities and gas column density or far-UV radiation fields, and correlations between selected line and line ratios. Our initial findings demonstrate that the relations between line (ratio) intensities and the environment in GMCs are more complicated than often assumed. Molecular column density, excitation, and above all chemistry contribute to the observed line intensity distributions. They must be considered together when developing the next generation of extra-galactic molecular line diagnostics of mass, density, temperature and radiation field. The preprint for the paper is available here.

On 21 september, I successfully defended my HDR memorandum ("Habilitation à diriger des recherches") in front of the jury, composed of Hélène Sol (Observatoire de Paris), Rosine Lallement (Observatoire de Paris), Martin Houde (University of Western Ontario), Dimitra Rigopoulou (University of Oxford), François Boulanger (IAS), Julien Devriendt (University of Oxford), Diego Falceta-Gonçalves (Universidade de São Paulo), and Thomas Troland (University of Kentucky). The subject of the memorandum is on "The dynamical and magnetized interstellar medium", and covers what we have learnt, over the last few years, about the Galactic magnetic field and its interaction with structures of interstellar dust using the Planck polarization data. The memorandum can be found here, and slides of the defense can be found here.

The paper "Magnetic field morphology in nearby molecular clouds as revealed by starlight and submillimetre polarization", by Juan Diego Soler et al., has been accepted for publication in Astronomy & Astrophysics. It deals with the comparison of magnetic field orientations derived from submillimetre polarized thermal dust emission on the one hand, and starlight polarization in extinction on the other. We find a remrkable agreement between the two methods, underlining the common origin of these two phenomena. On the right is a figure which presents a map of the thermal emission from the Pipe Nebula measured by the Planck satellite at 353 GHz, with a "drapery" texture that represents the orientation of the magnetic field derived from the polarized emission, and segments that show the orientation of the magnetic field derived from starlight measurements. The preprint for the paper is available here.

The paper "Polarization measurement analysis III. Analysis of the polarization angle dispersion function with high precision polarization data", by D. Alina et al., has been accepted for publication in Astronomy & Astrophysics. It deals with the analysis of the statistical bias of the polarization angle dispersion function used in the analysis of Planck polarization data in the presence of noise. We show in particular that it can be positive or negative depending on the true value. We also study new estimators for this quantity, such as the dichotomic and the polynomial estimators. On the right is a plot of the statistical bias as a function of the signal-to-noise ratio, for various true values of the polarization angle dispersion function. The preprint for the paper is available here.

The paper "Magnetic field morphology in nearby molecular clouds as revealed by starlight and submillimetre polarization", by Juan Diego Soler et al., has been submitted for publication in Astronomy & Astrophysics. It deals with the comparison of magnetic field orientations derived from submillimetre polarized thermal dust emission on the one hand, and starlight polarization in extinction on the other. We find a remrkable agreement between the two methods, underlining the common origin of these two phenomena. On the right is a figure which presents a map of the thermal emission from the Pipe Nebula measured by the Planck satellite at 353 GHz, with a "drapery" texture that represents the orientation of the magnetic field derived from the polarized emission, and segments that show the orientation of the magnetic field derived from starlight measurements. The preprint for the paper is available here.

A series of nine papers from the Planck collaboration, which I co-signed, have been published in the issue number 586 of Astronomy & Astrophysics. This set includes three papers to which I contributed significantly, and which deal with the relative orientations of material filamentary structures and polarized thermal dust emission, the latter being linked to the geometry of the interstellar magnetic field. I was Planck Scientist in charge of the one entitled "Planck intermediate results. XXXV. Probing the role of the magnetic field in the formation of structure in molecular clouds", which was primarily authored by Juan Diego Soler. On the right is a figure from this paper, which presents a map of the thermal emission from the Taurus molecular cloud at 353 GHz, with a "drapery" texture that represents the orientation of the magnetic field derived from the polarization measurements. The preprint for the paper is available here.

