First M87 Event Horizon Telescope Results. I. The Shadow of the Supermassive Black Hole

First M87 Event Horizon Telescope Results. I. The Shadow of the Supermassive Black Hole The Event Horizon Telescope Collaboration

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First M87 Event Horizon Telescope Results. I. The Shadow of the Supermassive Black Hole 2019 The Astrophysical Journal Letters / arXiv 10.3847/2041-8213/ab0ec7 1906.11238 eht2019-m87-black-hole eht2019-m87-black-hole.txt, the project's staged copy 4160271d4333ed81c2510b680d4c97877f329099 cc-by astronomy

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0 spans located by searching the stored text for the quote's exact words, allowing any whitespace between them existence Quotation withheld because this record is not cleared for redistribution. black hole shadow Quotation withheld because this record is not cleared for redistribution. observational-study observational-study Quotation withheld because this record is not cleared for redistribution. mechanisms the first images are made by four teams working independently and without interaction, in the authors' words to minimize shared bias - and each team nonetheless recovered a ring of similar diameter brightened to the south Quotation withheld because this record is not cleared for redistribution. mechanisms a parameter combination is admitted to the Top-Set only if it both fits the observed data AND reconstructs four known geometries - ring, crescent, filled disk, asymmetric double - from synthetic data, so the imaging parameters are validated against ground truth and not only against the object under study Quotation withheld because this record is not cleared for redistribution. mechanisms because the reconstructed resolutions differ between pipelines, each image is blurred with a circular Gaussian to one common and deliberately conservative resolution before use Quotation withheld because this record is not cleared for redistribution. mechanisms systematic baseline error is measured rather than assumed: three independent fringe-fitting pipelines, two polarizations and two frequency bands are compared against each other, and the residual disagreement between them IS the quoted systematic Quotation withheld because this record is not cleared for redistribution. mechanisms the two frequency bands are correlated on two separate software correlators at two institutions, and a few identical scans are passed through both so that any difference between the correlators would show up as a disagreement on the same input about this quote: 2026-08-16: THE STAGED TEXT SCRAMBLES A NAME INSIDE THIS QUOTE. It reads "at the MIT Haystack Observatory and at fur Radioastronomie" - the words "the Max-Planck-Institut" were displaced by the extraction and appear roughly 400 characters later, mid-sentence, in "At correlation, signals were aligned ... the Max-Planck-Institut". The two institutions are MIT Haystack and the Max-Planck-Institut fur Radioastronomie. The quote is an exact substring of the staged file and the file is wrong here, not the tag. NOT a furniture crossing - the extraction reordered words WITHIN a sentence, which no guard in our tools can see, because the result is contiguous, unique and verbatim. Quotation withheld because this record is not cleared for redistribution. mechanisms one highly sensitive station is used as the array's reference station, which is what enabled the ionospheric and tropospheric corrections at the other sites Quotation withheld because this record is not cleared for redistribution. mechanisms the absolute flux scale is refined using the array's own redundancy - pairs of telescopes that sit at the same site and therefore see the same baseline - rather than resting on each telescope's independently estimated sensitivity about this quote: 2026-08-16: THE STAGED TEXT SCRAMBLES A CITATION INSIDE THIS QUOTE. It reads "utilizing array redundancy via III), we refined the absolute network calibration (Paper amplitude calibration of telescopes" - the parenthetical "(Paper III)" has been split and its halves interleaved with the surrounding clause. Read as: "utilizing array redundancy via network calibration (Paper III), we refined the absolute amplitude calibration of telescopes that are colocated...". Verbatim of the file, and the file is wrong. Same class as [4]: a within-sentence reordering, invisible to every guard. Quotation withheld because this record is not cleared for redistribution. mechanisms the simulated images are put through the same VLBI simulation, the same observing schedule and weather, the same calibration and the same imaging pipeline as the real data, so that model and observation are compared after identical processing rather than before it Quotation withheld because this record is not cleared for redistribution. The interferometric sampling is sparse, so image reconstruction is an under-constrained inverse problem requiring extra assumptions. what this limits: every reconstructed image: BECAUSE THE (u, v) PLANE IS ONLY SPARSELY SAMPLED, THE