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The black contours are the M87 EHT image at 228 GHz from Figure 6. The color-scale and white contours are the 90 GHz image of M87 at 0.12 mas × 0.050 mas resolution publicly available (Kim et al. 2018b). The relative astrometry was set by convolving the EHT image to the 90 GHz resolution, and aligning the peaks.
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We present a reanalysis of the Event Horizon Telescope 228 GHz observations of M87. We apply traditional hybrid mapping techniques to the publicly available network-calibrated data. We explore the impact on the final image of different starting models, including the following: a point source, a disk, an annulus, a Gaussian, and an asymmetric double...
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... particular, on scales at the limit of their resolution (beam FWHM = 120 μas × 50 μas, major-axis position axis north-south; Kim et al. 2018a), they find in the inner ∼200 μas, the brightest limb of the jet extends in the southwest direction from the core, at a position angle of ≈15° south of west (255° east of north), similar to the observed direction of the extension in Figure 6 (left panel). For reference, we produce an overlay of the publicly available 90 GHz VLBI image ( Kim et al. 2018a), in Figure 7. ...
Citations
... Recently, using the observational data obtained by sub-millimeter 'Event Horizon Telescope' (EHT) based on the very-long baseline interferometry (VLBI), the images of the black hole M87 * at the center of the Virgo A galaxy and the black hole Sgr A * at the center of the Milky Way are derived directly [1,2]. Later, more observations are conducted to monitor the morphology of M87 * [3], the hybrid mapping of M87 * [4], the ringlike accretion structure in M87 connecting the black hole and jet [5], and the supermassive black hole in the early universe growing in the shadows [6], etc. These achievements help us to confirm the wide consensus in astrophysics that there are the supermassive black holes in the centers of most galaxies which could dominant the processes of formation and evolution of the galaxies, and the fundamental properties of the black holes can be used as the effective test for the theory of Einstein's general relativity (GR). ...
We investigate analytically the apparent shadows cast by Kerr-Newman black hole with surrounding perfect fluid matter in Rastall gravity theory. With the help of the Hamilton-Jacobi equation and Carter constant separable method, we derive the null geodesics of the black hole space-time and calculate the numerical results of the horizon structures. The results reveal that three horizons (Cauchy horizon r-, event horizon r+ and cosmological horizon rq) occur in the space-time, and the horizon structure could degenerate while the Rastall parameter kλ arrives the critical value. By fixing the value of equation state parameter ∼ω of surrounding substance for both cases of dark matter (∼ω = -1⁄3) and dark energy (∼ω = -2⁄3), we study the effects of the perfect fluid matter intensity Ns, the Rastall parameter kλ, the black hole spin a and the black hole charge Q on black hole shadows in detail. Furthermore, the effective potentials for black hole space-time and the energy emission rate of the black hole are also conducted and discussed.
... reveal the inner jet emission because of (u, v)-coverage limitations 6 (see also recent re-analysis results 7,8 ). ...
The nearby radio galaxy M87 is a prime target for studying black hole accretion and jet formation1,2. Event Horizon Telescope observations of M87 in 2017, at a wavelength of 1.3 mm, revealed a ring-like structure, which was interpreted as gravitationally lensed emission around a central black hole³. Here we report images of M87 obtained in 2018, at a wavelength of 3.5 mm, showing that the compact radio core is spatially resolved. High-resolution imaging shows a ring-like structure of 8.4−1.1+0.5\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${8.4}_{-1.1}^{+0.5}$$\end{document} Schwarzschild radii in diameter, approximately 50% larger than that seen at 1.3 mm. The outer edge at 3.5 mm is also larger than that at 1.3 mm. This larger and thicker ring indicates a substantial contribution from the accretion flow with absorption effects, in addition to the gravitationally lensed ring-like emission. The images show that the edge-brightened jet connects to the accretion flow of the black hole. Close to the black hole, the emission profile of the jet-launching region is wider than the expected profile of a black-hole-driven jet, suggesting the possible presence of a wind associated with the accretion flow.
