On the filamentary environment of galaxies

The correlation between the large-scale distribution of galaxies and their spectroscopic properties at z=1.5 is investigated using the Horizon MareNostrum cosmological run. We have extracted a large sample of 10^5 galaxies from this large hydrodynamical simulation featuring standard galaxy formation physics. Spectral synthesis is applied to these single stellar populations to generate spectra and colours for all galaxies. We use the skeleton as a tracer of the cosmic web and study how our galaxy catalogue depends on the distance to the skeleton. We show that galaxies closer to the skeleton tend to be redder, but that the effect is mostly due to the proximity of large haloes at the nodes of the skeleton, rather than the filaments themselves. This effects translate into a bimodality in the colour distribution of our sample. The origin of this bimodality is investigated and seems to follow from the ram pressure stripping of satellite galaxies within the more massive clusters of the simulation. The virtual catalogues (spectroscopical properties of the MareNostrum galaxies at various redshifts) are available online at http://www.iap.fr/users/pichon/MareNostrum/cataloguesComment: 18 pages, 27 figures, accepted for publication in MNRA

Simulations of Dust in Interacting Galaxies I: Dust Attenuation

A new Monte-Carlo radiative-transfer code, Sunrise, is used in conjunction with hydrodynamic simulations of major galaxy mergers to calculate the effects of dust in such systems. The simulations are in good agreement with observations of dust absorption in starburst galaxies, and the dust has a profound effect on their appearance. The dust attenuation increases with luminosity such that at peak luminosities ~90% of the bolometric luminosity is absorbed by dust. In general, the detailed appearance of the merging event depends on the stage of the merger and the geometry of the encounter. The fraction of bolometric energy absorbed by the dust, however, is a robust quantity that can be predicted from the intrinsic properties bolometric luminosity, baryonic mass, star-formation rate, and metallicity of the system. This paper presents fitting formulae, valid over a wide range of masses and metallicities, from which the absorbed fraction of luminosity (and consequently also the infrared dust luminosity) can be predicted. The attenuation of the luminosity at specific wavelengths can also be predicted, albeit with a larger scatter due to the variation with viewing angle. These formulae for dust attenuation appear to be valid for both isolated and interacting galaxies, are consistent with earlier studies, and would be suitable for inclusion in theoretical models, e.g. semi-analytic models of galaxy formation.Comment: 12 pages, 10 figures, submitted to Ap

Source-lens clustering effects on the skewness of the lensing convergence

The correlation between source galaxies and lensing potentials causes a systematic effect on measurements of cosmic shear statistics, known as the source-lens clustering (SLC) effect. The SLC effect on the skewness of lensing convergence, $S_3$, is examined using a nonlinear semi-analytic approach and is checked against numerical simulations. The semi-analytic calculations have been performed in a wide variety of generic models for the redshift distribution of source galaxies and power-law models for the bias parameter between the galaxy and dark matter distributions. The semi-analytic predictions are tested successfully against numerical simulations. We find the relative amplitude of the SLC effect on $S_3$ to be of the order of five to forty per cent. It depends significantly on the redshift distribution of sources and on the way the bias parameter evolves. We discuss possible measurement strategies to minimize the SLC effects.Comment: 14 pages, 14 figures, accepted for publication in MNRA

Innovative system identification methods for monitoring applications

Monitoring the modal parameters of civil and mechanical system received plenty of interest the last decades. Several approaches have been proposed and successfully applied in civil engineering for structural health monitoring of bridges (mainly based on the monitoring of the resonant frequencies and mode shapes). In applications such as the monitoring of offshore wind turbines and flight flutter testing the monitoring of the damping ratios are essential. For offshore wind turbine monitoring the presence of time-varying harmonic components, close to the modes of interest, can complicate the identification process. The difficulty related to flight flutter testing is that, in general, only short data records are available. The aim of this contribution is to introduce system identification methods and monitoring strategies that result in more reliable decisions and that can cope with complex monitoring applications. Basic concepts of system identification will be recapitulated with attention for monitoring aspects. The proposed monitoring methodology is based on the recently introduced Transmissibility-based Operational Modal Analysis (TOMA) approach

The Clustering of Extragalactic Extremely Red Objects

We have measured the angular and spatial clustering of 671 K5 Extremely Red Objects (EROs) from a 0.98 square degree sub-region of the NOAO Deep Wide-Field Survey (NDWFS). Our study covers nearly 5 times the area and has twice the sample size of any previous ERO clustering study. The wide field of view and BwRIK passbands of the NDWFS allow us to place improved constraints on the clustering of z=1 EROs. We find the angular clustering of EROs is slightly weaker than in previous measurements, and w(1')=0.25+/-0.05 for K<18.40 EROs. We find no significant correlation of ERO spatial clustering with redshift, apparent color or absolute magnitude, although given the uncertainties, such correlations remain plausible. We find the spatial clustering of K5 EROs is well approximated by a power-law, with r_0=9.7+/-1.1 Mpc/h in comoving coordinates. This is comparable to the clustering of 4L* early-type galaxies at z<1, and is consistent with the brightest EROs being the progenitors of the most massive ellipticals. There is evidence of the angular clustering of EROs decreasing with increasing apparent magnitude, when NDWFS measurements of ERO clustering are combined with those from the literature. Unless the redshift distribution of K>20 EROs is very broad, the spatial clustering of EROs decreases from r_0=9.7+/-1.1 Mpc/h for K20 EROs.Comment: Accepted for publication in the ApJ. 29 pages with 10 figures. The NOAO Deep Wide-Field Survey Bootes data release is available online at http://www.noao.edu/noao/noaodeep