INVERSE PROBLEM IS UNDER-CONSTRAINED Quotation withheld because this record is not cleared for redistribution. Visibility data lack absolute phase calibration and carry potentially large amplitude calibration uncertainties. what this limits: the visibility data underlying it: THE MEASURED VISIBILITIES LACK ABSOLUTE PHASE CALIBRATION AND CAN HAVE LARGE AMPLITUDE CALIBRATION UNCERTAINTIES Quotation withheld because this record is not cleared for redistribution. The geometric crescent fits measure the size of the emitting region, not the size of the shadow itself, and may be biased. what this limits: every diameter quoted from the crescent fits: THEY MEASURE Quotation withheld Quotation withheld because this record is not cleared for redistribution. Physically very different theoretical models fit the data equally well, so a good fit does not select a preferred model. what this limits: any inference from goodness of fit to physics: ALTHOUGH THE FIT TO THE OBSERVATIONS IS EQUALLY GOOD IN THE THREE CASES, THEY REFER TO RADICALLY DIFFERENT PHYSICAL SCENARIOS Quotation withheld because this record is not cleared for redistribution. The illustrative thin-ring model used to interpret the visibility amplitudes does not account for all features of the data. what this limits: the illustrative thin-ring model: IT IS ONLY ILLUSTRATIVE AND DOES NOT FIT ALL FEATURES IN THE DATA Quotation withheld because this record is not cleared for redistribution. The headline mass is an average across three different modelling methods, not a single measurement. what this limits: the mass value as one measurement: it is the average of geometric models, GRMHD models and image domain ring extraction Quotation withheld because this record is not cleared for redistribution. The ring diameter depends on which extraction method is used, and the paper gives a range for that reason. what this limits: a single ring-diameter value: the paper states the value depends on the extraction method and gives a range accordingly Quotation withheld because this record is not cleared for redistribution. The observed ring diameter tracks the mass only up to several other factors, including instrument resolution and the structure of the emitting region. what this limits: converting the observed diameter directly to a mass: it also depends on observing resolution, spin vector, inclination, and the size and structure of the emitting region Quotation withheld because this record is not cleared for redistribution. Only some exotic alternatives to a black hole are excluded, and the exclusion depends on an assumed maximum-mass prior. what this limits: the result as excluding alternatives to black holes generally: only some exotic compact objects are excluded, and that rests on the maximum mass prior Quotation withheld because this record is not cleared for redistribution. The distance to M87 is adopted from other work rather than measured here, and it enters the mass. what this limits: the mass as independent of external inputs: the distance is adopted from three stellar population measurements reported elsewhere Quotation withheld because this record is not cleared for redistribution. three independent imaging pipelines run on the same data, cross-compared against each other and against the two polarizations and the two frequency bands eliminates: an artefact of one reduction chain - a ring produced by the algorithm rather than present in the sky. Three teams that never shared a pipeline have to agree before the image stands · outcome (stated by the tagger, no quotation): held Quotation withheld because this record is not cleared for redistribution. a Top-Set of imaging parameter combinations kept only if they BOTH fitted the observed data AND recovered accurate images from synthetic data with a known answer eliminates: parameters tuned until the expected picture appears - the synthetic data has a ground truth, so a setting that flatters the real data but fails the known case is discarded · outcome (stated by the tagger, no quotation): held Quotation withheld because this record is not cleared for redistribution. emission ring emission ring Quotation withheld because this record is not cleared for redistribution. photon ring photon ring Quotation withheld because this record is not cleared for redistribution. black hole shadow black hole shadow Quotation withheld because this record is not cleared for redistribution. maximum mass prior maximum mass prior Quotation withheld because this record is not cleared for redistribution. emitting regions emitting regions Quotation withheld because this record is not cleared for redistribution. shadows shadows Quotation withheld because this record is not cleared for redistribution. one-way causal boundary one-way causal boundary Quotation withheld because this record is not cleared for redistribution. Active galactic nuclei Active galactic nuclei Quotation withheld because this record is not cleared for redistribution. central bright regions central bright regions Quotation withheld because this record is not cleared