Search

ESPRESSO is the new high-resolution spectrograph of ESO's Very-Large Telescope (VLT). It was designed for ultra-high radial-velocity precision and extreme spectral fidelity with the aim of performing exoplanet research and fundamental astrophysical experiments with unprecedented precision and accuracy. It is able to observe with any of the four Unit Telescopes (UT) of the VLT at a spectral resolving power of 140,000 or 190,000 over the 378.2 to 788.7 nm wavelength range, or with all UTs together, turning the VLT into a 16-m diameter equivalent telescope in terms of collecting area, while still providing a resolving power of 70,000. We provide a general description of the ESPRESSO instrument, report on the actual on-sky performance, and present our Guaranteed-Time Observation (GTO) program with its first results. ESPRESSO was installed on the Paranal Observatory in fall 2017. Commissioning (on-sky testing) was conducted between December 2017 and September 2018. The instrument saw its official start of operations on October 1st, 2018, but improvements to the instrument and re-commissioning runs were conducted until July 2019. The measured overall optical throughput of ESPRESSO at 550 nm and a seeing of 0.65 arcsec exceeds the 10% mark under nominal astro-climatic conditions. We demonstrate a radial-velocity precision of better than 25 cm/s during one night and 50 cm/s over several months. These values being limited by photon noise and stellar jitter show that the performanceis compatible with an instrumental precision of 10 cm/s. No difference has been measured across the UTs neither in throughput nor RV precision. The combination of the large collecting telescope area with the efficiency and the exquisite spectral fidelity of ESPRESSO opens a new parameter space in RV measurements, the study of planetary atmospheres, fundamental constants, stellar characterisation and many other fields., 26 pages, 28 figures

Context. The quasar class of extreme Population A (xA) (also known as super-Eddington accreting massive black holes, SEAMBHs) has been hailed as potential distance indicators for cosmology. Aims. The aim of this paper is to define tight criteria for their proper identification, starting from the main selection criterion RFeII > 1, and to identify potential intruders that do not meet the selection criteria, which nonetheless have been selected as xA because of the coarseness of automatic searches. The inclusion of the spurious xA sources may dramatically increase the dispersion in the Hubble diagram of quasars, which were obtained from virial luminosity estimates. Methods. We studied a sample of 32 low-z quasars that were originally selected from the seventh data release of the Sloan Digital Sky Survey as xA or SEAMBHs, which have been proved to be almost certainly misclassified sources. All of them show moderate to strong Fe II emission and the large majority show strong absorption features in their spectra which are typical of fairly evolved stellar populations. We performed a simultaneous fit of a host galaxy spectrum, active galactic nucleus (AGN) continuum, FeII template, and emission lines to spectra, using the fitting technique based on ULySS, the full spectrum fitting package. We derived the main accretion parameters (i.e., luminosity, black hole mass, and Eddington ratio) and investigate the relation between host galaxy properties and AGN. Results. For sources in our sample with spectral types that correspond to a relatively low Eddington ratio, we find an overall consistency between HβNC, [O III]λλ4959,5007 line shifts, and the mean stellar velocity obtained from the host galaxy fit (within|60| km s-1). Only one source in our sample qualifies as a xA source. Conclusions. The correct classification of spectra that were contaminated by heavy absorption requires careful determination of the host galaxy spectrum. Contamination and misclassification are not usual in the identification of the xAs, nor at low z or at high z. We find a high fraction of host galaxy spectrum; in half of the sample this is even higher than 40%. When absorption lines are prominent, and the fraction of the host galaxy is high, host galaxy spectrum mimics FeII, which may result in a mistaken identification of FeII spectral features. We have identified several stellar absorption lines that, along with the continuum shape, may lead to an overestimate of RFeII, and therefore to the misclassification of sources as xA sources. © ESO 2020., This research is part of the projects 176001 "Astrophysical spectroscopy of extragalactic objects" and 176003 "Gravitation and the large scale structure of the Universe", funded by Ministry of Education, Science and Technological Development of the Republic of Serbia. PM and MDO acknowledge funding from the INAF PRIN-SKA 2017 program 1.05.01.88.04. PM also acknowledges the Programa de Estancias de Investigacion (PREI) No. DGAP/DFA/2192/2018 of UNAM. A.d.O. acknowledges financial support from the Spanish Ministry of Economy and Competitiveness through grant AYA2016-76682-C3-1-P and from the State Agency for Research of the Spanish MCIU through the "Center of Excellence Severo Ochoa" award for the Instituto de Astrofisica de Andalucia (SEV-2017-0709). ML. M. A. acknowledges financial support of National Science Centre, Poland, grant No. 2017/26/A/ST9/00756 (Maestro 9). DD acknowledges support from grants PAPIIT, UNAM 113719, Mexico D.F. 04510, Mexico. AN acknowledges support from grant CONACyT research fellow -Instituto de Astronomia, UNAM, Mexico D.F. 04510, Mexico. We thank to Pu Du for his help and constructive comments. Funding for the SDSS and SDSS-II has been provided by the Alfred P. Sloan Foundation, the Participating Institutions, the National Science Foundation, the U.S. Department of Energy, the National Aeronautics and Space Administration, the Japanese Monbukagakusho, the Max Planck Society, and the Higher Education Funding Council for England. The SDSS Web Site is http://www.sdss.org/.The SDSS is managed by the Astrophysical Research Consortium for the Participating Institutions. The Participating Institutions are the American Museum of Natural History, Astrophysical Institute Potsdam, University of Basel, University of Cambridge, Case Western Reserve University, University of Chicago, Drexel University, Fermilab, the Institute for Advanced Study, the Japan Participation Group, Johns Hopkins University, the Joint Institute for Nuclear Astrophysics, the Kavli Institute for Particle Astrophysics and Cosmology, the Korean Scientist Group, the Chinese Academy of Sciences (LAMOST), Los Alamos National Laboratory, the Max-Planck-Institute for Astronomy (MPIA), the Max-Planck-Institute for Astrophysics (MPA), New Mexico State University, Ohio State University, University of Pittsburgh, University of Portsmouth, Princeton University, the United States Naval Observatory, and the University of Washington.

