Publications
221 results found
Adam R, Ade PAR, Aghanim N, et al., 2016, Planck 2015 results VII. High Frequency Instrument data processing: Time-ordered information and beams, Astronomy & Astrophysics, Vol: 594, Pages: A7 - 1-A7 - 30, ISSN: 0004-6361
The Planck High Frequency Instrument (HFI) has observed the full sky at six frequencies (100, 143, 217, 353, 545, and 857 GHz) in intensity and at four frequencies in linear polarization (100, 143, 217, and 353 GHz). In order to obtain sky maps, the time-ordered information (TOI) containing the detector and pointing samples must be processed and the angular response must be assessed. The full mission TOI is included in the Planck 2015 release. This paper describes the HFI TOI and beam processing for the 2015 release. HFI calibration and map making are described in a companion paper. The main pipeline has been modified since the last release (2013 nominal mission in intensity only), by including a correction for the nonlinearity of the warm readout and by improving the model of the bolometer time response. The beam processing is an essential tool that derives the angular response used in all the Planck science papers and we report an improvement in the effective beam window function uncertainty of more than a factor of 10 relative to the2013 release. Noise correlations introduced by pipeline filtering function are assessed using dedicated simulations. Angular cross-power spectra using data sets that are decorrelated in time are immune to the main systematic effects.
Ade PAR, Aghanim N, Ashdown M, et al., 2016, Planck 2015 results VI. LFI mapmaking, ASTRONOMY & ASTROPHYSICS, Vol: 594, ISSN: 1432-0746
Ade PAR, Aghanim N, Ashdown M, et al., 2016, Planck 2015 results II. Low Frequency Instrument data processings, ASTRONOMY & ASTROPHYSICS, Vol: 594, ISSN: 1432-0746
Ade PAR, Aghanim N, Ashdown M, et al., 2016, Planck 2015 results IV. Low Frequency Instrument beams and window functions, ASTRONOMY & ASTROPHYSICS, Vol: 594, ISSN: 1432-0746
Leistedt B, Mortlock DJ, Peiris HV, 2016, Hierarchical Bayesian inference of galaxy redshift distributions from photometric surveys, Monthly Notices of the Royal Astronomical Society, Vol: 460, Pages: 4258-4267, ISSN: 1365-2966
Accurately characterizing the redshift distributions of galaxies is essential for analysing deep photometric surveys and testing cosmological models. We present a technique to simultaneously infer redshift distributions and individual redshifts from photometric galaxy catalogues. Our model constructs a piecewise constant representation (effectively a histogram) of the distribution of galaxy types and redshifts, the parameters of which are efficiently inferred from noisy photometric flux measurements. This approach can be seen as a generalization of template-fitting photometric redshift methods and relies on a library of spectral templates to relate the photometric fluxes of individual galaxies to their redshifts. We illustrate this technique on simulated galaxy survey data, and demonstrate that it delivers correct posterior distributions on the underlying type and redshift distributions, as well as on the individual types and redshifts of galaxies. We show that even with uninformative priors, large photometric errors and parameter degeneracies, the redshift and type distributions can be recovered robustly thanks to the hierarchical nature of the model, which is not possible with common photometric redshift estimation techniques. As a result, redshift uncertainties can be fully propagated in cosmological analyses for the first time, fulfilling an essential requirement for the current and future generations of surveys.
