Context.
The dynamics of the intracluster medium (ICM) is affected by turbulence driven by several processes, such as mergers, accretion and feedback from active galactic nuclei.
Aims.
X-ray surface ...brightness fluctuations have been used to constrain turbulence in galaxy clusters. Here, we use simulations to further investigate the relation between gas density and turbulent velocity fluctuations, with a focus on the effect of the stratification of the ICM.
Methods.
In this work, we studied the turbulence driven by hierarchical accretion by analysing a sample of galaxy clusters simulated with the cosmological code ENZO. We used a fixed scale filtering approach to disentangle laminar from turbulent flows.
Results.
In dynamically perturbed galaxy clusters, we found a relation between the root mean square of density and velocity fluctuations, albeit with a different slope than previously reported. The Richardson number is a parameter that represents the ratio between turbulence and buoyancy, and we found that this variable has a strong dependence on the filtering scale. However, we could not detect any strong relation between the Richardson number and the logarithmic density fluctuations, in contrast to results by recent and more idealised simulations. In particular, we find a strong effect from radial accretion, which appears to be the main driver for the gas fluctuations. The ubiquitous radial bias in the dynamics of the ICM suggests that homogeneity and isotropy are not always valid assumptions, even if the turbulent spectra follow Kolmogorov’s scaling. Finally, we find that the slope of the velocity and density spectra are independent of cluster-centric radii.
Context. The reason why some radio galaxies (RGs) grow to form so-called giant radio galaxies (GRGs) with sizes > 700 kpc, is still unknown. Aims. In this study, we compare the radio, optical and ...environmental properties of GRGs with those of a control sample of smaller RGs we found in the three LOw-Frequency ARray (LOFAR) deep fields, namely the Boötes, ELAIS-N1, Lockman Hole, for a total area of ≈95 deg 2 . Methods. We inspected the LOFAR deep fields and created a catalogue of 1609 extended radio galaxies (ERGs). By visual inspection, we identified their host galaxies and spectroscopically or photometrically classified 280 of these as GRGs. We studied their properties, such as their accretion state, stellar mass and star formation rate (SFR) using deep optical and infrared survey data. Moreover, we explored the environment in terms of the surface number density of neighbouring galaxies within these surveys. Integrated flux densities and radio luminosities were also determined for a subset of ERGs through available survey images at 50, 150, 610, and 1400 MHz to compute integrated spectral indices. Results. Considering the fraction of GRGs displaying an FRII morphology alongside the host galaxy properties, we suggest that GRGs consistently possess sufficient power to overcome jet frustration caused by the interstellar medium. Moreover, clear differences emerge in the environmental densities between GRGs and smaller RGs, using the number of neighbouring galaxies within 10 Mpc from the host galaxy as a proxy. GRGs preferentially reside in sparser environments compared to their smaller counterparts. In particular, only 3.6% of the GRGs reside within a 3D comoving distance of 5 Mpc from a previously reported galaxy cluster. We found that larger sources exhibit steeper integrated spectral indices, suggesting that GRGs are late-stage versions of RGs. These results suggest that GRGs are amongst the oldest radio sources with the most stable nuclear activity that reside in sparse environments.
ABSTRACT
Giant radio galaxies (GRGs) are radio galaxies that have projected linear extents of more than 700 kpc or 1 Mpc, depending on definition. We have carried out a careful visual inspection in ...search of GRGs of the Boötes LOw-Frequency ARray Deep Field image at 150 MHz. We identified 74 GRGs with a projected size larger than 0.7 Mpc of which 38 are larger than 1 Mpc. The resulting GRG sky density is about 2.8 (1.43) GRGs per square degree for GRGs with linear size larger than 0.7 (1) Mpc. We studied their radio properties and the accretion state of the host galaxies using deep optical and infrared survey data and determined flux densities for these GRGs from available survey images at both 54 MHz and 1.4 GHz to obtain integrated radio spectral indices. We show the location of the GRGs in the P–D diagram. The accretion mode on to the central black holes of the GRG hosts is radiatively inefficient suggesting that the central engines are not undergoing massive accretion at the time of the emission. Interestingly, 14 out of 35 GRGs for which optical spectra are available show a moderate star-formation rate (10–100 $\rm M_{\odot }\,yr^{-1}$). Based on the number density of optical galaxies taken from the Dark Energy Spectroscopic Instrument survey DR9 photometric redshift catalogue, we found no significant differences between the environments of GRGs and other radio galaxies, at least for redshift up to z = 0.7.