... refs. [6][7][8] ). 6 The ring-like structure observed at 3.5 mm differs from the one seen at 1.3 mm. ...
... By contrast, the thermal model ( Fig. 2b) is able to produce a ring-like structure consistent with the 3.5-mm observations (Fig. 2a), suggesting that the thermal synchrotron emission from the accretion flow region plays an important part in the interpretation of the 3.5 mm GMVA observations. 8 We note a marginal variability of the highest (a=0.9) and lowest spin (a=0.0), respectively. ...
The nearby radio galaxy M87 is a prime target for studying black hole accretion and jet formation^{1,2}. Event Horizon Telescope observations of M87 in 2017, at a wavelength of 1.3 mm, revealed a ring-like structure, which was interpreted as gravitationally lensed emission around a central black hole^3. Here we report images of M87 obtained in 2018, at a wavelength of 3.5 mm, showing that the compact radio core is spatially resolved. High-resolution imaging shows a ring-like structure of 8.4_{-1.1}^{+0.5} Schwarzschild radii in diameter, approximately 50% larger than that seen at 1.3 mm. The outer edge at 3.5 mm is also larger than that at 1.3 mm. This larger and thicker ring indicates a substantial contribution from the accretion flow with absorption effects in addition to the gravitationally lensed ring-like emission. The images show that the edge-brightened jet connects to the accretion flow of the black hole. Close to the black hole, the emission profile of the jet-launching region is wider than the expected profile of a black-hole-driven jet, suggesting the possible presence of a wind associated with the accretion flow.
... Each EHT paper presents specific aspects of scientific discovery. Several groups have independently validated the EHT results [7], [8], [9], [10]. This paper is not another independent analysis of the EHT results but describes the complete software, environment, and documentation needed to reproduce the published results. ...
This paper presents an interdisciplinary effort to develop and share sustainable knowledge necessary to analyze, understand, and use published scientific results to advance reproducibility in multi-messenger astrophysics. Specifically, we target the breakthrough work associated with generating the first image of a black hole called M87. The Event Horizon Telescope Collaboration computed the image. Based on the artifacts made available by EHT, we deliver documentation, code, and a computational environment to reproduce the first image of a black hole. Our deliverables support discovery in multi-messenger astrophysics by providing all the necessary tools for generalizing methods and findings from the EHT use case. Challenges encountered during the reproducibility of EHT results are reported. Our effort results in an open-source, containerized software package that enables the public to reproduce the first image of a black hole in the galaxy M87.
... Recently, 1.3 mm interferometric observations by the Event Horizon Telescope have resolved the horizon-scale emission from sources in the immediate vicinity of two nearby supermassive black holes: M87* [15], the central compact object at the core of our neighboring galaxy Messier 87, and Sgr A* [16], our own black hole at the center of the Milky Way. Their reconstructed images display a central brightness depression within a thick ring consistent with theoretical expectations for the direct image of the surrounding accretion flow [17][18][19][20][21]. ...
... (4) evaluated on Eqs. (19) for all the valuesr ∈ [r − ,r + ] such thatβ 2 ≥ 0. It is always closed, convex, and reflection-symmetric about the α axis [33]. 5 Here, 3 √ x denotes the real cube root of x if x is real, or else, the principal value of the function x 1/3 (that is, the cubic root with maximal real part.) ...
