arXiv subjects

Olga Mena

Publications and source records attributed to Olga Mena.

At least 145 records · Page 8Linked to original sources

arXiv2012

Thinking Outside the Box: Effects of Modes Larger than the Survey on Matter Power Spectrum Covariance

Considering the matter power spectrum covariance matrix, it has recently been found that there is a potentially dominant effect on mildly non-linear scales due to power in modes of size equal to and larger than the survey volume. This {\it beat coupling} effect has been derived analytically in perturbation theory and while it has been tested with simulations, some questions remain unanswered. Moreover, there is an additional effect of these large modes, which has so far not been included in analytic studies, namely the effect on the estimated {\it average} density which enters the power spectrum estimate. In this article, we work out analytic, perturbation theory based expressions including both the beat coupling and this {\it local average effect} and we show that while, when isolated, beat coupling indeed causes large excess covariance in agreement with the literature, in a realistic scenario this is compensated almost entirely by the local average effect, leaving only $\sim 10 %$ of the excess. We test our analytic expressions by comparison to a suite of large N-body simulations. For the variances, we find excellent agreement with the analytic expressions for $k < 0.2 h$Mpc$^{-1}$ at $z=0.5$, while the correlation coefficients agree to beyond $k=0.4 h$Mpc$^{-1}$. As expected, the range of agreement increases towards higher redshift and decreases slightly towards $z=0$. We finish by including the large-mode effects in a full covariance matrix description for arbitrary survey geometry and confirming its validity using simulations. This may be useful as a stepping stone towards building an actual galaxy (or other tracer's) power spectrum covariance matrix. [abridged]

astro-ph.CO↗

arXiv2012

The next-generation liquid-scintillator neutrino observatory LENA

We propose the liquid-scintillator detector LENA (Low Energy Neutrino Astronomy) as a next-generation neutrino observatory on the scale of 50 kt. The outstanding successes of the Borexino and KamLAND experiments demonstrate the large potential of liquid-scintillator detectors in low-energy neutrino physics. LENA's physics objectives comprise the observation of astrophysical and terrestrial neutrino sources as well as the investigation of neutrino oscillations. In the GeV energy range, the search for proton decay and long-baseline neutrino oscillation experiments complement the low-energy program. Based on the considerable expertise present in European and international research groups, the technical design is sufficiently mature to allow for an early start of detector realization.

astro-ph.IM↗

arXiv2012

Clustering of Sloan Digital Sky Survey III Photometric Luminous Galaxies: The Measurement, Systematics and Cosmological Implications

The Sloan Digital Sky Survey (SDSS) surveyed 14,555 square degrees, and delivered over a trillion pixels of imaging data. We present a study of galaxy clustering using 900,000 luminous galaxies with photometric redshifts, spanning between $z=0.45$ and $z=0.65$, constructed from the SDSS using methods described in Ross et al. (2011). This data-set spans 11,000 square degrees and probes a volume of $3h^{-3} \rm{Gpc}^3$, making it the largest volume ever used for galaxy clustering measurements. We present a novel treatment of the observational systematics and its applications to the clustering signals from the data set. In this paper, we measure the angular clustering using an optimal quadratic estimator at 4 redshift slices with an accuracy of ~15% with bin size of delta_l = 10 on scales of the Baryon Acoustic Oscillations (BAO) (at l~40-400). We derive cosmological constraints using the full-shape of the power-spectra. For a flat Lambda CDM model, when combined with Cosmic Microwave Background Wilkinson Microwave Anisotropy Probe 7 (WMAP7) and H_0 constraints from 600 Cepheids observed by HST, we find Ω_Λ= 0.73 +/- 0.019 and H_0 to be 70.5 +/- 1.6 km/s/Mpc. For an open Lambda CDM model, when combined with WMAP7 + HST, we find $Ω_K = 0.0035 +/- 0.0054, improved over WMAP7+HST alone by 40%. For a wCDM model, when combined with WMAP7+HST+SN, we find w = -1.071 +/- 0.078, and H_0 to be 71.3 +/- 1.7 km/s/Mpc, which is competitive with the latest large scale structure constraints from large spectroscopic surveys such as SDSS Data Release 7 (DR7) (Reid et al. 2010, Percival et al. 2010, Montesano et al. 2011) and WiggleZ (Blake et al. 2011). The SDSS-III Data Release 8 (SDSS-III DR8) Angular Clustering Data allows a wide range of investigations into the cosmological model, cosmic expansion (via BAO), Gaussianity of initial conditions and neutrino masses. (abridged)

astro-ph.CO↗

arXiv2012

New Neutrino Mass Bounds from Sloan Digital Sky Survey III Data Release 8 Photometric Luminous Galaxies