Context.
Galaxy clusters grow through the accretion of mass over cosmic time. Their observed properties are then shaped by how baryons distribute and energy is diffused. Thus, a better understanding ...of spatially resolved, projected thermodynamic properties of the intra-cluster medium (ICM) may provide a more consistent picture of how mass and energy act locally in shaping the X-ray observed quantities of these massive virialized or still collapsing structures.
Aims.
We study the perturbations in the temperature (and density) distribution to evaluate and characterize the level of inhomogeneities and the related dynamical state of the ICM.
Methods.
We obtain and analyze the temperature and density distribution for 28 clusters (2.4 × 10
14
M
⊙
<
M
500
< 1.2 × 10
15
M
⊙
; 0.07 <
z
< 0.45) selected from the CHEX-MATE sample. We use these spatially resolved two-dimensional distributions to measure the global and radial scatter and identify the regions that deviate the most from the average distribution. During this process, we introduce three dynamical state estimators and produce “clean” temperature profiles after removing the most deviant regions.
Results.
We find that the temperature distribution of most of the clusters is skewed towards high temperatures and is well described by a log-normal function. There is no indication that the number of regions deviating more than 1
σ
from the azimuthal value is correlated with the dynamical state inferred from morphological estimators. The removal of these regions leads to local temperature variations up to 10–20% and an average increase of ∼5% in the overall cluster temperatures. The measured relative intrinsic scatter within
R
500
,
σ
T, int
/
T
, has values of 0.17
−0.05
+0.08
, and is almost independent of the cluster mass and dynamical state. Comparing the scatter of temperature and density profiles to hydrodynamic simulations, we constrain the average Mach number regime of the sample to
Ṁ
3D
= 0.36
−0.09
+0.16
. We infer the ratio between the energy in turbulence and the thermal energy, and translate this ratio in terms of a predicted hydrostatic mass bias
b
, estimating an average value of
b
∼ 0.11 (covering a range between 0 and 0.37) within
R
500
.
Conclusions.
This study provides detailed temperature fluctuation measurements for 28 CHEX-MATE clusters which can be used to study turbulence, derive the mass bias, and make predictions on the scaling relation properties.
Summary
Propionate is an abundant carboxylic acid in nature. Microorganisms metabolize propionate aerobically via the 2‐methylcitrate pathway. This pathway depends on a series of three reactions in ...the citric acid cycle that leads to the conversion of succinate to oxaloacetate. Interestingly, the γ‐proteobacterium Escherichia coli can use propionate as a carbon and electron source under oxic but not under anoxic conditions. RT‐PCR and transcriptomic analysis revealed a posttranscriptional regulation of the prpBCDE‐gene cluster encoding the necessary enzymes for propionate metabolism. The polycistronic mRNA seems to be hydrolyzed in the 3′–5′ direction under anoxic conditions. This regulatory strategy is highly constructive because the last gene of the operon encodes the first enzyme of the propionate metabolism. Further analysis revealed that RNase R is involved in the hydrolysis of the prp transcripts. Consequently, an rnr‐deletion strain could metabolize propionate under anoxic conditions. To the best of our knowledge, this is the first study describing the influence of RNase R on the anaerobic metabolism of E. coli.
Escherichia coli K12 is able to utilize propionate as carbon and energy source only under oxic conditions. The propionate degradation pathway, also called 2‐methylcitrate cycle, is encoded by the prp‐operon. In this study, we revealed a posttranscriptional regulation of the prp‐operon under anoxic conditions. Different lines of evidence suggest a pivotal role of RNase R for the stability of the corresponding mRNA to the prp‐gene cluster. Although the data suggest a direct hydrolysis of the mRNA by RNase R, we cannot exclude a further indirect posttranscriptional regulation (indicated by an x), which is mediated by the RNA hydrolyzing enzyme.