Joachimi, B., et al., We present the methodology for a joint cosmological analysis of weak gravitational lensing from the fourth data release of the ESO Kilo-Degree Survey (KiDS-1000) and galaxy clustering from the partially overlapping Baryon Oscillation Spectroscopic Survey (BOSS) and the 2-degree Field Lensing Survey (2dFLenS). Cross-correlations between BOSS and 2dFLenS galaxy positions and source galaxy ellipticities have been incorporated into the analysis, necessitating the development of a hybrid model of non-linear scales that blends perturbative and non-perturbative approaches, and an assessment of signal contributions by astrophysical effects. All weak lensing signals were measured consistently via Fourier-space statistics that are insensitive to the survey mask and display low levels of mode mixing. The calibration of photometric redshift distributions and multiplicative gravitational shear bias has been updated, and a more complete tally of residual calibration uncertainties was propagated into the likelihood. A dedicated suite of more than 20 000 mocks was used to assess the performance of covariance models and to quantify the impact of survey geometry and spatial variations of survey depth on signals and their errors. The sampling distributions for the likelihood and the χ2 goodness-of-fit statistic have been validated, with proposed changes for calculating the effective number of degrees of freedom. The prior volume was explicitly mapped, and a more conservative, wide top-hat prior on the key structure growth parameter S8 = σ8 (ωm/0.3)1/2 was introduced. The prevalent custom of reporting S8 weak lensing constraints via point estimates derived from its marginal posterior is highlighted to be easily misinterpreted as yielding systematically low values of S8, and an alternative estimator and associated credible interval are proposed. Known systematic effects pertaining to weak lensing modelling and inference are shown to bias S8 by no more than 0.1 standard deviations, with the caveat that no conclusive validation data exist for models of intrinsic galaxy alignments. Compared to the previous KiDS analyses, S8 constraints are expected to improve by 20% for weak lensing alone and by 29% for the joint analysis.

Cosmological parameter estimation is entering a new era. Large collaborations need to coordinate high-stakes analyses using multiple methods; furthermore such analyses have grown in complexity due to sophisticated models of cosmology and systematic uncertainties. In this paper we argue that modularity is the key to addressing these challenges: calculations should be broken up into interchangeable modular units with inputs and outputs clearly defined. We present a new framework for cosmological parameter estimation, CosmoSIS, designed to connect together, share, and advance development of inference tools across the community. We describe the modules already available in CosmoSIS, including CAMB, Planck, cosmic shear calculations, and a suite of samplers. We illustrate it using demonstration code that you can run out-of-the-box with the installer available at http://bitbucket.org/joezuntz/cosmosis, Comment: Finally got around to updating to refereed version. 31 pages, 8 figures

The spectacular success of Type Ia supernovae (SNe Ia) in SN-cosmology is based on the assumption that their photometric and spectroscopic properties are invariant with redshift. However, this fundamental assumption needs to be tested with observations of high-z SNe Ia. To date, the majority of SNe Ia observed at moderate to large redshifts (0.4 ≤ z ≤ 1.0) are faint, and the resultant analyses are based on observations with modest signal-to-noise ratios that impart a degree of ambiguity in their determined properties. In rare cases, however, the Universe offers a helping hand: To date a few SNe Ia have been observed that have had their luminosities magnified by intervening galaxies and galaxy clusters acting as gravitational lenses. In this paper, we present long-slit spectroscopy of the lensed SN Ia 2016geu, which occurred at a redshift of z = 0.409, and was magnified by a factor of ≈55 by a galaxy located at z = 0.216. We compared our spectra, which were obtained a couple of weeks to a couple of months past peak light, with the spectroscopic properties of well-observed, nearby SNe Ia, finding that SN 2016geu's properties are commensurate with those of SNe Ia in the local Universe. Based primarily on the velocity and strength of the Si II λ6355 absorption feature, we find that SN 2016geu can be classified as a high-velocity, high-velocity-gradient and 'corenormal' SN Ia. The strength of various features (measured though their pseudo-equivalent widths) argue against SN 2016geu being a faint, broad-lined, cool or shallow-silicon SN Ia. We conclude that the spectroscopic properties of SN 2016geu imply that it is a normal SN Ia, and when taking previous results by other authors into consideration, there is very little, if any, evolution in the observational properties of SNe Ia up to z ≈ 0.4.© 2018 The Authors., ZC acknowledges support from the Juan de la Cierva Incorporacion fellowship IJCI-2014-21669. AdUP acknowledges support from funding associated with the Ramon y Cajal fellowship RyC-2012-09975. DAK acknowledges support from the Juan de la Cierva Incorporacion fellowship IJCI-2015-26153. ZC, DAK and AdUP acknowledge support from the Spanish research project AYA 2014-58381-P. CG was funded by the Carlsberg Foundation.

