Eric Hivon | UPMC Sorbonne Universités (original) (raw)

Papers by Eric Hivon

Research paper thumbnail of Noise Estimation in CMB Time-Streams and Fast Iterative Map-Making

ESO ASTROPHYSICS SYMPOSIA, 2001

We describe here an iterative method for jointly estimating the noise power spectrum from a CMB e... more We describe here an iterative method for jointly estimating the noise power spectrum from a CMB experiment’s time-ordered data, together with the maximum-likelihood map. We test the robustness of this method on simulated Boomerang datasets with realistic noise.

Research paper thumbnail of Planck early results. XXII. The submillimetre properties of a sample of Galactic cold clumps

Astronomy & Astrophysics, 2011

We perform a detailed investigation of sources from the Cold Cores Catalogue of Planck Objects (C... more We perform a detailed investigation of sources from the Cold Cores Catalogue of Planck Objects (C3PO). Our goal is to probe the reliability of the detections, validate the separation between warm and cold dust emission components, provide the first glimpse at the nature, internal morphology and physical characterictics of the Planck-detected sources. We focus on a sub-sample of ten sources from the C3PO list, selected to sample different environments, from high latitude cirrus to nearby (150 pc) and remote (2 kpc) molecular complexes. We present Planck surface brightness maps and derive the dust temperature, emissivity spectral index, and column densities of the fields. With the help of higher resolution Herschel and AKARI continuum observations and molecular line data, we investigate the morphology of the sources and the properties of the substructures at scales below the Planck beam size. The cold clumps detected by Planck are found to be located on large-scale filamentary (or cometary) structures that extend up to 20 pc in the remote sources. The thickness of these filaments ranges between 0.3 and 3 pc, for column densities N H 2 ∼ 0.1 to 1.6 × 10 22 cm −2 , and with linear mass density covering a broad range, between 15 and 400 M ⊙ pc −1 . The dust temperatures are low (between 10 and 15 K) and the Planck cold clumps correspond to local minima of the line-of-sight averaged dust temperature in these fields. These low temperatures are confirmed when AKARI and Herschel data are added to the spectral energy distributions. Herschel data reveal a wealth of substructure within the Planck cold clumps. In all cases (except two sources harbouring young stellar objects), the substructures are found to be colder, with temperatures as low as 7 K. Molecular line observations provide gas column densities which are consistent with those inferred from the dust. The linewidths are all supra-thermal, providing large virial linear mass densities in the range 10 to 300 M ⊙ pc −1 , comparable within factors of a few, to the gas linear mass densities. The analysis of this small set of cold clumps already probes a broad variety of structures in the C3PO sample, probably associated with different evolutionary stages, from cold and starless clumps, to young protostellar objects still embedded in their cold surrounding cloud. Because of the all-sky coverage and its sensitivity, Planck is able to detect and locate the coldest spots in massive elongated structures that may be the long-searched for progenitors of stellar clusters. also their large-scale environment. The characteristics of star formation, described by the stellar mass distribution, the formation efficiency, the evolutionary timescales, and by the modes of formation (clustered or isolated, spontaneous or triggered) are linked to the properties of the cold cores and those of their Galactic surroundings. Theory predicts that the initial mass func-2 The Planck collaboration: Planck Early Results: The submillimetre properties of a sample of Galactic cold clumps

Research paper thumbnail of Planck early results. VI. The High Frequency Instrument data processing

Astronomy & Astrophysics, 2011

We describe the processing of the 336 billion raw data samples from the High Frequency Instrument... more We describe the processing of the 336 billion raw data samples from the High Frequency Instrument (hereafter HFI) which we performed to produce six temperature maps from the first 295 days of Planck-HFI survey data. These maps provide an accurate rendition of the sky emission at 100, 143, 217, 353, 545 and 857 GHz with an angular resolution ranging from 9.9 to 4.4 . The white noise level is around 1.5 µK degree or less in the 3 main CMB channels (100-217 GHz). The photometric accuracy is better than 2 % at frequencies lower or equal to 353 GHz, and around 7 % at the two highest frequencies. The maps created by the HFI Data Processing Centre reach our goals in terms of sensitivity, resolution, and photometric accuracy. They are already sufficiently accurate and well-characterised to allow scientific analyses which are presented in an accompanying series of early papers. At this stage, HFI data appears to be of high quality and we expect that with further refinements of the data processing we should be able to achieve, or exceed, the science goals of the project.

Research paper thumbnail of A Measurement of the CMB 〈EE〉 Spectrum from the 2003 Flight of BOOMERANG

The Astrophysical Journal, 2006

We report measurements of the CMB polarization power spectra from the 2003 January Antarctic flig... more We report measurements of the CMB polarization power spectra from the 2003 January Antarctic flight of BOOMERANG. The primary results come from 6 days of observation of a patch covering 0.22% of the sky centered near R:A: ¼ 82N5, decl: ¼ À45 . The observations were made using four pairs of polarization-sensitive bolometers operating in bands centered at 145 GHz. Using two independent analysis pipelines, we measure a nonzero hEEi signal in the range 201 < l < 1000 with a significance of 4.8 , a 2 upper limit of 8.6 K 2 for any hBBi contribution, and a 2 upper limit of 7.0 K 2 for the hEBi spectrum. Estimates of foreground intensity fluctuations and the nondetection of hBBi and hEBi signals rule out any significant contribution from Galactic foregrounds. The results are consistent with a ÃCDM cosmology seeded by adiabatic perturbations. We note that this is the first detection of CMB polarization with bolometric detectors.

Research paper thumbnail of Analysis Issues for Large CMB Data Sets

Multi-frequency, high resolution, full sky measurements of the anisotropy in both temperature and... more Multi-frequency, high resolution, full sky measurements of the anisotropy in both temperature and polarisation of the cosmic microwave background radiation are the goals of the satellite missions MAP (NASA) and Planck (ESA). The ultimate data products of these missions - multiple microwave sky maps, each of which will have to comprise more than 10^6 pixels in order to render the

Research paper thumbnail of Planck intermediate results. XXV. The Andromeda galaxy as seen by Planck

