Nuclear regions as seen with LOFAR international baselines: A high-resolution study of the recurrent activity

Context. Radio galaxies dominate the sky at radio wavelengths and represent an essential piece in the galaxy evolution puzzle. High-resolution studies focussed on statistical samples of radio galaxies are expected to shed light on the triggering mechanisms of the active galactic nucleus in their centre, alternating between the phases of activity and quiescence.Aims. For this work, we zoomed in on the sub-arcsec radio structures in the central regions of the 35 radio galaxies in the area covering 6.6 deg2 of the Lockman Hole region. The sources studied here were previously classified as active, remnant, and candidate restarted radio galaxies based on the LOw Frequency ARray (LOFAR) observations at 150 MHz. We examined the morphologies and studied the spectral properties of their central regions to explore their evolutionary stages and to revise the morphological and spectral criteria used to select the initial sample.Methods. We used the newly available LOFAR 150 MHz image obtained using international baselines, yielding a resolution of 0.38″ × 0.30″, making this the first systematic study of the nuclear regions at such a high resolution and low frequency. We used publicly available images from the Faint Images of the Radio Sky at Twenty-cm survey at 1.4 GHz and the Karl G. Jansky Very Large Array (VLA) Sky Survey at 3 GHz to achieve our goals. In addition, for one of the restarted candidates, we present new dedicated observations with the VLA at 3 GHz.Results. We characterised the central regions of the radio galaxies in our sample and found various morphologies, some even mimicking well-known double-double radio galaxies but on a smaller scale, that is, a few tens of kiloparsecs for the size of the restarted activity. We also see the beginnings of active jets or distinct detections unrelated to the large-scale structure. Furthermore, we found a variety of radio spectra characterising the sources in our sample, such as flat, steep, or peaked in the frequency range between 150 MHz and 3 GHz, indicative of the different life-cycle phases of the sources in our sample. Based on these analyses, we confirm five out of six previously considered restarted candidates and identify three more restarted candidates from the active sample. As the number of restarted candidates still exceeds that of remnant candidates, this is consistent with previous results suggesting that the restarted phase can occur after a relatively short remnant phase (i.e. a few tens of millions of years)

A low frequency sub-arcsecond view of powerful radio galaxies in rich-cluster environments: 3C 34 and 3C 320

Models of radio galaxy physics have been primarily based on high frequency ($\geqslant$1 GHz) observations of their jets, hotspots, and lobes. Without highly resolved low frequency observations, which provide information on older plasma, our understanding of the dynamics of radio galaxies and their interaction with their environment is limited. Here, we present the first sub-arcsecond (0.3") resolution images at 144 MHz of two powerful radio galaxies situated in rich cluster environments, namely 3C 34 and 3C 320, using the International Low Frequency Array Telescope. We detect for the first time at low frequencies a plethora of structures in these objects, including strikingly large filaments across the base of the lobes in both sources, which are spatially associated with dense regions in the ambient medium. For 3C 34 we report a spectral flattening in the region of the central filament, suggesting that the origin of the filaments is related to the presence of large-scale ordered magnetic fields. We also report periodic total intensity and spectral index banding of diffuse emission in the eastern lobe, seen for the first time in radio galaxy lobes. The hotspot complexes are resolved into multiple fragments of varying structure and spectral index; we discuss the implications for particle acceleration and jet termination models. We find at most smooth gradients in the spectral behaviour of the hotspot structure suggesting that particle acceleration, if present, may be occurring throughout the complex, in contrast to simple models, but different jet termination models may apply to both sources.Comment: 16 pages, 7 figures, 2 tables. Accepted for publication in Monthly Notices of the Royal Astronomical Society, 2023 February 0

Measuring cavity powers of active galactic nuclei in clusters using a hybrid X-ray–radio method. A new window on feedback opened by subarcsecond LOFAR-VLBI observations

Measurements of the quantity of radio-mode feedback injected by an active galactic nucleus into the cluster environment have mostly relied on X-ray observations, which reveal cavities in the intracluster medium excavated by the radio lobes. However, the sensitivity required to accurately constrain the dimensions of these cavities has proven to be a major limiting factor and is the main bottleneck on high-redshift measurements. We describe a hybrid method based on a combination of X-ray and radio observations, which aims to enhance our ability to study radio-mode feedback. In this paper, we present one of the first samples of galaxy clusters observed with the International LOFAR Telescope (ILT) at 144 MHz and use this sample to test the hybrid method at lower frequencies than before. By comparing our measurements with results found in literature based on the traditional method using only X-ray observations, we find that the hybrid method provides consistent results to the traditional method. In addition, we find that the correlation between the traditional method and the hybrid method improves as the X-ray cavities are more clearly defined. This suggests that using radio lobes as proxies for cavities may help to circumvent systematic uncertainties in the cavity volume measurements. Encouraged by the high volume of unique ILT observations successfully processed, this hybrid method enables radio-mode feedback to be studied at high redshifts for the first time even for large samples of clusters