Several processes in the early Universe might lead to the formation of primordial black holes with different masses. These black holes would interact with the cosmic plasma through accretion and emission processes. Such interactions might have affected the dynamics of the Universe and generated a considerable amount of entropy. In this paper, we investigate the effects of the presence of primordial black holes on the evolution of the early Universe. We adopt a two-fluid cosmological model with radiation and a primordial black hole gas. The latter is modelled with different initial mass functions taking into account the available constraints over the initial primordial black hole abundances.We find that certain populations with narrow initial mass functions are capable to produce significant changes in the scalefactor and the entropy., Instituto Argentino de Radioastronomía, Facultad de Ciencias Astronómicas y Geofísicas

We measure the evolution of the velocity dispersion--temperature ($\sigma_{\rm v}$--$T_{\rm X}$) relation up to $z = 1$ using a sample of 38 galaxy clusters drawn from the \textit{XMM} Cluster Survey. This work improves upon previous studies by the use of a homogeneous cluster sample and in terms of the number of high redshift clusters included. We present here new redshift and velocity dispersion measurements for 12 $z > 0.5$ clusters observed with the GMOS instruments on the Gemini telescopes. Using an orthogonal regression method, we find that the slope of the relation is steeper than that expected if clusters were self-similar, and that the evolution of the normalisation is slightly negative, but not significantly different from zero ($\sigma_{\rm v} \propto T^{0.86 \pm 0.14} E(z)^{-0.37 \pm 0.33}$). We verify our results by applying our methods to cosmological hydrodynamical simulations. The lack of evolution seen in our data is consistent with simulations that include both feedback and radiative cooling., Comment: Accepted to MNRAS (3 August 2016); Paper: 15 pages, 12 figures; Appendix A: 1 table; Appendix B: 34 Tables; Appendix C: 2 Figures

We use data from the Disc Emission via a Bias-free Reconnaissance in the Infrared/Submillimetre (DEBRIS) survey, taken at 100 um with the Photoconductor Array Camera and Spectrometer instrument on board the Herschel Space Observatory, to make a cosmic variance independent measurement of the extragalactic number counts. These data consist of 323 small-area mapping observations performed uniformly across the sky, and thus represent a sparse sampling of the astronomical sky with an effective coverage of ~2.5 deg^2. We find our cosmic variance independent analysis to be consistent with previous count measurements made using relatively small area surveys. Furthermore, we find no statistically significant cosmic variance on any scale within the errors of our data. Finally, we interpret these results to estimate the probability of galaxy source confusion in the study of debris discs., Comment: Accepted for publication by MNRAS Letter

This paper presents an estimate for the spectral properties of the stochastic background of gravitational waves emitted by a population of hot, young, rapidly rotating neutron stars throughout the Universe undergoing $f$-mode instabilities, formed through either core-collapse supernova explosions or the merger of binary neutron star systems. Their formation rate, from which the gravitational wave event rate is obtained, is deduced from observation-based determinations of the cosmic star formation rate. The gravitational wave emission occurs during the spin-down phase of the $f$-mode instability. For low magnetized neutron stars and assuming 10\% of supernova events lead to $f$-mode unstable neutron stars, the background from supernova-derived neutron stars peaks at $\Omega_{\text{gw}} \sim 10^{-9}$ for the $l=m=2$ $f$-mode, which should be detectable by cross-correlating a pair of second generation interferometers (e.g. Advanced LIGO/Virgo) with an upper estimate for the signal-to-noise ratio of $\approx$ 9.8. The background from supramassive neutron stars formed from binary mergers peaks at $\Omega_{\text{gw}} \sim 10^{-10}$ and should not be detectable, even with third generation interferometers (e.g. Einstein Telescope).

By means of zoom-in hydrodynamic simulations we quantify the amount of neutral hydrogen (HI) hosted by groups and clusters of galaxies. Our simulations, which are based on an improved formulation of smoothed particle hydrodynamics (SPH), include radiative cooling, star formation, metal enrichment and supernova feedback, and can be split in two different groups, depending on whether feedback from active galactic nuclei (AGN) is turned on or off. Simulations are analyzed to account for HI self-shielding and the presence of molecular hydrogen. We find that the mass in neutral hydrogen of dark matter halos monotonically increases with the halo mass and can be well described by a power-law of the form $M_{\rm HI}(M,z)\propto M^{3/4}$. Our results point out that AGN feedback reduces both the total halo mass and its HI mass, although it is more efficient in removing HI. We conclude that AGN feedback reduces the neutral hydrogen mass of a given halo by $\sim50\%$, with a weak dependence on halo mass and redshift. The spatial distribution of neutral hydrogen within halos is also affected by AGN feedback, whose effect is to decrease the fraction of HI that resides in the halo inner regions. By extrapolating our results to halos not resolved in our simulations we derive astrophysical implications from the measurements of $\Omega_{\rm HI}(z)$: halos with circular velocities larger than $\sim25~{\rm km/s}$ are needed to host HI in order to reproduce observations. We find that only the model with AGN feedback is capable of reproducing the value of $\Omega_{\rm HI}b_{\rm HI}$ derived from available 21cm intensity mapping observations., Comment: 19 pages, 12 figures. Accepted for publication in MNRAS

