The radio-loud fraction of quasars at z > 6 Keller, Pascal M; Thyagarajan, Nithyanandan; Kumar, Ajay ...
Monthly notices of the Royal Astronomical Society,
02/2024, Volume:
528, Issue:
4
Journal Article
Peer reviewed
Open access
ABSTRACT
Quasars at redshifts z > 6 are an excellent probe of the formation and evolution of supermassive black holes in the early Universe. The population of radio-luminous quasars is of particular ...interest, as such quasars could potentially be used to study the neutral intergalactic medium during cosmic reionization via H i 21 cm absorption studies. However, the lack of deep radio observations of z > 6 quasars leaves the population poorly constrained, and suitable candidates for an H i 21 cm absorption study have yet to be found. In this work, we present Jansky Very Large Array (VLA) 1–2 GHz radio continuum observations of 138 quasars at redshifts 6.0 ≤ z < 7.6. We detect the radio continuum emission of the z = 6.1 quasar J1034−1425, with a 1.6 GHz flux density of $170\pm 36\, \mu$Jy. This quasar is radio-quiet with radio-loudness, R ≡ f5 GHz/fν, 4400 Å = 2.4 ± 0.5. In addition, we detect seven other quasars at z > 6, which have previously been characterized in the literature at these frequencies. Using the full sample, we estimate the radio-loud fraction to be $3.8^{+6.2}_{-2.4}\ \hbox{per cent}$, where the uncertainties are 95 per cent confidence intervals. This is lower than recent estimates of the radio-loud fraction in the literature, but is still marginally consistent with no redshift evolution of the radio-loud fraction. We explore the undetected quasar population by stacking their continuum images at their optical positions and obtain a median stacked flux density of 13.8 ± 3.9 µJy and luminosity of log L5 GHz/(W Hz−1) = 24.2 ± 0.1.
ABSTRACT
Gaia provided the largest ever catalogue of white dwarf stars. We use this catalogue, along with the third public data release of the Zwicky Transient Facility (ZTF), to identify new ...eclipsing white dwarf binaries. Our method exploits light-curve statistics and the box least-squares algorithm to detect periodic light-curve variability. The search revealed 18 new binaries, of which 17 are eclipsing. We use the position in the Gaia H-R diagram to classify these binaries and find that the majority of these white dwarfs have MS companions. We identify one system as a candidate eclipsing white dwarf–brown dwarf binary and a further two as extremely low-mass white dwarf binaries. We also provide identification spectroscopy for 17 of our 18 binaries. Running our search method on mock light curves with real ZTF sampling, we estimate our efficiency of detecting objects with light curves similar to the ones of the newly discovered binaries. Many more binaries are to be found in the ZTF footprint as the data releases grow, so our survey is ongoing.
A pan-susceptible
serovar Worthington isolate was detected in the stool of a man returning from Sri Lanka. Under ceftriaxone treatment, a third-generation cephalosporin (3GC)-resistant
Worthington ...was isolated after 8 days. Molecular analyses indicated that the two isolates were identical. However, the latter strain acquired a
-carrying IncFII plasmid probably from a
isolate colonizing the gut. This is the first report of
acquisition of plasmid-mediated resistance to 3GCs in
.
ABSTRACT
Radio interferometers aiming to measure the power spectrum of the redshifted 21 cm line during the Epoch of Reionization (EoR) need to achieve an unprecedented dynamic range to separate the ...weak signal from overwhelming foreground emissions. Calibration inaccuracies can compromise the sensitivity of these measurements to the effect that a detection of the EoR is precluded. An alternative to standard analysis techniques makes use of the closure phase, which allows one to bypass antenna-based direction-independent calibration. Similarly to standard approaches, we use a delay spectrum technique to search for the EoR signal. Using 94 nights of data observed with Phase I of the Hydrogen Epoch of Reionization Array (HERA), we place approximate constraints on the 21 cm power spectrum at z = 7.7. We find at 95 per cent confidence that the 21 cm EoR brightness temperature is ≤(372)2 ‘pseudo’ mK2 at 1.14 ‘pseudo’ h Mpc−1, where the ‘pseudo’ emphasizes that these limits are to be interpreted as approximations to the actual distance scales and brightness temperatures. Using a fiducial EoR model, we demonstrate the feasibility of detecting the EoR with the full array. Compared to standard methods, the closure phase processing is relatively simple, thereby providing an important independent check on results derived using visibility intensities, or related.