We present neutrino mass bounds using 900,000 luminous galaxies with photometric redshifts measured from Sloan Digital Sky Survey III Data Release Eight (SDSS DR8). The galaxies have photometric redshifts between $z = 0.45$ and $z = 0.65$, and cover 10,000 square degrees and thus probe a volume of 3$h^{-3}$Gpc$^3$, enabling tight constraints to be derived on the amount of dark matter in the form of massive neutrinos. A new bound on the sum of neutrino masses $\sum m_ν< 0.26$ eV, at 95% confidence level (CL), is obtained after combining our sample of galaxies, which we call "CMASS", with WMAP 7 year Cosmic Microwave Background (CMB) data and the most recent measurement of the Hubble parameter from the Hubble Space Telescope (HST). This constraint is obtained with a conservative multipole range choice of $30 < \ell < 200$ in order to minimize non-linearities, and a free bias parameter in each of the four redshift bins. We study the impact of assuming this linear galaxy bias model using mock catalogs, and find that this model causes a small ($\sim 1-1.5 σ$) bias in $Ω_{\rm DM} h^2$. For this reason, we also quote neutrino bounds based on a conservative galaxy bias model containing additional, shot noise-like free parameters. In this conservative case, the bounds are significantly weakened, e.g. $\sum m_ν< 0.36$ eV (95% confidence level) for WMAP+HST+CMASS ($\ell_{\rm max}=200$). We also study the dependence of the neutrino bound on multipole range ($\ell_{\rm max}=150$ vs $\ell_{\rm max}=200$) and on which combination of data sets is included as a prior. The addition of supernova and/or Baryon Acoustic Oscillation data does not significantly improve the neutrino mass bound once the HST prior is included. [abridged]

astro-ph.CO↗

arXiv2011

Constraints on massive sterile neutrino species from current and future cosmological data

Sterile massive neutrinos are a natural extension of the Standard Model of elementary particles. The energy density of the extra sterile massive states affects cosmological measurements in an analogous way to that of active neutrino species. We perform here an analysis of current cosmological data and derive bounds on the masses of the active and the sterile neutrino states as well as on the number of sterile states. The so-called (3+2) models with three sub-eV active massive neutrinos plus two sub-eV massive sterile species is well within the 95% CL allowed regions when considering cosmological data only. If the two extra sterile states have thermal abundances at decoupling, Big Bang Nucleosynthesis bounds compromise the viability of (3+2) models. Forecasts from future cosmological data on the active and sterile neutrino parameters are also presented. Independent measurements of the neutrino mass from tritium beta decay experiments and of the Hubble constant could shed light on sub-eV massive sterile neutrino scenarios.

astro-ph.CO↗

arXiv2011

Constraints on massive sterile plus active neutrino species in non minimal cosmologies

Cosmological measurements are affected by the energy density of both active and sterile massive neutrinos. We extend here a recent analysis of current cosmological data to non minimal cosmologies. Several possible scenarios are examined: a constant w \neq -1 dark energy equation of state, a non flat universe, a time varying dark energy component and coupled dark matter dark energy universes or modified gravity scenarios. When considering cosmological data only, (3+2) massive neutrino models with ~0.5 eV sterile species are allowed at 95% CL. This scenario has been shown to reconcile reactor, LSND and MiniBooNE positive signals with null results from other searches. Big Bang Nucleosynthesis bounds could compromise the viability of (3+2) models if the two sterile species are fully thermalized states at decoupling.

astro-ph.CO↗

arXiv2011

Determining the dark matter mass with DeepCore

Cosmological and astrophysical observations provide increasing evidence of the existence of dark matter in our Universe. Dark matter particles with a mass above a few GeV can be captured by the Sun, accumulate in the core, annihilate, and produce high energy neutrinos either directly or by subsequent decays of Standard Model particles. We investigate the prospects for indirect dark matter detection in the IceCube/DeepCore neutrino telescope and its capabilities to determine the dark matter mass.

hep-ph↗

arXiv2011

Future constraints on the Hu-Sawicki modified gravity scenario

We present current and future constraints on the Hu and Sawicki modified gravity scenario. This model can reproduce a late time accelerated universe and evade solar system constraints. While current cosmological data still allows for distinctive deviations from the cosmological constant picture, future measurements of the growth of structure combined with Supernova Ia luminosity distance data will greatly improve present constraints.

astro-ph.CO↗

arXiv2011

Future weak lensing constraints in a dark coupled universe

Coupled cosmologies can predict values for the cosmological parameters at low redshifts which may differ substantially from the parameters values within non-interacting cosmologies. Therefore, low redshift probes, as the growth of structure and the dark matter distribution via galaxy and weak lensing surveys constitute a unique tool to constrain interacting dark sector models. We focus here on weak lensing forecasts from future Euclid and LSST-like surveys combined with the ongoing Planck cosmic microwave background experiment. We find that these future data could constrain the dimensionless coupling to be smaller than a few $\times 10^{-2}$. The coupling parameter $ξ$ is strongly degenerate with the cold dark matter energy density $Ω_{c}h^2$ and the Hubble constant $H_0$.These degeneracies may cause important biases in the cosmological parameter values if in the universe there exists an interaction among the dark matter and dark energy sectors.

