Journals
2013 EN
Victoire de Lastours · Érika Ferrari Rafael da Silva · Michel Daudon
+4 more
Atazanavir has been associated with kidney stones and renal failure. We measured urine and plasma concentrations of recent protease inhibitors (PIs) and searched for PI crystals in the urine of asymptomatic patients.
Journals
2013 EN
Robert J. Byrne · Giacomo Bernardi · John C. Avise
The genus Leuresthes displays reproductive behavior unique among marine fish in which mature adults synchronously emerge completely out of the water to spawn on beach land. A limited number of sandy beaches, which are suitable for these spawning events, are present in discontinuous locations along the geographic range of the species, potentially limiting gene flow and the degree of genetic homogeneity between intraspecific populations. Here, we tested for molecular genetic differentiation between 363 individuals, representing 3 populations of California grunion, Leuresthes tenuis, by employing 2 mitochondrial and 4 nuclear DNA markers. We include temporally diverse sampling to evaluate contemporary and temporal divergence, and we also analyze 28 individuals from one population of Gulf grunion (restricted to the Gulf of California), Leuresthes sardina, at the same markers to evaluate the molecular evidence for their separate species distinction. We find no significant differences between temporal samples, but small significant differences among all populations of L. tenuis, and unequivocal support for the separate species distinction of L. sardina. Genetic data suggest that the Monterey Bay population of L. tenuis near the species' most northern range likely represents a relatively recent colonization event from populations along the species' more traditional range south of Point Conception, California. We conclude that both the topographic features of the California and Baja California coastlines and the grunions' unique reproductive behavior have influenced the genetic structure of the populations.
Journals
2013 EN
E. Carretti · S. Brown · L. Staveley-Smith
+6 more
We have detected a radio bridge of unpolarized synchrotron emissionconnecting the NW relic of the galaxy cluster Abell 3667 to its centralregions. We used data at 2.3 GHz from the S-band Polarization All Sky Survey(S-PASS) and at 3.3 GHz from a follow up observation, both conducted with theParkes Radio Telescope. This emission is further aligned with a diffuse X-raytail, and represents the most compelling evidence for an association betweenintracluster medium turbulence and diffuse synchrotron emission. This is thefirst clear detection of a bridge associated both with an outlying clusterrelic and X-ray diffuse emission. All the indicators point toward thesynchrotron bridge being related to the post-shock turbulent wake trailing theshock front generated by a major merger in a massive cluster. Althoughpredicted by simulations, this is the first time such emission is detected withhigh significance and clearly associated with the path of a confirmed shock.Although the origin of the relativistic electrons is still unknown, theturbulent re-acceleration model provides a natural explanation for thelarge-scale emission. The equipartition magnetic field intensity of the bridgeis B_eq = 2.2 +/- 0.3 \mu G. We further detect diffuse emission coincident withthe central regions of the cluster for the first time.
Journals
2013 EN
A. R. Offringa · A. G. de Bruyn · S. Zaroubi
+75 more
Faint undetected sources of radio-frequency interference (RFI) might becomevisible in long radio observations when they are consistently present overtime. Thereby, they might obstruct the detection of the weak astronomicalsignals of interest. This issue is especially important for Epoch ofReionisation (EoR) projects that try to detect the faint redshifted HI signalsfrom the time of the earliest structures in the Universe. We explore the RFIsituation at 30-163 MHz by studying brightness histograms of visibility dataobserved with LOFAR, similar to radio-source-count analyses that are used incosmology. An empirical RFI distribution model is derived that allows thesimulation of RFI in radio observations. The brightness histograms show an RFIdistribution that follows a power-law distribution with an estimated exponentaround -1.5. With several assumptions, this can be explained with a uniformdistribution of terrestrial radio sources whose radiation follows existingpropagation models. Extrapolation of the power law implies that the currentLOFAR EoR observations should be severely RFI limited if the strength of RFIsources remains strong after time integration. This is in contrast with actualobservations, which almost reach the thermal noise and are thought not to belimited by RFI. Therefore, we conclude that it is unlikely that there areundetected RFI sources that will become visible in long observations.Consequently, there is no indication that RFI will prevent an EoR detectionwith LOFAR.