Khanin A, Mortlock DJ, 2016, A Bayesian analysis of the 69 highest energy cosmic rays detected by the Pierre Auger Observatory, Monthly Notices of the Royal Astronomical Society, Vol: 460, Pages: 2765-2778, ISSN: 0035-8711
The origins of ultrahigh energy cosmic rays (UHECRs) remain an open question. Several attempts have been made to cross-correlate the arrival directions of the UHECRs with catalogues of potential sources, but no definite conclusion has been reached. We report a Bayesiananalysis of the 69 events, from the Pierre Auger Observatory (PAO), that aims to determine the fraction of the UHECRs that originate from known AGNs in the Veron-Cety & Verson (VCV) catalogue, as well as AGNs detected with the Swift Burst Alert Telescope (Swift-BAT),galaxies from the 2MASS Redshift Survey (2MRS), and an additional volume-limited sample of 17 nearby AGNs. The study makes use of a multilevel Bayesian model of UHECR injection, propagation and detection. We find that for reasonable ranges of prior parameters theBayes factors disfavour a purely isotropic model. For fiducial values of the model parameters, we report 68 per cent credible intervals for the fraction of source originating UHECRs of 0.09+0.05 −0.04, 0.25+0.09 −0.08, 0.24+0.12 −0.10, and 0.08+0.04 −0.03 for the VCV, Swift-BAT and 2MRS catalogues, and the sample of 17 AGNs, respectively.
Ade PAR, Aghanim N, Arnaud M, et al., 2016, Planck Intermediate Results. XXXVI. Optical identification andredshifts of Planck SZ sources with telescopes at the CanaryIslands Observatories, Astronomy & Astrophysics, Vol: 586, Pages: A139-A139, ISSN: 1432-0746
We present the results of approximately three years of observations of Planck Sunyaev-Zeldovich (SZ) sources with telescopes at the CanaryIslands observatories as part of the general optical follow-up programme undertaken by the Planck collaboration. In total, 78 SZ sources arediscussed. Deep-imaging observations were obtained for most of these sources; spectroscopic observations in either in long-slit or multi-objectmodes were obtained for many. We effectively used 37.5 clear nights. We found optical counterparts for 73 of the 78 candidates. This sampleincludes 53 spectroscopic redshift determinations, 20 of them obtained with a multi-object spectroscopic mode. The sample contains new redshiftsfor 27 Planck clusters that were not included in the first Planck SZ source catalogue (PSZ1).
Ade PAR, Aghanim N, Alves MIR, et al., 2016, Planck intermediate results. XXIX. All-sky dust modelling with Planck, IRAS, and WISE observations, Astronomy & Astrophysics, Vol: 586, ISSN: 0004-6361
We present all-sky modelling of the high resolution Planck, IRAS, and WISE infrared (IR) observations using the physical dust model presented by Draine & Li in 2007 (DL, ApJ, 657, 810). We study the performance and results of this model, and discuss implications for future dust modelling. The present work extends the DL dust modelling carried out on nearby galaxies using Herschel and Spitzer data to Galactic dust emission. We employ the DL dust model to generate maps of the dust mass surface density ΣMd, the dust optical extinction AV, and the starlight intensity heating the bulk of the dust, parametrized by Umin. The DL model reproduces the observed spectral energy distribution (SED) satisfactorily over most of the sky, with small deviations in the inner Galactic disk and in low ecliptic latitude areas, presumably due to zodiacal light contamination. In the Andromeda galaxy (M31), the present dust mass estimates agree remarkably well (within 10%) with DL estimates based on independent Spitzer and Herschel data. We compare the DL optical extinction AV for the diffuse interstellar medium (ISM) with optical estimates for approximately 2 × 105 quasi-stellar objects (QSOs) observed inthe Sloan Digital Sky Survey (SDSS). The DL AV estimates are larger than those determined towards QSOs by a factor of about 2, which depends on Umin. The DL fitting parameter Umin, effectively determined by the wavelength where the SED peaks, appears to trace variations in the far-IR opacity of the dust grains per unit AV, and not only in the starlight intensity. These results show that some of the physical assumptions of the DL model will need to be revised. To circumvent the model deficiency, we propose an empirical renormalization of the DL AV estimate, dependent of Umin, which compensates for the systematic differences found with QSO observations. This renormalization, made to match the AV estimates towards QSOs, also brings into agreement the DL AV estimates with those
Arnaud M, Ashdown M, Atrio-Barandela F, et al., 2016, Planck intermediate results XXXI. Microwave survey of Galactic supernova remnants, Astronomy & Astrophysics, Vol: 586, ISSN: 1432-0746
The all-sky Planck survey in 9 frequency bands was used to search for emission from all 274 known Galactic supernova remnants. Of these, 16 were detected in at least two Planck frequencies. The radio-through-microwave spectral energy distributions were compiled to determine the mechanism for microwave emission. In only one case, IC 443, is there high-frequency emission clearly from dust associated with the supernova remnant. In all cases, the low-frequency emission is from synchrotron radiation. As predicted for a population of relativistic particles with energy distribution that extends continuously to high energies, a single power law is evident for many sources, including the Crab and PKS 1209-51/52. A decrease in flux density relative to the extrapolation of radio emission is evident in several sources. Their spectral energy distributions can be approximated as broken power laws, Sν ∝ ν−α, with the spectral index, α, increasing by 0.5–1 above a break frequency in the range 10–60 GHz. The break could be due to synchrotron losses.