The paper "Magnetic fields and diffuse filaments in the Polaris Flare", by M. Berthet, F. Levrier, P. Hily-Blant, E. Falgarone, P. Bastien, and T. Sousbie, has been submitted for publication in Astronomy & Astrophysics. It presents a comparison between the orientation of the matter structures in the Polaris Flare diffuse molecular cloud, probed by thermal dust emission (from the IRAS satellite) and those of the magnetic field, derived from starlight polarization measurements obtained with the "Beauty and the Beast" polarimeter on Mont-Mégantic Observatory. We find that the magnetic field is marginally preferentially aligned with matter filaments. On the right is a map showing the "skeleton" of filamentary dust structures and the starlight polarization measurements. The preprint for the paper is available here.

The paper "Galactic interstellar filaments as probed by LOFAR and Planck", by S. Zaroubi et al. (including yours truly), has been accepted for publication in Astronomy & Astrophysics. It reports a surprising correlation between magnetic field structures as probed by thermal dust emission seen by Planck and a Faraday rotation structure seen at much lower frequencies with LOFAR, even though these structures orginate from very different media, through very different processes. On the right is a map showing structures at different Faraday depths seen with LOFAR (in colors) and grey lines that represent the orientation of the magnetic field derived from the Planck measurements. The preprint for the paper is available here on the arXiv.

The paper "Planck intermediate results. XXXV. Probing the role of the magnetic field in the formation of structure in molecular clouds", by the Planck collaboration, which was primarily authored by Juan Diego Soler, and for which I was the Planck Scientist in charge, has been accepted for publication in Astronomy & Astrophysics. It compares the relative orientations of material filamentary structures and polarized thermal dust emission, which is linked to the geometry of the magnetic field, showing that the latter has a significant impact on the formation of density structures seen in dust emission. On the right is a map of the thermal emission from the Taurus molecular cloud at 353 GHz, with a "drapery" texture that represents the orientation of the magnetic field derived from the polarization measurements. The preprint for the paper is available here on the arXiv.

The Planck collaboration has released a set of 20 papers presenting the results of the full mission, in both total intensity and polarization. These represent the first part of the 2015 release of the mission data analysis and products. All preprints are available on the arXiv (see here). On the right is a map of the thermal emission from Galactic dust at 353 GHz, with a "drapery" texture that represents the orientation of the magnetic field derived from the polarization measurements.

The papers "Polarisation measurements analysis I. Impact of the full covariance matrix on the polarisation fraction and angle measurements" and "Polarisation measurements analysis II. Best estimators of polarization fraction and angle", by Montier, Plaszczynski, Levrier, Tristram, Alina, Ristorcelli and Bernard, have been accepted for publication in "Astronomy & Astrophysics". The first deals with the description of the bias in polarisation fraction and angle when correlated noise between Stokes parameters is taken into account. The second paper deals with estimators of the true polarisation given measurements. On the right is an example of the probability distribution function of polarisation fraction and angle, given true values (crossing lines) and a non-trivial covariance matrix. The white cross shows the mean over the PDF, which does not yield the true values, hence the bias.

The paper "Planck intermediate results. XXX. The angular power spectrum of polarized dust emission at intermediate and high Galactic latitudes", by the Planck Collaboration, has been submitted to "Astronomy & Astrophysics". It presents an anlysis of the polarized dust emission well out of the Galactic plane, and shows that the dust content in the BICEP2 field is not negligible. In related news, the paper "Planck intermediate results. XX. Comparison of polarized thermal emission from Galactic dust with simulations of MHD turbulence", which I led, has been accepted for publication in "Astronomy & Astrophysics". See here for the link to the paper on arXiv.

The paper "First detection of [NII] 205 μm absorption in interstellar gas : Herschel-HIFI observations towards W31C, W49N, W51 and G34.3+0.1", by Persson, Gerin, Mookerjea, Black, Olberg, Goicoechea, Hassel, Falgarone, Levrier, Menten and Pety, has been published in "Astronomy & Astrophysics". It presents absorption spectra from ionized nitrogen towards bright star-forming regions in the Galaxy, observed with the heterodyne instrument HIFI onboard the Herschel Space Observatory. See here for a link to the paper.