for redistribution. low-luminosity active galactic nuclei low-luminosity active galactic nuclei Quotation withheld because this record is not cleared for redistribution. hot, tenuous accretion flows hot, tenuous accretion flows Quotation withheld because this record is not cleared for redistribution. photon capture radius photon capture radius Quotation withheld because this record is not cleared for redistribution. Schwarzschild radius Schwarzschild radius Quotation withheld because this record is not cleared for redistribution. unstable circular orbit unstable circular orbit Quotation withheld because this record is not cleared for redistribution. event horizon and light bending event horizon and light bending Quotation withheld because this record is not cleared for redistribution. dark “shadow” dark “shadow” Quotation withheld because this record is not cleared for redistribution. crescent crescent Quotation withheld because this record is not cleared for redistribution. Event Horizon Telescope Event Horizon Telescope Quotation withheld because this record is not cleared for redistribution. global VLBI array global VLBI array Quotation withheld because this record is not cleared for redistribution. complex visibilities complex visibilities Quotation withheld because this record is not cleared for redistribution. Fourier components Fourier components Quotation withheld because this record is not cleared for redistribution. inverse problem inverse problem Quotation withheld because this record is not cleared for redistribution. CLEAN CLEAN Quotation withheld because this record is not cleared for redistribution. inverse-modeling approach inverse-modeling approach Quotation withheld because this record is not cleared for redistribution. RML RML Quotation withheld because this record is not cleared for redistribution. forward-modeling approach forward-modeling approach Quotation withheld because this record is not cleared for redistribution. Top-Set Top-Set Quotation withheld because this record is not cleared for redistribution. geometric models geometric models Quotation withheld because this record is not cleared for redistribution. GRMHD simulations GRMHD simulations Quotation withheld because this record is not cleared for redistribution. turbulent, hot, magnetized disk turbulent, hot, magnetized disk Quotation withheld because this record is not cleared for redistribution. SANE accretion flows SANE accretion flows Quotation withheld because this record is not cleared for redistribution. MAD flows MAD flows Quotation withheld because this record is not cleared for redistribution. Standard and Normal Evolution Standard and Normal Evolution Quotation withheld because this record is not cleared for redistribution. Magnetically Arrested Disk Magnetically Arrested Disk Quotation withheld because this record is not cleared for redistribution. moderate dimensionless magnetic flux moderate dimensionless magnetic flux Quotation withheld because this record is not cleared for redistribution. geometric crescent models geometric crescent models Quotation withheld because this record is not cleared for redistribution. ring diameter ring diameter Quotation withheld because this record is not cleared for redistribution. null hypothesis of the Kerr metric null hypothesis of the Kerr metric Quotation withheld because this record is not cleared for redistribution. SANE accretion flows → Standard and Normal Evolution SANE expands to Standard and Normal Evolution. Acronym-expansion fits none of the eight relation types. Quotation withheld because this record is not cleared for redistribution. MAD flows → Magnetically Arrested Disk MAD expands to Magnetically Arrested Disk. Acronym-expansion fits none of the eight relation types. Quotation withheld because this record is not cleared for redistribution. emission ring - the bright ring of radiation that appears alongside the dark shadow, and is what the instrument resolves Quotation withheld because this record is not cleared for redistribution. shadow - what the observed image is said to be consistent with, rather than what was directly measured Quotation withheld because this record is not cleared for redistribution. photon ring - the lensed orbit at the critical impact parameter, which supplies most of the radiation in the observed ring Quotation withheld because this record is not cleared for redistribution. Event horizon - one-way causal boundary in spacetime from which not even light escapes Quotation withheld because this record is not cleared for redistribution. Active galactic nucleus - central bright region that can outshine its host galaxy's stars Quotation withheld because this record is not cleared for redistribution. Low-luminosity AGN - local nucleus fed by a hot, tenuous, low-rate accretion flow Quotation withheld because this record is not cleared for redistribution. Photon-capture radius - critical radius larger than the Schwarzschild event-horizon radius Quotation withheld because this record is not cleared for redistribution. Photon ring - lensed