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1.
  • Niemi, MEK, et al. (författare)
  • 2021
  • swepub:Mat__t
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2.
  • 2021
  • swepub:Mat__t
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3.
  • Algaba, Juan-Carlos, et al. (författare)
  • Broadband Multi-wavelength Properties of M87 during the 2017 Event Horizon Telescope Campaign
  • 2021
  • Ingår i: Astrophysical Journal Letters. - : American Astronomical Society. - 2041-8213 .- 2041-8205. ; 911:1
  • Forskningsöversikt (refereegranskat)abstract
    • In 2017, the Event Horizon Telescope (EHT) Collaboration succeeded in capturing the first direct image of the center of the M87 galaxy. The asymmetric ring morphology and size are consistent with theoretical expectations for a weakly accreting supermassive black hole of mass ∼6.5 × 109 M o˙. The EHTC also partnered with several international facilities in space and on the ground, to arrange an extensive, quasi-simultaneous multi-wavelength campaign. This Letter presents the results and analysis of this campaign, as well as the multi-wavelength data as a legacy data repository. We captured M87 in a historically low state, and the core flux dominates over HST-1 at high energies, making it possible to combine core flux constraints with the more spatially precise very long baseline interferometry data. We present the most complete simultaneous multi-wavelength spectrum of the active nucleus to date, and discuss the complexity and caveats of combining data from different spatial scales into one broadband spectrum. We apply two heuristic, isotropic leptonic single-zone models to provide insight into the basic source properties, but conclude that a structured jet is necessary to explain M87's spectrum. We can exclude that the simultaneous γ-ray emission is produced via inverse Compton emission in the same region producing the EHT mm-band emission, and further conclude that the γ-rays can only be produced in the inner jets (inward of HST-1) if there are strongly particle-dominated regions. Direct synchrotron emission from accelerated protons and secondaries cannot yet be excluded.
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4.
  • Kim, Jae-Young, et al. (författare)
  • Event Horizon Telescope imaging of the archetypal blazar 3C 279 at an extreme 20 microarcsecond resolution
  • 2020
  • Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 640
  • 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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6.
  • Paraschos, Georgios Filippos, et al. (författare)
  • Ordered magnetic fields around the 3C 84 central black hole
  • 2024
  • Ingår i: Astronomy and Astrophysics. - 0004-6361 .- 1432-0746. ; 682
  • Tidskriftsartikel (refereegranskat)abstract
    • Context . 3C 84 is a nearby radio source with a complex total intensity structure, showing linear polarisation and spectral patterns. A detailed investigation of the central engine region necessitates the use of very-long-baseline interferometry (VLBI) above the hitherto available maximum frequency of 86 GHz. Aims. Using ultrahigh resolution VLBI observations at the currently highest available frequency of 228 GHz, we aim to perform a direct detection of compact structures and understand the physical conditions in the compact region of 3C 84. Methods . We used Event Horizon Telescope (EHT) 228 GHz observations and, given the limited (u, v)-coverage, applied geometric model fitting to the data. Furthermore, we employed quasi-simultaneously observed, ancillary multi-frequency VLBI data for the source in order to carry out a comprehensive analysis of the core structure. Results . We report the detection of a highly ordered, strong magnetic field around the central, supermassive black hole of 3C 84. The brightness temperature analysis suggests that the system is in equipartition. We also determined a turnover frequency of νm = (113 ± 4) GHz, a corresponding synchrotron self-absorbed magnetic field of BSSA = (2.9 ± 1.6) G, and an equipartition magnetic field of Beq = (5.2 ± 0.6) G. Three components are resolved with the highest fractional polarisation detected for this object (mnet = (17.0 ± 3.9)%). The positions of the components are compatible with those seen in low-frequency VLBI observations since 2017-2018. We report a steeply negative slope of the spectrum at 228 GHz. We used these findings to test existing models of jet formation, propagation, and Faraday rotation in 3C 84. Conclusions . The findings of our investigation into different flow geometries and black hole spins support an advection-dominated accretion flow in a magnetically arrested state around a rapidly rotating supermassive black hole as a model of the jet-launching system in the core of 3C 84. However, systematic uncertainties due to the limited (u, v)-coverage, however, cannot be ignored. Our upcoming work using new EHT data, which offer full imaging capabilities, will shed more light on the compact region of 3C 84.
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7.
  • Roelofs, F., et al. (författare)
  • SYMBA: An end-to-end VLBI synthetic data generation pipeline: Simulating Event Horizon Telescope observations of M 87
  • 2020
  • Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 636
  • 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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8.
  • Akiyama, Kazunori, et al. (författare)
  • First M87 Event Horizon Telescope Results. IX. Detection of Near-horizon Circular Polarization
  • 2023
  • Ingår i: Astrophysical Journal Letters. - 2041-8213 .- 2041-8205. ; 957:2
  • Tidskriftsartikel (refereegranskat)abstract
    • Event Horizon Telescope (EHT) observations have revealed a bright ring of emission around the supermassive black hole at the center of the M87 galaxy. EHT images in linear polarization have further identified a coherent spiral pattern around the black hole, produced from ordered magnetic fields threading the emitting plasma. Here we present the first analysis of circular polarization using EHT data, acquired in 2017, which can potentially provide additional insights into the magnetic fields and plasma composition near the black hole. Interferometric closure quantities provide convincing evidence for the presence of circularly polarized emission on event-horizon scales. We produce images of the circular polarization using both traditional and newly developed methods. All methods find a moderate level of resolved circular polarization across the image (〈|v|〉 < 3.7%), consistent with the low image-integrated circular polarization fraction measured by the Atacama Large Millimeter/submillimeter Array (|vint| < 1%). Despite this broad agreement, the methods show substantial variation in the morphology of the circularly polarized emission, indicating that our conclusions are strongly dependent on the imaging assumptions because of the limited baseline coverage, uncertain telescope gain calibration, and weakly polarized signal. We include this upper limit in an updated comparison to general relativistic magnetohydrodynamic simulation models. This analysis reinforces the previously reported preference for magnetically arrested accretion flow models. We find that most simulations naturally produce a low level of circular polarization consistent with our upper limit and that Faraday conversion is likely the dominant production mechanism for circular polarization at 230 GHz in M87*
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9.
  • Akiyama, Kazunori, et al. (författare)
  • First Sagittarius A∗ Event Horizon Telescope Results. VII. Polarization of the Ring
  • 2024
  • Ingår i: Astrophysical Journal Letters. - 2041-8213 .- 2041-8205. ; 964:2
  • Tidskriftsartikel (refereegranskat)abstract
    • The Event Horizon Telescope observed the horizon-scale synchrotron emission region around the Galactic center supermassive black hole, Sagittarius A∗ (Sgr A∗), in 2017. These observations revealed a bright, thick ring morphology with a diameter of 51.8 ± 2.3 μas and modest azimuthal brightness asymmetry, consistent with the expected appearance of a black hole with mass M≈ 4 × 106 M⊙. From these observations, we present the first resolved linear and circular polarimetric images of Sgr A∗. The linear polarization images demonstrate that the emission ring is highly polarized, exhibiting a prominent spiral electric vector polarization angle pattern with a peak fractional polarization of ∼40% in the western portion of the ring. The circular polarization images feature a modestly (∼5%°-10%) polarized dipole structure along the emission ring, with negative circular polarization in the western region and positive circular polarization in the eastern region, although our methods exhibit stronger disagreement than for linear polarization. We analyze the data using multiple independent imaging and modeling methods, each of which is validated using a standardized suite of synthetic data sets. While the detailed spatial distribution of the linear polarization along the ring remains uncertain owing to the intrinsic variability of the source, the spiraling polarization structure is robust to methodological choices. The degree and orientation of the linear polarization provide stringent constraints for the black hole and its surrounding magnetic fields, which we discuss in an accompanying publication.
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10.
