| 1. |
- Kim, Jae-Young, et al.
(författare)
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Event Horizon Telescope imaging of the archetypal blazar 3C 279 at an extreme 20 microarcsecond resolution
- 2020
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 640
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Tidskriftsartikel (refereegranskat)abstract
- 3C 279 is an archetypal blazar with a prominent radio jet that show broadband flux density variability across the entire electromagnetic spectrum. We use an ultra-high angular resolution technique - global Very Long Baseline Interferometry (VLBI) at 1.3mm (230 GHz) - to resolve the innermost jet of 3C 279 in order to study its fine-scale morphology close to the jet base where highly variable-ray emission is thought to originate, according to various models. The source was observed during four days in April 2017 with the Event Horizon Telescope at 230 GHz, including the phased Atacama Large Millimeter/submillimeter Array, at an angular resolution of ∼20 μas (at a redshift of z = 0:536 this corresponds to ∼0:13 pc ∼ 1700 Schwarzschild radii with a black hole mass MBH = 8 × 108 M⊙). Imaging and model-fitting techniques were applied to the data to parameterize the fine-scale source structure and its variation.We find a multicomponent inner jet morphology with the northernmost component elongated perpendicular to the direction of the jet, as imaged at longer wavelengths. The elongated nuclear structure is consistent on all four observing days and across diffierent imaging methods and model-fitting techniques, and therefore appears robust. Owing to its compactness and brightness, we associate the northern nuclear structure as the VLBI "core". This morphology can be interpreted as either a broad resolved jet base or a spatially bent jet.We also find significant day-to-day variations in the closure phases, which appear most pronounced on the triangles with the longest baselines. Our analysis shows that this variation is related to a systematic change of the source structure. Two inner jet components move non-radially at apparent speeds of ∼15 c and ∼20 c (∼1:3 and ∼1:7 μas day-1, respectively), which more strongly supports the scenario of traveling shocks or instabilities in a bent, possibly rotating jet. The observed apparent speeds are also coincident with the 3C 279 large-scale jet kinematics observed at longer (cm) wavelengths, suggesting no significant jet acceleration between the 1.3mm core and the outer jet. The intrinsic brightness temperature of the jet components are ≤1010 K, a magnitude or more lower than typical values seen at ≥7mm wavelengths. The low brightness temperature and morphological complexity suggest that the core region of 3C 279 becomes optically thin at short (mm) wavelengths.
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| 2. |
- Eatough, Ralph P., et al.
(författare)
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Verification of Radiative Transfer Schemes for the EHT
- 2020
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Ingår i: Astrophysical Journal. - : American Astronomical Society. - 1538-4357 .- 0004-637X. ; 897:2
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Tidskriftsartikel (refereegranskat)abstract
- The Event Horizon Telescope (EHT) Collaboration has recently produced the first resolved images of the central supermassive black hole in the giant elliptical galaxy M87. Here we report on tests of the consistency and accuracy of the general relativistic radiative transfer codes used within the collaboration to model M87∗ and Sgr A∗. We compare and evaluate (1) deflection angles for equatorial null geodesics in a Kerr spacetime; (2) images calculated from a series of simple, parameterized matter distributions in the Kerr metric using simplified emissivities and absorptivities; (3) for a subset of codes, images calculated from general relativistic magnetohydrodynamics simulations using different realistic synchrotron emissivities and absorptivities; (4) observables for the 2017 configuration of EHT, including visibility amplitudes and closure phases. The error in total flux is of order 1% when the codes are run with production numerical parameters. The dominant source of discrepancies for small camera distances is the location and detailed setup of the software "camera"that each code uses to produce synthetic images. We find that when numerical parameters are suitably chosen and the camera is sufficiently far away the images converge and that for given transfer coefficients, numerical uncertainties are unlikely to limit parameter estimation for the current generation of EHT observations. The purpose of this paper is to describe a verification and comparison of EHT radiative transfer codes. It is not to verify EHT models more generally.
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| 3. |
- Broderick, Avery E., et al.