Journals
2013 EN
Hannes Jensen · Kanan K. Datta · Garrelt Mellema
+24 more
One of the most promising ways to study the epoch of reionization (EoR) isthrough radio observations of the redshifted 21-cm line emission from neutralhydrogen. These observations are complicated by the fact that the mapping ofredshifts to line-of-sight positions is distorted by the peculiar velocities ofthe gas. Such distortions can be a source of error if they are not properlyunderstood, but they also encode information about cosmology and astrophysics.We study the effects of redshift space distortions on the power spectrum of21-cm radiation from the EoR using large scale $N$-body and radiative transfersimulations. We quantify the anisotropy introduced in the 21-cm power spectrumby redshift space distortions and show how it evolves as reionizationprogresses and how it relates to the underlying physics. We go on to study theeffects of redshift space distortions on LOFAR observations, taking instrumentnoise and foreground subtraction into account. We find that LOFAR should beable to directly observe the power spectrum anisotropy due to redshift spacedistortions at spatial scales around $k \sim 0.1$ Mpc$^{-1}$ after $\gtrsim$1000 hours of integration time. At larger scales, sample errors become alimiting factor, while at smaller scales detector noise and foregrounds makethe extraction of the signal problematic. Finally, we show how theastrophysical information contained in the evolution of the anisotropy of the21-cm power spectrum can be extracted from LOFAR observations, and how it canbe used to distinguish between different reionization scenarios.
Journals
2013 EN
M. Bernardi · A. Meert · R. K. Sheth
+4 more
In addition to the large systematic differences arising from assumptionsabout the stellar mass-to-light ratio, the massive end of the stellar massfunction is rather sensitive to how one fits the light profiles of the mostluminous galaxies. We quantify this by comparing the luminosity and stellarmass functions based on SDSS cmodel magnitudes, and PyMorph single-Sersic andSersic-Exponential fits to the surface brightness profiles of galaxies in theSDSS. The PyMorph fits return more light, so that the predicted masses arelarger than when cmodel magnitudes are used. As a result, the total stellarmass density at z~0.1 is about 1.2x larger than in our previous analysis of theSDSS. The differences are most pronounced at the massive end, where themeasured number density of objects having M* > 6 x 10^{11} Msun is ~5x larger.Alternatively, at number densities of 10^{-6} Mpc^{-3}, the limiting stellarmass is 2x larger. The differences with respect to fits by other authors,typically based on Petrosian-like magnitudes, are even more dramatic, althoughsome of these differences are due to sky-subtraction problems, and aresometimes masked by large differences in the assumed $M_*/L$ (even afterscaling to the same IMF). Our results impact studies of the growth and assemblyof stellar mass in galaxies, and of the relation between stellar and halo mass,so we provide simple analytic fits to these new luminosity and stellar massfunctions and quantify how they depend on morphology, as well as the binnedcounts in electronic format.
Journals
2013 EN
B. McKinley · F. Briggs · B. M. Gaensler
+50 more
We present new wide-field observations of Centaurus A (Cen A) and thesurrounding region at 118 MHz with the Murchison Widefield Array (MWA) 32-tileprototype, with which we investigate the spectral-index distribution of Cen A'sgiant radio lobes. We compare our images to 1.4 GHz maps of Cen A and computespectral indices using temperature-temperature plots and spectral tomography.We find that the morphologies at 118 MHz and 1.4 GHz match very closely apartfrom an extra peak in the southern lobe at 118 MHz, which provides tentativeevidence for the existence of a southern counterpart to the northern middlelobe of Cen A. Our spatially-averaged spectral indices for both the northernand southern lobes are consistent with previous analyses, however we findsignificant spatial variation of the spectra across the extent of each lobe.Both the spectral-index distribution and the morphology at low radiofrequencies support a scenario of multiple outbursts of activity from thecentral engine. Our results are consistent with inverse-Compton modelling ofradio and gamma-ray data that supports a value for the lobe age of between 10and 80 Myr.