Astronomy & Astrophysics, 2015

The Andromeda Galaxy (M31) is one of a few galaxies that has sufficient angular size on the sky t... more The Andromeda Galaxy (M31) is one of a few galaxies that has sufficient angular size on the sky to be resolved by the Planck satellite. Planck has detected M31 in all of its frequency bands, and has mapped out the dust emission with the High Frequency Instrument, clearly resolving multiple spiral arms and sub-features. We examine the morphology of this long-wavelength dust emission as seen by Planck, including a study of its outermost spiral arms, and investigate the dust heating mechanism across M31. We find that dust dominating the longer wavelength emission ( 0.3 mm) is heated by the diffuse stellar population (as traced by 3.6 µm emission), with the dust dominating the shorter wavelength emission heated by a mix of the old stellar population and star-forming regions (as traced by 24 µm emission). We also fit spectral energy distributions (SEDs) for individual 5 pixels and quantify the dust properties across the galaxy, taking into account these different heating mechanisms, finding that there is a linear decrease in temperature with galactocentric distance for dust heated by the old stellar population, as would be expected, with temperatures ranging from around 22 K in the nucleus to 14 K outside of the 10 kpc ring. Finally, we measure the integrated spectrum of the whole galaxy, which we find to be well-fitted with a global dust temperature of (18.9 ± 0.9) K with a spectral index of 1.61 ± 0.11 (assuming a single modified blackbody), and a significant amount of free-free emission at intermediate frequencies, which when converted into a star formation rate agrees well with the star formation estimate from Hα emission of 0.4 M yr −1 . We see no evidence for spinning dust emission, with a 3σ upper limit of 1.26 Jy in the 20-60 GHz band.

Research paper thumbnail of Planck intermediate results. XX. Comparison of polarized thermal emission from Galactic dust with simulations of MHD turbulence

Astronomy & Astrophysics, 2015

Polarized emission observed by Planck HFI at 353 GHz towards a sample of nearby fields is present... more Polarized emission observed by Planck HFI at 353 GHz towards a sample of nearby fields is presented, focusing on the statistics of polarization fractions p and angles ψ. The polarization fractions and column densities in these nearby fields are representative of the range of values obtained over the whole sky. We find that: (i) the largest polarization fractions are reached in the most diffuse fields; (ii) the maximum polarization fraction p max decreases with column density N H in the more opaque fields with N H > 10 21 cm −2 ; and (iii) the polarization fraction along a given line of sight is correlated with the local spatial coherence of the polarization angle. These observations are compared to polarized emission maps computed in simulations of anisotropic magnetohydrodynamical (MHD) turbulence in which we assume a uniform intrinsic polarization fraction of the dust grains. We find that an estimate of this parameter may be recovered from the maximum polarization fraction p max in diffuse regions where the magnetic field is ordered on large scales and perpendicular to the line of sight. This emphasizes the impact of anisotropies of the magnetic field on the emerging polarization signal. The decrease of the polarization fraction with column density in nearby molecular clouds is well reproduced in the simulations, indicating that it is essentially due to the turbulent structure of the magnetic field: an accumulation of variously polarized structures along the line of sight leads to such an anti-correlation. In the simulations, polarization fractions are also found to anti-correlate with the angle dispersion function S. However, the dispersion of the polarization angle for a given polarization fraction is found to be larger in the simulations than in the observations, suggesting a shortcoming in the physical content of these numerical models. In summary, we find that the turbulent structure of the magnetic field is able to reproduce the main statistical properties of the dust polarization as observed in a variety of nearby clouds, dense cores excluded, and that the large-scale field orientation with respect to the line of sight plays a major role in the quantitative analysis of these statistical properties.

Research paper thumbnail of Planck intermediate results. XXI. Comparison of polarized thermal emission from Galactic dust at 353 GHz with interstellar polarization in the visible

Astronomy & Astrophysics, 2015

The Planck survey provides unprecedented full-sky coverage of the submillimetre polarized emissio... more The Planck survey provides unprecedented full-sky coverage of the submillimetre polarized emission from Galactic dust. In addition to the information on the direction of the Galactic magnetic field, this also brings new constraints on the properties of dust. The dust grains that emit the radiation seen by Planck in the submillimetre also extinguish and polarize starlight in the optical. Comparison of the polarization of the emission and of the interstellar polarization on selected lines of sight probed by stars provides unique new diagnostics of the emission and light scattering properties of dust, and therefore ultimately of the important model parameters, composition, size, shape, and alignment. Using ancillary catalogues of interstellar polarization and extinction of starlight, we obtain the degree of polarization, p V , and the optical depth in the V band to the star, τ V . We extract the submillimetre polarized intensity, P S , and total intensity, I S , measured toward these stars in the Planck 353 GHz channel. We compare the polarization direction (position angle) measured in the optical with that measured at 353 GHz, and compare the column density measure E(B − V) with that inferred from the Planck product map of the submillimetre dust optical depth. For those lines of sight with little CO integrated intensity, as well as having polarization directions close to orthogonal and comparable values of the estimated column density, we correlate the projected polarization efficiencies in emission, Q S /I S and U S /I S , with those in extinction, q V /τ V and u V /τ V , to measure the polarization ratio R S/V = (P S /I S )/(p V /τ V ). We find a polarization ratio R S/V = 4.3 with statistical and systematic uncertainties 0.2 and 0.4, respectively. We focus directly on the polarization properties of the aligned grain population alone via an alternative ratio, the relative efficiency R P/p = P S /p V = 5.6 MJy sr −1 , with statistical and systematic uncertainties 0.2 and 0.4 MJy sr −1 , respectively. Our estimate of R S/V is reasonably compatible with predictions based on a range of current dust models that have been developed for the diffuse interstellar medium, not yet very discriminating among them. However, the observed R P/p is a more discriminating diagnostic for the polarizing grain population and is not compatible with predictions, the observations being higher by a factor of about 2.5. These new diagnostics from Planck, including the spectral dependence in the submillimetre, will be important for constraining and understanding the full complexity of the grain models, and for further interpretation of the Planck thermal dust polarization and refining the separation of this contamination of the cosmic microwave background.

Research paper thumbnail of Planck intermediate results. XIX. An overview of the polarized thermal emission from Galactic dust

Astronomy & Astrophysics, 2015

This paper presents the large-scale polarized sky as seen by Planck HFI at 353 GHz, which is the ... more This paper presents the large-scale polarized sky as seen by Planck HFI at 353 GHz, which is the most sensitive Planck channel for dust polarization. We construct and analyse large-scale maps of dust polarization fraction and polarization direction, while taking account of noise bias and possible systematic effects. We find that the maximum observed dust polarization fraction is high (p max > 18 %), in particular in some of the intermediate dust column density (A V < 1 mag) regions. There is a systematic decrease in the dust polarization fraction with increasing dust column density, and we interpret the features of this correlation in light of both radiative grain alignment predictions and fluctuations in the magnetic field orientation. We also characterize the spatial structure of the polarization angle using the angle dispersion function and find that, in nearby fields at intermediate latitudes, the polarization angle is ordered over extended areas that are separated by filamentary structures, which appear as interfaces where the magnetic field sky projection rotates abruptly without apparent variations in the dust column density. The polarization fraction is found to be anti-correlated with the dispersion of the polarization angle, implying that the variations are likely due to fluctuations in the 3D magnetic field orientation along the line of sight sampling the diffuse interstellar medium. We also compare the dust emission with the polarized synchrotron emission measured with the Planck LFI, with low-frequency radio data, and with Faraday rotation measurements of extragalactic sources. The two polarized components are globally similar in structure along the plane and notably in the Fan and North Polar Spur regions. A detailed comparison of these three tracers shows, however, that dust and cosmic rays generally sample different parts of the line of sight and confirms that much of the variation observed in the Planck data is due to the 3D structure of the magnetic field.