  • Akiyama, Kazunori, et al. (författare)
  • First Sagittarius A∗ Event Horizon Telescope Results. VIII. Physical Interpretation of the Polarized Ring
  • 2024
  • Ingår i: Astrophysical Journal Letters. - 2041-8213 .- 2041-8205. ; 964:2
  • Tidskriftsartikel (refereegranskat)abstract
    • In a companion paper, we present the first spatially resolved polarized image of Sagittarius A∗ on event horizon scales, captured using the Event Horizon Telescope, a global very long baseline interferometric array operating at a wavelength of 1.3 mm. Here we interpret this image using both simple analytic models and numerical general relativistic magnetohydrodynamic (GRMHD) simulations. The large spatially resolved linear polarization fraction (24%-28%, peaking at ∼40%) is the most stringent constraint on parameter space, disfavoring models that are too Faraday depolarized. Similar to our studies of M87∗, polarimetric constraints reinforce a preference for GRMHD models with dynamically important magnetic fields. Although the spiral morphology of the polarization pattern is known to constrain the spin and inclination angle, the time-variable rotation measure (RM) of Sgr A∗ (equivalent to ≈ 46° ± 12° rotation at 228 GHz) limits its present utility as a constraint. If we attribute the RM to internal Faraday rotation, then the motion of accreting material is inferred to be counterclockwise, contrary to inferences based on historical polarized flares, and no model satisfies all polarimetric and total intensity constraints. On the other hand, if we attribute the mean RM to an external Faraday screen, then the motion of accreting material is inferred to be clockwise, and one model passes all applied total intensity and polarimetric constraints: a model with strong magnetic fields, a spin parameter of 0.94, and an inclination of 150°. We discuss how future 345 GHz and dynamical imaging will mitigate our present uncertainties and provide additional constraints on the black hole and its accretion flow.
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11.
  • Akiyama, Kazunori, et al. (författare)
  • The persistent shadow of the supermassive black hole of M 87: I. Observations, calibration, imaging, and analysis*
  • 2024
  • Ingår i: Astronomy and Astrophysics. - 0004-6361 .- 1432-0746. ; 681
  • Tidskriftsartikel (refereegranskat)abstract
    • In April 2019, the Event Horizon Telescope (EHT) Collaboration reported the first-ever event-horizon-scale images of a black hole, resolving the central compact radio source in the giant elliptical galaxy M 87. These images reveal a ring with a southerly brightness distribution and a diameter of ∼42 μas, consistent with the predicted size and shape of a shadow produced by the gravitationally lensed emission around a supermassive black hole. These results were obtained as part of the April 2017 EHT observation campaign, using a global very long baseline interferometric radio array operating at a wavelength of 1.3 mm. Here, we present results based on the second EHT observing campaign, taking place in April 2018 with an improved array, wider frequency coverage, and increased bandwidth. In particular, the additional baselines provided by the Greenland telescope improved the coverage of the array. Multiyear EHT observations provide independent snapshots of the horizon-scale emission, allowing us to confirm the persistence, size, and shape of the black hole shadow, and constrain the intrinsic structural variability of the accretion flow. We have confirmed the presence of an asymmetric ring structure, brighter in the southwest, with a median diameter of 43.3-3.1+1.5 μas. The diameter of the 2018 ring is remarkably consistent with the diameter obtained from the previous 2017 observations. On the other hand, the position angle of the brightness asymmetry in 2018 is shifted by about 30 relative to 2017. The perennial persistence of the ring and its diameter robustly support the interpretation that the ring is formed by lensed emission surrounding a Kerr black hole with a mass ∼6.5× 109M. The significant change in the ring brightness asymmetry implies a spin axis that is more consistent with the position angle of the large-scale jet.
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12.
  • Georgiev, Boris, et al. (författare)
  • A Universal Power-law Prescription for Variability from Synthetic Images of Black Hole Accretion Flows
  • 2022
  • Ingår i: Astrophysical Journal Letters. - : American Astronomical Society. - 2041-8213 .- 2041-8205. ; 930:2
  • Tidskriftsartikel (refereegranskat)abstract
    • We present a framework for characterizing the spatiotemporal power spectrum of the variability expected from the horizon-scale emission structure around supermassive black holes, and we apply this framework to a library of general relativistic magnetohydrodynamic (GRMHD) simulations and associated general relativistic ray-traced images relevant for Event Horizon Telescope (EHT) observations of Sgr A*. We find that the variability power spectrum is generically a red-noise process in both the temporal and spatial dimensions, with the peak in power occurring on the longest timescales and largest spatial scales. When both the time-averaged source structure and the spatially integrated light-curve variability are removed, the residual power spectrum exhibits a universal broken power-law behavior. On small spatial frequencies, the residual power spectrum rises as the square of the spatial frequency and is proportional to the variance in the centroid of emission. Beyond some peak in variability power, the residual power spectrum falls as that of the time-averaged source structure, which is similar across simulations; this behavior can be naturally explained if the variability arises from a multiplicative random field that has a steeper high-frequency power-law index than that of the time-averaged source structure. We briefly explore the ability of power spectral variability studies to constrain physical parameters relevant for the GRMHD simulations, which can be scaled to provide predictions for black holes in a range of systems in the optically thin regime. We present specific expectations for the behavior of the M87* and Sgr A* accretion flows as observed by the EHT.
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13.
  • Roelofs, F., et al. (författare)
  • Polarimetric Geometric Modeling for mm-VLBI Observations of Black Holes
  • 2023
  • Ingår i: Astrophysical Journal Letters. - 2041-8213 .- 2041-8205. ; 957:2
  • Tidskriftsartikel (refereegranskat)abstract
    • The Event Horizon Telescope (EHT) is a millimeter very long baseline interferometry (VLBI) array that has imaged the apparent shadows of the supermassive black holes M87* and Sagittarius A*. Polarimetric data from these observations contain a wealth of information on the black hole and accretion flow properties. In this work, we develop polarimetric geometric modeling methods for mm-VLBI data, focusing on approaches that fit data products with differing degrees of invariance to broad classes of calibration errors. We establish a fitting procedure using a polarimetric “m-ring” model to approximate the image structure near a black hole. By fitting this model to synthetic EHT data from general relativistic magnetohydrodynamic models, we show that the linear and circular polarization structure can be successfully approximated with relatively few model parameters. We then fit this model to EHT observations of M87* taken in 2017. In total intensity and linear polarization, the m-ring fits are consistent with previous results from imaging methods. In circular polarization, the m-ring fits indicate the presence of event-horizon-scale circular polarization structure, with a persistent dipolar asymmetry and orientation across several days. The same structure was recovered independently of observing band, used data products, and model assumptions. Despite this broad agreement, imaging methods do not produce similarly consistent results. Our circular polarization results, which imposed additional assumptions on the source structure, should thus be interpreted with some caution. Polarimetric geometric modeling provides a useful and powerful method to constrain the properties of horizon-scale polarized emission, particularly for sparse arrays like the EHT.
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14.
  • Eatough, Ralph P., et al. (författare)
  • Verification of Radiative Transfer Schemes for the EHT
  • 2020
  • Ingår i: Astrophysical Journal. - : American Astronomical Society. - 1538-4357 .- 0004-637X. ; 897:2
  • 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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15.
  • Janssen, Michael, et al. (författare)
  • Event Horizon Telescope observations of the jet launching and collimation in Centaurus A
  • 2021
  • Ingår i: Nature Astronomy. - : Springer Science and Business Media LLC. - 2397-3366. ; 5:10, s. 1017-1028
  • Tidskriftsartikel (refereegranskat)abstract
    • Very-long-baseline interferometry (VLBI) observations of active galactic nuclei at millimetre wavelengths have the power to reveal the launching and initial collimation region of extragalactic radio jets, down to 10–100 gravitational radii (rg ≡ GM/c2) scales in nearby sources1. Centaurus A is the closest radio-loud source to Earth2. It bridges the gap in mass and accretion rate between the supermassive black holes (SMBHs) in Messier 87 and our Galactic Centre. A large southern declination of −43° has, however, prevented VLBI imaging of Centaurus A below a wavelength of 1 cm thus far. Here we show the millimetre VLBI image of the source, which we obtained with the Event Horizon Telescope at 228 GHz. Compared with previous observations3, we image the jet of Centaurus A at a tenfold higher frequency and sixteen times sharper resolution and thereby probe sub-lightday structures. We reveal a highly collimated, asymmetrically edge-brightened jet as well as the fainter counterjet. We find that the source structure of Centaurus A resembles the jet in Messier 87 on ~500 rg scales remarkably well. Furthermore, we identify the location of Centaurus A’s SMBH with respect to its resolved jet core at a wavelength of 1.3 mm and conclude that the source’s event horizon shadow4 should be visible at terahertz frequencies. This location further supports the universal scale invariance of black holes over a wide range of masses5,6.
