1 to 7 June 2014, Angra do Heroísmo, Azores, Portugal
CMB anisotropies from a stochastic background of primordial magnetic fields with non-zero helicity
Mario Ballardini
We consider the impact of a stochastic background of primordial magnetic fields with non-vanishing helicity on CMB anisotropies in temperature and polarization. We compute the exact expressions for the energy-momentum tensor components including the helical contribution, given a power-law dependence for the spectra and a comoving cut-off to mimics the damping due to viscosity. Under the latter assumptions, we also compute the cross-correlation between the non-helical and helical parts of the stochastic background. We finally show the total impact of such stochastic background on CMB anisotropies generated by the vector and tensor perturbations, including the odd-parity cross-correlators TB and EB.
Slides
νGalileon: a new life for Galileon gravity from massive neutrinos
Alexandre Barreira
Galileon gravity offers a possible explanation for late-time cosmic acceleration. In this model, a Galilean invariant scalar field drives modifications to gravity on large scales, which can be suppressed near massive bodies to pass Solar System tests. The model was however thought to be ruled out due to residual modifications to gravity in the Solar System, enhanced matter clustering and strong ISW effect. I will show that, in the presence of massive neutrinos, the Galileon model can avoid these problems and yield a good fit to the CMB temperature, CMB lensing and BAO data. In this model, dubbed νGalileon, the physics is completely specified by the same physical parameters as in ΛCDM. The data provide strong evidence for nonzero neutrino masses, with the summed masses larger than 0.4 eV (95% CL). Present and future Earth-based neutrino experiments will be able to probe this range of masses and have a strong potential to test the model. Unlike LCDM, the νGalileon model is perfectly consistent with local determinations of the Hubble parameter. Further tests of the model can be obtained from data sensitive to the amplitude of matter fluctuations, which is substantially reduced by the massive neutrinos. As a first step in this direction, I will show results from the first N-body simulations and analytical models of structure formation for Galileon models without massive neutrinos.
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Cosmological implications from the eROSITA all-sky survey
Katharina Borm
eROSITA (extended ROentgen Survey with an Imaging Telescope Array) is the German core instrument aboard the Russian Spektrum-Roentgen-Gamma satellite which is scheduled for launch in 2015. The main driver for eROSITA is studying the nature of dark energy, which is especially imprinted in the redshift and mass distribution of galaxy clusters. eROSITA is expected to detect around 100 thousand clusters of galaxies in X-rays up to redshifts of z~2.0. We present forecasts for the observation power of this instrument and introduce the distribution of galaxy clusters with mass and redshift as it is expected to be observed during the all-sky survey. By means of simulations of galaxy cluster spectra, we quantify the accuracy and the precision with which eROSITA will determine the temperature of the intra-cluster medium and the cluster redshift directly from the survey data. According to these predictions, eROSITA will increase the current cluster sample with precise temperatures by a factor of 5-10. Based on the above computations and results, the constraints eROSITA will place on the cosmological parameters are predicted by means of Markov-Chain Monte Carlo simulations.
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Constraining the chameleon regime in f(R) gravity with cluster abundance data
Matteo Cataneo
Under modifications of General Relativity (GR) able to explain cosmic acceleration, large matter structures typically exhibit deviations from GR in their growth history. This is particularly the case for the abundance of massive galaxy clusters as a function of mass and redshift. Being these the largest collapsed objects in the Universe and extremely rare, this is a powerful probe of modified gravity models on large scales. To take full advantage of the currently available high quality data from X-ray cluster surveys, it is essential to properly model the halo mass function accounting for the non-linear suppressions required for such modifications of gravity to pass the stringent local tests consistent with GR. Previous works used the linearized approximation, which implies that the local value of the scalaron field is fixed to its background value. Time permitting, I will show improved constraints that overcome this theoretical limitation for a specific class of f(R) models.