Research paper thumbnail of Planck intermediate results. XXVIII. Interstellar gas and dust in the Chamaeleon clouds as seen by Fermi LAT and Planck

Astronomy & Astrophysics, 2015

Research paper thumbnail of The HEALPix Primer

HEALPix is a Hierarchical, Equal Area, and iso-Latitude Pixelisation of the sphere designed to su... more HEALPix is a Hierarchical, Equal Area, and iso-Latitude Pixelisation of the sphere designed to support efficiently - local operations on the pixel set, - a hierarchical tree structure for multi-resolution applications, and - the global Fast Spherical Harmonic transform. The HEALPix concept and the mathematical software based on it introduced in this primer meet the challenges which future high resolution and large volume CMB data sets including the MAP and Planck mission products will present.

Research paper thumbnail of The Pseudo-$C_l$ method: Cosmic microwave background anisotropy power spectrum statistics for high precision cosmology

As the era of high precision cosmology approaches, the empirically determined power spectrum of t... more As the era of high precision cosmology approaches, the empirically determined power spectrum of the microwave background anisotropy ClC_lCl will provide a crucial test for cosmological theories. We present an exact semi-analytic framework for the study of the ampling statistics of the ClC_lCl resulting from observations with partial sky coverage and anisotropic noise distributions. This includes space-borne, air-borne and ground-based experiments. We apply this theory to demonstrate its power for constructing fast but unbiased approximate methods for the joint estimation of cosmological parameters. Further applications, such as a test for possible non-Gaussianity of the underlying theory and a ``poor man's power spectrum estimator'' are suggested. An appendix derives recursion relations for the efficient computation of the couplings between spherical harmonics on the cut sky.

Research paper thumbnail of HEALPix --- a Framework for High Resolution, Fast Analysis on the Sphere

HEALPix Hierarchical Equal Area iso-Latitude Pixelization, provides a framework for efficient dis... more HEALPix Hierarchical Equal Area iso-Latitude Pixelization, provides a framework for efficient discretization and fast analysis/synthesis of functions defined on the sphere. A suite of Fortran90 and IDL codes which provide useful applications is distributed to the community freely from the web site. HEALPix will be used to format the forthcoming data from the NASA MAP and ESA Planck missions to accurately map the anisotropy of the cosmic microwave background radiation at high resolution and at many frequency bands. Because of its inherent hierarchical tree structure (it is built as a self-similarly refinable quadrilateral mesh on the sphere) HEALPix can naturally support efficient data bases for objects distributed on the sphere.

Research paper thumbnail of HEALPix: Hierarchical Equal Area isoLatitude Pixelization of a sphere

HEALPix is an acronym for Hierarchical Equal Area isoLatitude Pixelization of a sphere. As sugges... more HEALPix is an acronym for Hierarchical Equal Area isoLatitude Pixelization of a sphere. As suggested in the name, this pixelization produces a subdivision of a spherical surface in which each pixel covers the same surface area as every other pixel. Another property of the HEALPix grid is that the pixel centers occur on a discrete number of rings of constant latitude, the number of constant-latitude rings is dependent on the resolution of the HEALPix grid.

Research paper thumbnail of PolSpice: Spatially Inhomogeneous Correlation Estimator for Temperature and Polarisation

PolSpice (aka Spice) is a tool to statistically analyze Cosmic Microwave Background (CMB) data, a... more PolSpice (aka Spice) is a tool to statistically analyze Cosmic Microwave Background (CMB) data, as well as any other diffuse data pixelized on the sphere. This Fortran90 program measures the 2 point auto (or cross-) correlation functions w(?) and the angular auto- (or cross-) power spectra C(l) from one or (two) sky map(s) of Stokes parameters (intensity I and linear polarisation Q and U). It is based on the fast Spherical Harmonic Transforms allowed by isolatitude pixelisations such as Healpix [for Npix pixels over the whole sky, and a C(l) computed up to l=lmax, PolSpice complexity scales like Npix1/2 lmax2 instead of Npix lmax2]. It corrects for the effects of the masks and can deal with inhomogeneous weights given to the pixels of the map. In the case of polarised data, the mixing of the E and B modes due to the cut sky and pixel weights can be corrected for to provide an unbiased estimate of the "magnetic" (B) component of the polarisation power spectrum. Most of the ...

Research paper thumbnail of 3D Healpix-based Skymaps Visualization using Java

HEALPix {http://healpix.jpl.nasa.gov/} is useful for data analysis and visualization. Gaia is the... more HEALPix {http://healpix.jpl.nasa.gov/} is useful for data analysis and visualization. Gaia is the ESA space astrometry cornerstone mission the main objective of wich is to astrometrically and spectro-photometrically map 10^{9} celestial objects (mostly in our galaxy) with unprecedented accuracy. The data will be organized and stored in a central database at ESAC (Spain). The data treatment needs data analysis and visualization tools to accomplish a successful mission. The 3D Healpix-based skymaps are used as part of the interactive diagnostic tools as well as within the core processing. We present the HEALPix Java library and give some examples of its use within Gaia and Planck processing.