Adam R, Ade PAR, Aghanim N, et al., 2016, Planck intermediate results XXX. The angular power spectrum of polarized dust emission at intermediate and high Galactic latitudes, Astronomy & Astrophysics, Vol: 586, ISSN: 1432-0746
The polarized thermal emission from diffuse Galactic dust is the main foreground present in measurements of the polarization of the cosmic microwave background (CMB) at frequencies above 100 GHz. In this paper we exploit the uniqueness of the Planck HFI polarization data from 100 to 353 GHz to measure the polarized dust angular power spectra CℓEE and CℓBB over the multipole range 40 <ℓ< 600 well away from the Galactic plane. These measurements will bring new insights into interstellar dust physics and allow a precise determination of the level of contamination for CMB polarization experiments. Despite the non-Gaussian and anisotropic nature of Galactic dust, we show that general statistical properties of the emission can be characterized accurately over large fractions of the sky using angular power spectra. The polarization power spectra of the dust are well described by power laws in multipole, Cℓ ∝ ℓα, with exponents αEE,BB = −2.42 ± 0.02. The amplitudes of the polarization power spectra vary with the average brightness in a way similar to the intensity power spectra. The frequency dependence of the dust polarization spectra is consistent with modified blackbody emission with βd = 1.59 and Td = 19.6 K down to the lowest Planck HFI frequencies. We find a systematic difference between the amplitudes of the Galactic B- and E-modes, CℓBB/CℓEE = 0.5. We verify that these general properties are preserved towards high Galactic latitudes with low dust column densities. We show that even in the faintest dust-emitting regions there are no “clean” windows in the sky where primordial CMB B-mode polarization measurements could be made without subtraction of foreground emission. Finally, we investigate the level of dust polarization in the specific field recently targeted by the BICEP2 experiment. Extrapolation of the Planck 353 GHz data to 150 GHz gives a dust power ℓBB ≡ ℓ(ℓ+1)CℓBB/(2&pi
Adam R, Ade PAR, Aghanim N, et al., 2016, Planck intermediate results XXXII. The relative orientation between the magnetic field and structures traced by interstellar dust, Astronomy & Astrophysics, Vol: 586, ISSN: 1432-0746
The role of the magnetic field in the formation of the filamentary structures observed in the interstellar medium (ISM) is a debated topic owing to the paucity of relevant observations needed to test existing models. The Planck all-sky maps of linearly polarized emission from dust at 353 GHz provide the required combination of imaging and statistics to study the correlation between the structures of the Galactic magnetic field and of interstellar matter over the whole sky, both in the diffuse ISM and in molecular clouds. The data reveal that structures, or ridges, in the intensity map have counterparts in the Stokes Q and/or U maps. We focus our study on structures at intermediate and high Galactic latitudes, which cover two orders of magnitude in column density, from 1020 to 1022 cm-2. We measure the magnetic field orientation on the plane ofthe sky from the polarization data, and present an algorithm to estimate the orientation of the ridges from the dust intensity map. We use analytical models to account for projection effects. Comparing polarization angles on and off the structures, we estimate the mean ratio between the strengths of the turbulent and mean components of the magnetic field to be between 0.6 and 1.0, with a preferred value of 0.8. We find that the ridges are usually aligned with the magnetic field measured on the structures. This statistical trend becomes more striking for increasing polarization fraction and decreasing column density. There is no alignment for the highest column density ridges. We interpret the increase in alignment with polarization fraction as a consequence of projection effects. We present maps to show that the decrease in alignment for high column density is not due to a loss of correlation between the distribution of matter and the geometry of the magnetic field. In molecular complexes, we also observe structures perpendicular to the magnetic field, which, statistically, cannot be accounted for by projection effects. This fi
Ade PAR, Aghanim N, Alves MIR, et al., 2016, Planck intermediate results XXXIII. Signature of the magnetic field geometry of interstellar filaments in dust polarization maps, Astronomy & Astrophysics, Vol: 586, ISSN: 1432-0746