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The importance of being warm (during inflation)
Rafael Cerezo
The amplitude of primordial curvature perturbations is enhanced when a warm radiation bath at a temperature T > H is sustained during inflation by dissipative particle production, which is particularly significant when a non-trivial statistical ensemble of inflaton fluctuations is also generated. Since gravitational modes are oblivious to dissipative dynamics, this generically lowers the tensor-to-scalar ratio and yields a modified consistency relation for warm inflation, as well changing the tilt of the scalar spectrum. We show that this alters the landscape of observationally allowed inflationary models, with for example the quartic chaotic potential being in very good agreement with the Planck results for nearly-thermal inflaton fluctuations and essentially ruled out for an underlying vacuum state. We also discuss other simple models that are in agreement with the Planck data within a renormalizable model of warm inflation.
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3D Power Spectra for H1 Intensity with a Scale Dependent Bias
Dagoberto Contreras
One of the promising new measurements in cosmology is the spin flip of neutral hydrogen in its ground state. In the literature it is claimed that this measurement at late times will tell us about the evolution of dark energy. These claims rely on the assumption that hydrogen is a tracer of the matter. Recent results suggest that the bias is instead scale dependent and in fact negative at large scales. Full power spectra are generated at linear order in perturbation theory. The implications for 21cm experiments are explored.
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Constraint on drifting proton-to-electron mass ratio through analysis of molecular absorption lines
Mario Dapra
The Standard Model does not fix the strength of the fundamental forces, thus leaving space for the hypothesis of coupling constants varying over space and time. A time variation of the proton-to-electron mass ratio μ can be probed through measurements of molecular line spectra in various cosmological epochs. Two different analysis are presented, to put a constraint on a possible cosmological variation in μ at different redshifts. At low redshift methanol transitions are used, since they have a high sensitivity, while ultraviolet spectral lines of H2 are used to investigate galaxies at higher redshift. Observations from three different radiotelescopes (Effelbserg 100m, IRAM 30m and ALMA) of 10 methanol transitions at redshift z=0.89 in the PKS1830-211 lensing galaxy were used to put a limit on Δμ/μ, quantifying systematic effects of chemical segregation, excitation temperature, frequency dependence and time variability of the background source. More than 110 rovibronic molecular hydrogen H2 transitions, from the Very Large Telescope Ultraviolet and Visual Echelle Spectrograph, at redshift z=2.69 toward the background quasar J1237+0674 are presented, to put a constraint on a possible cosmological variation in the proton-to-electron mass ratio. The goodness of the result is tested for underlying velocity structures that can mimic a variation of μ. Particular attention is dedicated to the long range distortions due to a wavelength dependent velocity drift, that is known to happen in UVES.
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A Bayesian hunt for systematics and new signals
Caroline Heneka
We employ advanced Bayesian methods to study the robustness of Type Ia supernova data sets used for cosmological inference. This is crucial for the identification and removal of systematic errors, hidden correlations, as well as unaccounted for cosmological signals. I will present a series of analyses that we developed to look for potential subsets of the data displaying a deviating behaviour with respect to the overall data set and discuss our findings.
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Weak gravitational lensing by rotating tidal charged black holes
Zsolt Horvath
We discuss the weak gravitational lensing by the axially symmetric tidal charged black hole. We calculate the bending angle and examine image formation and magnification. We refer and compare the Kerr and the tidal charged Reissner-Nordstr�m limits of the results.
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The ALHAMBRA Survey: Evolution of Galaxy Clustering with Segregation
Lluís Hurtado-Gil
We study the clustering of galaxies as function of luminosity and redshift
in the range 0.35 < z < 1.25 using data from the Advanced Large Homogeneous
Area Medium Band Redshift Astronomical (ALHAMBRA) survey. The ALHAMBRA data
used in this work covers 2.38deg2 in 7 independent fields, after applying
a detailed angular selection mask, with accurate photometric redshifts,
σz < 0.014(1+z), down to IAB < 24. Given the depth of the survey we
select samples in B-band luminosity down to Lth = 0.16L* at z=0.9. We
mesure the real-space clustering using the projected correlation function,
accounting for photometric redshift uncertainties. In addition, for
galaxies with MthB < -18.6, we perform the clustering evolution with
segregated populations using ALHAMBRA templates, separating in early and
late type galaxies. The high quality of ALHAMBRA photometric redshift and
its high density field allow us to extend the projected correlation
function down to 0.03 h-1 Mpc, below any other calculations before.