A series of four papers presenting the first view of the polarized submillimeter thermal emission from dust in our Galaxy as observed by Planck has been submitted for publication in "Astronomy & Astrophysics". I have led the second of these papers, dealing with the comparison of Planck results in nearby molecular clouds with simulated maps. See here for the ESA press release, from which the "magnetic fingerprint" on the left is taken, and here for links to the papers on arXiv.

The paper "First detection of [NII] 205 μm absorption in interstellar gas : Herschel-HIFI observations towards W31C, W49N, W51 and G34.3+0.1", by Persson, Gerin, Mookerjea, Black, Olberg, Goicoechea, Hassel, Falgarone, Levrier, Menten and Pety, has been submitted for publication in "Astronomy & Astrophysics". It presents absorption spectra from ionized nitrogen towards bright star-forming regions in the Galaxy, observed with the heterodyne instrument HIFI onboard the Herschel Space Observatory.

The paper "A novel estimator of the polarization amplitude from normally distributed Stokes parameters", by Plaszczynski, Montier, Levrier and Tristram, has been accepted for publication in "Monthly Notices of the Royal Astronomical Society". It presents a new estimator of polarization fraction, called modified asymptotic (MAS), that minimizes the bias due to the non-linearity of polarization fractions with respect to the Stokes parameters. This paper is part of a set of three dealing with estimators of the true polarisation given noisy measurements. On the right is the transformation curve from measurement to MAS (in red) compared to other estimators. See here for the ArXiv preprint.

The paper "A novel estimator of the polarization amplitude from normally distributed Stokes parameters", by Plaszczynski, Montier, Levrier and Tristram, has been submitted for publication in "Monthly Notices of the Royal Astronomical Society". It presents a new estimator of polarization fraction, called modified asymptotic (MAS), that minimizes the bias due to the non-linearity of polarization fractions with respect to the Stokes parameters. This paper is part of a set of three dealing with estimators of the true polarisation given noisy measurements. On the right is the transformation curve from measurement to MAS (in red) compared to other estimators. See here for the ArXiv preprint.

The paper "Polarisation measurements analysis I. Impact of the full covariance matrix on the polarisation fraction and angle measurements", by Montier, Plaszczynski, Levrier, Tristram, Alina, Ristorcelli and Bernard, has been submitted for publication in "Astronomy & Astrophysics". It deals with the description of the bias in polarisation fraction and angle when correlated noise between Stokes parameters is taken into account. It lays the ground for a forthcoming second paper dealing with estimators of the true polarisation given measurements. On the right is an example of the probability distribution function of polarisation fraction and angle, given true values (crossing lines) and a non-trivial covariance matrix. The white cross shows the mean over the PDF, which does not yield the true values, hence the bias.

The paper "Synthetic observations of first hydrostatic cores in collapsing low-mass dense cores. II. Simulated ALMA dust emission maps", by Commerçon, Levrier, Maury, Henning and Launhardt, has been accepted for publication in "Astronomy & Astrophysics". It deals with the ability of the forthcoming ALMA interferometer to establish firm diagnostics on the physical processes at work in the early phases of gravitational collapse leading to star formation. On the right is a realistically-simulated ALMA observation of a fragmented prestellar core. See here for a link to the paper.

The paper "Synthetic observations of first hydrostatic cores in collapsing low-mass dense cores. II. Simulated ALMA dust emission maps", by Commerçon, Levrier, Maury, Henning and Launhardt, has been submitted to "Astronomy & Astrophysics". It deals with the ability of the forthcoming ALMA interferometer to establish firm diagnostics on the physical processes at work in the early phases of gravitational collapse leading to star formation. On the right is a realistically-simulated ALMA observation of a fragmented prestellar core. For a copy of the submitted version of the manuscript, please contact Benoît Commerçon.

The paper "UV-driven chemistry in simulations of the interstellar medium I: Post-processed chemistry with the Meudon PDR code", written with F. Le Petit, P. Hennebelle, P. Lesaffre, M. Gerin and E. Falgarone, has been accepted for publication in "Astronomy & Astrophysics". It deals with the combined effects of density fluctuations along the line of sight and ambient UV radiation on the chemical structure of interstellar clouds, while previous models assumed homogeneous media. The submitted version of the manuscript is available here.