(författare)
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THEMIS: A Parameter Estimation Framework for the Event Horizon Telescope
- 2020
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Ingår i: Astrophysical Journal. - : American Astronomical Society. - 1538-4357 .- 0004-637X. ; 897:2
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Tidskriftsartikel (refereegranskat)abstract
- The Event Horizon Telescope (EHT) provides the unprecedented ability to directly resolve the structure and dynamics of black hole emission regions on scales smaller than their horizons. This has the potential to critically probe the mechanisms by which black holes accrete and launch outflows, and the structure of supermassive black hole spacetimes. However, accessing this information is a formidable analysis challenge for two reasons. First, the EHT natively produces a variety of data types that encode information about the image structure in nontrivial ways; these are subject to a variety of systematic effects associated with very long baseline interferometry and are supplemented by a wide variety of auxiliary data on the primary EHT targets from decades of other observations. Second, models of the emission regions and their interaction with the black hole are complex, highly uncertain, and computationally expensive to construct. As a result, the scientific utilization of EHT observations requires a flexible, extensible, and powerful analysis framework. We present such a framework, Themis, which defines a set of interfaces between models, data, and sampling algorithms that facilitates future development. We describe the design and currently existing components of Themis, how Themis has been validated thus far, and present additional analyses made possible by Themis that illustrate its capabilities. Importantly, we demonstrate that Themis is able to reproduce prior EHT analyses, extend these, and do so in a computationally efficient manner that can efficiently exploit modern high-performance computing facilities. Themis has already been used extensively in the scientific analysis and interpretation of the first EHT observations of M87.
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| 4. |
- Roelofs, F., et al.
(författare)
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SYMBA: An end-to-end VLBI synthetic data generation pipeline: Simulating Event Horizon Telescope observations of M 87
- 2020
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 636
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Tidskriftsartikel (refereegranskat)abstract
- Context. Realistic synthetic observations of theoretical source models are essential for our understanding of real observational data. In using synthetic data, one can verify the extent to which source parameters can be recovered and evaluate how various data corruption effects can be calibrated. These studies are the most important when proposing observations of new sources, in the characterization of the capabilities of new or upgraded instruments, and when verifying model-based theoretical predictions in a direct comparison with observational data. Aims. We present the SYnthetic Measurement creator for long Baseline Arrays (SYMBA), a novel synthetic data generation pipeline for Very Long Baseline Interferometry (VLBI) observations. SYMBA takes into account several realistic atmospheric, instrumental, and calibration effects. Methods. We used SYMBA to create synthetic observations for the Event Horizon Telescope (EHT), a millimetre VLBI array, which has recently captured the first image of a black hole shadow. After testing SYMBA with simple source and corruption models, we study the importance of including all corruption and calibration effects, compared to the addition of thermal noise only. Using synthetic data based on two example general relativistic magnetohydrodynamics (GRMHD) model images of M 87, we performed case studies to assess the image quality that can be obtained with the current and future EHT array for different weather conditions. Results. Our synthetic observations show that the effects of atmospheric and instrumental corruptions on the measured visibilities are significant. Despite these effects, we demonstrate how the overall structure of our GRMHD source models can be recovered robustly with the EHT2017 array after performing calibration steps, which include fringe fitting, a priori amplitude and network calibration, and self-calibration. With the planned addition of new stations to the EHT array in the coming years, images could be reconstructed with higher angular resolution and dynamic range. In our case study, these improvements allowed for a distinction between a thermal and a non-thermal GRMHD model based on salient features in reconstructed images.
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| 5. |
- Lassmann-Klee, P. G., et al.
(författare)
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Parallel gradients in F-ENO and in the prevalences of asthma and atopy in adult general populations of Sweden, Finland and Estonia - A Nordic EpiLung study
- 2020
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Ingår i: Respiratory Medicine. - : Elsevier BV. - 0954-6111 .- 1532-3064. ; 173
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Tidskriftsartikel (refereegranskat)abstract
- The prevalence of asthma is higher in Sweden and Finland than in neighbouring eastern countries including Estonia. Corresponding difference in bronchial eosinophilic inflammation could be studied by FENO measurements. We aimed to compare FENO in adult general populations of Sweden, Finland, and Estonia, to test the plausibility of the west-east disparity hypothesis of allergic diseases. We conducted clinical interviews (N = 2658) with participants randomly selected from the general populations in Sweden (Stockholm and dOrebro), Finland (Helsinki), and Estonia (Narva and Saaremaa), and performed FENO (n = 1498) and skin prick tests (SPT) in 1997-2003. The median (interquartile range) of FENO (ppb) was 15.5 (9.3) in Sweden, 15.4 (13.6) in Finland and 12.5 (9.6) in Estonia. We found the lowest median FENO values in the Estonian centres Saaremaa 13.1 (9.5) and Narva 11.8 (8.6). In the pooled population, asthma was associated with FENO >= 25 ppb, odds ratio (OR) 3.91 (95% confidence intervals: 2.29-6.32) after adjusting for SPT result, smoking, gender and study centre. A positive SPT test increased the likelihood of asthma OR 3.19 (2.02-5.11). Compared to Saaremaa, the likelihood of having asthma was higher in Helsinki OR 2.40 (1.04-6.02), Narva OR 2.45 (1.05-6.19), dOrebro OR 3.38 (1.59-8.09), and Stockholm OR 5.54 (2.18-14.79). There was a higher prevalence of asthma and allergic airway inflammation in adult general populations of Sweden and Finland compared to those of Estonia. Atopy and elevated FEND level were independently associated with an increased risk of asthma. In conclusion, the findings support the earlier west-east disparity hypothesis of allergic diseases.
