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[en] Recently, Warm (keV scale) Dark Matter emerged impressively over CDM (Cold Dark Matter) as the leading Dark Matter candidate. In the context of this new Dark Matter situation, which implies novelties in the astrophysical, cosmological and keV particle physics context, this 16. Paris Colloquium 2012 is devoted to the LambdaWDM Standard Model of the Universe. The topics of the colloquium are as follows: -) observational and theoretical progress on the nature of dark matter: keV scale warm dark matter, -) large and small scale structure formation in agreement with observations at large scales and small galactic scales, and -) neutrinos in astrophysics and cosmology. This document gathers the slides of the presentations.
[en] In this contribution we describe the constraints on departures from general relativity (GR) at cosmological length scales due to cosmic microwave background (CMB). For a more detailed discussion, see Phys. Rev. D 79, 101301 (R) (2009). The departure from GR is measured by the ratio, parameterized as 1+ω-bar0(1+z)-S, between the gravitational potentials conventionally appearing in the geodesic equation and the Poisson equation. Current CMB data indicate ω-bar0=1.671.87+3.07 at the 2σ confidence level, while S remains unconstrained. The departure from GR affects the lensing conversion of E-mode into B-mode polarization. Hence, the lensing measurements from a future CMBpol experiment should be able to improve the constraints to ω-bar0<0.30 for a fiducial ω-bar0=0 model and independent of S.
[en] One of the most viable explanations for the accelerated expansion of the universe at the present epoch entails a mysterious dark energy component in the energy budget of the universe. Although the existence of dark energy has been corroborated by several independent studies over the past decade, there is no compelling theoretical explanation for its existence. In order to learn more about this mysterious dark energy, a number of current and future observational studies are aimed at constraining its equation of state (EOS; w(z)) with unprecedented precision. Here we address the heart of some of these projects. We first try to motivate a model-independent approach to constrain the EOS. We then concentrate on two potential sources of uncertainties in the EOS: systematics incorporated due to the lensing of supernova (SN), and systematics based on the the existence of two different SN populations.
[en] We present an improved and extended analysis of the cross-correlation between the map of the cosmic microwave background (CMB) lensing potential derived from the Planck mission data and the high-redshift galaxies detected by the Herschel Astrophysical Terahertz Large Area Survey (H-ATLAS) in the photometric redshift range . We compare the results based on the 2013 and 2015 Planck datasets, and investigate the impact of different selections of the H-ATLAS galaxy samples. Significant improvements over our previous analysis have been achieved thanks to the higher signal-to-noise ratio of the new CMB lensing map recently released by the Planck collaboration. The effective galaxy bias parameter, b, for the full galaxy sample, derived from a joint analysis of the cross-power spectrum and of the galaxy auto-power spectrum is found to be . Furthermore, a first tomographic analysis of the cross-correlation signal is implemented by splitting the galaxy sample into two redshift intervals: and . A statistically significant signal was found for both bins, indicating a substantial increase with redshift of the bias parameter: for the lower and for the higher redshift bin. Consistent with our previous analysis, we find that the amplitude of the cross-correlation signal is a factor of higher than expected from the standard ΛCDM model for the assumed redshift distribution. The robustness of our results against possible systematic effects has been extensively discussed, although the tension is mitigated by passing from 4 to 3σ.
[en] Numerical simulations of cosmological structure formation show that the universe’s most massive clusters, and the galaxies living in those clusters, assemble rapidly at early times (). While more than 20 proto-clusters have been observed at based on associations of 5–40 galaxies around rare sources, the observational evidence for rapid cluster formation is weak. Here we report observations of an asymmetric filamentary structure at z = 2.47 containing 7 starbursting, submillimeter-luminous galaxies and 5 additional active galactic nuclei (AGNs) within a comoving volume of 15,000 Mpc3. As the expected lifetime of both the luminous AGN and starburst phase of a galaxy is ∼100 Myr, we conclude that these sources were likely triggered in rapid succession by environmental factors or, alternatively, the duration of these cosmologically rare phenomena is much longer than prior direct measurements suggest. The stellar mass already built up in the structure is ∼1012 and we estimate that the cluster mass will exceed that of the Coma supercluster at . The filamentary structure is in line with hierarchical growth simulations that predict that the peak of cluster activity occurs rapidly at .
[en] Interplanetary dust (IPD) scatters solar radiation which results in the zodiacal light that dominates the celestial diffuse brightness at optical and near-infrared wavelengths. Both asteroid collisions and cometary ejections produce the IPD, but the relative contribution from these two sources is still unknown. The low resolution spectrometer (LRS) onboard the Cosmic Infrared Background ExpeRiment (CIBER) observed the astrophysical sky spectrum between 0.75 and 2.1 μm over a wide range of ecliptic latitude. The resulting zodiacal light spectrum is redder than the solar spectrum, and shows a broad absorption feature, previously unreported, at approximately 0.9 μm, suggesting the existence of silicates in the IPD material. The spectral shape of the zodiacal light is isotropic at all ecliptic latitudes within the measurement error. The zodiacal light spectrum, including the extended wavelength range to 2.5 μm using Infrared Telescope in Space (IRTS) data, is qualitatively similar to the reflectance of S-type asteroids. This result can be explained by the proximity of S-type asteroidal dust to Earth's orbit, and the relatively high albedo of asteroidal dust compared with cometary dust.