Recent interferometric observations by the Event Horizon Telescope have resolved the horizon-scale emission from sources in the vicinity of nearby supermassive black holes. Future space-based interferometers promise to measure the ''photon ring''--a narrow, ring-shaped, lensed feature predicted by general relativity, but not yet observed--and thereby open a new window into strong gravity. Here we present AART: an Adaptive Analytical Ray-Tracing code that exploits the integrability of light propagation in the Kerr spacetime to rapidly compute high-resolution simulated black hole images, together with the corresponding radio visibility accessible on very long space-ground baselines. The code samples images on a nonuniform adaptive grid that is specially tailored to the lensing behavior of the Kerr geometry and therefore particularly well-suited to studying photon rings. This numerical approach guarantees that interferometric signatures are correctly computed on long baselines, and the modularity of the code allows for detailed studies of equatorial sources with complex emission profiles and time variability. To demonstrate its capabilities, we use AART to simulate a black hole movie of a stochastic, non-stationary, non-axisymmetric equatorial source; by time-averaging the visibility amplitude of each snapshot, we are able to extract the projected diameter of the photon ring and recover the shape predicted by general relativity.
... These observations revealed the presence of a bright ring of approximately 40 µas in diameter that surrounds a much darker central region. While these basic image features are undisputed and have in fact been independently confirmed (Arras et al. 2022;Carilli & Thyagarajan 2022;Lockhart & Gralla 2022), several aspects of their theoretical interpretation remain open. One example is whether the dark area should be associated with the "black hole shadow" (Falcke et al. 2000), as originally proposed (EHT L1), or with the apparent position of the equatorial event horizon, as the data now seem to suggest (Chael et al. 2021). ...
Context. High-frequency very-long-baseline interferometry (VLBI) observations can now resolve the event-horizon-scale emission from sources in the immediate vicinity of nearby supermassive black holes. Future space-VLBI observations will access highly lensed features of black hole images – photon rings – that will provide particularly sharp probes of strong-field gravity.
Aims. Focusing on the particular case of the supermassive black hole M 87*, our goal is to explore a wide variety of accretion flows onto a Kerr black hole and to understand their corresponding images and visibilities. We are particularly interested in the visibility on baselines to space, which encodes the photon ring shape and whose measurement could provide a stringent test of the Kerr hypothesis.
Methods. We developed a fully analytical model of stationary, axisymmetric accretion flows with a variable disk thickness and a matter four-velocity that can smoothly interpolate between purely azimuthal rotation and purely radial infall. To determine the observational appearance of such flows, we numerically integrated the general-relativistic radiative transfer equation in the Kerr spacetime, taking care to include the effects of thermal synchrotron emission and absorption. We then Fourier transformed the resulting images and analyzed their visibility amplitudes along the directions parallel and orthogonal to the black hole spin projected on the observer sky.
Results. Our images generically display a wedding cake structure composed of discrete, narrow photon rings ( n = 1, 2, …) stacked on top of broader primary emission that surrounds a central brightness depression of model-dependent size. At 230 GHz, the n = 1 ring is always visible, but the n = 2 ring is sometimes suppressed due to absorption. At 345 GHz, the medium is optically thinner and the n = 2 ring displays clear signatures in both the image and visibility domains. We also examine the thermal synchrotron emissivity in the equatorial plane and show that it exhibits an exponential dependence on the radius for the preferred M 87* parameters.
Conclusions. The black hole shadow is a model-dependent phenomenon – even for diffuse, optically thin sources – and should not be regarded as a generic prediction of general relativity. Observations at 345 GHz are promising for future space-VLBI measurements of the photon ring shape, since at this frequency the signal of the n = 2 ring persists despite the disk thickness and nonzero absorption featured in our models. Future work is needed to investigate whether this conclusion holds in a larger variety of reasonable models.
... No other interferometric data set has ever been vetted so extensively by such a large and dedicated group of experts. It also has been reproduced by a number of groups in the meantime (Carilli and Thyagarajan 2022;Arras et al. 2022;Lockhart and Gralla 2022;Patel et al. 2022) 17 as well as by the EHT itself (Event Horizon Telescope Collaboration et al. 2021). However, competitive collaboration can also be exhausting and stressful. ...