We cross-match galaxy cluster candidates selected via their Sunyaev–Zel'dovich effect (SZE) signatures in 129.1 deg[superscript 2] of the South Pole Telescope 2500d SPT-SZ survey with optically identified clusters selected from the Dark Energy Survey science verification data. We identify 25 clusters between 0.1 ≲ z ≲ 0.8 in the union of the SPT-SZ and redMaPPer (RM) samples. RM is an optical cluster finding algorithm that also returns a richness estimate for each cluster. We model the richness λ-mass relation with the following function 〈ln λ|M500〉 ∝ Bλln M500 + Cλln E(z) and use SPT-SZ cluster masses and RM richnesses λ to constrain the parameters. We find Bλ=1.14[superscript +0.21][subscript −0.18 and Cλ=0.73[superscript +0.77][subscript −0.75]. The associated scatter in mass at fixed richness is σlnM|λ=0.18[superscript +0.08][subscript −0.05] at a characteristic richness λ = 70. We demonstrate that our model provides an adequate description of the matched sample, showing that the fraction of SPT-SZ-selected clusters with RM counterparts is consistent with expectations and that the fraction of RM-selected clusters with SPT-SZ counterparts is in mild tension with expectation. We model the optical-SZE cluster positional offset distribution with the sum of two Gaussians, showing that it is consistent with a dominant, centrally peaked population and a subdominant population characterized by larger offsets. We also cross-match the RM catalogue with SPT-SZ candidates below the official catalogue threshold significance ξ = 4.5, using the RM catalogue to provide optical confirmation and redshifts for 15 additional clusters with ξ ∈ [4, 4.5]., Kavli Foundation, Gordon and Betty Moore Foundation (Grant GBMF 947)

The large-number hypothesis conjectures that fundamental constants may vary. Accordingly, the spacetime variation of fundamental constants has been an active subject of research for decades. Recently, using data obtained with large telescopes a phenomenological model in which the fine structure constant might vary spatially has been proposed. We test whether this hypothetical spatial variation of {\alpha}, which follows a dipole law, is compatible with the data of distant thermonuclear supernovae. Unlike previous works, in our calculations we consider not only the variation of the luminosity distance when a varying {\alpha} is adopted, but we also take into account the variation of the peak luminosity of Type Ia supernovae resulting from a variation of {\alpha}. This is done using an empirical relation for the peak bolometric magnitude of thermonuclear supernovae that correctly reproduces the results of detailed numerical simulations. We find that there is no significant difference between the several phenomenological models studied here and the standard one, in which {\alpha} does not vary spatially. We conclude that the present set of data of Type Ia supernovae is not able to distinguish the standard model from the dipole models, and thus cannot be used to discard nor to confirm the proposed spatial variation of {\alpha}., Comment: 8 pages, 4 figures. Accepted for publication in Ap&SS

Wilkinson Microwave Anisotropy Probe has provided cosmic microwave background (CMB) maps of the full sky. The raw data are subject toforeground contamination, in particular near to the Galactic plane. Foreground-cleaned maps have been derived, e.g. the internal linearcombination map of Bennett et al., and the reduced foreground TOH map ofTegmark et al. Using S statistics, we examine whether residual foreground contamination is left over in the foreground-cleaned maps. Inparticular, we specify which parts of the foreground-cleaned maps are sufficiently accurate for the circle-in-the-sky signature. We generalizethe S statistic, called D statistic, such that the circle test can dealwith CMB maps in which the contaminated regions of the sky are excludedwith masks.

Next-generation cosmological surveys will probe ever larger volumes of the Universe, including the largest scales, near and beyond the horizon. On these scales, the galaxy power spectrum carries signatures of local primordial non-Gaussianity (PNG) and horizon-scale general relativistic (GR) effects. However, cosmic variance limits the detection of horizon-scale effects. Combining different surveys via the multi-tracer method allows us to reduce the effect down cosmic variance. This method benefits from large bias differences between two tracers of the underlying dark matter distribution, which suggests a multi-wavelength combination of large volume surveys that are planned on a similar timescale. We show that the combination of two contemporaneous surveys, a large neutral hydrogen intensity mapping survey in SKA Phase1 and a Euclid-like photometric survey, will provide unprecedented constraints on PNG as well as detection of the GR effects. We forecast that the error on local PNG will break through the cosmic variance limit on cosmic microwave background surveys and achieve $\sigma(f_{NL})\simeq1.4-0.5$, depending on assumed priors, bias, and sky coverage. GR effects are more robust to changes in the assumed fiducial model, and we forecast that they can be detected with a signal-to-noise of about $14$., Comment: Typos corrected; Accepted for publication by the Astrophysical Journal Letters; 5 pages, 3 figures, 2 tables

We study the shapes of subhalo distributions from four dark-matter-only simulations of Milky Way type haloes. Comparing the shapes derived from the subhalo distributions at high resolution to those of the underlying dark matter fields we find the former to be more triaxial if theanalysis is restricted to massive subhaloes. For three of the four analysed haloes the increased triaxiality of the distributions of massive subhaloes can be explained by a systematic effect caused by the low number of objects. Subhaloes of the fourth halo show indications for anisotropic accretion via their strong triaxial distribution and orbit alignment with respect to the dark matter field. These results are independent of the employed subhalo finder. Comparing the shape of the observed Milky Way satellite distribution to those of high-resolution subhalo samples from simulations, we find an agreement for samples of bright satellites, but significant deviations if faint satellites are included in the analysis. These deviations might result from observational incompleteness., 15 pages, 11 figures, 2 tables. 1 figure removed to reduce paper extension, shorter discussion, accepted for publication in MNRAS