Planck observations at 353 GHz provide the first fully sampled maps of the polarized dust emission towards interstellar filaments and their backgrounds (i.e., the emission observed in the surroundings of the filaments). The data allow us to determine the intrinsic polarization properties of the filaments and therefore to provide insight into the structure of their magnetic field (B). We present the polarization maps of three nearby (several parsecs long) star-forming filaments of moderate column density (NH about 1022 cm-2): Musca, B211, and L1506. These three filaments are detected above the background in dust total and polarized emission. We use the spatial information to separate Stokes I, Q, and U of the filaments from those of their backgrounds, an essential step in measuring the intrinsic polarization fraction (p) and angle (ψ) of each emission component. We find that the polarization angles in the three filaments (ψfil) are coherent along their lengths and not the same as in their backgrounds (ψbg). The differences between ψfil and ψbg are 12° and 54° for Musca and L1506, respectively, and only 6° in the case of B211. These differences forMusca and L1506 are larger than the dispersions of ψ, both along the filaments and in their backgrounds. The observed changes of ψ are direct evidence of variations of the orientation of the plane of the sky (POS) projection of the magnetic field. As in previous studies, we find a decrease of several per cent in p with NH from the backgrounds to the crest of the filaments. We show that the bulk of the drop in p within the filaments cannot be explained by random fluctuations of the orientation of the magnetic field because they are too small (σψ< 10°). We recognize the degeneracy between the dust alignment efficiency (by, e.g., radiative torques) and the structure of the B-field in causing variations in p, but we argue that the decrease in p from the backg
Aghanim N, Alves MIR, Arnaud M, et al., 2016, Planck intermediate results XXXIV. The magnetic field structure in the Rosette Nebula, ASTRONOMY & ASTROPHYSICS, Vol: 586, ISSN: 1432-0746
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-of-sight component of the magnetic field of about 3 μG (towards the observer) in the Rosette Nebula, for a uniform electron density of about 12 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 asa 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 6.5–9 μG. The present analytical model is able to reproduce the RM distribution across the ionized neb
Ade PAR, Aghanim N, Alves MIR, et al., 2016, Planck intermediate results XXXV. Probing the role of the magnetic field in the formation of structure in molecular clouds, Astronomy & Astrophysics, Vol: 586, ISSN: 1432-0746
Within ten nearby (d < 450 pc) Gould belt molecular clouds we evaluate statistically the relative orientation between the magnetic field projected on the plane of sky, inferred from the polarized thermal emission of Galactic dust observed by Planck at 353 GHz, and the gas column density structures, quantified by the gradient of the column density, NH. The selected regions, covering several degrees in size, are analysed at an effective angular resolution of 10′ FWHM, thus sampling physical scales from 0.4 to 40 pc in the nearest cloud. The column densities in the selected regions range from NH≈ 1021 to1023 cm-2, and hence they correspond to the bulk of the molecular clouds. The relative orientation is evaluated pixel by pixel and analysed in bins of column density using the novel statistical tool called “histogram of relative orientations”. Throughout this study, we assume that the polarized emission observed by Planck at 353 GHz is representative of the projected morphology of the magnetic field in each region, i.e., we assume a constant dust grain alignment efficiency, independent of the local environment. Within most clouds we find that the relative orientation changes progressively with increasing NH, from mostly parallel or having no preferred orientation to mostly perpendicular. In simulations of magnetohydrodynamic turbulence in molecular clouds this trend in relative orientation is a signature of Alfvénic or sub-Alfvénic turbulence, implying that the magnetic field is significant for the gas dynamics at the scales probed by Planck. We compare the deduced magnetic field strength with estimates we obtain from other methods and discuss the implications of the Planck observations for the general picture of molecular cloud formation and evolution.