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| 6. |
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| 7. |
- Hetland, M. L., et al.
(författare)
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Active conventional treatment and three different biological treatments in early rheumatoid arthritis: phase IV investigator initiated, randomised, observer blinded clinical trial
- 2020
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Ingår i: Bmj-British Medical Journal. - : BMJ. - 1756-1833. ; 371
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVE To evaluate and compare benefits and harms of three biological treatments with different modes of action versus active conventional treatment in patients with early rheumatoid arthritis. DESIGN Investigator initiated, randomised, open label, blinded assessor, multiarm, phase IV study. SETTING Twenty nine rheumatology departments in Sweden, Denmark, Norway, Finland, the Netherlands, and Iceland between 2012 and 2018. PARTICIPANTS Patients aged 18 years and older with treatment naive rheumatoid arthritis, symptom duration less than 24 months, moderate to severe disease activity, and rheumatoid factor or anti-citrullinated protein antibody positivity, or increased C reactive protein. INTERVENTIONS Randomised 1:1:1:1, stratified by country, sex, and anti-citrullinated protein antibody status. All participants started methotrexate combined with (a) active conventional treatment (either prednisolone tapered to 5 mg/day, or sulfasalazine combined with hydroxychloroquine and intraarticular corticosteroids), (b) certolizumab pegol, (c) abatacept, or (d) tocilizumab. MAIN OUTCOME MEASURES The primary outcome was adjusted clinical disease activity index remission (CDAI <= 2.8) at 24 weeks with active conventional treatment as the reference. Key secondary outcomes and analyses included CDAI remission at 12 weeks and over time, other remission criteria, a non-inferiority analysis, and harms. RESULTS 812 patients underwent randomisation. The mean age was 54.3 years (standard deviation 14.7) and 68.8% were women. Baseline disease activity score of 28 joints was 5.0 (standard deviation 1.1). Adjusted 24 week CDAI remission rates were 42.7% (95% confidence interval 36.1% to 49.3%) for active conventional treatment, 46.5% (39.9% to 53.1%) for certolizumab pegol, 52.0% (45.5% to 58.6%) for abatacept, and 42.1% (35.3% to 48.8%) for tocilizumab. Corresponding absolute differences were 3.9% (95% confidence interval -5.5% to 13.2%) for certolizumab pegol, 9.4% (0.1% to 18.7%) for abatacept, and -0.6% (-10.1% to 8.9%) for tocilizumab. Key secondary outcomes showed no major differences among the four treatments. Differences in CDAI remission rates for active conventional treatment versus certolizumab pegol and tocilizumab, but not abatacept, remained within the prespecified non-inferiority margin of 15% (per protocol population). The total number of serious adverse events was 13 (percentage of patients who experienced at least one event 5.6%) for active conventional treatment, 20 (8.4%) for certolizumab pegol, 10 (4.9%) for abatacept, and 10 (4.9%) for tocilizumab. Eleven patients treated with abatacept stopped treatment early compared with 20-23 patients in the other arms. CONCLUSIONS All four treatments achieved high remission rates. Higher CDAI remission rate was observed for abatacept versus active conventional treatment, but not for certolizumab pegol or tocilizumab versus active conventional treatment. Other remission rates were similar across treatments. Non-inferiority analysis indicated that active conventional treatment was non-inferior to certolizumab pegol and tocilizumab, but not to abatacept. The results highlight the efficacy and safety of active conventional treatment based on methotrexate combined with corticosteroids, with nominally better results for abatacept, in treatment naive early rheumatoid arthritis.
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| 8. |
- Pasquali, L, et al.