Objective To evaluate the ability of the third-generation (3.01) of FloTrac/Vigileo monitor (Edwards Lifesciences, Irvine, CA) to follow variations in cardiac output (∆CO) using the new polar plot ...approach. Design Prospective interventional study. Setting Single hospital university study. Participants Twenty-five patients referred for cardiac surgery. Interventions CO was measured simultaneously by 3 to 5 bolus thermodilution (COtd measurements), using a pulmonary artery catheter and by arterial pulse contour analysis, using the FloTrac/Vigileo (COvi). Data were collected at eight time points: before incision, after sternotomy, before and after protamine sulfate infusion, at the start of sternal closure, at the end of surgery, on arrival to intensive care unit, and after a standardized volume expansion with 500 mL of hetastarch 6%. Measurements and Main Results One-hundred thirty-five pairs of CO data were collected; the mean bias of all CO measurements corrected for repeated measures was 0.2 L/min with limits of agreements of −3.3 L/min and +2.9 L/min. The percentage error was 66.5%. The polar plot analysis included 71 significant ∆CO and showed a mean polar angle of −3.4 degrees with 95% polar percentage error equivalent limits of −61 to 55; 69% of analysed data points fell within the 30-degree limits and provided a correct polar concordance rate. Conclusions Third-generation FloTrac/Vigileo software still lacks the accuracy to reliably detect changes in cardiac output (∆CO) in cardiac surgery. Improvements to FloTrac/Vigileo CO algorithm and software still are needed in this particular setting.
Radio-loud fraction of z>6 quasars Keller, Pascal M; Thyagarajan, Nithyanandan; Kumar, Ajay ...
arXiv.org,
02/2024
Paper, Journal Article
Open access
Quasars at redshifts \(z>6\) are an excellent probe of the formation and evolution of supermassive black holes in the early Universe. The population of radio-luminous quasars is of particular ...interest, as such quasars could potentially be used to study the neutral intergalactic medium during cosmic reionisation via H\(\,\)I 21\(\,\)cm absorption studies. However, the lack of deep radio observations of \(z>6\) quasars leaves the population poorly constrained, and suitable candidates for an H\(\,\)I 21\(\,\)cm absorption study have yet to be found. In this work, we present Jansky Very Large Array (VLA) 1\(-\)2 GHz radio continuum observations of 138 quasars at redshifts \(6.0 \leq z<7.6\). We detect the radio continuum emission of the \(z=6.1\) quasar J1034-1425, with a 1.6 GHz flux density of \(170\pm 36\,\mu\)Jy. This quasar is radio-quiet with radio-loudness, \(R \equiv f_{5\text{~GHz}}/f_{\nu,\text{4400 A}} = 2.4\pm0.5\). In addition, we detect 7 other quasars at z>6, which have previously been characterised in the literature at these frequencies. Using the full sample, we estimate the radio-loud fraction to be \(3.8^{+6.2}_{-2.4}\%\), where the uncertainties are 95% confidence intervals. This is lower than recent estimates of the radio-loud fraction in the literature, but is still marginally consistent with no redshift evolution of the radio-loud fraction. We explore the undetected quasar population by stacking their continuum images at their optical positions and obtain a median stacked flux density of \(13.8\pm 3.9~\mu\)Jy and luminosity of \(\log{L_{5~\mathrm{GHz}}/(\mathrm{W~Hz}^{-1})}=24.2\pm0.1\).
Robust and optimal H∞ control in LabVIEW Zeugin, Pascal M.; Keller, Jurg P.
2017 IEEE Conference on Control Technology and Applications (CCTA),
2017-Aug.
Conference Proceeding
State of the art computer-aided control system design (CACSD) tools for robust control offer only very basic commands and consequently require a very detailed mathematical background and advanced ...user knowledge about syntax and data structures. Also many typical controller design problems have to be reformulated over and over. This contribution therefore aims to tackle these matters by introducing a CACSD-tool with a user-friendly graphical user interface based on LabVIEW. Although not providing quite the flexibility of common low-level design tools, it offers a set of comfortable, ready-to-use solutions for robust H ∞ controller design and implementation including the field-testing of the control system with a laboratory plant. The structure of the tool provides the possibility to solve a whole range of different MIMO H ∞ problems, without needing to do tedious algebraic calculations for each respective problem. The originality of this tool thereby lies in the fact that it allows to attain the design goals interactively, i.e. one can infer the consequences of minor changes in the control specifications on the closed-loop system immediately. This provides a deductive approach to understanding H ∞ control without the necessity to learn complicated mathematical formalisms and syntax.
Gaia provided the largest-ever catalogue of white dwarf stars. We use this catalogue, along with the third public data release of the Zwicky Transient Facility (ZTF), to identify new eclipsing white ...dwarf binaries. Our method exploits light curve statistics and the Box Least Squares algorithm to detect periodic light curve variability. The search revealed 18 new binaries, of which 17 are eclipsing. We use the position in the Gaia H-R diagram to classify these binaries and find that the majority of these white dwarfs have main sequence companions. We identify one system as a candidate eclipsing white dwarf--brown dwarf binary and a further two as extremely low mass (ELM) white dwarf binaries. We also provide identification spectroscopy for 17 of our 18 binaries. Running our search method on mock light curves with real ZTF sampling, we estimate our efficiency of detecting objects with light curves similar to the ones of the newly discovered binaries. Many more binaries are to be found in the ZTF footprint as the data releases grow, so our survey is ongoing.