Research paper thumbnail of Planck intermediate results. XXXIV. The magnetic field structure in the Rosette Nebula

Astronomy & Astrophysics, 2015

Planck has mapped the polarized dust emission over the whole sky, making it possible to trace the... more Planck has mapped the polarized dust emission over the whole sky, making it possible to trace the Galactic magnetic field structure that pervades the interstellar medium (ISM). We combine polarization data from Planck with rotation measure (RM) observations towards a massive star-forming region, the Rosette Nebula in the Monoceros molecular cloud, to study its magnetic field structure and the impact of an expanding H ii region on the morphology of the field. We derive an analytical solution for the magnetic field, assumed to evolve from an initially uniform configuration following the expansion of ionized gas and the formation of a shell of swept-up ISM. From the RM data we estimate a mean value of the line-ofsight component of the magnetic field of about +3 µG in the Rosette nebula, for a uniform electron density of about 11 cm −3 . The dust shell that surrounds the Rosette H ii region is clearly observed in the Planck intensity map at 353 GHz, with a polarization signal significantly different from that of the local background when considered as a whole. The Planck observations constrain the plane-of-the-sky orientation of the magnetic field in the Rosette's parent molecular cloud to be mostly aligned with the large-scale field along the Galactic plane. The Planck data are compared with the analytical model, which predicts the mean polarization properties of a spherical and uniform dust shell for a given orientation of the field. This comparison leads to an upper limit of about 45 • on the angle between the line of sight and the magnetic field in the Rosette complex, for an assumed intrinsic dust polarization fraction of 4 %. This field direction can reproduce the RM values detected in the ionized region if the magnetic field strength in the Monoceros molecular cloud is in the range 9-12.5 µG. The present analytical model is able to reproduce the RM distribution across the ionized nebula, as well as the mean dust polarization properties of the swept-up shell, and can be directly applied to other similar objects.

Research paper thumbnail of Planck intermediate results. XXII. Frequency dependence of thermal emission from Galactic dust in intensity and polarization

Astronomy & Astrophysics, 2015

Planck has mapped the intensity and polarization of the sky at microwave frequencies with unprece... more Planck has mapped the intensity and polarization of the sky at microwave frequencies with unprecedented sensitivity. We use these data to characterize the frequency dependence of dust emission. We make use of the Planck 353 GHz I, Q, and U Stokes maps as dust templates, and cross-correlate them with the Planck and WMAP data at 12 frequencies from 23 to 353 GHz, over circular patches with 10 • radius. The cross-correlation analysis is performed for both intensity and polarization data in a consistent manner. The results are corrected for the chance correlation between the templates and the anisotropies of the cosmic microwave background. We use a mask that focuses our analysis on the diffuse interstellar medium at intermediate Galactic latitudes. We determine the spectral indices of dust emission in intensity and polarization between 100 and 353 GHz, for each sky-patch. Both indices are found to be remarkably constant over the sky. The mean values, 1.63 ± 0.03 for polarization and 1.52 ± 0.02 for intensity, for a mean dust temperature of 18.7 K, are close, but significantly different. We determine the mean spectral energy distribution (SED) of the microwave emission, correlated with the 353 GHz dust templates, by averaging the results of the correlation over all sky-patches. We find that the mean SED increases for decreasing frequencies at ν < 60 GHz, for both intensity and polarization. The rise of the polarization SED towards low frequencies may be accounted for by a synchrotron component correlated with dust, with no need for any polarization of the anomalous microwave emission. We use a spectral model to separate the synchrotron and dust polarization and to characterize the spectral dependence of the dust polarization fraction. The polarization fraction (p) of the dust emission decreases by (34 ± 10) % from 353 to 70 GHz. We discuss this result within the context of existing dust models. The decrease of p could indicate differences in polarization efficiency among components of interstellar dust (e.g., carbon versus silicate grains), or, alternatively, it could be a signature of magnetic dipole emission from ferromagnetic inclusions within interstellar grains. Our observational results provide inputs to quantify and optimize the separation between Galactic and cosmological polarization.

Research paper thumbnail of Planck intermediate results. XXIII. Galactic plane emission components derived from Planck with ancillary data

Astronomy & Astrophysics, 2015

Planck data when combined with ancillary data provide a unique opportunity to separate the diffus... more Planck data when combined with ancillary data provide a unique opportunity to separate the diffuse emission components of the inner Galaxy. The purpose of the paper is to elucidate the morphology of the various emission components in the strong star-formation region lying inside the solar radius and to clarify the relationship between the various components. The region of the Galactic plane covered is l = 300 • → 0 • → 60 • where star-formation is highest and the emission is strong enough to make meaningful component separation. The latitude widths in this longitude range lie between 1 • and 2 • , which correspond to FWHM z-widths of 100-200 pc at a typical distance of 6 kpc. The four emission components studied here are synchrotron, free-free, anomalous microwave emission (AME), and thermal (vibrational) dust emission. These components are identified by constructing spectral energy distributions (SEDs) at positions along the Galactic plane using the wide frequency coverage of Planck (28.4-857 GHz) in combination with low-frequency radio data at 0.408-2.3 GHz plus WMAP data at 23-94 GHz, along with far-infrared (FIR) data from COBE-DIRBE and IRAS. The free-free component is determined from radio recombination line (RRL) data. AME is found to be comparable in brightness to the free-free emission on the Galactic plane in the frequency range 20-40 GHz with a width in latitude similar to that of the thermal dust; it comprises 45 ± 1 % of the total 28.4 GHz emission in the longitude range l = 300 • →0 • →60 • . The free-free component is the narrowest, reflecting the fact that it is produced by current star-formation as traced by the narrow distribution of OB stars. It is the dominant emission on the plane between 60 and 100 GHz. RRLs from this ionized gas are used to assess its distance, leading to a free-free z-width of FWHM ≈ 100 pc. The narrow synchrotron component has a low-frequency brightness spectral index β synch ≈ −2.7 that is similar to the broad synchrotron component indicating that they are both populated by the cosmic ray electrons of the same spectral index. The width of this narrow synchrotron component is significantly larger than that of the other three components, suggesting that it is generated in an assembly of older supernova remnants that have expanded to sizes of order 150 pc in 3 × 10 5 yr; pulsars of a similar age have a similar spread in latitude. The thermal dust is identified in the SEDs with average parameters of T dust = 20.4 ± 0.4 K, β FIR = 1.94 ± 0.03 (> 353 GHz), and β mm = 1.67 ± 0.02 (< 353 GHz). The latitude distributions of gamma-rays, CO, and the emission in high-frequency Planck bands have similar widths, showing that they are all indicators of the total gaseous matter on the plane in the inner Galaxy.

Research paper thumbnail of Measuring CMB polarization with Boomerang

New Astronomy Reviews, 2003

Boomerang is a balloon-borne telescope designed for long duration (LDB) flights around Antarctica... more Boomerang is a balloon-borne telescope designed for long duration (LDB) flights around Antarctica. The second LDB Flight of Boomerang took place in January 2003. The primary goal of this flight was to measure the polarization of the CMB. The receiver uses polarization sensitive bolometers at 145 GHz. Polarizing grids provide polarization sensitivity at 245 and 345 GHz. We describe the Boomerang telescope noting changes made for 2003 LDB flight, and discuss some of the issues involved in the measurement of polarization with bolometers. Lastly, we report on the 2003 flight and provide an estimate of the expected results.