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16.
  • Broderick, Avery E., et al. (författare)
  • THEMIS: A Parameter Estimation Framework for the Event Horizon Telescope
  • 2020
  • Ingår i: Astrophysical Journal. - : American Astronomical Society. - 1538-4357 .- 0004-637X. ; 897:2
  • 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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17.
  • Chen, Hao Yu, et al. (författare)
  • Association of FADS1/2 Locus Variants and Polyunsaturated Fatty Acids With Aortic Stenosis
  • 2020
  • Ingår i: JAMA cardiology. - : American Medical Association (AMA). - 2380-6583 .- 2380-6591. ; 5:6, s. 694-702
  • Tidskriftsartikel (refereegranskat)abstract
    • Importance: Aortic stenosis (AS) has no approved medical treatment. Identifying etiological pathways for AS could identify pharmacological targets.Objective: To identify novel genetic loci and pathways associated with AS.Design, Setting, and Participants: This genome-wide association study used a case-control design to evaluate 44 703 participants (3469 cases of AS) of self-reported European ancestry from the Genetic Epidemiology Research on Adult Health and Aging (GERA) cohort (from January 1, 1996, to December 31, 2015). Replication was performed in 7 other cohorts totaling 256 926 participants (5926 cases of AS), with additional analyses performed in 6942 participants from the Cohorts for Heart and Aging Research in Genomic Epidemiology (CHARGE) Consortium. Follow-up biomarker analyses with aortic valve calcium (AVC) were also performed. Data were analyzed from May 1, 2017, to December 5, 2019.Exposures: Genetic variants (615 643 variants) and polyunsaturated fatty acids (ω-6 and ω-3) measured in blood samples.Main Outcomes and Measures: Aortic stenosis and aortic valve replacement defined by electronic health records, surgical records, or echocardiography and the presence of AVC measured by computed tomography.Results: The mean (SD) age of the 44 703 GERA participants was 69.7 (8.4) years, and 22 019 (49.3%) were men. The rs174547 variant at the FADS1/2 locus was associated with AS (odds ratio [OR] per C allele, 0.88; 95% CI, 0.83-0.93; P = 3.0 × 10-6), with genome-wide significance after meta-analysis with 7 replication cohorts totaling 312 118 individuals (9395 cases of AS) (OR, 0.91; 95% CI, 0.88-0.94; P = 2.5 × 10-8). A consistent association with AVC was also observed (OR, 0.91; 95% CI, 0.83-0.99; P = .03). A higher ratio of arachidonic acid to linoleic acid was associated with AVC (OR per SD of the natural logarithm, 1.19; 95% CI, 1.09-1.30; P = 6.6 × 10-5). In mendelian randomization, increased FADS1 liver expression and arachidonic acid were associated with AS (OR per unit of normalized expression, 1.31 [95% CI, 1.17-1.48; P = 7.4 × 10-6]; OR per 5-percentage point increase in arachidonic acid for AVC, 1.23 [95% CI, 1.01-1.49; P = .04]; OR per 5-percentage point increase in arachidonic acid for AS, 1.08 [95% CI, 1.04-1.13; P = 4.1 × 10-4]).Conclusions and Relevance: Variation at the FADS1/2 locus was associated with AS and AVC. Findings from biomarker measurements and mendelian randomization appear to link ω-6 fatty acid biosynthesis to AS, which may represent a therapeutic target.
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21.
  • Jorstad, S.G., et al. (författare)
  • The Event Horizon Telescope Image of the Quasar NRAO 530
  • 2023
  • Ingår i: Astrophysical Journal. - : American Astronomical Society. - 1538-4357 .- 0004-637X. ; 943:2
  • Tidskriftsartikel (refereegranskat)abstract
    • We report on the observations of the quasar NRAO 530 with the Event Horizon Telescope (EHT) on 2017 April 5-7, when NRAO 530 was used as a calibrator for the EHT observations of Sagittarius A*. At z = 0.902, this is the most distant object imaged by the EHT so far. We reconstruct the first images of the source at 230 GHz, at an unprecedented angular resolution of similar to 20 mu as, both in total intensity and in linear polarization (LP). We do not detect source variability, allowing us to represent the whole data set with static images. The images reveal a bright feature located on the southern end of the jet, which we associate with the core. The feature is linearly polarized, with a fractional polarization of similar to 5%-8%, and it has a substructure consisting of two components. Their observed brightness temperature suggests that the energy density of the jet is dominated by the magnetic field. The jet extends over 60 mu as along a position angle similar to -28 degrees. It includes two features with orthogonal directions of polarization (electric vector position angle), parallel and perpendicular to the jet axis, consistent with a helical structure of the magnetic field in the jet. The outermost feature has a particularly high degree of LP, suggestive of a nearly uniform magnetic field. Future EHT observations will probe the variability of the jet structure on microarcsecond scales, while simultaneous multiwavelength monitoring will provide insight into the high-energy emission origin.
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22.
  • Akiyama, Kazunori, et al. (författare)
  • First Sagittarius A* Event Horizon Telescope Results. II. EHT and Multiwavelength Observations, Data Processing, and Calibration
  • 2022
  • Ingår i: Astrophysical Journal Letters. - : American Astronomical Society. - 2041-8213 .- 2041-8205. ; 930:2
  • Tidskriftsartikel (refereegranskat)abstract
    • We present Event Horizon Telescope (EHT) 1.3 mm measurements of the radio source located at the position of the supermassive black hole Sagittarius A* (Sgr A*), collected during the 2017 April 5-11 campaign. The observations were carried out with eight facilities at six locations across the globe. Novel calibration methods are employed to account for Sgr A*'s flux variability. The majority of the 1.3 mm emission arises from horizon scales, where intrinsic structural source variability is detected on timescales of minutes to hours. The effects of interstellar scattering on the image and its variability are found to be subdominant to intrinsic source structure. The calibrated visibility amplitudes, particularly the locations of the visibility minima, are broadly consistent with a blurred ring with a diameter of similar to 50 mu as, as determined in later works in this series. Contemporaneous multiwavelength monitoring of Sgr A* was performed at 22, 43, and 86 GHz and at near-infrared and X-ray wavelengths. Several X-ray flares from Sgr A* are detected by Chandra, one at low significance jointly with Swift on 2017 April 7 and the other at higher significance jointly with NuSTAR on 2017 April 11. The brighter April 11 flare is not observed simultaneously by the EHT but is followed by a significant increase in millimeter flux variability immediately after the X-ray outburst, indicating a likely connection in the emission physics near the event horizon. We compare Sgr A*'s broadband flux during the EHT campaign to its historical spectral energy distribution and find that both the quiescent emission and flare emission are consistent with its long-term behavior.
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23.
  • Akiyama, Kazunori, et al. (författare)
  • First Sagittarius A* Event Horizon Telescope Results. III. Imaging of the Galactic Center Supermassive Black Hole
  • 2022
  • Ingår i: Astrophysical Journal Letters. - : American Astronomical Society. - 2041-8213 .- 2041-8205. ; 930:2
  • Tidskriftsartikel (refereegranskat)abstract
    • We present the first event-horizon-scale images and spatiotemporal analysis of Sgr A* taken with the Event Horizon Telescope in 2017 April at a wavelength of 1.3 mm. Imaging of Sgr A* has been conducted through surveys over a wide range of imaging assumptions using the classical CLEAN algorithm, regularized maximum likelihood methods, and a Bayesian posterior sampling method. Different prescriptions have been used to account for scattering effects by the interstellar medium toward the Galactic center. Mitigation of the rapid intraday variability that characterizes Sgr A* has been carried out through the addition of a "variability noise budget" in the observed visibilities, facilitating the reconstruction of static full-track images. Our static reconstructions of Sgr A* can be clustered into four representative morphologies that correspond to ring images with three different azimuthal brightness distributions and a small cluster that contains diverse nonring morphologies. Based on our extensive analysis of the effects of sparse (u, v)-coverage, source variability, and interstellar scattering, as well as studies of simulated visibility data, we conclude that the Event Horizon Telescope Sgr A* data show compelling evidence for an image that is dominated by a bright ring of emission with a ring diameter of similar to 50 mu as, consistent with the expected "shadow" of a 4 x 10(6) M (circle dot) black hole in the Galactic center located at a distance of 8 kpc.