Ade PAR, Aghanim N, Arnaud M, et al., 2016, Planck intermediate results XXXVII. Evidence of unbound gas from the kinetic Sunyaev-Zeldovich effect, Astronomy & Astrophysics, Vol: 586, ISSN: 1432-0746
By looking at the kinetic Sunyaev-Zeldovich effect (kSZ) in Planck nominal mission data, we present a significant detection of baryons participating in large-scale bulk flows around central galaxies (CGs) at redshift z ≈ 0.1. We estimate the pairwise momentum of the kSZ temperature fluctuations at the positions of the Central Galaxy Catalogue (CGC) samples extracted from Sloan Digital Sky Survey (SDSS-DR7) data. For the foreground-cleaned SEVEM, SMICA, NILC, and COMMANDER maps, we find 1.8–2.5σ detections of the kSZ signal, which are consistent with the kSZ evidence found in individualPlanck raw frequency maps, although lower than found in the WMAP-9yr W-band (3.3σ). We further reconstruct the peculiar velocity field from the CG density field, and compute for the first time the cross-correlation function between kSZ temperature fluctuations and estimates of CG radial peculiar velocities. This correlation function yields a 3.0–3.7σ detection of the peculiar motion of extended gas on Mpc scales in flows correlated up to distances of 80–100 h-1 Mpc. Both the pairwise momentum estimates and the kSZ temperature-velocity field correlation find evidence for kSZ signatures out to apertures of 8 arcmin and beyond, corresponding to a physical radius of >1 Mpc, more than twice the mean virial radius of halos. This is consistent with the predictions from hydrodynamical simulations that most of the baryons are outside the virialized halos. We fit a simple model, in which the temperature-velocity cross-correlation is proportional to the signal seen in a semi-analytic model built upon N-body simulations, and interpret the proportionality constant as an effective optical depth to Thomson scattering. We find τT = (1.4 ± 0.5) × 10-4; the simplest interpretation of this measurement is that much of the gas is in a diffuse phase, which contributes little signal to X-ray or thermal Sunyaev-Zeldovich observ
Ade PAR, Aghanim N, Arnaud M, et al., 2016, <i>Planck</i> intermediate results XXXVIII. <i>E</i>- and <i>B</i>-modes of dust polarization from the magnetized filamentary structure of the interstellar medium, ASTRONOMY & ASTROPHYSICS, Vol: 586, ISSN: 0004-6361
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- Citations: 38
Mortlock D, 2016, Quasars as probes of cosmological reionization, Understanding the Epoch of Cosmic Reionization, Publisher: Springer International Publishing, Pages: 187-226, ISBN: 9783319219561
Quasars are the most luminous non-transient sources in the epoch of cosmological reionization (which ended a billion years after the Big Bang, corresponding to a redshift of z ≃ 5), and are powerful probes of the inter-galactic medium at that time. This review covers current efforts to identify high-redshift quasars and how they have been used to constrain the reionization history. This includes a full description of the various processes by which neutral hydrogen atoms can absorb/scatter ultraviolet photons, and which lead to the Gunn-Peterson effect, dark gap and dark pixel analyses, quasar near zones and damping wing absorption. Finally, the future prospects for using quasars as probes of reionization are described.