The images of the supermassive black holes Sgr A* and M87* by the Event Horizon Telescope (EHT) collaboration mark a special milestone in the history of the subject. For the first time we are able to see the shadow of black holes, testing basic predictions of the theory of general relativity. We are also now learning more about the fundamental astrophysical processes close to the event horizon that help to shape entire galaxies and even parts of our cosmos. The ultimate result was only possible due to a large collaborative effort of scientists and institutions around the world. The road towards these images was the result of a long sociological and scientific process. It started with early pathfinder experiments and a few simple ideas that were remarkably successful in predicting the basic observational signatures to look for. This was based on the premise that black holes are inherently simple objects. Here I describe this journey and some lessons learned from a personal perspective.
... The EHT images of M87 are among the most vetted interferometric images ever published (Event Horizon Telescope Collaboration et al., 2019a,b). Four independent analyses (Arras et al., 2022;Carilli & Thyagarajan, 2022;Lockhart & Gralla, 2022;Patel et al., 2022) have reconstructed the ring-like structure of M87, employing a diverse set of techniques. These efforts complement the three imaging and two modeling techniques in the 2019 EHTC papers presenting the first M87 results. ...
... In the above, EHTC's claim consists of the following five points: (b) Four independent analyses (Arras et al., 2022;Carilli & Thyagarajan, 2022;Lockhart & Gralla, 2022;Patel et al., 2022) have reconstructed the ring-like structure of M87, employing a diverse set of techniques. ...
... Concerning point (b), it is important whether the analyses in four papers are really independent and supporting the EHTC result or not. So we have carefully studied the "Four independent analyses" and have found that, one of them, Carilli & Thyagarajan (2022) actually obtains the result very similar to ours, using the imaging algorithm similar to what we have used (the so-called hybrid mapping). In Figure 4 of Carilli & Thyagarajan (2022) it is shown that an annulus appears when they use a ring or a disk as initial models, but it is also shown that something else appears when they use a single point, double points or extended Gaussian as initial models. ...
On June 14, 2022, the EHT collaboration (hereafter EHTC) made the web page (https://eventhorizontelescope.org/blog/imaging-reanalyses-eht-data) with the title "Imaging Reanalyses of EHT Data," in which they made comments on our recent Miyoshi et al .2022 published in the Astrophysical Journal. We investigated the EHTC comments and found that all of the five points raised by the EHTC are subjective and unsubstantiated claims. Thus they do not prove the correctness of the result of EHTC. Sincerely we hope that the EHTC will publish, not a collection of unsubstantiated claims, but a discussion based on scientific arguments.
... The ring diameter was approximately 42 μas, which is consistent with that expected from the mass of M87 SMBH (6 × 10 9 M e ) obtained using stellar dynamics (Gebhardt et al. 2011). 5 Three research groups have followed up with analyses using EHTC's open data (Arras et al 2022;Carilli & Thyagarajan 2022;Lockhart & Gralla 2022). ...
We report the result of our independent image reconstruction of the M87 from the public data of the Event Horizon Telescope Collaborators (EHTC). Our result is different from the image published by the EHTC. Our analysis shows that (a) the structure at 230 GHz is consistent with those of lower-frequency very long baseline interferometry observations, (b) the jet structure is evident at 230 GHz extending from the core to a few milliarcsecond, although the intensity rapidly decreases along the axis, and (c) the “unresolved core” is resolved into three bright features presumably showing an initial jet with a wide opening angle of ∼70°. The ring-like structures of the EHTC can be created not only from the public data but also from the simulated data of a point image. Also, the rings are very sensitive to the field-of-view (FOV) size. The u − v coverage of the Event Horizon Telescope (EHT) lacks ∼ 40 μ as fringe spacings. Combining with a very narrow FOV, it created the ∼40 μ as ring structure. We conclude that the absence of the jet and the presence of the ring in the EHTC result are both artifacts owing to the narrow FOV setting and the u − v data sampling bias effect of the EHT array. Because the EHTC's simulations only take into account the reproduction of the input image models, and not those of the input noise models, their optimal parameters can enhance the effects of sampling bias and produce artifacts such as the ∼40 μ as ring structure, rather than reproducing the correct image.
