Optimal and fast E/B separation with a dual messenger field [CEA]


We adapt our recently proposed dual messenger algorithm for spin field reconstruction and showcase its efficiency and effectiveness in Wiener filtering polarized cosmic microwave background (CMB) maps. Unlike conventional preconditioned conjugate gradient (PCG) solvers, our preconditioner-free technique can deal with high-resolution joint temperature and polarization maps with inhomogeneous noise distributions and arbitrary mask geometries with relative ease. Various convergence diagnostics illustrate the high quality of the dual messenger reconstruction. In contrast, the PCG implementation fails to converge to a reasonable solution for the specific problem considered. The implementation of the dual messenger method is straightforward and guarantees numerical stability and convergence. We show how the algorithm can be modified to generate fluctuation maps, which, combined with the Wiener filter solution, yield unbiased constrained signal realizations, consistent with observed data. This algorithm presents a pathway to exact global analyses of high-resolution and high-sensitivity CMB data for a statistically optimal separation of E and B modes. It is therefore relevant for current and next-generation CMB experiments, in the quest for the elusive primordial B-mode signal.

Read this paper on arXiv…

D. Ramanah, G. Lavaux and B. Wandelt
Wed, 17 Jan 18

Comments: 11 pages, 5 figures, 1 table. Submitted to MNRAS

Cosmological inference from standard sirens without redshift measurements [CEA]


The purpose of this work is to investigate the prospects of using the future standard siren data without redshift measurements to constrain cosmological parameters. With successful detections of gravitational wave (GW) signals an era of GW astronomy has begun. Unlike the electromagnetic domain, GW signals allow direct measurements of luminosity distances to the sources, while their redshifts remain to be measured by identifying electromagnetic counterparts. This leads to significant technical problems for almost all possible BH-BH systems. It is the major obstacle to cosmological applications of GW standard sirens. In this paper, we introduce the general framework of using luminosity distances alone for cosmological inference. The idea is to use the prior knowledge of the redshift probability distribution for coalescing sources from the intrinsic merger rates assessed with population synthesis codes. Then the posterior probability distributions for cosmological parameters can be calculated. We demonstrate the performance of our method on the simulated mock data and show that $5\%$ uncertainty of the luminosity distance measurement would enable an accurate determination of cosmological parameters. At least $10\%$ uncertainty of $D_L$ is required to derive unbiased parameters fits. We also find that in order to get $1\%$ accuracy in $H_0$ we need about $10^5$ events with $D_L$ measured at $10\%$ uncertainty level.

Read this paper on arXiv…

X. Ding, M. Biesiada, X. Zheng, et. al.
Wed, 17 Jan 18

Comments: 12 pages, 3 figures, 1 table. To be submitted to JCAP

Optical identifications of high-redshift galaxy clusters from Planck Sunyaev-Zeldovich survey [CEA]


We present the results of optical identifications and spectroscopic redshifts measurements for galaxy clusters from 2-nd Planck catalogue of Sunyaev-Zeldovich sources (PSZ2), located at high redshifts, $z\approx0.7-0.9$. We used the data of optical observations obtained with Russian-Turkish 1.5-m telescope (RTT150), Sayan observatory 1.6-m telescope, Calar Alto 3.5-m telescope and 6-m SAO RAS telescope (Bolshoi Teleskop Alt-azimutalnyi, BTA). Spectroscopic redshift measurements were obtained for seven galaxy clusters, including one cluster, PSZ2 G126.57+51.61, from the cosmological sample of PSZ2 catalogue. In central regions of two clusters, PSZ2 G069.39+68.05 and PSZ2 G087.39-34.58, the strong gravitationally lensed background galaxies are found, one of them at redshift $z=4.262$. The data presented below roughly double the number of known galaxy clusters in the second Planck catalogue of Sunyaev-Zeldovich sources at high redshifts, $z\approx0.8$.

Read this paper on arXiv…

R. Burenin, I. Bikmaev, I. Khamitov, et. al.
Tue, 16 Jan 18

Comments: 12 pages, 9 figures. Accepted for publication in Astronomy Letters

Primordial deuterium abundance at z=2.504 towards Q1009+2956 [CEA]


The z_abs = 2.504 Lyman Limit absorption system (LLS) towards Q1009+2956 has previously been used to estimate the primordial deuterium abundance. Since the initial measurement by Burles & Tytler, this quasar has been observed extensively with the Keck telescope, providing a substantial increase in signal-to-noise (from 60 to 147 at continuum level of Ly-alpha at z_abs=2.504). We explore a set of different models for the absorption system and find that the deuterium feature is contaminated by Ly-alpha absorption from a low column density H I cloud. This significantly limits precision to which one can estimate the D/H ratio in this LLS. Our final result for this system D/H =2.48^{+0.41}_{-0.35}*10^{-5} has the same relative uncertainty of 17% as the previous estimate by Burles & Tytler despite the far higher signal-to-noise of our dataset. A weighted mean of 13 D/H measurements available in the literature (including our result) gives the primordial deuterium abundance of (D/H)_p = (2.545 +/- 0.025)*10^{-5} and the corresponding baryon density of the Universe of Omega_b h^2 = 0.02174 +/- 0.00025 marginally inconsistent with the 2015 Planck CMB data.