Context. After the so-called cosmic recombination, the expanding universe entered into a period of darkness since most of the matter was in a neutral state. About a billion years later, however, the intergalactic space was once again ionized. The process, known as the cosmic reionization, required the operation of mechanisms that are not well understood. Among other ionizing sources, Population III stars, mini-quasars, and X-ray emitting microquasars have been invoked. Aims. We propose that primordial cosmic rays, accelerated at the termination points of the jets of the first microquasars, may have contributed to the reionization of the intergalactic space as well. Methods. We quantify the ionization power of cosmic rays (electrons and protons) in the primordial intergalactic medium. This power is calculated using extensive particle cascade simulations. Results. We establish that, depending on the fraction of electrons to protons accelerated in the microquasar jets, cosmic rays should have contributed to the reionization of the primordial intergalactic medium as much as X-rays from microquasar accretion disks. If the primordial magnetic field was of the order of 10-17 G, as some models suggest, cosmic rays had an important role in ionizing the neutral material far beyond the birth places of the first stars., Facultad de Ciencias Astronómicas y Geofísicas

The development of Planck has been supported by: ESA; CNES and CNRS/INSU-IN2P3-INP (France); ASI, CNR, and INAF (Italy); NASA and DoE (USA); STFC and UKSA (UK); CSIC, MICINN, JA and RES (Spain); Tekes, AoF and CSC (Finland); DLR and MPG (Germany); CSA (Canada); DTU Space (Denmark); SER/SSO (Switzerland); RCN (Norway); SFI (Ireland); FCT/MCTES (Portugal); and PRACE (EU). A description of the Planck Collaboration and a list of its members, including the technical or scientific activities in which they have been involved, can be found at http://www.sciops.esa.int/index.php?project=planck&page=Planck_Collaboration. We acknowledge the use of resources from the Norewegian national super computing facilities NOTUR. The modal and KSW bispectrum estimator analysis was performed on the COSMOS supercomputer, part of the STFC DiRAC HPC Facility. We further acknowledge the computer resources and technical assistance provided by the Spanish Supercomputing Network nodes at Universidad de Cantabria and Universidad Politecnica de Madrid as well as by the Advanced Computing and e-Science team at IFCA. Some of the results in this paper have been derived using the HEALPix package., The two fundamental assumptions of the standard cosmological model – that the initial fluctuations are statistically isotropic and Gaussian – are rigorously tested using maps of the cosmic microwave background (CMB) anisotropy from the Planck satellite. The detailed results are based on studies of four independent estimates of the CMB that are compared to simulations using a fiducial ΛCDM model and incorporating essential aspects of the Planck measurement process. Deviations from isotropy have been found and demonstrated to be robust against component separation algorithm, mask choice, and frequency dependence. Many of these anomalies were previously observed in the WMAP data, and are now confirmed at similar levels of significance (about 3σ). However, we find little evidence of non-Gaussianity, with the exception of a few statistical signatures that seem to be associated with specific anomalies. In particular, we find that the quadrupole-octopole alignment is also connected to a low observed variance in the CMB signal. A power asymmetry is now found to persist on scales corresponding to about ‘ = 600 and can be described in the low-‘ regime by a phenomenological dipole modulation model. However, any primordial power asymmetry is strongly scale-dependent and does not extend to arbitrarily small angular scales. Finally, it is plausible that some of these features may be reflected in the angular power spectrum of the data, which shows a deficit of power on similar scales. Indeed, when the power spectra of two hemispheres defined by a preferred direction are considered separately, one shows evidence of a deficit in power, while its opposite contains oscillations between odd and even modes that may be related to the parity violation and phase correlations also detected in the data. Although these analyses represent a step forward in building an understanding of the anomalies, a satisfactory explanation based on physically motivated models is still lacking., European Space Agency, Centre National D'etudes Spatiales, CNRS/INSU-IN2P3-INP (France), Italian Space Agency (ASI), Italian National Research Council, Istituto Nazionale Astrofisica (INAF), National Aeronautics & Space Administration (NASA), United States Department of Energy (DOE), UKSA (UK), Consejo Superior de Investigaciones Cientificas (CSIC), Spanish Government, JA (Spain), RES (Spain), Finnish Funding Agency for Technology & Innovation (TEKES), AoF (Finland), CSC (Finland), Helmholtz Association, German Aerospace Centre (DLR), Max Planck Society, CSA (Canada), DTU Space (Denmark), SER/SSO (Switzerland), RCN (Norway), Science Foundation Ireland, Portuguese Foundation for Science and Technology, European Union (EU), Science & Technology Facilities Council (STFC) ST/G003874/1 ST/H008586/1 ST/K003674/1 ST/L001314/1 ST/M007685/1 ST/I005765/1 ST/K000985/1 ST/K002899/1 ST/K001051/1 ST/J000388/1 ST/I002006/1 ST/J005673/1 ST/H001239/1 ST/J001368/1 ST/K004131/1 ST/K00333X/1 ST/L000768/1 ST/K002805/1 ST/K000977/1 ST/J004812/1