Ade PAR, Aghanim N, Aniano G, et al., 2015, Planck intermediate results XXVIII. Interstellar gas and dust in the Chamaeleon clouds as seen by Fermi LAT and Planck, ASTRONOMY & ASTROPHYSICS, Vol: 582, ISSN: 1432-0746
The nearby Chamaeleon clouds have been observed in γ rays by the Fermi Large Area Telescope (LAT) and in thermal dust emission by Planck and IRAS. Cosmic rays and large dust grains, if smoothly mixed with gas, can jointly serve with the H i and 12CO radio data to (i) map the hydrogen column densities, NH, in the different gas phases, in particular at the dark neutral medium (DNM) transition between the H i-bright and CO-bright media; (ii) constrain the CO-to-H2 conversion factor, XCO; and (iii) probe the dust properties per gas nucleon in each phase and map their spatial variations across the clouds. We have separated clouds at local, intermediate, and Galactic velocities in H i and 12CO line emission to model in parallel the γ-ray intensity recorded between 0.4 and 100 GeV; the dust optical depth at 353 GHz, τ353; the thermal radiance of the large grains; and an estimate of the dust extinction, AVQ, empirically corrected for the starlight intensity. The dust and γ-ray models have been coupled to account for the DNM gas. The consistent γ-ray emissivity spectra recorded in the different phases confirm that the GeV–TeV cosmic rays probed by the LAT uniformly permeate all gas phases up to the 12CO cores. The dust and cosmic rays both reveal large amounts of DNM gas, with comparable spatial distributions and twice as much mass as in the CO-bright clouds. We give constraints on the H i-DNM-CO transitions for five separate clouds. CO-dark H2 dominates the molecular columns up to AV ≃ 0.9 and its mass often exceeds the one-third of the molecular mass expected by theory. The corrected AVQ extinction largely provides the best fit to the total gas traced by the γ rays. Nevertheless, we find evidence for a marked rise in AVQ/NH with increasing NH and molecular fraction, and with decreasing dust temperature. The rise in τ353/NH is even steeper. We observe variations of lesser amplitude and orderlines
Ade PAR, Aghanim N, Arnaud M, et al., 2015, Planck intermediate results. XXVI. Optical identification and redshifts of Planck clusters with the RTT150 telescope, Astronomy & Astrophysics, Vol: 582, ISSN: 1432-0746
We present the results of approximately three years of observations of Planck Sunyaev-Zeldovich (SZ) sources with the Russian-Turkish 1.5 m telescope (RTT150), as a part of the optical follow-up programme undertaken by the Planck collaboration. During this time period approximately 20% of all dark and grey clear time available at the telescope was devoted to observations of Planck objects. Some observations of distant clusters were also done at the 6 m Bolshoi Telescope Alt-azimutalnyi (BTA) of the Special Astrophysical Observatory of the Russian Academy of Sciences. In total, deep, direct images of more than one hundred fields were obtained in multiple filters. We identified 47 previously unknown galaxy clusters, 41 of which are included in the Planck catalogue of SZ sources. The redshifts of 65 Planck clusters were measured spectroscopically and 14 more were measured photometrically. We discuss the details of cluster optical identifications and redshift measurements. We also present new spectroscopic redshifts for 39 Planck clusters that were not included in the Planck SZ source catalogue and are published here for the first time.