Radio interferometers aiming to measure the power spectrum of the redshifted 21 cm line during the Epoch of Reionisation (EoR) need to achieve an unprecedented dynamic range to separate the weak ...signal from overwhelming foreground emissions. Calibration inaccuracies can compromise the sensitivity of these measurements to the effect that a detection of the EoR is precluded. An alternative to standard analysis techniques makes use of the closure phase, which allows one to bypass antenna-based direction-independent calibration. Similarly to standard approaches, we use a delay spectrum technique to search for the EoR signal. Using 94 nights of data observed with Phase I of the Hydrogen Epoch of Reionization Array (HERA), we place approximate constraints on the 21 cm power spectrum at \(z=7.7\). We find at 95% confidence that the 21 cm EoR brightness temperature is \(\le\)(372)\(^2\) "pseudo" mK\(^2\) at 1.14 "pseudo" \(h\) Mpc\(^{-1}\), where the "pseudo" emphasises that these limits are to be interpreted as approximations to the actual distance scales and brightness temperatures. Using a fiducial EoR model, we demonstrate the feasibility of detecting the EoR with the full array. Compared to standard methods, the closure phase processing is relatively simple, thereby providing an important independent check on results derived using visibility intensities, or related.
Structural MRI abnormalities are inconsistently reported in epilepsy. In the largest neuroimaging study to date, Whelan et al. report robust structural alterations across and within epilepsy ...syndromes, including shared volume loss in the thalamus, and widespread cortical thickness differences. The resulting neuroanatomical map will guide prospective studies of disease progression.
Abstract
Progressive functional decline in the epilepsies is largely unexplained. We formed the ENIGMA-Epilepsy consortium to understand factors that influence brain measures in epilepsy, pooling data from 24 research centres in 14 countries across Europe, North and South America, Asia, and Australia. Structural brain measures were extracted from MRI brain scans across 2149 individuals with epilepsy, divided into four epilepsy subgroups including idiopathic generalized epilepsies (n =367), mesial temporal lobe epilepsies with hippocampal sclerosis (MTLE; left, n = 415; right, n = 339), and all other epilepsies in aggregate (n = 1026), and compared to 1727 matched healthy controls. We ranked brain structures in order of greatest differences between patients and controls, by meta-analysing effect sizes across 16 subcortical and 68 cortical brain regions. We also tested effects of duration of disease, age at onset, and age-by-diagnosis interactions on structural measures. We observed widespread patterns of altered subcortical volume and reduced cortical grey matter thickness. Compared to controls, all epilepsy groups showed lower volume in the right thalamus (Cohen's d = −0.24 to −0.73; P < 1.49 × 10−4), and lower thickness in the precentral gyri bilaterally (d = −0.34 to −0.52; P < 4.31 × 10−6). Both MTLE subgroups showed profound volume reduction in the ipsilateral hippocampus (d = −1.73 to −1.91, P < 1.4 × 10−19), and lower thickness in extrahippocampal cortical regions, including the precentral and paracentral gyri, compared to controls (d = −0.36 to −0.52; P < 1.49 × 10−4). Thickness differences of the ipsilateral temporopolar, parahippocampal, entorhinal, and fusiform gyri, contralateral pars triangularis, and bilateral precuneus, superior frontal and caudal middle frontal gyri were observed in left, but not right, MTLE (d = −0.29 to −0.54; P < 1.49 × 10−4). Contrastingly, thickness differences of the ipsilateral pars opercularis, and contralateral transverse temporal gyrus, were observed in right, but not left, MTLE (d = −0.27 to −0.51; P < 1.49 × 10−4). Lower subcortical volume and cortical thickness associated with a longer duration of epilepsy in the all-epilepsies, all-other-epilepsies, and right MTLE groups (beta, b < −0.0018; P < 1.49 × 10−4). In the largest neuroimaging study of epilepsy to date, we provide information on the common epilepsies that could not be realistically acquired in any other way. Our study provides a robust ranking of brain measures that can be further targeted for study in genetic and neuropathological studies. This worldwide initiative identifies patterns of shared grey matter reduction across epilepsy syndromes, and distinctive abnormalities between epilepsy syndromes, which inform our understanding of epilepsy as a network disorder, and indicate that certain epilepsy syndromes involve more widespread structural compromise than previously assumed.
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