Research paper thumbnail of Noise Estimation in CMB Time-Streams and Fast Iterative Map-Making

ESO ASTROPHYSICS SYMPOSIA, 2001

We describe here an iterative method for jointly estimating the noise power spectrum from a CMB e... more We describe here an iterative method for jointly estimating the noise power spectrum from a CMB experiment’s time-ordered data, together with the maximum-likelihood map. We test the robustness of this method on simulated Boomerang datasets with realistic noise.

Research paper thumbnail of Planck early results. XXII. The submillimetre properties of a sample of Galactic cold clumps

Astronomy & Astrophysics, 2011

We perform a detailed investigation of sources from the Cold Cores Catalogue of Planck Objects (C... more We perform a detailed investigation of sources from the Cold Cores Catalogue of Planck Objects (C3PO). Our goal is to probe the reliability of the detections, validate the separation between warm and cold dust emission components, provide the first glimpse at the nature, internal morphology and physical characterictics of the Planck-detected sources. We focus on a sub-sample of ten sources from the C3PO list, selected to sample different environments, from high latitude cirrus to nearby (150 pc) and remote (2 kpc) molecular complexes. We present Planck surface brightness maps and derive the dust temperature, emissivity spectral index, and column densities of the fields. With the help of higher resolution Herschel and AKARI continuum observations and molecular line data, we investigate the morphology of the sources and the properties of the substructures at scales below the Planck beam size. The cold clumps detected by Planck are found to be located on large-scale filamentary (or cometary) structures that extend up to 20 pc in the remote sources. The thickness of these filaments ranges between 0.3 and 3 pc, for column densities N H 2 ∼ 0.1 to 1.6 × 10 22 cm −2 , and with linear mass density covering a broad range, between 15 and 400 M ⊙ pc −1 . The dust temperatures are low (between 10 and 15 K) and the Planck cold clumps correspond to local minima of the line-of-sight averaged dust temperature in these fields. These low temperatures are confirmed when AKARI and Herschel data are added to the spectral energy distributions. Herschel data reveal a wealth of substructure within the Planck cold clumps. In all cases (except two sources harbouring young stellar objects), the substructures are found to be colder, with temperatures as low as 7 K. Molecular line observations provide gas column densities which are consistent with those inferred from the dust. The linewidths are all supra-thermal, providing large virial linear mass densities in the range 10 to 300 M ⊙ pc −1 , comparable within factors of a few, to the gas linear mass densities. The analysis of this small set of cold clumps already probes a broad variety of structures in the C3PO sample, probably associated with different evolutionary stages, from cold and starless clumps, to young protostellar objects still embedded in their cold surrounding cloud. Because of the all-sky coverage and its sensitivity, Planck is able to detect and locate the coldest spots in massive elongated structures that may be the long-searched for progenitors of stellar clusters. also their large-scale environment. The characteristics of star formation, described by the stellar mass distribution, the formation efficiency, the evolutionary timescales, and by the modes of formation (clustered or isolated, spontaneous or triggered) are linked to the properties of the cold cores and those of their Galactic surroundings. Theory predicts that the initial mass func-2 The Planck collaboration: Planck Early Results: The submillimetre properties of a sample of Galactic cold clumps

Research paper thumbnail of Planck early results. VI. The High Frequency Instrument data processing

Astronomy & Astrophysics, 2011

We describe the processing of the 336 billion raw data samples from the High Frequency Instrument... more We describe the processing of the 336 billion raw data samples from the High Frequency Instrument (hereafter HFI) which we performed to produce six temperature maps from the first 295 days of Planck-HFI survey data. These maps provide an accurate rendition of the sky emission at 100, 143, 217, 353, 545 and 857 GHz with an angular resolution ranging from 9.9 to 4.4 . The white noise level is around 1.5 µK degree or less in the 3 main CMB channels (100-217 GHz). The photometric accuracy is better than 2 % at frequencies lower or equal to 353 GHz, and around 7 % at the two highest frequencies. The maps created by the HFI Data Processing Centre reach our goals in terms of sensitivity, resolution, and photometric accuracy. They are already sufficiently accurate and well-characterised to allow scientific analyses which are presented in an accompanying series of early papers. At this stage, HFI data appears to be of high quality and we expect that with further refinements of the data processing we should be able to achieve, or exceed, the science goals of the project.

Research paper thumbnail of A Measurement of the CMB 〈EE〉 Spectrum from the 2003 Flight of BOOMERANG

The Astrophysical Journal, 2006

We report measurements of the CMB polarization power spectra from the 2003 January Antarctic flig... more We report measurements of the CMB polarization power spectra from the 2003 January Antarctic flight of BOOMERANG. The primary results come from 6 days of observation of a patch covering 0.22% of the sky centered near R:A: ¼ 82N5, decl: ¼ À45 . The observations were made using four pairs of polarization-sensitive bolometers operating in bands centered at 145 GHz. Using two independent analysis pipelines, we measure a nonzero hEEi signal in the range 201 < l < 1000 with a significance of 4.8 , a 2 upper limit of 8.6 K 2 for any hBBi contribution, and a 2 upper limit of 7.0 K 2 for the hEBi spectrum. Estimates of foreground intensity fluctuations and the nondetection of hBBi and hEBi signals rule out any significant contribution from Galactic foregrounds. The results are consistent with a ÃCDM cosmology seeded by adiabatic perturbations. We note that this is the first detection of CMB polarization with bolometric detectors.

Research paper thumbnail of Analysis Issues for Large CMB Data Sets

Multi-frequency, high resolution, full sky measurements of the anisotropy in both temperature and... more Multi-frequency, high resolution, full sky measurements of the anisotropy in both temperature and polarisation of the cosmic microwave background radiation are the goals of the satellite missions MAP (NASA) and Planck (ESA). The ultimate data products of these missions - multiple microwave sky maps, each of which will have to comprise more than 10^6 pixels in order to render the

Research paper thumbnail of Planck intermediate results. XXV. The Andromeda galaxy as seen by Planck

