Thunderbolts Forum v3.0

New data, same appearance for M87*

This new M87* image was produced with key contributions from an imaging team at Caltech, including Professor Katherine (Katie) L. Bouman, assistant professor of computing and mathematical sciences, electrical engineering, and astronomy; former Caltech Ph.D. student Nitika Yadlapalli Yurk, Ph.D.; and current Caltech postdoctoral research associate in computing and mathematical sciences Aviad Levis.

Bouman is a coordinator of the EHT Imaging Working Group and was a postdoctoral fellow at the Harvard Smithsonian Center for Astrophysics and co-lead of the EHT imaging team when the original image was published in 2019. In that role, she helped develop the algorithms that assembled the trove of data collected by the EHT's multiple radio telescopes into a single, cohesive image. … snip … She also co-led the imaging of the Milky Way's supermassive black hole published in 2022.

Yurk joined the EHT Collaboration in 2020 and played an active role in the imaging team for the latest M87* image. Her main contributions included developing synthetic datasets to be used in the training and validation of the imaging algorithms. Yurk also wrote software that was used in the exploration of image candidates.

Imaging an object like M87* with the EHT is very different than imaging a planet like Saturn with a conventional telescope. Instead of seeing light, the EHT observes the radio waves emitted by objects and must computationally combine the information to form a picture.

"The raw data that comes out of these telescopes are basically just voltage values," Yurk says. "I like to describe radio telescopes as the world's most sensitive volt meters, and they collect voltages really accurately from different parts of the sky."

Turning those voltage values into an image is tricky, Bouman says, because the information the researchers are working with is incomplete, and there is nothing to compare the image against since no one has seen M87* with their own eyes.

"We don't want to plug in our expectations of what the black hole should look like when we're computationally forming the image," Bouman says. "Otherwise, it might lead us to an image that we expect rather than one that captures reality."

To avoid that problem, the researchers test their image processing algorithms with what is known as synthetic data, a suite of simulated images with simple geometric shapes.

Reproducibility with independent data is a big deal, too.

subjective and unsubstantiated claims

a) The EHT images of M87 are among the most vetted interferometric images ever published (Event Horizon Telescope Collaboration et al., 2019a,b).

(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.

(c) The EHTC and its members have published two additional papers, employing newly developed and independent techniques, that confirm the original results (Event Horizon Telescope Collaboration et al., 2021; Sun & Bouman, 2021).

(d) The EHTC has determined that a new re-analysis (Miyoshi et al., 2022) is based on a flawed understanding of EHTC data and its methods.

(e) Ring-like structures are unambiguously recovered under a broad range of imaging assump- tions, including field of view. Additionally, large-scale jet structures are unconstrained by this high-resolution data.

Point (a) is the subjective claim of the EHTC without any supporting data or fact. In our paper we have demonstrated that this claim is not true.

Concerning point (b), it is important whether the analyses in four papers are really in- dependent 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) ac- tually obtains the result very similar to ours, using the imaging algorithm similar to what we have used (the so-called hybrid mapping). … snip … Therefore, one of the four papers the EHTC listed as ”have reconstructed the ring-like structure” prove the validity of our result as well. Therefore, EHTC’s statement ”new re-analysis (Miyoshi et al., 2022) is based on a flawed understanding of EHTC data and its methods, leading to erroneous conclusions.” doesn’t make sense.

Concerning the other three papers, Lockhart & Gralla (2022) started from a ring, Arras et al. (2022) used essentially the same method as that of EHTC, and Patel et al. (2022) used the EHTC software itself. Therefore these three papers cannot be regarded as ”independent analyses”.

Point (c) does not really add anything new to point (a), since the methods they used in these papers have the same problems as those in their original papers. Event Horizon Telescope Collaboration et al. (2021) tried to determine the polarization but the imaging software is the same as that used in Paper IV(SMILI). Sun & Bouman (2021) used a machine-learning technique, and apparently their training input images are all compact. Thus, most likely the neural network of Sun & Bouman (2021) is trained to find compact structure, even when the data actually contain emissions from a wider region.

In point (d), the EHTC claimed our re-analysis is based on ”a flawed understanding of EHTC data and its methods.” However, the EHTC did not make clear where our understanding is flawed. Moreover, as we have stated above, one of the ”Four independent analyses”, Carilli & Thyagarajan (2022), have actually obtained the result very similar to ours. Since the method and results of Carilli & Thyagarajan (2022) are quite close to ours, EHTC should make clear what is ”a flawed understanding of their data and methods”, not only for our work but also for Carilli & Thyagarajan (2022).

In point (e), the EHTC claimed that Ring-like structures are recovered under a broad range of imaging assumptions, including the field of view. However, the actual fields of view set by the EHTC are limited to a very narrow area. In Miyoshi et al. (2022), we have calculated and shown the range of the field of view (FOV) over which the data contains information. The FOV settings of the EHTC are two orders of magnitude narrower than ours.

In conclusion, 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.

Otherwise, they should retract the statement of ”new re-analysis(Miyoshi et al., 2022) is based on a flawed understanding of EHTC data and its methods, leading to erroneous conclusions.”

We saw the supermassive black hole at the centre of our galaxy in 2022

Physicists dispute a claim of detecting a black hole’s ‘photon ring’

… snip …

Creating images with EHT isn’t a simple point-and-shoot affair (SN: 4/10/19). Researchers stitch together data from EHT’s squad of observatories scattered across the globe, using various computational techniques to reconstruct an image. Broderick and colleagues created a new black hole image assuming it featured both a diffuse emission and a thin ring. On three out of four days of observations, the data better matched an image with the added thin ring than one without the ring.

But that method has drawn harsh criticism. “The claim of a photon ring detection is preposterous,” says physicist Sam Gralla of the University of Arizona in Tucson.

A main point of contention: The photon ring is brighter than expected, emitting around 60 percent of the light in the image. According to predictions, it should be more like 20 percent. “That’s a giant red flag,” says physicist Alex Lupsasca of Vanderbilt University in Nashville. More light should come from the black hole’s main glowing doughnut than from the thin photon ring.

This unexpected brightness, Broderick and colleagues say, occurs because some of the light from the main glow gets lumped in with the photon ring. So the ring’s apparent brightness doesn’t depend only on the light coming from the ring. The researchers note that the same effect appeared when testing the method on simulated data.

But that mishmash of purported photon ring light with other light doesn’t make for a very convincing detection, critics say. “If you want to claim that you’ve seen a photon ring, I think you have to do a better job than this,” says astrophysicist Dan Marrone of the University of Arizona, a member of the EHT collaboration who was not a coauthor on the new paper.

The new result suggests only that an added thin ring gives a better match to the data, Marrone says, not whether that shape is associated with the photon ring. So it raises the question of whether scientists are seeing a photon ring at all, or just picking out an unrelated structure in the image.

…. snip …

Meanwhile, in a similar, independent analysis, Gralla and physicist Will Lockhart, also of the University of Arizona, find no evidence for a photon ring, they report in a paper submitted August 22 at arXiv.org. Their analysis differed from Broderick and colleagues’ in part because it limited how bright the photon ring could be.