  •  
24.
  • Akiyama, Kazunori, et al. (författare)
  • First Sagittarius A* Event Horizon Telescope Results. IV. Variability, Morphology, and Black Hole Mass
  • 2022
  • Ingår i: Astrophysical Journal Letters. - : American Astronomical Society. - 2041-8213 .- 2041-8205. ; 930:2
  • Tidskriftsartikel (refereegranskat)abstract
    • In this paper we quantify the temporal variability and image morphology of the horizon-scale emission from Sgr A*, as observed by the EHT in 2017 April at a wavelength of 1.3 mm. We find that the Sgr A* data exhibit variability that exceeds what can be explained by the uncertainties in the data or by the effects of interstellar scattering. The magnitude of this variability can be a substantial fraction of the correlated flux density, reaching similar to 100% on some baselines. Through an exploration of simple geometric source models, we demonstrate that ring-like morphologies provide better fits to the Sgr A* data than do other morphologies with comparable complexity. We develop two strategies for fitting static geometric ring models to the time-variable Sgr A* data; one strategy fits models to short segments of data over which the source is static and averages these independent fits, while the other fits models to the full data set using a parametric model for the structural variability power spectrum around the average source structure. Both geometric modeling and image-domain feature extraction techniques determine the ring diameter to be 51.8 +/- 2.3 mu as (68% credible intervals), with the ring thickness constrained to have an FWHM between similar to 30% and 50% of the ring diameter. To bring the diameter measurements to a common physical scale, we calibrate them using synthetic data generated from GRMHD simulations. This calibration constrains the angular size of the gravitational radius to be 4.8(-0.7)(+1.4) mu as, which we combine with an independent distance measurement from maser parallaxes to determine the mass of Sgr A* to be 4.0(-0.6)(+1.1) x 10(6) M-circle dot.
  •  
25.
  • Akiyama, Kazunori, et al. (författare)
  • First Sagittarius A* Event Horizon Telescope Results. V. Testing Astrophysical Models of the Galactic Center Black Hole
  • 2022
  • Ingår i: Astrophysical Journal Letters. - : American Astronomical Society. - 2041-8213 .- 2041-8205. ; 930:2
  • Tidskriftsartikel (refereegranskat)abstract
    • In this paper we provide a first physical interpretation for the Event Horizon Telescope's (EHT) 2017 observations of Sgr A*. Our main approach is to compare resolved EHT data at 230 GHz and unresolved non-EHT observations from radio to X-ray wavelengths to predictions from a library of models based on time-dependent general relativistic magnetohydrodynamics simulations, including aligned, tilted, and stellar-wind-fed simulations; radiative transfer is performed assuming both thermal and nonthermal electron distribution functions. We test the models against 11 constraints drawn from EHT 230 GHz data and observations at 86 GHz, 2.2 mu m, and in the X-ray. All models fail at least one constraint. Light-curve variability provides a particularly severe constraint, failing nearly all strongly magnetized (magnetically arrested disk (MAD)) models and a large fraction of weakly magnetized models. A number of models fail only the variability constraints. We identify a promising cluster of these models, which are MAD and have inclination i <= 30 degrees. They have accretion rate (5.2-9.5) x 10(-9) M (circle dot) yr(-1), bolometric luminosity (6.8-9.2) x 10(35) erg s(-1), and outflow power (1.3-4.8) x 10(38) erg s(-1). We also find that all models with i >= 70 degrees fail at least two constraints, as do all models with equal ion and electron temperature; exploratory, nonthermal model sets tend to have higher 2.2 mu m flux density; and the population of cold electrons is limited by X-ray constraints due to the risk of bremsstrahlung overproduction. Finally, we discuss physical and numerical limitations of the models, highlighting the possible importance of kinetic effects and duration of the simulations.
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26.
  • Akiyama, Kazunori, et al. (författare)
  • First Sagittarius A* Event Horizon Telescope Results. VI. Testing the Black Hole Metric
  • 2022
  • Ingår i: Astrophysical Journal Letters. - : American Astronomical Society. - 2041-8213 .- 2041-8205. ; 930:2
  • Tidskriftsartikel (refereegranskat)abstract
    • Astrophysical black holes are expected to be described by the Kerr metric. This is the only stationary, vacuum, axisymmetric metric, without electromagnetic charge, that satisfies Einstein's equations and does not have pathologies outside of the event horizon. We present new constraints on potential deviations from the Kerr prediction based on 2017 EHT observations of Sagittarius A* (Sgr A*). We calibrate the relationship between the geometrically defined black hole shadow and the observed size of the ring-like images using a library that includes both Kerr and non-Kerr simulations. We use the exquisite prior constraints on the mass-to-distance ratio for Sgr A* to show that the observed image size is within similar to 10% of the Kerr predictions. We use these bounds to constrain metrics that are parametrically different from Kerr, as well as the charges of several known spacetimes. To consider alternatives to the presence of an event horizon, we explore the possibility that Sgr A* is a compact object with a surface that either absorbs and thermally reemits incident radiation or partially reflects it. Using the observed image size and the broadband spectrum of Sgr A*, we conclude that a thermal surface can be ruled out and a fully reflective one is unlikely. We compare our results to the broader landscape of gravitational tests. Together with the bounds found for stellar-mass black holes and the M87 black hole, our observations provide further support that the external spacetimes of all black holes are described by the Kerr metric, independent of their mass.
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27.
  • Broderick, Avery E., et al. (författare)
  • Characterizing and Mitigating Intraday Variability: Reconstructing Source Structure in Accreting Black Holes with mm-VLBI
  • 2022
  • Ingår i: Astrophysical Journal Letters. - : American Astronomical Society. - 2041-8213 .- 2041-8205. ; 930:2
  • Tidskriftsartikel (refereegranskat)abstract
    • The extraordinary physical resolution afforded by the Event Horizon Telescope has opened a window onto the astrophysical phenomena unfolding on horizon scales in two known black holes, M87* and Sgr A*. However, with this leap in resolution has come a new set of practical complications. Sgr A* exhibits intraday variability that violates the assumptions underlying Earth aperture synthesis, limiting traditional image reconstruction methods to short timescales and data sets with very sparse (u, v) coverage. We present a new set of tools to detect and mitigate this variability. We develop a data-driven, model-agnostic procedure to detect and characterize the spatial structure of intraday variability. This method is calibrated against a large set of mock data sets, producing an empirical estimator of the spatial power spectrum of the brightness fluctuations. We present a novel Bayesian noise modeling algorithm that simultaneously reconstructs an average image and statistical measure of the fluctuations about it using a parameterized form for the excess variance in the complex visibilities not otherwise explained by the statistical errors. These methods are validated using a variety of simulated data, including general relativistic magnetohydrodynamic simulations appropriate for Sgr A* and M87*. We find that the reconstructed source structure and variability are robust to changes in the underlying image model. We apply these methods to the 2017 EHT observations of M87*, finding evidence for variability across the EHT observing campaign. The variability mitigation strategies presented are widely applicable to very long baseline interferometry observations of variable sources generally, for which they provide a data-informed averaging procedure and natural characterization of inter-epoch image consistency.
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28.