We present a new photometric identification technique for SN 1991bg-like type Ia supernovae (SNe Ia), i.e. objects with light-curve characteristics such as later primary maxima and absence of secondary peak in redder filters. This method is capable of selecting out this sub-group from the normal type Ia population. Furthermore, we find that recently identified peculiar sub-types such as SNe Iax and super-Chandrasekhar SNe Ia have similar photometric characteristics as 91bg-like SNe Ia, namely the absence of secondary maxima and shoulders at longer wavelengths, and can also be classified with our technique. The similarity of these different SN Ia sub-groups perhaps suggests common physical conditions. This typing methodology permits the photometric identification of peculiar SNe Ia in large up-coming wide field surveys either to study them further or to obtain a pure sample of normal SNe Ia for cosmological studies., Comment: 28 pages, 12 figures, 4 tables

J. Delabrouille et al., We present the Planck Sky Model (PSM), a parametric model for generating all-sky, few arcminute resolution maps of sky emission at submillimetre to centimetre wavelengths, in both intensity and polarisation. Several options are implemented to model the cosmic microwave background, Galactic diffuse emission (synchrotron, free-free, thermal and spinning dust, CO lines), Galactic H ii regions, extragalactic radio sources, dusty galaxies, and thermal and kinetic Sunyaev-Zeldovich signals from clusters of galaxies. Each component is simulated by means of educated interpolations/extrapolations of data sets available at the time of the launch of the Planck mission, complemented by state-of-the-art models of the emission. Distinctive features of the simulations are spatially varying spectral properties of synchrotron and dust; different spectral parameters for each point source; modelling of the clustering properties of extragalactic sources and of the power spectrum of fluctuations in the cosmic infrared background. The PSM enables the production of random realisations of the sky emission, constrained to match observational data within their uncertainties. It is implemented in a software package that is regularly updated with incoming information from observations. The model is expected to serve as a useful tool for optimising planned microwave and sub-millimetre surveys and testing data processing and analysis pipelines. It is, in particular, used to develop and validate data analysis pipelines within the Planck collaboration. A version of the software that can be used for simulating the observations for a variety of experiments is made available on a dedicated website. © 2013 ESO., SB has been supported by a postdoctoral grant from the “Physique des deux Infinis” (P2I) Consortium. CD acknowledges an STFC Advanced Fellowship and an ERC IRG grant under the FP7.

We investigate the environment dependence of dark matter halos in the symmetron modified gravity scenario. The symmetron is one of three known mechanisms for screening a fifth-force and thereby recovering General Relativity in dense environments. The effectiveness of the screening depends on both the mass of the object and the environment it lies in. Using high-resolution N-body simulations we find a significant difference, which depends on the halos mass and environment, between the lensing and dynamical masses of dark matter halos similar to the f(R) modified gravity. The symmetron can however yield stronger signatures due to a freedom in the strength of the coupling to matter., 10 pages, 5 figures

The AzTEC 1.1 mm survey of the SCUBA HAlf Degree Extragalactic Survey (SHADES) fields is the largest (0.7 deg2) blank-field millimetre-wavelength survey undertaken to date at a resolution of ~18" and a depth of ~1 mJy. We have used the deep optical-to-radio multi-wavelength data in the SHADES Lockman Hole East and SXDF/UDS fields to obtain galaxy identifications for ~64% (~80% with tentative identifications) of the 148 AzTEC-SHADES 1.1 mm sources, exploiting deep radio and 24 um data complemented by methods based on 8 um flux-density and red optical-infrared (i-K) colour. This unusually high identification rate can be attributed to the relatively bright millimetre-wavelength flux-density threshold, combined with the relatively deep supporting multi-frequency data. We have further exploited the optical-mid-infrared-radio data to derive a ~60% (~75% with tentative identifications) complete redshift distribution for the AzTEC-SHADES sources, yielding a median redshift of z~2.2, with a high-redshift tail extending to at least z~4. Despite the larger area probed by the AzTEC survey relative to the original SCUBA SHADES imaging, the redshift distribution of the AzTEC sources is consistent with that displayed by the SCUBA sources, and reinforces tentative evidence that the redshift distribution of mm/sub-mm sources in the Lockman Hole field is significantly different from that found in the SXDF/UDS field. Comparison with simulated surveys of similar scale extracted from semi-analytic models based on the Millennium simulation indicates that this is as expected if the mm/sub-mm sources are massive (M>10^11 Mo) star-forming galaxies tracing large-scale structures over scales of 10-20 Mpc. This confirms the importance of surveys covering several square degrees (as now underway with SCUBA2) to obtain representative samples of bright (sub)mm-selected galaxies., Accepted to MNRAS. 15 pages (+38 as appendix), 10 figures, 7 tables. Machine-readable versions of tables B1-B4 are available as 'Ancillary files' and from the source file. V2: added the ID success rate separately for each method; added a discussion on the distribution of the ID separation; added the category flag and the 'best ID' flag in the machine readable files; some minor changes