Aghanim N, Altieri B, Arnaud M, et al., 2015, Planck intermediate results XXVII. High-redshift infrared galaxy overdensity candidates and lensed sources discovered by Planck and confirmed by Herschel-SPIRE, Astronomy & Astrophysics, Vol: 582, ISSN: 1432-0746
We have used the Planck all-sky submillimetre and millimetre maps to search for rare sources distinguished by extreme brightness, a few hundred millijanskies, and their potential for being situated at high redshift. These “cold” Planck sources, selected using the High Frequency Instrument (HFI) directly from the maps and from the Planck Catalogue of Compact Sources (PCCS), all satisfy the criterion of having their rest-frame far-infrared peak redshifted to the frequency range 353–857 GHz. This colour-selection favours galaxies in the redshift range z = 2–4, which we consider as cold peaks in the cosmic infrared background. With a beam at the four highest frequencies, our sample is expected to include overdensities of galaxies in groups or clusters, lensed galaxies, and chance line-of-sight projections. We perform a dedicated Herschel-SPIRE follow-up of 234 such Planck targets, finding a significant excess of red 350 and 500μm sources, in comparison to reference SPIRE fields. About 94% of the SPIRE sources in the Planck fields are consistent with being overdensities of galaxies peaking at 350μm, with 3% peaking at 500μm, and none peaking at 250μm. About 3% are candidate lensed systems, all 12 of which have secure spectroscopic confirmations, placing them at redshifts z> 2.2. Only four targets are Galactic cirrus, yielding a success rate in our search strategy for identifying extragalactic sources within the Planck beam of better than 98%. The galaxy overdensities are detected with high significance, half of the sample showing statistical significance above 10σ. The SPIRE photometric redshifts of galaxies in overdensities suggest a peak at z ≃ 2, assuming a single common dust temperature for the sources of Td = 35 K. Under this assumption, we derive an infrared (IR) luminosity for each SPIRE source of about 4 × 1012L⊙, yielding star formation rates of typically 700 M⊙ yr-1. If the observed overdensities are actual gr
Ade PAR, Aghanim N, Arnaud M, et al., 2015, Planck intermediate results XXV. The Andromeda galaxy as seen by Planck, Astronomy & Astrophysics, Vol: 582, ISSN: 1432-0746
The Andromeda galaxy (M 31) is one of a few galaxies that has sufficient angular size on the sky to be resolved by the Planck satellite. Planck has detected M 31 in all of its frequency bands, and has mapped out the dust emission with the High Frequency Instrument, clearly resolving multiple spiralarms 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 M 31. 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 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 (18.2 ± 1.0) K with a spectral index of 1.62 ± 0.11 (assuming a single modified blackbody), and a significant amount of free-free emission at intermediate frequencies of 20–60 GHz, which corresponds to a star formation rate of around 0.12 M⊙ yr-1. We find a 2.3σ detection of the presence of spinning dust emission, with a 30 GHz amplitude of 0.7 ± 0.3 Jy, which is in line with expectations from our Galaxy.
Ade PAR, Aghanim N, Armitage-Caplan C, et al., 2015, Planck 2013 results. XXXII. The updated Planck catalogue of Sunyaev-Zeldovich sources, Astronomy & Astrophysics, Vol: 581, ISSN: 1432-0746
We update the all-sky Planck catalogue of 1227 clusters and cluster candidates (PSZ1) published in March 2013, derived from detections of the Sunyaev–Zeldovich (SZ) effect using the first 15.5 months of Planck satellite observations. As an addendum, we deliver an updated version of the PSZ1 catalogue, reporting the further confirmation of 86 Planck-discovered clusters. In total, the PSZ1 now contains 947 confirmed clusters, of which 214 were confirmed as newly discovered clusters through follow-up observations undertaken by the Planck Collaboration. The updated PSZ1 contains redshifts for 913 systems, of which 736 (~ 80.6%) are spectroscopic, and associated mass estimates derived from the Yz mass proxy. We also provide a new SZ quality flag for the remaining 280 candidates. This flag was derived from a novel artificial neural-network classification of the SZ signal. Based on this assessment, the purity of the updated PSZ1 catalogue is estimated to be 94%. In this release, we provide the full updated catalogue and an additional readme file with further information on the Planck SZ detections.