  • Chen, H. Y., et al. (författare)
  • Genome-wide association meta-analysis in 652,134 participants identifies 9 novel susceptibility loci for aortic stenosis
  • 2020
  • Ingår i: European Heart Journal. - : Oxford University Press. - 0195-668X .- 1522-9645. ; 41:Suppl 2, s. 1862-1862
  • Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
    • Background: Aortic stenosis (AS) is the most common form of incident valvular heart disease. While valve replacement is effective, the absence of an approved medical therapy provides no alternatives to patients with contraindications or mild disease. An improved understanding of the genetics of AS could identify targets for pharmacological intervention.Methods: An inverse variance-weighted, fixed effects meta-analysis of the association of 11,591,806 variants with AS was undertaken using data from 10 European cohorts totalling 652,134 participants (13,758 cases of AS). We queried publicly available datasets to characterize the functional consequences of genome-wide significant variants, conducted a phenome-wide association study to assess their association with other outcomes, and constructed polygenic risk scores to examine their association with AS. We also performed gene- and gene-set enrichment analyses, estimated genetic correlation with cardiovascular traits, and assessed whether five lipid or immunological biomarkers were causally associated with AS using Mendelian randomization.Results: Eighteen independent variants at 16 loci attained genome-wide significance in the meta-analysis, including variants at all seven previously reported loci. Many of the significant variants were intronic or intergenic, and the phenome-wide association study revealed extensive pleiotropy with apolipoprotein B, C-reactive protein, and other cardiovascular and immunological traits. A weighted polygenic risk score composed of the 18 variants was strongly associated with AS (adjusted OR per SD, 1.38; 95% CI, 1.33 to 1.44; p=4.6×10–57), and improved the discriminatory ability for AS when added to a model that contained clinical risk factors (difference in the area under the curve p=2.0×10–11). Gene-based approaches indicated higher IL6R expression in the blood among AS cases compared to controls (p=3.1×10–6), and the association of LDLR with AS (p=2.3×10–10). Gene set analyses revealed that genes bound by the transcription factor TCF7 or micro-RNAs miR-21, miR-219, miR-491, and miR-19 were differentially expressed in the liver depending on AS status (p≤5.7×10–4), suggesting disease development may be mediated by tissue-specific transcriptional and post-transcriptional regulation. Mendelian randomization supported a causal association of five lipid and immunological biomarkers with AS, including low-density lipoprotein cholesterol (OR per mmol/L, 1.61; 95% CI, 1.48 to 1.75; p=1.3×10–30).Conclusions: Evidence from large-scale genetic analyses indicate that lipid metabolism, inflammation, and calcification are key contributors to AS.
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29.
  • Goddi, Ciriaco, et al. (författare)
  • Polarimetric Properties of Event Horizon Telescope Targets from ALMA
  • 2021
  • Ingår i: Astrophysical Journal Letters. - : American Astronomical Society. - 2041-8213 .- 2041-8205. ; 910:1
  • Tidskriftsartikel (refereegranskat)abstract
    • We present the results from a full polarization study carried out with the Atacama Large Millimeter/submillimeter Array (ALMA) during the first Very Long Baseline Interferometry (VLBI) campaign, which was conducted in 2017 April in the lambda 3 mm and lambda 1.3 mm bands, in concert with the Global mm-VLBI Array (GMVA) and the Event Horizon Telescope (EHT), respectively. We determine the polarization and Faraday properties of all VLBI targets, including Sgr A*, M87, and a dozen radio-loud active galactic nuclei (AGNs), in the two bands at several epochs in a time window of 10 days. We detect high linear polarization fractions (2%-15%) and large rotation measures (RM > 10(3.3)-10(5.5) rad m(-2)), confirming the trends of previous AGN studies at millimeter wavelengths. We find that blazars are more strongly polarized than other AGNs in the sample, while exhibiting (on average) order-of-magnitude lower RM values, consistent with the AGN viewing angle unification scheme. For Sgr A* we report a mean RM of (-4.2 0.3) x 10(5) rad m(-2) at 1.3 mm, consistent with measurements over the past decade and, for the first time, an RM of (-2.1 0.1) x 10(5) rad m(-2) at 3 mm, suggesting that about half of the Faraday rotation at 1.3 mm may occur between the 3 mm photosphere and the 1.3 mm source. We also report the first unambiguous measurement of RM toward the M87 nucleus at millimeter wavelengths, which undergoes significant changes in magnitude and sign reversals on a one year timescale, spanning the range from -1.2 to 0.3 x 10(5) rad m(-2) at 3 mm and -4.1 to 1.5 x 10(5) rad m(-2) at 1.3 mm. Given this time variability, we argue that, unlike the case of Sgr A*, the RM in M87 does not provide an accurate estimate of the mass accretion rate onto the black hole. We put forward a two-component model, comprised of a variable compact region and a static extended region, that can simultaneously explain the polarimetric properties observed by both the EHT (on horizon scales) and ALMA (which observes the combined emission from both components). These measurements provide critical constraints for the calibration, analysis, and interpretation of simultaneously obtained VLBI data with the EHT and GMVA.
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30.
  • Hickey, J. W., et al. (författare)
  • Spatial mapping of protein composition and tissue organization : a primer for multiplexed antibody-based imaging
  • 2022
  • Ingår i: Nature Methods. - : Nature Research. - 1548-7091 .- 1548-7105. ; 19:3, s. 284-295
  • Tidskriftsartikel (refereegranskat)abstract
    • Tissues and organs are composed of distinct cell types that must operate in concert to perform physiological functions. Efforts to create high-dimensional biomarker catalogs of these cells have been largely based on single-cell sequencing approaches, which lack the spatial context required to understand critical cellular communication and correlated structural organization. To probe in situ biology with sufficient depth, several multiplexed protein imaging methods have been recently developed. Though these technologies differ in strategy and mode of immunolabeling and detection tags, they commonly utilize antibodies directed against protein biomarkers to provide detailed spatial and functional maps of complex tissues. As these promising antibody-based multiplexing approaches become more widely adopted, new frameworks and considerations are critical for training future users, generating molecular tools, validating antibody panels, and harmonizing datasets. In this Perspective, we provide essential resources, key considerations for obtaining robust and reproducible imaging data, and specialized knowledge from domain experts and technology developers.
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31.
  • Issaoun, Sara, et al. (författare)
  • Resolving the Inner Parsec of the Blazar J1924-2914 with the Event Horizon Telescope
  • 2022
  • Ingår i: Astrophysical Journal. - : American Astronomical Society. - 1538-4357 .- 0004-637X. ; 934:2
  • Tidskriftsartikel (refereegranskat)abstract
    • The blazar J1924-2914 is a primary Event Horizon Telescope (EHT) calibrator for the Galactic center's black hole Sagittarius A*. Here we present the first total and linearly polarized intensity images of this source obtained with the unprecedented 20 mu as resolution of the EHT. J1924-2914 is a very compact flat-spectrum radio source with strong optical variability and polarization. In April 2017 the source was observed quasi-simultaneously with the EHT (April 5-11), the Global Millimeter VLBI Array (April 3), and the Very Long Baseline Array (April 28), giving a novel view of the source at four observing frequencies, 230, 86, 8.7, and 2.3 GHz. These observations probe jet properties from the subparsec to 100 pc scales. We combine the multifrequency images of J1924-2914 to study the source morphology. We find that the jet exhibits a characteristic bending, with a gradual clockwise rotation of the jet projected position angle of about 90 degrees between 2.3 and 230 GHz. Linearly polarized intensity images of J1924-2914 with the extremely fine resolution of the EHT provide evidence for ordered toroidal magnetic fields in the blazar compact core.
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32.
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33.