Short severe energy restriction with refueling reduces body mass without altering training-associated performance improvement

Purpose We investigated short-term (9 d) exposure to low energy availability (LEA) in elite endurance athletes during a block of intensified training on self-reported well-being, body composition, and performance. Methods Twenty-three highly trained race walkers undertook an ~3-wk research-embedded training camp during which they undertook baseline testing and 6 d of high energy/carbohydrate (HCHO) availability (40 kcal·kg FFM−1·d−1) before being allocated to 9 d continuation of this diet (n = 10 M, 2 F) or a significant decrease in energy availability to 15 kcal·kg FFM−1·d−1 (LEA: n = 10 M, 1 F). A real-world 10,000-m race walking event was undertaken before (baseline) and after (adaptation) these phases, with races being preceded by standardized carbohydrate fueling (8 g·kg body mass [BM]−1 for 24 h and 2 g·kg BM−1 prerace meal). Results Dual-energy x-ray absorptiometry–assessed body composition showed BM loss (2.0 kg, P < 0.001), primarily due to a 1.6-kg fat mass reduction (P < 0.001) in LEA, with smaller losses (BM = 0.9 kg, P = 0.008; fat mass = 0.9 kg, P < 0.001) in HCHO. The 76-item Recovery–Stress Questionnaire for Athletes, undertaken at the end of each dietary phase, showed significant diet–trial effects for overall stress (P = 0.021), overall recovery (P = 0.024), sport-specific stress (P = 0.003), and sport-specific recovery (P = 0.012). However, improvements in race performance were similar: 4.5% ± 4.1% and 3.5% ± 1.8% for HCHO and LEA, respectively (P < 0.001). The relationship between changes in performance and prerace BM was not significant (r = −0.08 [−0.49 to 0.35], P = 0.717). Conclusions A series of strategically timed but brief phases of substantially restricted energy availability might achieve ideal race weight as part of a long-term periodization of physique by high-performance athletes, but the relationship between BM, training quality, and performance in weight-dependent endurance sports is complicated

A novel Bayesian approach for decomposing the radio emission of quasars: I. Modelling the radio excess in red quasars

© 2024 The Author(s). Published by Oxford University Press on behalf of Royal Astronomical Society. This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY), https://creativecommons.org/licenses/by/4.0/Studies show that both radio jets from the active galactic nuclei (AGNs) and the star formation (SF) activity in quasar host galaxies contribute to the quasar radio emission; yet their relative contributions across the population remain unclear. Here, we present an improved parametric model that allows us to statistically separate the SF and AGN components in observed quasar radio flux density distributions, and investigate how their relative contributions evolve with AGN bolometric luminosity (\L\mathrm\bol\\) and redshift (z) using a fully Bayesian method. Based on the newest data from LOw-Frequency ARray Two-metre Sky Survey data release 2, our model gives robust fitting results out to \z\\, showing a quasar host galaxy SF rate (SFR) evolution that increases with bolometric luminosity and with redshift out to \z\\. This differs from the global cosmic SFR density, perhaps due to the importance of galaxy mergers. The prevalence of radio AGN emissions increases with quasar luminosity, but has little dependence on redshift. Furthermore, our new methodology and large sample size allow us to subdivide our data set to investigate the role of other parameters. Specifically, in this paper, we explore quasar colour and demonstrate that the radio excess in red quasars is due to an enhancement in AGN-related emission, since the host galaxy SF contribution to the total radio emission is independent of quasar colour. We also find evidence that this radio enhancement occurs mostly in quasars with weak or intermediate radio power.Peer reviewe

The impact of acute calcium intake on bone turnover markers during a training day in elite male rowers

Introduction: While an acute exercise session typically increases bone turnover markers (BTM), the impact of subsequent sessions and the interaction with pre-exercise calcium intake remains unclear despite the application to the ‘real life’ training of many competitive athletes. Methods: Using a randomized crossover design, elite male rowers (n = 16) completed two trials, a week apart, consisting of two 90-minute rowing ergometer sessions (Ex1, Ex2) separated by 150 minutes. Prior to each trial, participants consumed a high (CAL: ~1000 mg) or isocaloric low (CON: \u3c 10 mg) calcium meal. Biochemical markers including parathyroid hormone: PTH; serum ionised calcium (iCa) and bone turnover markers (C-terminal telopeptide of type I collagen: β-CTX-I; osteocalcin: OC) were monitored from baseline to 3 hours post Ex2. Results: While each session caused perturbances of serum iCa, CAL maintained calcium concentrations above those of CON for most time points, 4.5 and 2.4 % higher post EX1 and EX2 respectively. The decrease in iCa in CON was associated with an elevation of blood PTH (p \u3c 0.05) and β-CTX-I (p \u3c 0.0001) over this period of repeated training sessions and their recovery, particularly during and after Ex2. Pre-exercise intake of calcium-rich foods lowered BTM over the course of a day with several training sessions. Conclusions: Pre-exercise intake of a calcium-rich meal prior to training sessions undertaken within the same day had a cumulative and prolonged effect on the stabilisation of blood iCa during exercise. In turn, this reduced the post-exercise PTH response, potentially attenuating the increase in markers of bone resorption. Such practical strategies may be integrated into the athlete’s overall sports nutrition plan, with the potential to safeguard long term bone health and reduce the risk of bone stress injuries

How does the radio enhancement of broad absorption line quasars relate to colour and accretion rate?