Astronomy & Astrophysics, 2015

The Andromeda Galaxy (M31) is one of a few galaxies that has sufficient angular size on the sky t... more The Andromeda Galaxy (M31) is one of a few galaxies that has sufficient angular size on the sky to be resolved by the Planck satellite. Planck has detected M31 in all of its frequency bands, and has mapped out the dust emission with the High Frequency Instrument, clearly resolving multiple spiral arms and sub-features. We examine the morphology of this long-wavelength dust emission as seen by Planck, including a study of its outermost spiral arms, and investigate the dust heating mechanism across M31. We find that dust dominating the longer wavelength emission ( 0.3 mm) is heated by the diffuse stellar population (as traced by 3.6 µm emission), with the dust dominating the shorter wavelength emission heated by a mix of the old stellar population and star-forming regions (as traced by 24 µm emission). We also fit spectral energy distributions (SEDs) for individual 5 pixels and quantify the dust properties across the galaxy, taking into account these different heating mechanisms, finding that there is a linear decrease in temperature with galactocentric distance for dust heated by the old stellar population, as would be expected, with temperatures ranging from around 22 K in the nucleus to 14 K outside of the 10 kpc ring. Finally, we measure the integrated spectrum of the whole galaxy, which we find to be well-fitted with a global dust temperature of (18.9 ± 0.9) K with a spectral index of 1.61 ± 0.11 (assuming a single modified blackbody), and a significant amount of free-free emission at intermediate frequencies, which when converted into a star formation rate agrees well with the star formation estimate from Hα emission of 0.4 M yr −1 . We see no evidence for spinning dust emission, with a 3σ upper limit of 1.26 Jy in the 20-60 GHz band.

Research paper thumbnail of Planck intermediate results. XX. Comparison of polarized thermal emission from Galactic dust with simulations of MHD turbulence

Astronomy & Astrophysics, 2015

Polarized emission observed by Planck HFI at 353 GHz towards a sample of nearby fields is present... more Polarized emission observed by Planck HFI at 353 GHz towards a sample of nearby fields is presented, focusing on the statistics of polarization fractions p and angles ψ. The polarization fractions and column densities in these nearby fields are representative of the range of values obtained over the whole sky. We find that: (i) the largest polarization fractions are reached in the most diffuse fields; (ii) the maximum polarization fraction p max decreases with column density N H in the more opaque fields with N H > 10 21 cm −2 ; and (iii) the polarization fraction along a given line of sight is correlated with the local spatial coherence of the polarization angle. These observations are compared to polarized emission maps computed in simulations of anisotropic magnetohydrodynamical (MHD) turbulence in which we assume a uniform intrinsic polarization fraction of the dust grains. We find that an estimate of this parameter may be recovered from the maximum polarization fraction p max in diffuse regions where the magnetic field is ordered on large scales and perpendicular to the line of sight. This emphasizes the impact of anisotropies of the magnetic field on the emerging polarization signal. The decrease of the polarization fraction with column density in nearby molecular clouds is well reproduced in the simulations, indicating that it is essentially due to the turbulent structure of the magnetic field: an accumulation of variously polarized structures along the line of sight leads to such an anti-correlation. In the simulations, polarization fractions are also found to anti-correlate with the angle dispersion function S. However, the dispersion of the polarization angle for a given polarization fraction is found to be larger in the simulations than in the observations, suggesting a shortcoming in the physical content of these numerical models. In summary, we find that the turbulent structure of the magnetic field is able to reproduce the main statistical properties of the dust polarization as observed in a variety of nearby clouds, dense cores excluded, and that the large-scale field orientation with respect to the line of sight plays a major role in the quantitative analysis of these statistical properties.

Research paper thumbnail of Planck intermediate results. XXI. Comparison of polarized thermal emission from Galactic dust at 353 GHz with interstellar polarization in the visible

Astronomy & Astrophysics, 2015

The Planck survey provides unprecedented full-sky coverage of the submillimetre polarized emissio... more The Planck survey provides unprecedented full-sky coverage of the submillimetre polarized emission from Galactic dust. In addition to the information on the direction of the Galactic magnetic field, this also brings new constraints on the properties of dust. The dust grains that emit the radiation seen by Planck in the submillimetre also extinguish and polarize starlight in the optical. Comparison of the polarization of the emission and of the interstellar polarization on selected lines of sight probed by stars provides unique new diagnostics of the emission and light scattering properties of dust, and therefore ultimately of the important model parameters, composition, size, shape, and alignment. Using ancillary catalogues of interstellar polarization and extinction of starlight, we obtain the degree of polarization, p V , and the optical depth in the V band to the star, τ V . We extract the submillimetre polarized intensity, P S , and total intensity, I S , measured toward these stars in the Planck 353 GHz channel. We compare the polarization direction (position angle) measured in the optical with that measured at 353 GHz, and compare the column density measure E(B − V) with that inferred from the Planck product map of the submillimetre dust optical depth. For those lines of sight with little CO integrated intensity, as well as having polarization directions close to orthogonal and comparable values of the estimated column density, we correlate the projected polarization efficiencies in emission, Q S /I S and U S /I S , with those in extinction, q V /τ V and u V /τ V , to measure the polarization ratio R S/V = (P S /I S )/(p V /τ V ). We find a polarization ratio R S/V = 4.3 with statistical and systematic uncertainties 0.2 and 0.4, respectively. We focus directly on the polarization properties of the aligned grain population alone via an alternative ratio, the relative efficiency R P/p = P S /p V = 5.6 MJy sr −1 , with statistical and systematic uncertainties 0.2 and 0.4 MJy sr −1 , respectively. Our estimate of R S/V is reasonably compatible with predictions based on a range of current dust models that have been developed for the diffuse interstellar medium, not yet very discriminating among them. However, the observed R P/p is a more discriminating diagnostic for the polarizing grain population and is not compatible with predictions, the observations being higher by a factor of about 2.5. These new diagnostics from Planck, including the spectral dependence in the submillimetre, will be important for constraining and understanding the full complexity of the grain models, and for further interpretation of the Planck thermal dust polarization and refining the separation of this contamination of the cosmic microwave background.

Research paper thumbnail of Planck intermediate results. XIX. An overview of the polarized thermal emission from Galactic dust

Astronomy & Astrophysics, 2015

This paper presents the large-scale polarized sky as seen by Planck HFI at 353 GHz, which is the ... more This paper presents the large-scale polarized sky as seen by Planck HFI at 353 GHz, which is the most sensitive Planck channel for dust polarization. We construct and analyse large-scale maps of dust polarization fraction and polarization direction, while taking account of noise bias and possible systematic effects. We find that the maximum observed dust polarization fraction is high (p max > 18 %), in particular in some of the intermediate dust column density (A V < 1 mag) regions. There is a systematic decrease in the dust polarization fraction with increasing dust column density, and we interpret the features of this correlation in light of both radiative grain alignment predictions and fluctuations in the magnetic field orientation. We also characterize the spatial structure of the polarization angle using the angle dispersion function and find that, in nearby fields at intermediate latitudes, the polarization angle is ordered over extended areas that are separated by filamentary structures, which appear as interfaces where the magnetic field sky projection rotates abruptly without apparent variations in the dust column density. The polarization fraction is found to be anti-correlated with the dispersion of the polarization angle, implying that the variations are likely due to fluctuations in the 3D magnetic field orientation along the line of sight sampling the diffuse interstellar medium. We also compare the dust emission with the polarized synchrotron emission measured with the Planck LFI, with low-frequency radio data, and with Faraday rotation measurements of extragalactic sources. The two polarized components are globally similar in structure along the plane and notably in the Fan and North Polar Spur regions. A detailed comparison of these three tracers shows, however, that dust and cosmic rays generally sample different parts of the line of sight and confirms that much of the variation observed in the Planck data is due to the 3D structure of the magnetic field.