feature produced at the unstable critical photon orbit Quotation withheld because this record is not cleared for redistribution. Dark shadow / bright emission ring - paired appearance caused by event horizon plus light bending Quotation withheld because this record is not cleared for redistribution. Crescent - ring appearance shaped by rapid rotation and relativistic beaming Quotation withheld because this record is not cleared for redistribution. Event Horizon Telescope - global 1.3-mm VLBI array for imaging M87* and Sgr A* shadows Quotation withheld because this record is not cleared for redistribution. Complex visibility - Fourier component of the sky brightness distribution at a sampled spatial frequency Quotation withheld because this record is not cleared for redistribution. Inverse problem - image reconstruction under-constrained by sparse EHT spatial-frequency sampling Quotation withheld because this record is not cleared for redistribution. CLEAN - inverse-modeling deconvolution of the interferometer point-spread function Quotation withheld because this record is not cleared for redistribution. RML - forward-modeling search favoring data-consistent smooth or compact images Quotation withheld because this record is not cleared for redistribution. Top-Set - cross-pipeline images consistently showing an asymmetric ring near 40 microarcseconds Quotation withheld because this record is not cleared for redistribution. GRMHD simulation - turbulent magnetized Kerr-disk model predicting a shadow and asymmetric emission ring Quotation withheld because this record is not cleared for redistribution. SANE flow - Standard and Normal Evolution accretion with moderate magnetic flux Quotation withheld because this record is not cleared for redistribution. MAD flow - Magnetically Arrested Disk comparison regime with stronger field and larger funnel Quotation withheld because this record is not cleared for redistribution. Geometric crescent model - direct visibility fit for ring diameter and fractional width Quotation withheld because this record is not cleared for redistribution. Kerr-metric null hypothesis - assumption that the M87* black hole is described by Kerr geometry Quotation withheld because this record is not cleared for redistribution. builds-on → general relativity (Kerr black hole shadow prediction) Quotation withheld because this record is not cleared for redistribution. extends → Doeleman et al. 2012; Akiyama et al. 2015 (earlier 1.3 mm VLBI measurements of M87*) Quotation withheld because this record is not cleared for redistribution. builds-on → Falcke et al. 2000a (prediction that a black hole shadow plus emission ring should be detectable with VLBI) Quotation withheld because this record is not cleared for redistribution. photon ring —part-of→ emission ring photon ring emission ring strength of the relation: 1 Quotation withheld because this record is not cleared for redistribution. emitting regions —distinct-from→ shadows emitting regions shadows the relation itself is separately evidenced · strength of the relation: 1 · note: RE-GROUNDS the record's 'emission ring --distinct-from--> black hole shadow', whose span named neither endpoint. Endpoints are the words of the sentence that states the distinction; 'normalised' maps them onto the concepts the record already has. · the relation stated: what was measured is the size of the EMITTING REGION, not the size of the shadow Quotation withheld because this record is not cleared for redistribution. photon capture radius —distinct-from→ Schwarzschild radius photon capture radius Schwarzschild radius the relation itself is separately evidenced · strength of the relation: 1 · note: The paper explicitly states that the photon-capture radius is larger than the Schwarzschild radius. Quotation withheld because this record is not cleared for redistribution. unstable circular orbit —causes→ photon ring unstable circular orbit photon ring the relation itself is separately evidenced · strength of the relation: 1 · note: Photons on the unstable critical orbit are said to produce the lensed photon ring. Quotation withheld because this record is not cleared for redistribution. event horizon and light bending —causes→ dark “shadow” event horizon and light bending dark “shadow” the relation itself is separately evidenced · strength of the relation: 1 · note: The paper states that event horizon plus light bending leads to the dark shadow's appearance. Quotation withheld because this record is not cleared for redistribution. event horizon and light bending —causes→ emission ring event horizon and light bending emission ring the relation itself is separately evidenced · strength of the relation: 1 · note: The same unhedged mechanism is stated to lead to the accompanying bright emission ring. Quotation withheld because this record is not cleared for redistribution. CLEAN —is-a→ inverse-modeling approach CLEAN inverse-modeling approach the relation itself is separately evidenced · strength of the relation: 1 · note: The paper explicitly states that CLEAN is an inverse-modeling approach. Quotation withheld because this record is not cleared for redistribution. RML —is-a→ forward-modeling approach RML forward-modeling approach the relation itself is separately evidenced · strength of the relation: 1 · note: The paper explicitly states that RML is a forward-modeling approach. Quotation withheld because this record is not cleared for redistribution. SANE accretion flows —distinct-from→ MAD flows SANE accretion flows MAD flows the relation itself is separately evidenced · strength of the relation: 1 · note: The paper distinguishes the two regimes by magnetic flux, initial field strength, and funnel opening angle. Quotation withheld because this record is not cleared for redistribution. 