astro-ph.CO↗

arXiv2011

Signatures of photon and axion-like particle mixing in the gamma-ray burst jet

Photons couple to Axion-Like Particles (ALPs) or more generally to any pseudo Nambu-Goldstone boson in the presence of an external electromagnetic field. Mixing between photons and ALPs in the strong magnetic field of a Gamma-Ray Burst (GRB) jet during the prompt emission phase can leave observable imprints on the gamma-ray polarization and spectrum. Mixing in the intergalactic medium is not expected to modify these signatures for ALP mass > 10^(-14) eV and/or for < nG magnetic field. We show that the depletion of photons due to conversion to ALPs changes the linear degree of polarization from the values predicted by the synchrotron model of gamma ray emission. We also show that when the magnetic field orientation in the propagation region is perpendicular to the field orientation in the production region, the observed synchrotron spectrum becomes steeper than the theoretical prediction and as detected in a sizable fraction of GRB sample. Detection of the correlated polarization and spectral signatures from these steep-spectrum GRBs by gamma-ray polarimeters can be a very powerful probe to discover ALPs. Measurement of gamma-ray polarization from GRBs in general, with high statistics, can also be useful to search for ALPs.

astro-ph.HE↗

arXiv2010

Robust Neutrino Constraints by Combining Low Redshift Observations with the CMB

We illustrate how recently improved low-redshift cosmological measurements can tighten constraints on neutrino properties. In particular we examine the impact of the assumed cosmological model on the constraints. We first consider the new HST H0 = 74.2 +/- 3.6 measurement by Riess et al. (2009) and the sigma8*(Omegam/0.25)^0.41 = 0.832 +/- 0.033 constraint from Rozo et al. (2009) derived from the SDSS maxBCG Cluster Catalog. In a Lambda CDM model and when combined with WMAP5 constraints, these low-redshift measurements constrain sum mnu<0.4 eV at the 95% confidence level. This bound does not relax when allowing for the running of the spectral index or for primordial tensor perturbations. When adding also Supernovae and BAO constraints, we obtain a 95% upper limit of sum mnu<0.3 eV. We test the sensitivity of the neutrino mass constraint to the assumed expansion history by both allowing a dark energy equation of state parameter w to vary, and by studying a model with coupling between dark energy and dark matter, which allows for variation in w, Omegak, and dark coupling strength xi. When combining CMB, H0, and the SDSS LRG halo power spectrum from Reid et al. 2009, we find that in this very general model, sum mnu < 0.51 eV with 95% confidence. If we allow the number of relativistic species Nrel to vary in a Lambda CDM model with sum mnu = 0, we find Nrel = 3.76^{+0.63}_{-0.68} (^{+1.38}_{-1.21}) for the 68% and 95% confidence intervals. We also report prior-independent constraints, which are in excellent agreement with the Bayesian constraints.

astro-ph.CO↗

arXiv2010

Coupled dark matter-dark energy in light of near Universe observations

Cosmological analysis based on currently available observations are unable to rule out a sizeable coupling among the dark energy and dark matter fluids. We explore a variety of coupled dark matter-dark energy models, which satisfy cosmic microwave background constraints, in light of low redshift and near universe observations. We illustrate the phenomenology of different classes of dark coupling models, paying particular attention in distinguishing between effects that appear only on the expansion history and those that appear in the growth of structure. We find that while a broad class of dark coupling models are effectively models where general relativity (GR) is modified --and thus can be probed by a combination of tests for the expansion history and the growth of structure--, there is a class of dark coupling models where gravity is still GR, but the growth of perturbations is, in principle modified. While this effect is small in the specific models we have considered, one should bear in mind that an inconsistency between reconstructed expansion history and growth may not uniquely indicate deviations from GR. Our low redshift constraints arise from cosmic velocities, redshift space distortions and dark matter abundance in galaxy voids. We find that current data constrain the dimensionless coupling to be |xi|<0.2, but prospects from forthcoming data are for a significant improvement. Future, precise measurements of the Hubble constant, combined with high-precision constraints on the growth of structure, could provide the key to rule out dark coupling models which survive other tests. We shall exploit as well weak equivalence principle violation arguments, which have the potential to highly disfavour a broad family of coupled models.