This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©: 2011 RAS © 2011 The AuthorsPublished by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved, We have studied the mass assembly and star formation histories of massive galaxies identified at low redshift in different cosmological hydrodynamical simulations. To this end, we have carried out a detailed follow-up backwards in time of their constituent mass elements (sampled by particles) of different types. After that, the configurations they depict at progressively higher zs were carefully analysed. The analyses show that these histories share common generic patterns, irrespective of particular circumstances. In any case, however, the results we have found are different depending on the particle type. The most outstanding differences follow. We have found that by z∼ 3.5-6, mass elements identified as stellar particles at z= 0 exhibit a gaseous cosmic-web-like morphology with scales of ∼1 physical Mpc, where the densest mass elements have already turned into stars by z∼ 6. These settings are in fact the densest pieces of the cosmic web, where no hot particles show up, and dynamically organized as a hierarchy of flow convergence regions (FCRs), that is, attraction basins for mass flows. At high z FCRs undergo fast contractive deformations with very low angular momentum, shrinking them violently. Indeed, by z∼ 1 most of the gaseous or stellar mass they contain shows up as bound to a massive elliptical-like object at their centres, with typical half-mass radii of rmass star∼ 2-3kpc. After this, a second phase comes about where the mass assembly rate is much slower and characterized by mergers involving angular momentum. On the other hand, mass elements identified at the diffuse hot coronae surrounding massive galaxies at z= 0 do not display a clear web-like morphology at any z. Diffuse gas is heated when FCRs go through contractive deformations. Most of this gas remains hot and with low density throughout the evolution. To shed light on the physical foundations of the behaviour revealed by our analyses (i.e. a two-phase formation process with different implications for diffuse or shocked mass elements), as well as on their possible observational implications, these patterns have been confronted with some generic properties of singular flows as described by the adhesion model (i.e. potential character of the velocity field, singular versus regular points, dressing, locality when a spectrum of perturbations is implemented). We have found that the common patterns the simulations show can be interpreted as a natural consequence of flow properties that, moreover, could explain different generic observational results from massive galaxies or their samples. We briefly discuss some of them, This work was partially supported by the DGES (Spain) through the grants AYA2009-12792-C03-02 and AYA2009-12792- C03-03 from the PNAyA, as well as by the regional Madrid V PRICIT programme through the ASTROMADRID network (CAM S2009/ESP-1496)

Scalar fields, strongly coupled to matter, can be present in nature and still be invisible to local experiments if they are subject to a screening mechanism. The symmetron is one such mechanism which relies on restoration of a spontaneously broken symmetry in regions of high density to shield the scalar fifth force. We have investigated structure formation in the symmetron model by using N-body simulations and find strong observable signatures in both the linear and nonlinear matter power spectrum and on the halo mass function. The mechanism for suppressing the scalar fifth force in high density regions is also found to work very well., Comment: 18 pages, 15 figures

This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society © 2011 RAS © 2011 The authors Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved, We present a detailed comparison of fundamental dark matter halo properties retrieved by a substantial number of different halo finders. These codes span a wide range of techniques including friends-of-friends, spherical-overdensity and phase-space-based algorithms. We further introduce a robust (and publicly available) suite of test scenarios that allow halo finder developers to compare the performance of their codes against those presented here. This set includes mock haloes containing various levels and distributions of substructure at a range of resolutions as well as a cosmological simulation of the large-scale structure of the universe. All the halo-finding codes tested could successfully recover the spatial location of our mock haloes. They further returned lists of particles (potentially) belonging to the object that led to coinciding values for the maximum of the circular velocity profile and the radius where it is reached. All the finders based in configuration space struggled to recover substructure that was located close to the centre of the host halo, and the radial dependence of the mass recovered varies from finder to finder. Those finders based in phase space could resolve central substructure although they found difficulties in accurately recovering its properties. Through a resolution study we found that most of the finders could not reliably recover substructure containing fewer than 30-40 particles. However, also here the phase-space finders excelled by resolving substructure down to 10-20 particles. By comparing the halo finders using a high-resolution cosmological volume, we found that they agree remarkably well on fundamental properties of astrophysical significance (e.g. mass, position, velocity and peak of the rotation curve). We further suggest to utilize the peak of the rotation curve, vmax, as a proxy for mass, given the arbitrariness in defining a proper halo edge, We are greatly indebted to the ASTROSIM network of the European Science Foundation (Science Meeting 2910) for financially supporting the workshop ‘Haloes going MAD’ held in Miraflores de la Sierra near Madrid in 2010 May where all of this work was initiated.AK is supported by the Spanish Ministerio de Ciencia e Innovación (MICINN) in Spain through the Ramón y Cajal programme as well as the grants AYA 2009-13875-C03-02, AYA2009- 12792-C03-03, CSD2009-00064 and CAM S2009/ESP-1496. SRK acknowledges the support by the MICINN under the Consolider-Ingenio, SyeC project CSD-2007-00050. SP and VQ have also been supported by the MICINN (grants AYA2010-21322-C03-01 and CONSOLIDER2007-00050) and the Generalitat Valenciana (grant PROMETEO-2009-103). MZ is supported by NSF grant AST-0708087. GY acknowledges financial support from MICINN (Spain) under project AYA 2009-13875-C03-02 and the ASTROMADRID project S2009/ESP-1496 financed by Comunidad de Madrid