Ratio of carbon dioxide veno-arterial difference to oxygen arterial-venous difference is not associated with lactate decrease after fluid bolus in critically ill patients with hyperlactatemia: results from a prospective observational study

Background: High ratio of the carbon dioxide veno-arterial difference to the oxygen arterial-venous difference (PvaCO2/CavO2) is associated with fluid bolus (FB) induced increase in oxygen consumption (VO2). This study investigated whether PvaCO2/CavO2 was associated with decreases in blood-lactate levels FB in critically ill patients with hyperlactatemia. Methods: This prospective observational study examined adult patients in the intensive care unit (ICU) with lactate levels &gt; 1.5&nbsp;mmol/L who received FBs. Blood-lactate levels were measured before and after FB under unchanged metabolic, respiratory, and hemodynamic conditions. The primary outcome was blood-lactate levels after FB. Significant decreases in blood-lactate levels were considered as blood-lactate levels &lt; 1.5&nbsp;mmol/L or a decrease of more than 10% compared to baseline. Results: The study enrolled 40 critically ill patients, and their median concentration of blood lactate was 2.6 [IQR:1.9 − 3.8] mmol/L. There were 27 (68%) patients with PvaCO2/CavO2 ≥ 1.4&nbsp;mmHg/ml, and 10 of them had an increase in oxygen consumption (dVO2) ≥ 15% after FB, while 13 (32%) patients had PvaCO2/CavO2 &lt; 1.4&nbsp;mmHg/ml before FB, and none of them had dVO2 ≥ 15% after FB. FB increased the cardiac index in patients with high and low preinfusion PvaCO2/CavO2 (13.4% [IQR: 8.3 − 20.2] vs. 8.8% [IQR: 2.9 − 17.4], p = 0.34). Baseline PvaCO2/CavO2 was not found to be associated with a decrease in blood lactate after FB (OR: 0.88 [95% CI: 0.39 − 1.98], p = 0.76). A positive correlation was observed between changes in blood lactate and baseline PvaCO2/CavO2 (r = 0.35, p = 0.02). Conclusions: In critically ill patients with hyperlactatemia, PvaCO2/CavO2 before FB cannot be used to predict decreases in blood-lactate levels after FB. Increased PvaCO2/CavO2 is associated with less decrease in blood-lactate levels

IR observations of MS 1054-03: Star Formation and its Evolution in Rich Galaxy Clusters

We study the infrared (IR) properties of galaxies in the cluster MS 1054-03 at z=0.83 by combining MIPS 24 micron data with spectra of more than 400 galaxies and a very deep K-band selected catalog. 19 IR cluster members are selected spectroscopically, and an additional 15 are selected by their photometric redshifts. We derive the IR luminosity function of the cluster and find strong evolution compared to the similar-mass Coma cluster. The best fitting Schechter function gives L*_{IR}=11.49 +0.30/-0.29 L_sun with a fixed faint end slope, about one order of magnitude larger than that in Coma. The rate of evolution of the IR luminosity from Coma to MS 1054-03 is consistent with that found in field galaxies, and it suggests that some internal mechanism, e.g., the consumption of the gas fuel, is responsible for the general decline of the cosmic star formation rate (SFR) in different environments. The mass-normalized integrated SFR within 0.5R_200 in MS 1054-03 also shows evolution compared with other rich clusters at lower redshifts, but the trend is less conclusive if the mass selection effect is considered. A nonnegligible fraction (13%) of cluster members, are forming stars actively and the overdensity of IR galaxies is about 20 compared to the field. It is unlikely that clusters only passively accrete star forming galaxies from the surrounding fields and have their star formation quenched quickly afterward; instead, many cluster galaxies still have large amounts of gas, and their star formation may be enhanced by the interaction with the cluster.Comment: 49 pages, 9 figures, accepted by Ap

Vibration based structural health monitoring of the substructures of five offshore wind turbines

In 2011 a first vibration monitoring system was installed on a single Belgian offshore wind turbine to research the possibility to monitor the structural integrity of the wind turbines substructure using accelerometers. From 2011 to 2017 four more wind turbines have been equipped with a similar setup. A combined total of 15 years of vibration measurements on all five turbines has been collected. In this contribution we will focus how vibration measurements using accelerometers can be used to support operators in decisions on the structural health of their assets. In the first part of this contribution the vibration behavior of a (offshore) wind turbine will be discussed using measurements obtained from the five monitored turbines. It will be shown how wind conditions, such as wind speed and turbulence, have an effect on the vibration levels of the turbine. In addition the interaction between loads and the tower dynamics will be investigated. In the second part the focus will be put on the automated operational modal analysis (OMA) that is applied to the measured accelerations. From this automated OMA a large dataset of resonance frequencies and damping values was obtained. The paper will discuss how results from monitoring the resonance frequencies can be used to detect bottom-erosion (i.e. scour) and potentially can be used to monitor the condition of the rotor