  • Satapathy, Kaushik, et al. (författare)
  • The Variability of the Black Hole Image in M87 at the Dynamical Timescale
  • 2022
  • Ingår i: Astrophysical Journal. - : American Astronomical Society. - 1538-4357 .- 0004-637X. ; 925:1
  • Tidskriftsartikel (refereegranskat)abstract
    • The black hole images obtained with the Event Horizon Telescope (EHT) are expected to be variable at the dynamical timescale near their horizons. For the black hole at the center of the M87 galaxy, this timescale (5-61 days) is comparable to the 6 day extent of the 2017 EHT observations. Closure phases along baseline triangles are robust interferometric observables that are sensitive to the expected structural changes of the images but are free of station-based atmospheric and instrumental errors. We explored the day-to-day variability in closure-phase measurements on all six linearly independent nontrivial baseline triangles that can be formed from the 2017 observations. We showed that three triangles exhibit very low day-to-day variability, with a dispersion of similar to 3 degrees-5 degrees. The only triangles that exhibit substantially higher variability (similar to 90 degrees-180 degrees) are the ones with baselines that cross the visibility amplitude minima on the u-v plane, as expected from theoretical modeling. We used two sets of general relativistic magnetohydrodynamic simulations to explore the dependence of the predicted variability on various black hole and accretion-flow parameters. We found that changing the magnetic field configuration, electron temperature model, or black hole spin has a marginal effect on the model consistency with the observed level of variability. On the other hand, the most discriminating image characteristic of models is the fractional width of the bright ring of emission. Models that best reproduce the observed small level of variability are characterized by thin ring-like images with structures dominated by gravitational lensing effects and thus least affected by turbulence in the accreting plasmas.
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34.
  • Torne, Pablo, et al. (författare)
  • A Search for Pulsars around Sgr A* in the First Event Horizon Telescope Data Set
  • 2023
  • Ingår i: Astrophysical Journal. - 1538-4357 .- 0004-637X. ; 959:1
  • Tidskriftsartikel (refereegranskat)abstract
    • In 2017 the Event Horizon Telescope (EHT) observed the supermassive black hole at the center of the Milky Way, Sagittarius A* (Sgr A*), at a frequency of 228.1 GHz (lambda = 1.3 mm). The fundamental physics tests that even a single pulsar orbiting Sgr A* would enable motivate searching for pulsars in EHT data sets. The high observing frequency means that pulsars-which typically exhibit steep emission spectra-are expected to be very faint. However, it also negates pulse scattering, an effect that could hinder pulsar detections in the Galactic center. Additionally, magnetars or a secondary inverse Compton emission could be stronger at millimeter wavelengths than at lower frequencies. We present a search for pulsars close to Sgr A* using the data from the three most sensitive stations in the EHT 2017 campaign: the Atacama Large Millimeter/submillimeter Array, the Large Millimeter Telescope, and the IRAM 30 m Telescope. We apply three detection methods based on Fourier-domain analysis, the fast folding algorithm, and single-pulse searches targeting both pulsars and burst-like transient emission. We use the simultaneity of the observations to confirm potential candidates. No new pulsars or significant bursts were found. Being the first pulsar search ever carried out at such high radio frequencies, we detail our analysis methods and give a detailed estimation of the sensitivity of the search. We conclude that the EHT 2017 observations are only sensitive to a small fraction (less than or similar to 2.2%) of the pulsars that may exist close to Sgr A*, motivating further searches for fainter pulsars in the region.
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35.
  • Wielgus, Maciek, et al. (författare)
  • Millimeter Light Curves of Sagittarius A* Observed during the 2017 Event Horizon Telescope Campaign
  • 2022
  • Ingår i: Astrophysical Journal Letters. - : American Astronomical Society. - 2041-8213 .- 2041-8205. ; 930:2
  • Tidskriftsartikel (refereegranskat)abstract
    • The Event Horizon Telescope (EHT) observed the compact radio source, Sagittarius A* (Sgr A*), in the Galactic Center on 2017 April 5-11 in the 1.3 mm wavelength band. At the same time, interferometric array data from the Atacama Large Millimeter/submillimeter Array and the Submillimeter Array were collected, providing Sgr A* light curves simultaneous with the EHT observations. These data sets, complementing the EHT very long baseline interferometry, are characterized by a cadence and signal-to-noise ratio previously unattainable for Sgr A* at millimeter wavelengths, and they allow for the investigation of source variability on timescales as short as a minute. While most of the light curves correspond to a low variability state of Sgr A*, the April 11 observations follow an X-ray flare and exhibit strongly enhanced variability. All of the light curves are consistent with a red-noise process, with a power spectral density (PSD) slope measured to be between -2 and -3 on timescales between 1 minute and several hours. Our results indicate a steepening of the PSD slope for timescales shorter than 0.3 hr. The spectral energy distribution is flat at 220 GHz, and there are no time lags between the 213 and 229 GHz frequency bands, suggesting low optical depth for the event horizon scale source. We characterize Sgr A*'s variability, highlighting the different behavior observed just after the X-ray flare, and use Gaussian process modeling to extract a decorrelation timescale and a PSD slope. We also investigate the systematic calibration uncertainties by analyzing data from independent data reduction pipelines.
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36.
  • Akiyama, Kazunori, et al. (författare)
  • First M87 Event Horizon Telescope Results. VII. Polarization of the Ring
  • 2021
  • Ingår i: Astrophysical Journal Letters. - : American Astronomical Society. - 2041-8213 .- 2041-8205. ; 910:1
  • Tidskriftsartikel (refereegranskat)abstract
    • In 2017 April, the Event Horizon Telescope (EHT) observed the near-horizon region around the supermassive black hole at the core of the M87 galaxy. These 1.3 mm wavelength observations revealed a compact asymmetric ring-like source morphology. This structure originates from synchrotron emission produced by relativistic plasma located in the immediate vicinity of the black hole. Here we present the corresponding linear-polarimetric EHT images of the center of M87. We find that only a part of the ring is significantly polarized. The resolved fractional linear polarization has a maximum located in the southwest part of the ring, where it rises to the level of similar to 15%. The polarization position angles are arranged in a nearly azimuthal pattern. We perform quantitative measurements of relevant polarimetric properties of the compact emission and find evidence for the temporal evolution of the polarized source structure over one week of EHT observations. The details of the polarimetric data reduction and calibration methodology are provided. We carry out the data analysis using multiple independent imaging and modeling techniques, each of which is validated against a suite of synthetic data sets. The gross polarimetric structure and its apparent evolution with time are insensitive to the method used to reconstruct the image. These polarimetric images carry information about the structure of the magnetic fields responsible for the synchrotron emission. Their physical interpretation is discussed in an accompanying publication.
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37.
  • Akiyama, Kazunori, et al. (författare)
  • First M87 Event Horizon Telescope Results. VIII. Magnetic Field Structure near The Event Horizon
  • 2021
  • Ingår i: Astrophysical Journal Letters. - : American Astronomical Society. - 2041-8213 .- 2041-8205. ; 910:1
  • Tidskriftsartikel (refereegranskat)abstract
    • Event Horizon Telescope (EHT) observations at 230 GHz have now imaged polarized emission around the supermassive black hole in M87 on event-horizon scales. This polarized synchrotron radiation probes the structure of magnetic fields and the plasma properties near the black hole. Here we compare the resolved polarization structure observed by the EHT, along with simultaneous unresolved observations with the Atacama Large Millimeter/submillimeter Array, to expectations from theoretical models. The low fractional linear polarization in the resolved image suggests that the polarization is scrambled on scales smaller than the EHT beam, which we attribute to Faraday rotation internal to the emission region. We estimate the average density n(e) similar to 10(4-7) cm(-3), magnetic field strength B similar to 1-30 G, and electron temperature T-e similar to (1-12) x 10(10) K of the radiating plasma in a simple one-zone emission model. We show that the net azimuthal linear polarization pattern may result from organized, poloidal magnetic fields in the emission region. In a quantitative comparison with a large library of simulated polarimetric images from general relativistic magnetohydrodynamic (GRMHD) simulations, we identify a subset of physical models that can explain critical features of the polarimetric EHT observations while producing a relativistic jet of sufficient power. The consistent GRMHD models are all of magnetically arrested accretion disks, where near-horizon magnetic fields are dynamically important. We use the models to infer a mass accretion rate onto the black hole in M87 of (3-20) x 10(-4) M yr(-1).
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38.
  • Alef, Walter, et al. (författare)
  • Geodetic data analysis of VGOS experiments
  • 2021
  • Ingår i: 2021 34th General Assembly and Scientific Symposium of the International Union of Radio Science, URSI GASS 2021.