Research paper thumbnail of Planck intermediate results. XXVIII. Interstellar gas and dust in the Chamaeleon clouds as seen by Fermi LAT and Planck

Astronomy & Astrophysics, 2015

Research paper thumbnail of The HEALPix Primer

HEALPix is a Hierarchical, Equal Area, and iso-Latitude Pixelisation of the sphere designed to su... more HEALPix is a Hierarchical, Equal Area, and iso-Latitude Pixelisation of the sphere designed to support efficiently - local operations on the pixel set, - a hierarchical tree structure for multi-resolution applications, and - the global Fast Spherical Harmonic transform. The HEALPix concept and the mathematical software based on it introduced in this primer meet the challenges which future high resolution and large volume CMB data sets including the MAP and Planck mission products will present.

Research paper thumbnail of The Pseudo-$C_l$ method: Cosmic microwave background anisotropy power spectrum statistics for high precision cosmology

As the era of high precision cosmology approaches, the empirically determined power spectrum of t... more As the era of high precision cosmology approaches, the empirically determined power spectrum of the microwave background anisotropy ClC_lCl will provide a crucial test for cosmological theories. We present an exact semi-analytic framework for the study of the ampling statistics of the ClC_lCl resulting from observations with partial sky coverage and anisotropic noise distributions. This includes space-borne, air-borne and ground-based experiments. We apply this theory to demonstrate its power for constructing fast but unbiased approximate methods for the joint estimation of cosmological parameters. Further applications, such as a test for possible non-Gaussianity of the underlying theory and a ``poor man's power spectrum estimator'' are suggested. An appendix derives recursion relations for the efficient computation of the couplings between spherical harmonics on the cut sky.

Research paper thumbnail of HEALPix --- a Framework for High Resolution, Fast Analysis on the Sphere

HEALPix Hierarchical Equal Area iso-Latitude Pixelization, provides a framework for efficient dis... more HEALPix Hierarchical Equal Area iso-Latitude Pixelization, provides a framework for efficient discretization and fast analysis/synthesis of functions defined on the sphere. A suite of Fortran90 and IDL codes which provide useful applications is distributed to the community freely from the web site. HEALPix will be used to format the forthcoming data from the NASA MAP and ESA Planck missions to accurately map the anisotropy of the cosmic microwave background radiation at high resolution and at many frequency bands. Because of its inherent hierarchical tree structure (it is built as a self-similarly refinable quadrilateral mesh on the sphere) HEALPix can naturally support efficient data bases for objects distributed on the sphere.

Research paper thumbnail of HEALPix: Hierarchical Equal Area isoLatitude Pixelization of a sphere

HEALPix is an acronym for Hierarchical Equal Area isoLatitude Pixelization of a sphere. As sugges... more HEALPix is an acronym for Hierarchical Equal Area isoLatitude Pixelization of a sphere. As suggested in the name, this pixelization produces a subdivision of a spherical surface in which each pixel covers the same surface area as every other pixel. Another property of the HEALPix grid is that the pixel centers occur on a discrete number of rings of constant latitude, the number of constant-latitude rings is dependent on the resolution of the HEALPix grid.

Research paper thumbnail of PolSpice: Spatially Inhomogeneous Correlation Estimator for Temperature and Polarisation

PolSpice (aka Spice) is a tool to statistically analyze Cosmic Microwave Background (CMB) data, a... more PolSpice (aka Spice) is a tool to statistically analyze Cosmic Microwave Background (CMB) data, as well as any other diffuse data pixelized on the sphere. This Fortran90 program measures the 2 point auto (or cross-) correlation functions w(?) and the angular auto- (or cross-) power spectra C(l) from one or (two) sky map(s) of Stokes parameters (intensity I and linear polarisation Q and U). It is based on the fast Spherical Harmonic Transforms allowed by isolatitude pixelisations such as Healpix [for Npix pixels over the whole sky, and a C(l) computed up to l=lmax, PolSpice complexity scales like Npix1/2 lmax2 instead of Npix lmax2]. It corrects for the effects of the masks and can deal with inhomogeneous weights given to the pixels of the map. In the case of polarised data, the mixing of the E and B modes due to the cut sky and pixel weights can be corrected for to provide an unbiased estimate of the "magnetic" (B) component of the polarisation power spectrum. Most of the ...

Research paper thumbnail of 3D Healpix-based Skymaps Visualization using Java

HEALPix {http://healpix.jpl.nasa.gov/} is useful for data analysis and visualization. Gaia is the... more HEALPix {http://healpix.jpl.nasa.gov/} is useful for data analysis and visualization. Gaia is the ESA space astrometry cornerstone mission the main objective of wich is to astrometrically and spectro-photometrically map 10^{9} celestial objects (mostly in our galaxy) with unprecedented accuracy. The data will be organized and stored in a central database at ESAC (Spain). The data treatment needs data analysis and visualization tools to accomplish a successful mission. The 3D Healpix-based skymaps are used as part of the interactive diagnostic tools as well as within the core processing. We present the HEALPix Java library and give some examples of its use within Gaia and Planck processing.