1.3 — EHT observing wavelength Quotation withheld because this record is not cleared for redistribution. 42±3 — diameter of the bright emission ring Quotation withheld because this record is not cleared for redistribution. 10:1 — ring brightness vs central depression Quotation withheld because this record is not cleared for redistribution. (6.5±0.7)e9 — derived central black-hole mass of M87 Quotation withheld because this record is not cleared for redistribution. 4 — days over which the ring stayed stable Quotation withheld because this record is not cleared for redistribution. 230 — observing frequency equivalent to 1.3 mm Quotation withheld because this record is not cleared for redistribution. the image matches the shadow of a Kerr black hole predicted by GR Quotation withheld because this record is not cleared for redistribution. ring brightness asymmetry is explained by relativistic beaming Quotation withheld because this record is not cleared for redistribution. the result is powerful evidence for supermassive black holes in galaxy centers Quotation withheld because this record is not cleared for redistribution. the ring diameter scales with the capture radius and so with the black hole's mass, but also depends on observing resolution, spin, inclination and the emitting region Quotation withheld because this record is not cleared for redistribution. projected diameter projected diameter Quotation withheld because this record is not cleared for redistribution. central mass central mass about this quote: THE NUMBER IN THIS QUOTE IS CORRUPTED IN THE STAGED TEXT AND THE TRUE VALUE IS NOT WHAT IT READS. The superscript was flattened into the line: the paper says 6.5 x 10^9 solar masses and the staged text says 'x 109'. 'Me' is 'M_sun' with the solar-mass symbol rendered as an 'e', and each '\uf0a0' is a private-use non-breaking space. The quote was previously cut at 'mass of M', immediately before the value - extended here so the phrase is complete, and annotated because a variables tag that carries a wrong number silently is worse than one that carries none. Repair needs the source PDF. Quotation withheld because this record is not cleared for redistribution. photon capture radius photon capture radius Quotation withheld because this record is not cleared for redistribution. impact parameter b impact parameter b Quotation withheld because this record is not cleared for redistribution. event horizon event horizon Quotation withheld because this record is not cleared for redistribution. dark shadow dark shadow Quotation withheld because this record is not cleared for redistribution. Event Horizon Telescope Event Horizon Telescope Quotation withheld because this record is not cleared for redistribution. active galactic nuclei (AGNs) active galactic nuclei (AGNs) Quotation withheld because this record is not cleared for redistribution. Bayesian Bayesian Quotation withheld because this record is not cleared for redistribution. correlation correlation Quotation withheld because this record is not cleared for redistribution. hypothesis-testing hypothesis-testing about this quote: THE QUOTE CONTINUES A SENTENCE THAT THIS COPY CUTS IN TWO - a page footer stands between it and the words it follows, which read 'Third, because'. Quotation withheld because this record is not cleared for redistribution. mean mean Quotation withheld because this record is not cleared for redistribution. median median about this quote: THE QUOTE CONTINUES A SENTENCE THAT THIS COPY CUTS IN TWO - the caption of Figure 1 and a page footer stand between it and the words it follows, which read 'Weather was uniformly good to excellent with nightly'. Quotation withheld because this record is not cleared for redistribution. null-hypothesis null-hypothesis about this quote: THE QUOTE CONTINUES A SENTENCE THAT THIS COPY CUTS IN TWO - a page footer stands between it and the words it follows, which read 'Third, because'. Quotation withheld because this record is not cleared for redistribution. variance variance Quotation withheld because this record is not cleared for redistribution.

The full text of this article is not redistributable, so it is not included here. The evidence sentences are withheld with it; the tag layer and its grounding status remain. The article itself is at https://doi.org/10.3847/2041-8213/ab0ec7.