Slides
Testing the consistency of different supernova surveys
Natallia Karpenka
SNe catalogues consist of SNe from different surveys. In constraining cosmological parameters, most studies perform a joint analysis of the full joint SN catalogue. The key assumption underlying these joint analyses is the consistency between different SN data-sets. It is possible, however, to have some unaccounted systematics in SN data-sets, so it is extremely important to establish whether these data-sets are mutually consistent before performing a coherent joint analysis. I am currently working on performing robust statistical tests to determine whether different SNe catalogues are consistent or inconsistent with each other, also I am developing a coherent statistical approach that can automatically deal with inconsistencies between the data-sets through the introduction of additional hyper-parameters in the data model.
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Detection of a supervoid aligned with the CMB Cold Spot
Andras Kovacs
We used the WISE-2MASS infrared galaxy catalog matched with Pan-STARRS1 optical colors to search for a supervoid in the direction the Cosmic Microwave Background Cold Spot. Our imaging catalog peaks around z=0.15, and we obtain photo-metric redshifts derived from our optical colors to create a tomographic map of the galaxy distribution. The radial profile centered on the Cold Spot Region shows a large low density region, extending over 10\'s of degrees. We test for under-density at two angular radii 5 deg, and 15 deg based on previous Cosmic Microwave Background results. The counts in photo-metric redshift bins show significantly low densities at very high significance for the two fiducial radii. Our counts are consistent with a large r > 100 Mpc/h supervoid with depth of −0.15 embedding a smaller but deeper void in the center. Visual inspection suggests that the centers of the Cold Spot and the deepest part of the supervoid are well aligned, thus a chance alignment is unlikely.
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Regularizing cosmological singularities by varying physical constants
Konrad Marosek
Varying physical constant cosmologies were claimed to solve standard cosmological problems such as the horizon, the flatness and the Lambda problem. We suggest yet another important application of these theories: solving the singularity problem. By specifying some examples we show that various cosmological singularities may be regularized provided the physical constants evolve in time in an appropriate way.
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The effect of a Starobinsky gravity correction combined with small-scale inhomogeneities in cosmology
Anthony Preston
The Starobinsky R^2 correction to General Relativity is motivated theoretically by quantum gravity and observationally by inflation, especially by Planck data. We interpret the effect of Starobinsky gravity together with small-scale inhomogeneities in terms of an effective stress energy tensor. We follow Green and Wald in adapting Burnett's shortwave approximation to study inhomogeneity, now using the Starobinsky model. We derive the form of the effective stress-energy tensor and interpret it cosmologically.
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Wide angle effects on Redshift-space distortions
Paulo Reimberg
The effect of peculiar velocities of galaxies on their distance determination can bias the data from galaxies catalogs. When looking at galaxies in virialized regions in galaxy clusters, highly non-linear effects come into play, giving birth to effects such as fingers-of-god. We will restrict ourselves to the complementary region: we assume that the peculiar velocities are small compared with the Hubble flow, and focus on wide-angle effects on redshift space distortions. We will show that, in linear theory, the corrections to the two-point correlation function due to peculiar velocities can be introduced through simple differential operators acting on the shape of the triangle formed by observer-galaxy-galaxy.
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Incorporating Particle Physics Phenomenology into Cosmological Simulations of Dark Matter
Andrew Robertson
Motivated by particle physics models with a rich dark sector, and some potential problems with ΛCDM on small scales, we investigate the effect of a dark matter particle with a significant cross-section for self-interactions. Observations of colliding clusters such as the Bullet Cluster have allowed constraints on dark matter self-interactions to be made, but obtaining tight constraints from these major mergers is made difficult by the small sample size, and large uncertainties over the exact orientations of the systems. Another place to look for evidence of self-interacting dark matter is in minor mergers. Most clusters have some infalling sub-haloes, the abundance of such systems making it possible to more robustly infer their statistical properties. This talk will describe Cosmological simulations that incorporate self-interacting dark matter, which we are using to interpret recent HST observations of a separation between the galaxies and the dark matter of infalling sub-haloes. Our statistical approach will allow us to generalise this analysis to Euclid's survey of tens of thousands of clusters, and distinguish between particle physics models beyond the standard model.