(författare)
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Circulating microRNAs in extracellular vesicles as potential biomarkers for psoriatic arthritis in patients with psoriasis
- 2020
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Ingår i: Journal of the European Academy of Dermatology and Venereology. - : Wiley. - 0926-9959 .- 1468-3083. ; 34:6, s. 1248-1256
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Psoriatic arthritis (PsA) develops in ~30% of patients with psoriasis. The diagnosis of PsA is challenging, and there are no reliable molecular markers in clinical use. MicroRNAs are short non-coding regulatory RNAs, which can be actively packaged into extracellular vesicles (EVs) and secreted to the circulation.OBJECTIVES: To explore whether plasma-derived EV microRNAs may serve as biomarkers for PsA in patients with psoriasis.METHODS: Plasma samples were obtained from patients with cutaneous-only psoriasis (PsC) and patients with psoriasis and PsA. Plasma EVs were isolated using miRCURY™ Exosome Isolation Kit. RNA sequencing was used to identify differentially expressed EV miRNAs in the discovery phase (PsC, n = 15; PsA, n = 14). In the validation phase (PsC, n = 29; PsA, n = 28), 41 selected miRNAs were analysed in plasma EVs by qPCR. The association of the identified miRNAs with PsA was assessed by logistic regression analysis.RESULTS: RNA sequencing identified 19 plasma EV miRNAs with significantly different levels between PsA and PsC in the discovery cohort. Significantly lower levels of plasma EV let-7b-5p and miR-30e-5p in PsA vs. PsC were confirmed in the validation cohort, and their decreased levels were found to be associated with the presence of PsA. ROC analysis revealed an AUC of 0.68 (95% CI 0.53-0.83) for let-7b-5p and 0.69 (95% CI 0.55-0.84) for miR-30e-5p.CONCLUSIONS: Circulating EV microRNA levels are altered in patients with PsA as compared with PsC. Findings of this exploratory study suggest that circulating EV microRNAs may serve as biomarkers for arthritis in psoriasis patients.
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| 9. |
- Eastwood, J. P., et al.
(författare)
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Energy Flux Densities near the Electron Dissipation Region in Asymmetric Magnetopause Reconnection
- 2020
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Ingår i: Physical Review Letters. - : American Physical Society (APS). - 0031-9007 .- 1079-7114. ; 125:26
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Tidskriftsartikel (refereegranskat)abstract
- Magnetic reconnection is of fundamental importance to plasmas because of its role in releasing and repartitioning stored magnetic energy. Previous results suggest that this energy is predominantly released as ion enthalpy flux along the reconnection outflow. Using Magnetospheric Multiscale data we find the existence of very significant electron energy flux densities in the vicinity of the magnetopause electron dissipation region, orthogonal to the ion energy outflow. These may significantly impact models of electron transport, wave generation, and particle acceleration.
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| 10. |
- Ergun, R. E., et al.
(författare)
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Observations of Particle Acceleration in Magnetic Reconnection-driven Turbulence
- 2020
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Ingår i: Astrophysical Journal. - : IOP PUBLISHING LTD. - 0004-637X .- 1538-4357. ; 898:2
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Tidskriftsartikel (refereegranskat)abstract
- The Magnetospheric Multiscale Mission observes, in detail, charged particle heating and substantial nonthermal acceleration in a region of strong turbulence (vertical bar delta B vertical bar/vertical bar B vertical bar similar to 1, where B is the magnetic field) that surrounds a magnetic reconnection X-line. Magnetic reconnection enables magnetic field annihilation in a volume that far exceeds that of the diffusion region. The formidable magnetic field annihilation breaks into strong, intermittent turbulence with magnetic field energy as the driver. The strong, intermittent turbulence appears to generate the necessary conditions for nonthermal acceleration. It creates intense, localized currents (J) and unusually large-amplitude electric fields (E). The combination of turbulence-generated E and J results in a significant net positive mean of J center dot E, which signifies particle energization. Ion and electron heating rates are such that they experience a fourfold increase from their initial temperature. Importantly, the strong turbulence also generates magnetic holes or depletions in vertical bar B vertical bar that can trap particles. Trapping considerably increases the dwell time of a subset of particles in the turbulent region, which results in significant nonthermal particle acceleration. The direct observation of strong turbulence that is enabled by magnetic reconnection with nonthermal particle acceleration has far-reaching implications, since turbulence in plasmas is pervasive and may occupy significant volumes of the interstellar medium and intergalactic space. For example, strong turbulence from magnetic field annihilation in the supernova nebulae may dominate large volumes. As such, this observed energization process could plausibly contribute to the supply and development of the cosmic-ray spectrum.
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