The paper "Hydride spectroscopy of the diffuse interstellar medium: new clues on the fraction of molecular gas and cosmic ray ionization rate in relation to H₃⁺", by Gerin, Levrier, Falgarone et al., has been accepted for publication in Philosophical Transactions A. It presents an analysis of two sight-lines of the Herschel PRISMAS project, towards the star forming regions W49N and W51. By combining the information extracted from the detected spectral lines, it gives an analysis of the physical properties of the diffuse interstellar gas including the electronic abundance, the fraction of gas in molecular form and constraints on the cosmic ray ionization rate and the gas density. Contact Maryvonne Gerin for a copy.

The paper "UV-driven chemistry in simulations of the interstellar medium I: Post-processed chemistry with the Meudon PDR code", written with F. Le Petit, P. Hennebelle, P. Lesaffre, M. Gerin and E. Falgarone, has been submitted to "Astronomy & Astrophysics". It deals with the combined effects of density fluctuations along the line of sight and ambient UV radiation on the chemical structure of interstellar clouds, while previous models assumed homogeneous media. The submitted version of the manuscript is available here.

Using the parallel implementation of the S3-Tools on the 640-core SAL cluster of the Oxford Supercomputing Center, Ian Heywood (Oxford Astrophysics) built a 2048-channel cube showing the HI emission over a square degree from over 1.5 million galaxies between redshifts 2.15 and 4.47 in the S3-SAX simulation, with 0.9 arcsecond resolution. Shown here is a movie made out of that 257GB FITS cube, at 24 fps. Each spot represents a single simulated galaxy, and one can see the clustering of these objects due to gravitational potential wells in the dark matter distribution. Looking more closely, one can see the variation of the HI emission from a single galaxy across several frames, corresponding to the rotation of the disc.
Watch it in HD (720p) and full-screen for maximum awesomeness...

The STARFORMAT database now allows extraction of simulation data products in a FITS format. Users can simply specify "FITS" when requesting a slice or cube extraction (full data or clumps) from RAMSES simulation results (colliding flows, decaying turbulence, barotropic dense core collapse) and will receive a link to a .tar.gz file containing the FITS file and a plain ascii version.

The S3-Tools have underwent a major phase of debugging, optimization and parallelization during my visit to Oxford in January-March 2011. Consequently, the software is now available again for download with a revised user's guide, extensive README file and an automated installation script. Check out the S3 section of the site for all these goodies. Note that parallel implementations are currently reserved to the Oxford group, as I am in the process of writing the documentation for that part.

Up-to-date configurations for ALMA in the format suitable for the GILDAS simulator are now available for download here

A new version of the S3Map is now available, with a number of bug fixes and a significant speed-up of the data processing by skipping out-of-bounds galaxies. To get your copy of the revised S3Tools, it's here.

The S3Process GUI, part of the S3-Tools, is now available to post-process query results from the S3-SEX database. It allows the application of space density and luminosity decline functions as a function of redshift. To use it, you need the new version of the Tools, available here.

Alternate HI emission templates for S3-SAX, made by Rense Boomsma (Kapteyn Institute) are now available in the S3-Tools. Templates and the latest version of the software are available here.

The Epoch of Reionization signal simulations by Mario Santos (IST) are now implemented in the S3-Tools. Go here to download the new version of the Tools and necessary templates.

The paper "Mapping the SKA Simulated Skies with the S3-Tools", written for the proceedings of the final SKADS conference in Limelette (4-6 November 2009), is now available here.

The paper "Simulated [CII] observations for SPICA/SAFARI", written for the proceedings of the SPICA workshop in Oxford (6-8 July 2009), is now available here.

The S-Cubed SAX paper by Obreschkow, Klöckner, Heywood, Levrier & Rawlings has been accepted for publication in the Astrophysical Journal. It can be found here.

Neil is here. He was born on 23.08.2008 in Paris. Weighing in at 3.17 kg for 48 cm at birth, he’s undoubtedly the cutest baby in the world...