Read this paper on arXiv…

E. Zavarygin, J. Webb, S. Riemer-Sorensen, et. al.
Tue, 16 Jan 18

Comments: 7 pages, 3 figures, conference proceedings from PhysicA.SPb 2017

Observational bounds on extended theories of gravity from energy conditions [CEA]


The attempt to describe the recent accelerated expansion of the universe includes different propositions for dark energy models and modified gravity theories. Establish their features in order to discriminate and even rule out part of these models using observational data is a fundamental issue of cosmology. In the present work we consider a class of extended theories of gravity (ETGs) that are minimally coupled to the ordinary matter fields. In this context, and assuming a homogeneous and isotropic spacetime, we derive the energy conditions for this ETG class, which provide bounds for the ETG modifications. We then put constraints on these bounds using a model-independent approach to reconstruct the deceleration function along with the Joint Light-curve Analysis (JLA) supernova sample, 11 baryon acoustic oscillation and 22 cosmic-chronometer measurements. We also obtain an additional bound imposing the strong energy condition only on the ordinary matter. The main result of this work is a set of bounds that every considered ETG must fulfill given the aforementioned assumptions. We apply these bounds to verify the fulfillment/violation of the energy conditions in the context of general relativity. For instance, the strong energy condition is violated, corresponding to an accelerated expansion, with more than $5.22\sigma$ confidence interval considering the whole reconstruction interval. Finally, we show how these bounds can restrict the dynamics of the ETGs by imposing general assumptions on the ETG effective energy density. In this case, there is a preference for a phantom like behavior depending on how this quantity evolves.

Read this paper on arXiv…

M. Penna-Lima, S. Vitenti, M. Alves, et. al.
Tue, 16 Jan 18

Comments: 13 pages, 5 figures

Cosmic web dependence of galaxy clustering and quenching in SDSS [CEA]


Galaxies exhibit different clustering and quenching properties in clusters, filaments, and the field, but it is still uncertain whether such differences are imprints of the tidal environment on galaxy formation, or if they reflect the variation of the underlying halo mass function across the cosmic web. We measure the dependence of galaxy clustering and quenching on the cosmic web in the Sloan Digital Sky Survey, characterized by the combination of spherical overdensity $\delta_8$ and tidal anisotropy $\alpha_5$ centred on each galaxy. We find that the galaxy clustering is a non-monotonic function of either $\delta_8$ or $\alpha_5$, and the large-scale galaxy bias shows complex and rich behaviour on the $\delta_8$ vs. $\alpha_5$ plane. Using the mean galaxy colour as a proxy for the average quenched level of galaxies, we find that galaxy quenching is primarily a function of $\delta_8$, with some subtle yet non-trivial dependence on $\alpha_5$ at fixed $\delta_8$. The quenched galaxies generally show stronger small-scale clustering than the star-forming ones at fixed $\delta_8$ or $\alpha_5$, while the characteristic scale at which the amplitude of clustering becomes comparable for both galaxy population varies with $\delta_8$ and $\alpha_5$. Remarkably, those observed cosmic web dependences of galaxy clustering and quenching can be well reproduced by a mock galaxy catalogue constructed from the iHOD model, which places quenched and star-forming galaxies inside dark matter haloes based on the stellar-to-halo mass relation and the halo quenching model — the $\delta_8$ and $\alpha_5$ dependences of iHOD galaxies are solely derived from the cosmic web modulation of the halo mass function. The success of the simple iHOD model suggests that any direct effect of the large-scale tidal field on galaxy formation is not currently detectable.[Abridged]

Read this paper on arXiv…

S. Alam, Y. Zu, J. Peacock, et. al.
Tue, 16 Jan 18

Comments: 15 pages, 8 figures, comments welcome

Cosmic transparency and acceleration [CEA]


In this paper, by considering an absorption probability independent of photon wavelength, we show that current type Ia supernovae (SNe Ia) and gamma ray bursts (GRBs) observations plus high redshift measurements of the cosmic microwave background radiation (CMB) temperature support the cosmic acceleration regardless the transparent universe assumption. Two flat scenarios are considered in our analyses: $\Lambda$CDM model and a kinematic model. We consider $\tau(z)=2\ln(1+z)^{\varepsilon}$, where $\tau(z)$ denote the opacity between an observer at $z=0$ and a source at $z$. This choice is equivalent to deform the cosmic distance duality relation as $D_LD^{-1}A = (1 + z)^{2+\varepsilon}$ and, if the absorption probability is independent of photon wavelength, the CMB temperature evolution law is $T{CMB}(z)=T_0(1+z)^{1+2\varepsilon/3 }$. By marginalizing on the $\varepsilon$ parameter, our analyses rule out a decelerating universe at 99.99 \% c.l. for all scenarios considered. Interestingly, by considering only SNe Ia and GRBs observations, we obtain that a decelerated universe, indicated by $\Omega_{\Lambda} \leq 0.33$ and $q_0 > 0$, is ruled out around 1.5$\sigma$ c.l. and 2$\sigma$ c.l., respectively, regardless the transparent universe assumption.

Read this paper on arXiv…

R. Holanda, S. Pereira and D. Jain
Tue, 16 Jan 18

Comments: 11 pages, 4 figures, I table, accepted for publication in the Physical Review D