Aims.
Previous studies reported an alignment of the major axes of radio galaxies on various angular scales. Here, we study the alignment of radio galaxies in the ELAIS-N1 Low Frequency ARray (LOFAR) ...deep field, which covers an area of 25 deg
2
.
Methods.
The low noise level of about 20 μJy beam
−1
of the LOFAR deep field observations at 150 MHz enabled the identification of 447 extended (> 30″) radio galaxies for which we measured the position angle of the major axis. We find that 95% of these sources have either photometric or spectroscopic redshifts, which we then used for a three-dimensional (3D) analysis.
Results.
We show the distribution of the position angles of radio galaxies in the ELAIS-N1 field and the results of multiple statistical tests carried out to decipher whether the radio galaxies are randomly oriented. We find that the distribution of position angles is consistent with being uniform. Two peaks around position angles of 50 and 140 deg are spurious and are not caused by an alignment, as shown by a 3D analysis. In conclusion, our results do not support a 2D or 3D alignment of radio galaxies on scales of smaller than ∼4 deg.
The evolution of active galactic nuclei (AGNs) is closely connected to their host galaxies and surroundings. Via feedback processes, AGNs can counteract the cooling of the intracluster medium (ICM) ...and suppress star formation in their host galaxies. Radio observations at low frequencies provide a glimpse into the history of AGN activity. The Virgo cluster is a substantial reservoir of nearby galaxies and provides an ideal laboratory for the study of AGNs as well as their feedback mechanisms. The aim of our work is to characterise the AGN population within the Virgo cluster down to low radio luminosities, constrain the AGN duty cycle, and investigate environmental feedback in cluster member galaxies. We analysed 144\,MHz and 1.3\,GHz radio observations of early-type galaxies from the ACS Virgo Cluster Survey (ACSVCS) taken with LOFAR and MeerKAT. We detect 12 of these galaxies at 144\,MHz, five of which show clearly extended radio emission. The radio luminosity shows a strong dependence on the stellar mass of the host galaxy, in agreement with previous results. As a notable outlier, the massive elliptical galaxy NGC\,4365 ($M_*=2.2 \,M_ is not detected as compact source in the LOFAR observations. Instead, it is surrounded by diffuse, low-surface brightness emission, which hints towards a past phase of stronger nuclear activity. Furthermore, we find a cavity in NGC\,4472 (= M\,49) inflated by the wide-angle tail only visible in the LOFAR data, which implies that the cavity was created by a past outburst. The corresponding cavity power is of the same order of magnitude as the jet power in the present duty cycle of the AGN.
Aortic arch debranching and thoracic endovascular repair De Rango, Paola, MD, PhD; Cao, Piergiorgio, MD, FRCS; Ferrer, Ciro, MD ...
Journal of vascular surgery,
2014, January 2014, 2014-Jan, 2014-01-00, 20140101, Letnik:
59, Številka:
1
Journal Article
Recenzirano
Odprti dostop
Objective Currently, the best approach to the aortic arch remains unsupported by robust evidence. Most of the available data rely on small sample numbers, heterogeneous settings, and limited ...follow-up. The objective of this study was to evaluate early and midterm results of arch debranching and endovascular procedures. Methods From 2005 through 2013, 104 consecutive patients underwent elective arch treatment with debranching and thoracic endovascular aortic repair. Rates of perioperative (30-day) mortality and neurological complications, and mortality, endoleak, supra-aortic vessel patency, and arch diameter changes at 5 years were analyzed. Results Patients' mean age was 69.8 years, and 90 were males. Twenty arches were repaired for dissection. Nineteen patients required total debranching for diseases extended to zone 0. In 59, debranching and thoracic endovascular aortic repair procedures were staged. At 30 days, death, stroke, and spinal cord ischemia occurred in six, four, and three patients, respectively. Extension to ascending aorta (zone 0 landing) was the only multivariate independent predictor for perioperative mortality (odds ratio, 9.6; 95% confidence interval, 1.54-59.90; P = .015), but not for stroke. Four retrograde dissections, two fatal, occurred during the perioperative period. At 1, 3, and 5 years, Kaplan-Meier survival rates were 89.0%, 82.8%, and 70.9%, and freedom from persistent endoleak rates were 96.1%, 92.5%, and 88.3%, respectively. Over 5-year follow-up, 34 aneurysms shrank ≥5 mm, and four grew. Five reinterventions were required. Two supra-aortic vessel occlusions and no late aorta-related mortalities were recorded. Conclusions Despite the perioperative mortality risk, the late outcome of endovascular arch repair presents a low rate of aorta-related deaths and reinterventions and acceptable midterm survival. Furthermore, more than one-third of the aneurysms' diameters decrease over 5 years as a measure of the long-term efficacy of treatment. Retrograde type A dissection remains a major concern in the perioperative period and careful arch approach is required.