[en] We report measurements of the diffuse galactic light (DGL) spectrum in the near-infrared, spanning the wavelength range 0.95–1.65 μm by the Cosmic Infrared Background ExpeRiment. Using the low-resolution spectrometer calibrated for absolute spectro-photometry, we acquired long-slit spectral images of the total diffuse sky brightness toward six high-latitude fields spread over four sounding rocket flights. To separate the DGL spectrum from the total sky brightness, we correlated the spectral images with a 100 μm intensity map, which traces the dust column density in optically thin regions. The measured DGL spectrum shows no resolved features and is consistent with other DGL measurements in the optical and at near-infrared wavelengths longer than 1.8 μm. Our result implies that the continuum is consistently reproduced by models of scattered starlight in the Rayleigh scattering regime with a few large grains
[en] We present the first measurement of the correlation between the map of the cosmic microwave background (CMB) lensing potential derived from the Planck nominal mission data and galaxies detected by the Herschel-ATLAS (H-ATLAS) survey covering about , i.e., about 1.4% of the sky. We reject the hypothesis that there is no correlation between CMB lensing and galaxy detection at a significance, checking the result by performing a number of null tests. The significance of the detection of the theoretically expected cross-correlation signal is found to be . The galaxy bias parameter, b, derived from a joint analysis of the cross-power spectrum and of the autopower spectrum of the galaxy density contrast is found to be , consistent with earlier estimates for H-ATLAS galaxies at similar redshifts. On the other hand, the amplitude of the cross-correlation is found to be a factor 1.62 ± 0.16 higher than expected from the standard model and also found by cross-correlation analyses with other tracers of the large-scale structure. The enhancement due to lensing magnification can account for only a fraction of the excess cross-correlation signal. We suggest that part of it may be due to an incomplete removal of the contamination of the cosmic infrared background, which includes the H-ATLAS sources we are cross-correlating with. In any case, the highly significant detection reported here using a catalog covering only 1.4% of the sky demonstrates the potential of CMB lensing correlations with submillimeter surveys.
[en] An unambiguous manifestation of the magnification bias is the cross-correlation between two source samples with non-overlapping redshift distributions. In this work we measure and study the cross-correlation signal between a foreground sample of GAMA galaxies with spectroscopic redshifts in the range 0.2< z <0.8, and a background sample of H-ATLAS galaxies with photometric redshifts ∼>1.2. It constitutes a substantial improvement over the cross-correlation measurements made by Gonzalez-Nuevo et al. (2014) with updated catalogues and wider area (with S / N ∼> 5 below 10 arcmin and reaching S / N ∼ 20 below 30 arcsec). The better statistics allow us to split the sample in different redshift bins and to perform a tomographic analysis (with S / N ∼> 3 below 10 arcmin and reaching S / N ∼ 15 below 30 arcsec). Moreover, we implement a halo model to extract astrophysical information about the background galaxies and the deflectors that are producing the lensing link between the foreground (lenses) and background (sources) samples. In the case of the sources, we find typical mass values in agreement with previous studies: a minimum halo mass to host a central galaxy, M min∼ 1012.26 M ⊙, and a pivot halo mass to have at least one sub-halo satellite, M 1∼ 1012.84 M ⊙. However, the lenses are massive galaxies or even galaxy groups/clusters, with minimum mass of M minlens∼ 1013.06 M ⊙. Above a mass of M 1lens∼ 1014.57 M ⊙ they contain at least one additional satellite galaxy which contributes to the lensing effect. The tomographic analysis shows that, while M 1lens is almost redshift independent, there is a clear evolution of increase M minlens with redshift in agreement with theoretical estimations. Finally, the halo modeling allows us to identify a strong lensing contribution to the cross-correlation for angular scales below 30 arcsec. This interpretation is supported by the results of basic but effective simulations.
[en] We present new Herschel-SPIRE imaging spectroscopy (194-671 μm) of the bright starburst galaxy M82. Covering the CO ladder from J = 4 → 3 to J = 13 → 12, spectra were obtained at multiple positions for a fully sampled ∼3 × 3 arcmin map, including a longer exposure at the central position. We present measurements of 12CO, 13CO, [C I], [N II], HCN, and HCO+ in emission, along with OH+, H2O+, and HF in absorption and H2O in both emission and absorption, with discussion. We use a radiative transfer code and Bayesian likelihood analysis to model the temperature, density, column density, and filling factor of multiple components of molecular gas traced by 12CO and 13CO, adding further evidence to the high-J lines tracing a much warmer (∼500 K), less massive component than the low-J lines. The addition of 13CO (and [C I]) is new and indicates that [C I] may be tracing different gas than 12CO. No temperature/density gradients can be inferred from the map, indicating that the single-pointing spectrum is descriptive of the bulk properties of the galaxy. At such a high temperature, cooling is dominated by molecular hydrogen. Photon-dominated region (PDR) models require higher densities than those indicated by our Bayesian likelihood analysis in order to explain the high-J CO line ratios, though cosmic-ray-enhanced PDR models can do a better job reproducing the emission at lower densities. Shocks and turbulent heating are likely required to explain the bright high-J emission.