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Measuring the BAO peak with DES
Ana Isabel Salvador
The pressure waves between baryons and photons created before photon decoupling are called baryon acoustic oscillations (BAO) and the distance they have traveled at photon decoupling is known as the sound horizon. Today, this sound horizon distance is about 450 million light years, and it provides a standard ruler for cosmological distance measurements. Des will measure the clustering on the sky of hundreds of millions of galaxies at different distances from us. These measurements will determine the angular scale of the sound horizon for galaxies at different redshifts.
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Weak gravitational lensing of supernovae
Dario Scovacricci
Supernovae type Ia (SNIa) have played a major role in cosmology for the last two decades, leading to the discovery of the accelerated expansion of our Universe, driven by Dark Energy. As we strive to improve SNIa as distance indicators we must include important new physical effects like weak gravitational lensing: the star can be magnified or de-magnified, depending on the matter-energy distribution along the light path. For this reason, the weak lensing adds a statistical noise on the Hubble diagram, degrading the estimate of the cosmological parameters. On the other hand, it can be used as a new cosmological probe, since it depends on the cosmology itself, especially the distribution of the matter along the line-of-sight. In this talk I will review the current approach to weak lensing analysis of standard candles and I will show predictions for the weak lensing effects of SN for DES, LSST and Euclid.
Probing accelerating gravity models in the growth indexes parameter space
Heinrich Steigerwald
The growth index of cosmological perturbations is one of the most powerful probes of the nature of Dark Energy (DE), the mysterious mechanism driving the late epoch acceleration of the universe. Unlike classical geometrical observables, such as distances, which only probe the background sector of a cosmological model, this observable provides insight into first order dynamical effects, and it is therefore a key test for modified gravity scenarios often invoked to explain away the DE issue. In this talk I will first show how the whole information about the growth rate history of linear cosmic structures can be precisely encoded into a small set of growth index parameters whose amplitude can be analytically predicted by theory. Then I will go on demonstrating how these parameters naturally define a space where theoretical predictions can be compared against data in a model independent way. Finally, by exploiting the Effective Field Theory of dark energy, a formalism which describes virtually all the gravitational theories containing a single scalar degree of freedom in addition to the metric, I will explore which alternative cosmological scenarios are not in conflict with current growth data.
Slides
Cosmological constraints on the Higgs portal
Tommi Tenkanen
During the last year Planck satellite provided the most accurate data of the cosmic microwave backround radiation ever measured and the LHC verified the discovery of the Standard Model higgs boson. This new data provides unseen possibilities for probing the early universe, its particle content and interactions between them. We study the cosmological constraints on a Standard Model extension with a real singlet scalar. In this talk I will briefly introduce some of the main constraints on formation and decay of the scalar condensates in order to consider the generation of baryon asymmetry and the effect of scalar field fluctuations on a large scale structure of the Universe.
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X-ray Study of a fossil Group out to the virial Radius
Sophia Th�lken
Up to now, only roughly 10% of the volume of galaxy clusters have been studied in detail in terms of gas content. The largest fraction - the so called outskirts - remains mostly unexplored although interesting physical effects may act there, that can be dominated by structure formation, such as accretion shocks or non-equilibrium states. The instrumental limitation and strong fore- and background emission make it difficult to study the gas in the outer regions of galaxy clusters and in particular of galaxy groups. In the past years, the low and stable instrumental background of Suzaku helped to improve the understanding of these regions and several analyses were performed concerning the outskirts of galaxy clusters. But regarding galaxy groups, a clear lack of detailed studies exists. Here, an X-ray analysis using Suzaku data of the outskirts of the fossil group UGC03957 is presented. The temperature, metallicity and entropy profiles from the center out to the virial radius are obtained and possible azimuthal deviations are investigated.
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Evolution of the fine-structure constant in runaway dilaton models
Pauline Vielzeuf
We study the detailed evolution of the fine-structure constant α in the string-inspired runaway dilaton class of models of Damour, Piazza and Veneziano. We provide constraints on this scenario using the most recent observational datasets and explore possible ways to distinguish these models from alternative models for varying α. Our analysis indicates that in the range of model parameters compatible with current observations the redshift drift signal differs from that of the canonical ΛCDM paradigm. Measurements of this signal by the forthcoming European Extremely Large Telescope (E-ELT) will be able to distinguish the two scenarios.
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