Abstract Objective Long-term results of abdominal aortic aneurysm (AAA) endovascular repair are affected by graft design renewals that tend to improve the performance of older generation prostheses ...but usually reset the follow-up times to zero. The present study investigated the long-term outcomes of endovascular AAA repair (EVAR) using the Zenith graft, still in use without major modification, in a single center experience. Methods Between 2000 and 2011, 610 patients underwent elective EVAR using the Zenith endograft (Cook Inc, Bloomington, Ind) and represent the study group. Primary outcomes were overall survival, freedom from AAA rupture, and freedom from AAA-related death. Secondary outcomes included freedom from late (>30 days) reintervention, freedom from late (>30 days) conversion to open repair, freedom from aneurysm sac enlargement >5.0 mm and freedom from EVAR failure, defined as a composite of AAA-related death, AAA rupture, AAA growth >5 mm, and any reintervention. Results Mean age was 73.2 years. Mean aneurysm diameter was 55.3 mm. There were five perioperative deaths (0.8%) and three intraoperative conversions. At a mean follow-up of 99.2 (range, 0-175) months, seven AAA ruptures occurred, all fatal except one. Overall survival was 92.8% ± 1.1% at 1 year, 70.1% ± 1.9% at 5 years, 37.8% ± 2.9% at 10 years, and 24 ± 4% at 14 years. Freedom from AAA-rupture was 99.8% ± 0.02 at 1 year (one case), 99.4% ± 0.04 at 5 years (three cases), and 98.1% ± 0.07 at 10 and 14 years. Freedom from late reintervention and conversion was 98% ± 0.6 at 1 year, 87.7% ± 1.5 at 5 years, 75.7% ± 3.2 at 10 years, and 69.9% ± 5.2 at 14 years. Freedom from aneurysm sac growth >5.0 mm was 99.8% at 1 year, 96.6% ± 0.7 at 5 years, 81.0% ± 3.4 at 10 years, and 74.1% ± 5.8% at 14 years. EVAR failure occurred in 132 (21.6%) patients at 14 years. At multivariate analysis, independent predictors of EVAR failure resulted type I and III endoleak (hazard ratio HR, 6.7; 95% confidence interval CI, 4.6- 9.7; P < .001, type II endoleak (HR, 2.3; 95% CI, 1.6-3.4; P < .001), and American Society of Anesthesiologists grade 4 (HR, 1.6; 95% CI, 1.0-2.6; P = .034). Conclusions EVAR with Zenith graft represents a safe and durable repair. Risk of rupture and aneurysm-related death is low, whereas overall long-term survival remains poor. Novel endograft models should be tested and evaluated considering that one-fourth of the operated patients will still be alive after 14 years.
Patients with autoimmune disease, and specifically lupus erythematosus, have an increased risk of developing aortic pathology, including aneurysm and dissections. We report a case of a 49-year-old ...woman with lupus erythematosus treated surgically for an abdominal aortic aneurysm in 2009, who developed type B aortic dissection 1 year later, treated by endovascular means. Dissection furtherly underwent aneurysm evolution, and the patient finally was brought to vascular attention with a fatal thoracic aneurysm rupture. A review of literature of cases of aortic aneurysm and dissection in patients with lupus erythematosus published between 2009 and 2016 has been added.
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