The origin of radio emission in different populations of radio-quiet quasars is relatively unknown, but recent work has uncovered various drivers of increased radio-detection fraction. In this work, we pull together three known factors: optical colour (g - i), C IV distance (a proxy for L/LEdd), and whether or not the quasar contains broad absorption lines (BALQSOs) which signify an outflow. We use SDSS (Sloan Digital Sky Survey) DR14 spectra along with the LOFAR Two Metre Sky Survey Data Release 2 and find that each of these properties have an independent effect. BALQSOs are marginally more likely to be radio-detected than non-BALQSOs at similar colours and L/LEdd, moderate reddening significantly increases the radio-detection fraction and the radio detection increases with L/LEdd above a threshold for all populations. We test a widely used simple model for radio wind shock emission and calculate energetic efficiencies that would be required to reproduce the observed radio properties. We discuss interpretations of these results concerning radio-quiet quasars more generally. We suggest that radio emission in BALQSOs is connected to a different physical origin than the general quasar population since they show different radio properties independent of colour and C IV distance

Spectral analysis of spatially resolved 3C295 (sub-arcsecond resolution) with the International LOFAR Telescope

3C295 is a bright, compact steep spectrum source with a well-studied integrated radio spectral energy distribution (SED) from 132 MHz to 15 GHz. However, spatially resolved spectral studies have been limited due to a lack of high resolution images at low radio frequencies. These frequencies are crucial for measuring absorption processes, and anchoring the overall spectral modelling of the radio SED. In this paper, we use International LOw-Frequency ARray (LOFAR) Telescope (ILT) observations of 3C295 to study its spatially resolved spectral properties with sub-arcsecond resolution at 132 MHz. Combining our new 132 MHz observation with archival data at 1.6, 4.8, and 15 GHz, we are able to carry out a resolved radio spectral analysis. The spectral properties of the hotspots provides evidence for low frequency flattening. In contrast, the spectral shape across the lobes is consistent with a Jaffe-Perola spectral ageing model. Using the integrated spectral information for each component, we then fitted low-frequency absorption models to the hotspots, finding that both free-free absorption and synchrotron self-absorption models provide a better fit to the data than a standard power law. Although we can say there is low-frequency absorption present in the hotspots of 3C295, future observations with the Low Band Antenna of the ILT at 55 MHz may allow us to distinguish the type of absorption

Integrative genomic analysis of trisomy 12 abnormality in B-cell chronic lymphocytic leukemia

Background: Flow cytometry allows specific assessment of the expression of ZAP-70, a promising new prognostic factor in B-cell chronic lymphocytic leukemia (B-CLL), but suffers from a lack of multicenter standardization. Design and Methods: An optimized method for direct detection of ZAP-70 in flow cytometry was tested in a multicenter fashion. Adapted for frozen cells, this method includes a normalization step by addition of B cells from a pool of peripheral blood mononuclear cells collected from normal donors. ZAP-70 expression levels were assessed for 153 patients with typical B-cell chronic lymphocytic leukemia chronic lymphocytic leukemia. Results were expressed as the ratio of ZAP-70 mean fluorescence intensity between B-CLL cells and normal B cells. Results: The statistically optimized cut-off of ZAP-70 positivity was a ratio of 1.4. Concordance between ZAP-70 and CD38 expression was 67%. Concordance between the mutational status of IgVH genes and ZAP-70 or CD38 expression was 87% and 65%, respectively. ZAP-70 was significantly expressed in 28%, 54% and 61% of patients with Binet stages A, B and C B-cell chronic lymphocytic leukemia, respectively (p=0.008). The absence of ZAP-70 expression was associated with isolated del(13q14), a cytogenetic abnormality with a good prognosis, while most patients with the del(17p13) poor prognosis cytogenetic marker expressed ZAP-70 (p&lt;10-5). ZAP-70 expression was not related to the other poor prognosis cytogenetic abnormality del(11q22.3) nor to trisomy 12. Conclusions: This new technique provides highly reliable results well correlated with the mutational status of IgVH genes, CD38 expression, Binet stage and cytogenetic abnormalities. This robust discriminative technique appears of particular interest for routine diagnosis and assessment of ZAP-70 expression in large, prospective, multicenter therapeutic trials