  • Konferensbidrag (refereegranskat)abstract
    • Very Long Baseline Interferometry (VLBI) serves as one of the common geodetic methods to define the global reference frames and monitor Earth's orientation variations. The technical upgrade of the VLBI method known as the VLBI Global Observing System (VGOS) includes a critical re-design of the observed frequencies from the dual band mode (S and X band, i.e. 2 GHz and 8 GHz) to observations in a broadband (2-14 GHz). Since 2019 the first VGOS experiments are available for the geodetic analysis in free access at the International VLBI service for Geodesy and Astrometry (IVS). Also regional-only subnetworks such as European VLBI stations have succeeded already in VGOS mode. Based on these brand-new observations we review the current geodetic data analysis workflow to build a bridge between geodetic observed delays derived from different bands.
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39.
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40.
  • Chemaly, RF, et al. (författare)
  • A Phase 2, Randomized, Double-blind, Placebo-Controlled Trial of Presatovir for the Treatment of Respiratory Syncytial Virus Upper Respiratory Tract Infection in Hematopoietic-Cell Transplant Recipients
  • 2020
  • Ingår i: Clinical infectious diseases : an official publication of the Infectious Diseases Society of America. - : Oxford University Press (OUP). - 1537-6591. ; 71:11, s. 2777-2786
  • Tidskriftsartikel (refereegranskat)abstract
    • BackgroundHematopoietic-cell transplant (HCT) recipients are at risk for severe respiratory syncytial virus (RSV) infection. We evaluated the RSV fusion inhibitor presatovir in a randomized, double-blind, Phase II trial in HCT recipients with RSV upper respiratory tract infections.MethodsPatients were stratified by lymphopenia (&lt;200/µL) and ribavirin use; were randomized, stratified by lymphopenia (&lt;200/μL) and ribavirin use, to receive oral presatovir at 200 mg or a placebo on Days 1, 5, 9, 13, and 17, and were followed through Day 28. The coprimary efficacy endpoints were the time-weighted average change in the nasal RSV viral load between Days 1 and 9 and the proportion of patients developing lower respiratory tract complications (LRTCs) through Day 28.ResultsFrom 23 January 2015 to 16 June 2017, 189 patients were randomly assigned to treatment (96 to presatovir and 93 to the placebo). Presatovir treatment, compared with the placebo treatment, did not significantly affect (prespecified α = 0.01) a time-weighted average decline in the RSV viral load from Day 1 to 9 (treatment difference, −0.33 log10 copies/mL; 95% confidence interval [CI] −.64 to −.02 log10 copies/mL; P = .040) or the progression to LRTC (11.2% vs 19.5%, respectively; odds ratio, 0.50; 95% CI, .22–1.18; P = .11). In a post hoc analysis among patients with lymphopenia, presatovir decreased LRTC development by Day 28 (2/15 [13.3%] vs 9/14 [64.3%], respectively; P = .008), compared with the placebo. Adverse events were similar for patients receiving presatovir and the placebo.ConclusionsPresatovir had a favorable safety profile in adult HCT recipients with RSV but did not achieve the coprimary endpoints. Exploratory analyses suggest an antiviral effect among patients with lymphopenia.Clinical Trials RegistrationNCT02254408; EUDRA-CT#2014-002474-36.
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41.
  • Christiansen, Colette, et al. (författare)
  • Adipose methylome integrative-omic analyses reveal genetic and dietary metabolic health drivers and insulin resistance classifiers
  • 2022
  • Ingår i: Genome Medicine. - : Springer Science and Business Media LLC. - 1756-994X. ; 14:1
  • Tidskriftsartikel (refereegranskat)abstract
    • Background: There is considerable evidence for the importance of the DNA methylome in metabolic health, for example, a robust methylation signature has been associated with body mass index (BMI). However, visceral fat (VF) mass accumulation is a greater risk factor for metabolic disease than BMI alone. In this study, we dissect the subcutaneous adipose tissue (SAT) methylome signature relevant to metabolic health by focusing on VF as the major risk factor of metabolic disease. We integrate results with genetic, blood methylation, SAT gene expression, blood metabolomic, dietary intake and metabolic phenotype data to assess and quantify genetic and environmental drivers of the identified signals, as well as their potential functional roles. Methods: Epigenome-wide association analyses were carried out to determine visceral fat mass-associated differentially methylated positions (VF-DMPs) in SAT samples from 538 TwinsUK participants. Validation and replication were performed in 333 individuals from 3 independent cohorts. To assess functional impacts of the VF-DMPs, the association between VF and gene expression was determined at the genes annotated to the VF-DMPs and an association analysis was carried out to determine whether methylation at the VF-DMPs is associated with gene expression. Further epigenetic analyses were carried out to compare methylation levels at the VF-DMPs as the response variables and a range of different metabolic health phenotypes including android:gynoid fat ratio (AGR), lipids, blood metabolomic profiles, insulin resistance, T2D and dietary intake variables. The results from all analyses were integrated to identify signals that exhibit altered SAT function and have strong relevance to metabolic health. Results: We identified 1181 CpG positions in 788 genes to be differentially methylated with VF (VF-DMPs) with significant enrichment in the insulin signalling pathway. Follow-up cross-omic analysis of VF-DMPs integrating genetics, gene expression, metabolomics, diet, and metabolic traits highlighted VF-DMPs located in 9 genes with strong relevance to metabolic disease mechanisms, with replication of signals in FASN, SREBF1, TAGLN2, PC and CFAP410. PC methylation showed evidence for mediating effects of diet on VF. FASN DNA methylation exhibited putative causal effects on VF that were also strongly associated with insulin resistance and methylation levels in FASN better classified insulin resistance (AUC=0.91) than BMI or VF alone. Conclusions: Our findings help characterise the adiposity-associated methylation signature of SAT, with insights for metabolic disease risk.
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42.
  • Farah, Joseph, et al. (författare)
  • Selective Dynamical Imaging of Interferometric Data
  • 2022
  • Ingår i: Astrophysical Journal Letters. - : American Astronomical Society. - 2041-8213 .- 2041-8205. ; 930:2
  • Tidskriftsartikel (refereegranskat)abstract
    • Recent developments in very long baseline interferometry (VLBI) have made it possible for the Event Horizon Telescope (EHT) to resolve the innermost accretion flows of the largest supermassive black holes on the sky. The sparse nature of the EHT's (u, v)-coverage presents a challenge when attempting to resolve highly time-variable sources. We demonstrate that the changing (u, v)-coverage of the EHT can contain regions of time over the course of a single observation that facilitate dynamical imaging. These optimal time regions typically have projected baseline distributions that are approximately angularly isotropic and radially homogeneous. We derive a metric of coverage quality based on baseline isotropy and density that is capable of ranking array configurations by their ability to produce accurate dynamical reconstructions. We compare this metric to existing metrics in the literature and investigate their utility by performing dynamical reconstructions on synthetic data from simulated EHT observations of sources with simple orbital variability. We then use these results to make recommendations for imaging the 2017 EHT Sgr A* data set.
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43.
  • Narayan, Ramesh, et al. (författare)
  • The Polarized Image of a Synchrotron-emitting Ring of Gas Orbiting a Black Hole
  • 2021
  • Ingår i: Astrophysical Journal. - : American Astronomical Society. - 1538-4357 .- 0004-637X. ; 912:1
  • Tidskriftsartikel (refereegranskat)abstract
    • Synchrotron radiation from hot gas near a black hole results in a polarized image. The image polarization is determined by effects including the orientation of the magnetic field in the emitting region, relativistic motion of the gas, strong gravitational lensing by the black hole, and parallel transport in the curved spacetime. We explore these effects using a simple model of an axisymmetric, equatorial accretion disk around a Schwarzschild black hole. By using an approximate expression for the null geodesics derived by Beloborodov and conservation of the Walker-Penrose constant, we provide analytic estimates for the image polarization. We test this model using currently favored general relativistic magnetohydrodynamic simulations of M87*, using ring parameters given by the simulations. For a subset of these with modest Faraday effects, we show that the ring model broadly reproduces the polarimetric image morphology. Our model also predicts the polarization evolution for compact flaring regions, such as those observed from Sgr A* with GRAVITY. With suitably chosen parameters, our simple model can reproduce the EVPA pattern and relative polarized intensity in Event Horizon Telescope images of M87*. Under the physically motivated assumption that the magnetic field trails the fluid velocity, this comparison is consistent with the clockwise rotation inferred from total intensity images.