Research paper thumbnail of Planck intermediate results. XXXIV. The magnetic field structure in the Rosette Nebula

Astronomy & Astrophysics, 2015

Planck has mapped the polarized dust emission over the whole sky, making it possible to trace the... more Planck has mapped the polarized dust emission over the whole sky, making it possible to trace the Galactic magnetic field structure that pervades the interstellar medium (ISM). We combine polarization data from Planck with rotation measure (RM) observations towards a massive star-forming region, the Rosette Nebula in the Monoceros molecular cloud, to study its magnetic field structure and the impact of an expanding H ii region on the morphology of the field. We derive an analytical solution for the magnetic field, assumed to evolve from an initially uniform configuration following the expansion of ionized gas and the formation of a shell of swept-up ISM. From the RM data we estimate a mean value of the line-ofsight component of the magnetic field of about +3 µG in the Rosette nebula, for a uniform electron density of about 11 cm −3 . The dust shell that surrounds the Rosette H ii region is clearly observed in the Planck intensity map at 353 GHz, with a polarization signal significantly different from that of the local background when considered as a whole. The Planck observations constrain the plane-of-the-sky orientation of the magnetic field in the Rosette's parent molecular cloud to be mostly aligned with the large-scale field along the Galactic plane. The Planck data are compared with the analytical model, which predicts the mean polarization properties of a spherical and uniform dust shell for a given orientation of the field. This comparison leads to an upper limit of about 45 • on the angle between the line of sight and the magnetic field in the Rosette complex, for an assumed intrinsic dust polarization fraction of 4 %. This field direction can reproduce the RM values detected in the ionized region if the magnetic field strength in the Monoceros molecular cloud is in the range 9-12.5 µG. The present analytical model is able to reproduce the RM distribution across the ionized nebula, as well as the mean dust polarization properties of the swept-up shell, and can be directly applied to other similar objects.

Research paper thumbnail of Planck intermediate results. XXII. Frequency dependence of thermal emission from Galactic dust in intensity and polarization

Astronomy & Astrophysics, 2015

Planck has mapped the intensity and polarization of the sky at microwave frequencies with unprece... more Planck has mapped the intensity and polarization of the sky at microwave frequencies with unprecedented sensitivity. We use these data to characterize the frequency dependence of dust emission. We make use of the Planck 353 GHz I, Q, and U Stokes maps as dust templates, and cross-correlate them with the Planck and WMAP data at 12 frequencies from 23 to 353 GHz, over circular patches with 10 • radius. The cross-correlation analysis is performed for both intensity and polarization data in a consistent manner. The results are corrected for the chance correlation between the templates and the anisotropies of the cosmic microwave background. We use a mask that focuses our analysis on the diffuse interstellar medium at intermediate Galactic latitudes. We determine the spectral indices of dust emission in intensity and polarization between 100 and 353 GHz, for each sky-patch. Both indices are found to be remarkably constant over the sky. The mean values, 1.63 ± 0.03 for polarization and 1.52 ± 0.02 for intensity, for a mean dust temperature of 18.7 K, are close, but significantly different. We determine the mean spectral energy distribution (SED) of the microwave emission, correlated with the 353 GHz dust templates, by averaging the results of the correlation over all sky-patches. We find that the mean SED increases for decreasing frequencies at ν < 60 GHz, for both intensity and polarization. The rise of the polarization SED towards low frequencies may be accounted for by a synchrotron component correlated with dust, with no need for any polarization of the anomalous microwave emission. We use a spectral model to separate the synchrotron and dust polarization and to characterize the spectral dependence of the dust polarization fraction. The polarization fraction (p) of the dust emission decreases by (34 ± 10) % from 353 to 70 GHz. We discuss this result within the context of existing dust models. The decrease of p could indicate differences in polarization efficiency among components of interstellar dust (e.g., carbon versus silicate grains), or, alternatively, it could be a signature of magnetic dipole emission from ferromagnetic inclusions within interstellar grains. Our observational results provide inputs to quantify and optimize the separation between Galactic and cosmological polarization.

Research paper thumbnail of Planck intermediate results. XXIII. Galactic plane emission components derived from Planck with ancillary data

Astronomy & Astrophysics, 2015

Planck data when combined with ancillary data provide a unique opportunity to separate the diffus... more Planck data when combined with ancillary data provide a unique opportunity to separate the diffuse emission components of the inner Galaxy. The purpose of the paper is to elucidate the morphology of the various emission components in the strong star-formation region lying inside the solar radius and to clarify the relationship between the various components. The region of the Galactic plane covered is l = 300 • → 0 • → 60 • where star-formation is highest and the emission is strong enough to make meaningful component separation. The latitude widths in this longitude range lie between 1 • and 2 • , which correspond to FWHM z-widths of 100-200 pc at a typical distance of 6 kpc. The four emission components studied here are synchrotron, free-free, anomalous microwave emission (AME), and thermal (vibrational) dust emission. These components are identified by constructing spectral energy distributions (SEDs) at positions along the Galactic plane using the wide frequency coverage of Planck (28.4-857 GHz) in combination with low-frequency radio data at 0.408-2.3 GHz plus WMAP data at 23-94 GHz, along with far-infrared (FIR) data from COBE-DIRBE and IRAS. The free-free component is determined from radio recombination line (RRL) data. AME is found to be comparable in brightness to the free-free emission on the Galactic plane in the frequency range 20-40 GHz with a width in latitude similar to that of the thermal dust; it comprises 45 ± 1 % of the total 28.4 GHz emission in the longitude range l = 300 • →0 • →60 • . The free-free component is the narrowest, reflecting the fact that it is produced by current star-formation as traced by the narrow distribution of OB stars. It is the dominant emission on the plane between 60 and 100 GHz. RRLs from this ionized gas are used to assess its distance, leading to a free-free z-width of FWHM ≈ 100 pc. The narrow synchrotron component has a low-frequency brightness spectral index β synch ≈ −2.7 that is similar to the broad synchrotron component indicating that they are both populated by the cosmic ray electrons of the same spectral index. The width of this narrow synchrotron component is significantly larger than that of the other three components, suggesting that it is generated in an assembly of older supernova remnants that have expanded to sizes of order 150 pc in 3 × 10 5 yr; pulsars of a similar age have a similar spread in latitude. The thermal dust is identified in the SEDs with average parameters of T dust = 20.4 ± 0.4 K, β FIR = 1.94 ± 0.03 (> 353 GHz), and β mm = 1.67 ± 0.02 (< 353 GHz). The latitude distributions of gamma-rays, CO, and the emission in high-frequency Planck bands have similar widths, showing that they are all indicators of the total gaseous matter on the plane in the inner Galaxy.

Research paper thumbnail of Measuring CMB polarization with Boomerang

New Astronomy Reviews, 2003

Boomerang is a balloon-borne telescope designed for long duration (LDB) flights around Antarctica... more Boomerang is a balloon-borne telescope designed for long duration (LDB) flights around Antarctica. The second LDB Flight of Boomerang took place in January 2003. The primary goal of this flight was to measure the polarization of the CMB. The receiver uses polarization sensitive bolometers at 145 GHz. Polarizing grids provide polarization sensitivity at 245 and 345 GHz. We describe the Boomerang telescope noting changes made for 2003 LDB flight, and discuss some of the issues involved in the measurement of polarization with bolometers. Lastly, we report on the 2003 flight and provide an estimate of the expected results.