Ade PAR, Aghanim N, Arnaud M, et al., 2015, Planck intermediate results XXIII. Galactic plane emission components derived from Planck with ancillary data, Astronomy & Astrophysics, Vol: 580, ISSN: 1432-0746
Mortlock DJ, 2015, Bayesian model comparison in cosmology, Statistical Challenges in 21st Century Cosmology, Publisher: Cambridge University Press (CUP), Pages: 5-8, ISSN: 1743-9213
The standard Bayesian model formalism comparison cannot be applied to mostcosmological models as they lack well-motivated parameter priors. However, ifthe data-set being used is separable then it is possible to use some of thedata to obtain the necessary parameter distributions, the rest of the databeing retained for model comparison. While such methods are not fullyprescriptive, they provide a route to applying Bayesian model comparison incosmological situations where it could not otherwise be used.
Ade PAR, Alves MIR, Aniano G, et al., 2015, <i>Planck</i> intermediate results. XXII. Frequency dependence of thermal emission from Galactic dust in intensity and polarization, ASTRONOMY & ASTROPHYSICS, Vol: 576, ISSN: 0004-6361
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- Citations: 109
Ade PAR, Aghanim N, Alina D, et al., 2015, <i>Planck</i> intermediate results. XXI. Comparison of polarized thermal emission from Galactic dust at 353 GHz with interstellar polarization in the visible, ASTRONOMY & ASTROPHYSICS, Vol: 576, ISSN: 0004-6361
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- Citations: 20
Ade PAR, Aghanim N, Alina D, et al., 2015, <i>Planck</i> intermediate results. XX. Comparison of polarized thermal emission from Galactic dust with simulations of MHD turbulence, ASTRONOMY & ASTROPHYSICS, Vol: 576, ISSN: 0004-6361
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- Citations: 48
Ade PAR, Aghanim N, Alina D, et al., 2015, <i>Planck</i> intermediate results. XIX. An overview of the polarized thermal emission from Galactic dust, ASTRONOMY & ASTROPHYSICS, Vol: 576, ISSN: 0004-6361
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- Citations: 280
Ade PAR, Aghanim N, Ahmed Z, et al., 2015, Joint Analysis of BICEP2/Keck Array and Planck Data, Physical Review Letters, Vol: 114, ISSN: 1079-7114
Skrzypek N, Warren SJ, Faherty JK, et al., 2015, Photometric brown-dwarf classification I. A method to identify and accurately classify large samples of brown dwarfs without spectroscopy, Astronomy & Astrophysics, Vol: 574, ISSN: 1432-0746
Aims. We present a method, named photo-type, to identify and accurately classify L and T dwarfs onto the standard spectral classification system using photometry alone. This enables the creation of large and deep homogeneous samples of these objects efficiently, without the need for spectroscopy.Methods. We created a catalogue of point sources with photometry in 8 bands, ranging from 0.75 to 4.6 μm, selected from an area of 3344 deg2, by combining SDSS, UKIDSS LAS, and WISE data. Sources with 13.0 <J< 17.5, and Y − J> 0.8, were then classified by comparison against template colours of quasars, stars, and brown dwarfs. The L and T templates, spectral types L0 to T8, were created by identifying previously known sources with spectroscopic classifications, and fitting polynomial relations between colour and spectral type.Results. Of the 192 known L and T dwarfs with reliable photometry in the surveyed area and magnitude range, 189 are recovered by our selection and classification method. We have quantified the accuracy of the classification method both externally, with spectroscopy, and internally, by creating synthetic catalogues and accounting for the uncertainties. We find that, brighter than J = 17.5, photo-type classifications are accurate to one spectral sub-type, and are therefore competitive with spectroscopic classifications. The resultant catalogue of 1157 L and T dwarfs will be presented in a companion paper.
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