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44.
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45.
  • Vik, Eline S., et al. (författare)
  • Country of first birth and neonatal outcomes in migrant and Norwegian-born parous women in Norway : a population-based study
  • 2020
  • Ingår i: BMC Health Services Research. - : BMC. - 1472-6963. ; 20:1
  • Tidskriftsartikel (refereegranskat)abstract
    • Background This study compares subsequent birth outcomes in migrant women who had already had a child before arriving in Norway with those in migrant women whose first birth occurred in Norway. The aim of this study was to investigate the associations between country of first birth and adverse neonatal outcomes (very preterm birth, moderately preterm birth, post-term birth, small for gestational age, large for gestational age, low Apgar score, stillbirth and neonatal death) in parous migrant and Norwegian-born women. Methods National population-based study including second and subsequent singleton births in Norway from 1990 to 2016. Data were retrieved from the Medical Birth Registry of Norway and Statistics Norway. Neonatal outcomes were compared between births to: 1) migrant women with a first birthbeforeimmigration to Norway (n = 30,062) versus those with a first birthafterimmigration (n = 66,006), and 2) Norwegian-born women with a first birthoutsideNorway (n = 6205) versus those with a first birthinNorway (n = 514,799). Associations were estimated as crude and adjusted odds ratios (aORs) with 95% confidence intervals (CIs) using multiple logistic regression. Results Migrant women with a first birthbeforeimmigrating to Norway had increased odds of adverse outcomes in subsequent births relative to those with a first birthafterimmigration: very preterm birth (22-31 gestational weeks; aOR = 1.27; CI 1.09-1.48), moderately preterm birth (32-36 gestational weeks; aOR = 1.10; CI 1.02-1.18), post-term birth (>= 42 gestational weeks; aOR = 1.19; CI 1.11-1.27), low Apgar score (< 7 at 5 min; aOR = 1.27; CI 1.16-1.39) and stillbirth (aOR = 1.29; CI 1.05-1.58). Similar results were found in the sample of births to Norwegian-born women. Conclusions The increased odds of adverse neonatal outcomes for migrantandNorwegian-born women who had their first births outside Norway should serve as a reminder of the importance of taking a careful obstetric history in these parous women to ensure appropriate care for their subsequent pregnancies and births in Norway.
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46.
  • Vik, Eline S., et al. (författare)
  • Paternal country of origin and adverse neonatal outcomes in births to foreign-born women in Norway : A population-based cohort study
  • 2020
  • Ingår i: PLoS Medicine. - : PUBLIC LIBRARY SCIENCE. - 1549-1277 .- 1549-1676. ; 17:11
  • Tidskriftsartikel (refereegranskat)abstract
    • Background: Migration is a risk factor for adverse neonatal outcomes. The various impacts of maternal origin have been reported previously. The aim of this study was to investigate associations between paternal origin and adverse neonatal outcomes in births to migrant and Norwegian-born women in Norway.Methods and findings: This nationwide population-based study included births to migrant (n = 240,759, mean age 29.6 years [+/- 5.3 SD]) and Norwegian-born women (n = 1,232,327, mean age 29.0 years [+/- 5.1 SD]) giving birth in Norway in 1990-2016. The main exposure was paternal origin (Norwegian-born, foreign-born, or unregistered). Neonatal outcomes were very preterm birth (22(+0)-31(+6) gestational weeks), moderately preterm birth (32(+0)-36(+6) gestational weeks), small for gestational age (SGA), low Apgar score (<7 at 5 minutes), and stillbirth. Associations were investigated in migrant and Norwegian-born women separately using multiple logistic regression and reported as adjusted odds ratios (aORs) with 95% confidence intervals (CIs), adjusted for year of birth, parity, maternal and paternal age, marital status, maternal education, and mother's gross income. In births to migrant women, a foreign-born father was associated with increased odds of very preterm birth (1.1% versus 0.9%, aOR 1.20; CI 1.08-1.33, p = 0.001), SGA (13.4% versus 9.5%, aOR 1.48; CI 1.43-1.53, p < 0.001), low Apgar score (1.7% versus 1.5%, aOR 1.14; CI 1.05-1.23, p = 0.001), and stillbirth (0.5% versus 0.3%, aOR 1.26; CI 1.08-1.48, p = 0.004) compared with a Norwegian-born father. In Norwegian-born women, a foreign-born father was associated with increased odds of SGA (9.3% versus 8.1%, aOR 1.13; CI 1.09-1.16, p < 0.001) and decreased odds of moderately preterm birth (4.3% versus 4.4%, aOR 0.95; CI 0.91-0.99, p = 0.015) when compared with a Norwegian-born father. In migrant women, unregistered paternal origin was associated with increased odds of very preterm birth (2.2% versus 0.9%, aOR 2.29; CI 1.97-2.66, p < 0.001), moderately preterm birth (5.6% versus 4.7%, aOR 1.15; CI 1.06-1.25, p = 0.001), SGA (13.0% versus 9.5%, aOR 1.50; CI 1.42-1.58, p < 0.001), low Apgar score (3.4% versus 1.5%, aOR 2.23; CI 1.99-2.50, p < 0.001), and stillbirth (1.5% versus 0.3%, aOR 4.87; CI 3.98-5.96, p < 0.001) compared with a Norwegian-born father. In Norwegian-born women, unregistered paternal origin was associated with increased odds of very preterm birth (4.6% versus 1.0%, aOR 4.39; CI 4.05-4.76, p < 0.001), moderately preterm birth (7.8% versus 4.4%, aOR 1.62; CI 1.53-1.71, p < 0.001), SGA (11.4% versus 8.1%, aOR 1.30; CI 1.24-1.36, p < 0.001), low Apgar score (4.6% versus 1.3%, aOR 3.51; CI 3.26-3.78, p < 0.001), and stillbirth (3.2% versus 0.4%, aOR 9.00; CI 8.15-9.93, p < 0.001) compared with births with a Norwegian-born father. The main limitations of this study were the restricted access to paternal demographics and inability to account for all lifestyle factors.Conclusion: We found that a foreign-born father was associated with adverse neonatal outcomes among births to migrant women, but to a lesser degree among births to nonmigrant women, when compared with a Norwegian-born father. Unregistered paternal origin was associated with higher odds of adverse neonatal outcomes in births to both migrant and nonmigrant women when compared with Norwegian-born fathers.Increased attention to paternal origin may help identify women in maternity care at risk for adverse neonatal outcomes.
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47.
  • Wielgus, Maciek, et al. (författare)
  • Monitoring the Morphology of M87* in 2009-2017 with the Event Horizon Telescope
  • 2020
  • Ingår i: Astrophysical Journal. - : American Astronomical Society. - 1538-4357 .- 0004-637X. ; 901:1
  • Tidskriftsartikel (refereegranskat)abstract
    • The Event Horizon Telescope (EHT) has recently delivered the first resolved images of M87*, the supermassive black hole in the center of the M87 galaxy. These images were produced using 230 GHz observations performed in 2017 April. Additional observations are required to investigate the persistence of the primary image feature-a ring with azimuthal brightness asymmetry-and to quantify the image variability on event horizon scales. To address this need, we analyze M87* data collected with prototype EHT arrays in 2009, 2011, 2012, and 2013. While these observations do not contain enough information to produce images, they are sufficient to constrain simple geometric models. We develop a modeling approach based on the framework utilized for the 2017 EHT data analysis and validate our procedures using synthetic data. Applying the same approach to the observational data sets, we find the M87* morphology in 2009-2017 to be consistent with a persistent asymmetric ring of similar to 40 mu as diameter. The position angle of the peak intensity varies in time. In particular, we find a significant difference between the position angle measured in 2013 and 2017. These variations are in broad agreement with predictions of a subset of general relativistic magnetohydrodynamic simulations. We show that quantifying the variability across multiple observational epochs has the potential to constrain the physical properties of the source, such as the accretion state or the black hole spin.
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