astro-ph.CO↗

arXiv2010

High Energy Neutrinos from Novae in Symbiotic Binaries: The Case of V407 Cygni

Detection of high-energy (~> 100 MeV) gamma rays by the Fermi Large Area Telescope (LAT) from a nova in the symbiotic binary system V407 Cygni has opened possibility of high-energy neutrino detection from this type of sources. Thermonuclear explosion on the white dwarf surface sets off a nova shell in motion that expands and slows down in a dense surrounding medium provided by the red giant companion. Particles are accelerated in the shocks of the shell, and interact with surrounding medium to produce observed gamma rays. We show that proton-proton interaction, which is most likely responsible for producing gamma rays via neutral pion decay, produces ~> 0.1 GeV neutrinos that can be detected by the current and future experiments at ~> 10 GeV.

astro-ph.HE↗

arXiv2010

Atmospheric neutrinos in ice and measurement of neutrino oscillation parameters

The main goal of the IceCube Deep Core Array is to search for neutrinos of astrophysical origins. Atmospheric neutrinos are commonly considered as a background for these searches. We show that the very high statistics atmospheric neutrino data can be used to obtain precise measurements of the main oscillation parameters.

hep-ph↗

arXiv2010

Impact of general reionization scenarios on extraction of inflationary parameters

Determination of whether the Harrison--Zel'dovich spectrum for primordial scalar perturbations is consistent with observations is sensitive to assumptions about the reionization scenario. In light of this result, we revisit constraints on inflationary models using more general reionization scenarios. While the bounds on the tensor-to-scalar ratio are largely unmodified, when different reionization schemes are addressed, hybrid models are back into the inflationary game. In the general reionization picture, we reconstruct both the shape and amplitude of the inflaton potential. We find a broader spectrum of potential shapes when relaxing the simple reionization restriction. An upper limit of $10^{16}$ GeV to the amplitude of the potential is found, regardless of the assumptions on the reionization history.

astro-ph.CO↗

arXiv2010

Higher-order coupled quintessence

We study a coupled quintessence model in which the interaction with the dark matter sector is a function of the quintessence potential. Such a coupling can arise from a field dependent mass term for the dark matter field. The dynamical analysis of a standard quintessence potential coupled with the interaction explored here shows that the system possesses a late time accelerated attractor. In light of these results, we perform a fit to the most recent Supernovae Ia, Cosmic Microwave Background and Baryon Acoustic Oscillation data sets. Constraints arising from weak equivalence principle violation arguments are also discussed.

astro-ph.CO↗

arXiv2010

Summary report of MINSIS workshop in Madrid

Recent developments on tau detection technologies and the construction of high intensity neutrino beams open the possibility of a high precision search for non-standard μ - τ flavour transition with neutrinos at short distances. The MINSIS - Main Injector Non-Standard Interaction Search- is a proposal under discussion to realize such precision measurement. This document contains the proceedings of the workshop which took place on 10-11 December 2009 in Madrid to discuss both the physics reach as well as the experimental requirements for this proposal.

hep-ph↗

arXiv2010

Cosmological Parameters Degeneracies and Non-Gaussian Halo Bias

We study the impact of the cosmological parameters uncertainties on the measurements of primordial non-Gaussianity through the large-scale non-Gaussian halo bias effect. While this is not expected to be an issue for the standard LCDM model, it may not be the case for more general models that modify the large-scale shape of the power spectrum. We consider the so-called local non-Gaussianity model and forecasts from planned surveys, alone and combined with a Planck CMB prior. In particular, we consider EUCLID- and LSST-like surveys and forecast the correlations among $f_{\rm NL}$ and the running of the spectral index $α_s$, the dark energy equation of state $w$, the effective sound speed of dark energy perturbations $c^2_s$, the total mass of massive neutrinos $M_ν=\sum m_ν$, and the number of extra relativistic degrees of freedom $N_ν^{rel}$. Neglecting CMB information on $f_{\rm NL}$ and scales $k > 0.03 h$/Mpc, we find that, if $N_ν^{\rm rel}$ is assumed to be known, the uncertainty on cosmological parameters increases the error on $f_{\rm NL}$ by 10 to 30% depending on the survey. Thus the $f_{\rm NL}$ constraint is remarkable robust to cosmological model uncertainties. On the other hand, if $N_ν^{\rm rel}$ is simultaneously constrained from the data, the $f_{\rm NL}$ error increases by $\sim 80%$. Finally, future surveys which provide a large sample of galaxies or galaxy clusters over a volume comparable to the Hubble volume can measure primordial non-Gaussianity of the local form with a marginalized 1--$σ$ error of the order $Δf_{\rm NL} \sim 2-5$, after combination with CMB priors for the remaining cosmological parameters. These results are competitive with CMB bispectrum constraints achievable with an ideal CMB experiment.

astro-ph.CO↗