We have studied the Bekenstein-Sandvik-Barrow-Magueijo (BSBM) model for the spatial and temporal variations of the fine structure constant, alpha, with the aid of full N-body simulations which explicitly and self-consistently solve for the scalar field driving the alpha-evolution. We focus on the scalar field (or equivalently alpha) inside the dark matter halos and find that the profile of the scalar field is essentially independent of the BSBM model parameter. This means that given the density profile of an isolated halo and the background value of the scalar field, we can accurately determine the scalar field perturbation in that halo. We also derive an analytic expression for the scalar-field perturbation using the Navarro-Frenk-White halo profile, and show that it agrees well with numerical results, at least for isolated halos; for non-isolated halos this prediction differs from numerical result by a (nearly) constant offset which depends on the environment of the halo., 11 pages, 6 figures

We present the first results from the largest deep extragalactic millimetre-wavelength survey undertaken to date. These results are derived from maps covering over 0.7 deg^2, made at 1.1mm, using the AzTEC continuum camera mounted on the James Clerk Maxwell Telescope. The maps were made in the two fields originally targeted at 0.85mm with SCUBA in the SHADES project, namely the Lockman Hole East (mapped to a depth of 0.9-1.3 mJy rms) and the Subaru XMM Deep Field (1.0-1.7 mJy rms). The wealth of existing and forthcoming deep multi-frequency data in these two fields will allow the bright mm source population revealed by these images to be explored in detail in subsequent papers. Here we present the maps themselves, a catalogue of 114 high-significance sub-millimetre galaxy detections, and a thorough statistical analysis leading to the most robust determination to date of the 1.1mm source number counts. Through careful comparison, we find that both the COSMOS and GOODS North fields, also imaged with AzTEC, contain an excess of mm sources over the new 1.1mm source-count baseline established here. In particular, our new AzTEC/SHADES results indicate that very luminous high-redshift dust enshrouded starbursts (S_{1.1} > 3 mJy) are 25-50% less common than would have been inferred from these smaller surveys, thus highlighting the potential roles of cosmic variance and clustering in such measurements. We compare number count predictions from recent models of the evolving mm/sub-mm source population to these SMG surveys, which provide important constraints for the ongoing refinement of semi-analytic and hydrodynamical models of galaxy formation, and find that all recent models over-predict the number of bright sub-millimetre galaxies found in this survey., 19 pages, 10 figures, 7 tables - Very minor revisions; accepted for publication in MNRAS

Here, we analyze the primordial magnetic field transition between a radiative and a matter-dominated universe. The gravitational structure formation affects its evolution and energy spectrum. The structure excitation can trigger magnetic field amplification and the steepening of its energy density spectrum., 8 pages, 2 figures, accepted for A&A

Nonlinear growth of one-dimensional density structures with a frozen-in magnetic field is investigated in Newtonian cosmology. A mechanism of magnetic field amplification is discussed. We discuss the relation between the initial conditions for the velocity field and the basic time-scales determining the growth of the magnetized structure., Comment: 7 pages, 3 figures included; A&A accepted

We derive the amplification of the cosmological magnetic field associated with forming gravitational structure. The self-similar solutions of magnetohydrodynamic equations are computed both in linear and nonlinear regimes. We find that the relatively fast magnetic field enhancement becomes substantial in the nonlinear phase., Comment: 10 pages, 4 figures included; accepted to A&A

We study the dark energy equation of state as a function of redshift in a non-parametric way, without imposing any {\it a priori} $w(z)$ (ratio of pressure over energy density) functional form. As a check of the method, we test our scheme through the use of synthetic data sets produced from different input cosmological models which have the same relative errors and redshift distribution as the real data. Using the luminosity-time $L_{X}-T_{a}$ correlation for GRB X-ray afterglows (the Dainotti et al. correlation), we are able to utilize GRB sample from the {\it Swift} satellite as probes of the expansion history of the Universe out to $z \approx 10$. Within the assumption of a flat FLRW universe and combining SNeIa data with BAO constraints, the resulting maximum likelihood solutions are close to a constant $w=-1$. If one imposes the restriction of a constant $w$, we obtain $w=-0.99 \pm 0.06$ (consistent with a cosmological constant) with the present day Hubble constant as $H_{0}=70.0 \pm 0.6$ ${\rm km} \, {\rm s}^{-1} {\rm Mpc}^{-1}$ and density parameter as $\Omega_{\Lambda 0}=0.723 \pm 0.025$, while non-parametric $w(z)$ solutions give us a probability map which is centred at $H_{0}=70.04 \pm 1$ ${\rm km} \, {\rm s}^{-1} {\rm Mpc}^{-1}$ and $\Omega_{\Lambda 0}=0.724 \pm 0.03$. Our chosen GRB data sample with full correlation matrix allows us to estimate the amount, as well as quality (errors) of data, needed to constrain $w(z)$ in the redshift range extending an order of magnitude in beyond the farthest SNeIa measured., Comment: 17 pages, 13 figures, accepted for publication in the ApJ

The transition from acoustic noise in the radiation-dominated universe to the density structures in the matter dominated epoch is considered. The initial state is a stochastic field of sound waves moving in different directions. The construction of the initial state is compatible with the hyperbolic type of propagation equation for density perturbations, and parallel to the theory of stochastic background of gravitational waves. Instantaneous transition between the cosmological epochs is assumed, and Darmois-Israel joining conditions are applied to match solutions for sound waves with growing or decaying modes at the decoupling. As a result a substantial amplification of the low scale structures is obtained., Comment: 11 pages, 6 figures, accepted to A&A