Journals
2013 EN
and X. H. Sun · and B. M. Gaensler · and E. Carretti
+4 more
We present high sensitivity and absolutely calibrated images of diffuse radiopolarisation at a resolution of about 10 arcmin covering the range 10 degr<l<34 degr and |b|<5 degr at 2.3 GHz from the S-band Parkes All Sky Survey andat 4.8 GHz from the Sino-German 6 cm polarisation survey of the Galactic plane.Strong depolarisation near the Galactic plane is seen at 2.3 GHz, whichcorrelates with strong Halpha emission. We ascribe the depolarisation tospatial Faraday rotation measure fluctuations of about 65 rad/m2 on scalessmaller than 6-9 pc. We argue that most (about 90%) of the polarised emissionseen at 4.8 GHz originates from a distance of 3-4 kpc in the Scutum arm andthat the random magnetic field dominates the regular field there. A branchextending from the North Polar Spur towards lower latitudes can be identifiedfrom the polarisation image at 4.8 GHz but only partly from the polarised imageat 2.3 GHz, implying the branch is at a distance larger than 2-3 kpc. We showthat comparison of structure functions of complex polarised intensity withthose of polarised intensity can indicate whether the observed polarisedstructures are intrinsic or caused by Faraday screens. The probabilitydistribution function of gradients from the polarisation images at 2.3 GHzindicates the turbulence in the warm ionised medium is transonic.
Journals
2013 EN
Kyu-Hyun Chae · Mariangela Bernardi · Andrey V. Kravtsov
We assemble a statistical set of global mass models for ~2,000 nearlyspherical SDSS galaxies at a mean redshift of 0.12 based on their aperturevelocity dispersions and newly derived luminosity profiles in conjunction withpublished velocity dispersion profiles and empirical properties and relationsof galaxy and halo parameters. When two-component (i.e. stellar plus dark) massmodels are fitted to the SDSS aperture velocity dispersions, the predictedvelocity dispersion profile (VP) slopes within the effective radius R_eff matchwell the distribution in observed elliptical galaxies. In contrast, thesingle-component models cannot reproduce the VP slope distribution. From anumber of input variations the models exhibit for the radial range 0.1 R_eff =(1.865+/-0.008)+(-4.93+/-0.15)where is the mean slope absolute value of the total mass density and is the mean slope of the velocity dispersion profile, which leads to asuper-isothermal = 2.15+/-0.04 for =-0.058+/-0.008 in observedelliptical galaxies. Furthermore, the successful two-component models appear toimply a typical slope curvature pattern in the total mass profile because forthe observed steep luminosity (stellar mass) profile and the weak lensinginferred halo profile at large radii a total mass profile with monotonicallyvarying slope would require too high DM density in the optical region givingrise to too large aperture velocity dispersion and too shallow VP.
Journals
2013 EN
M. E. Bell · T. Murphy · D. L. Kaplan
+55 more
We present a search for transient and variable radio sources at 154 MHz withthe Murchison Widefield Array 32-tile prototype. Fifty-one images were obtainedthat cover a field of view of 1430 deg^2 centred on Hydra A. The observationswere obtained over three days in 2010 March and three days in 2011 April andMay. The mean cadence of the observations was 26 minutes and there wasadditional temporal information on day and year timescales. We explore thevariability of a sample of 105 low frequency radio sources within the field.Four bright (S > 6 Jy) candidate variable radio sources were identified thatdisplayed low levels of short timescale variability (26 minutes). We concludethat this variability is likely caused by simplifications in the calibrationstrategy or ionospheric effects. On the timescale of one year we find twosources that show significant variability. We attribute this variability toeither refractive scintillation or intrinsic variability. No radio transientswere identified and we place an upper limit on the surface density of sourcesrho 5.5 Jy, and characteristictimescales of both 26 minutes and one year.