Black Hole Cam

First image of the supermassive black hole at the centre of our own Milky Way galaxy

Astrid Spiering — Thu, 12 May 2022 13:07:00 +0000

Astronomers have unveiled the first image of the supermassive black hole at the centre of our own Milky Way galaxy. This result adds overwhelming evidence – over length scales comparable with the event horizon – that the object was indeed a black hole and yielded valuable clues about the workings of such giants, which are thought to reside at the centre of most galaxies. The image, in unprecedented resolution, was produced by Event Horizon Telescope (EHT), a global scientific collaboration, where scientists funded by the European Research Council, through BlackHoleCam project, have played a key role.

The breakthrough follows the EHT collaboration’s 2019 release of the first image of a black hole, called M87*, at the centre of the more distant Messier 87 galaxy. The new image is a long-anticipated look at the massive object that sits at the very centre of our own galaxy. Scientists had previously seen stars orbiting around something invisible, ultra-compact, and very massive at the centre of the Milky Way. This shows beyond reasonable doubt that this object known as Sagittarius A* is a black hole, and today’s image provides the first direct visual evidence of it.

Left to right: Professors Michael Kramer, Luciano Rezzolla and Heino Falcke at the Effelsberg Radio Telescope.

“The idea that our own Milky Way may harbour a supermassive black hole always intrigued and motivated me. Now we can finally see that it is really there. This is a lifelong dream come true,” said Heino Falcke Professor of Astroparticle Physics and Radio Astronomy at Radboud University in Nijmegen, Netherlands.

Professor Falcke together with Professors Michael Kramer from the Max Planck Institute for Radioastronomy, and Luciano Rezzolla from Goethe University Frankfurt, and their teams of postdocs and PhD students and research staff, led BlackHoleCam. The project, proposed in 2013 and supported with an ERC Synergy Grant from 2014 to 2020, aimed not only to produce the first-ever image of a black hole, but also “turn our Galactic Centre into a fundamental-physics laboratory to measure the fabric of space and time with unprecedented precision.” Now these objectives have been fully accomplished.

Although we cannot see the event horizon of the black hole because it is completely dark, hot and glowing gas around it reveals a telltale signature: a dark central region, called a “shadow”, surrounded by a bright ring-like structure. The new view captures light bent by the powerful gravity of the black hole, which is four million times more massive than our Sun. The EHT team’s results are being published today in a special issue of The Astrophysical Journal Letters.

“For me the image of Sgr A* is even more exciting than our first black hole image of M87,” said Professor Kramer. “For Sgr A*, we already knew the mass and distance of the black hole from other measurements. This allows the prediction of the size of the shadow, assuming the general relativity is correct, which we can now compare with the observations. In other words, we can do an exciting test of Einstein’s theory! He wins again!”

Picture calculated in 2000 as a prediction of the black hole image, and suggesting that it should be possible to observe a black hole using a global network of telescopes at millimetre-waves. Falcke, Melia, Agol 2000, Astrophysical Journal Letters 528, p17 https://ui.adsabs.harvard.edu/abs/2000ApJ…528L..13F/abstract

Because the black hole is about 27,000 light-years away from Earth, it appears to us to have about the same size in the sky as a donut placed on the Moon. To image it, the team created the powerful EHT, which linked together eight existing radio observatories across the planet to form a single “Earth-sized” virtual telescope. The EHT observed Sgr A* on multiple nights, collecting data for many hours in a row, similar to using a long exposure time on a camera.

The two black holes that so far have been imaged – M87* and Sgr A* – look remarkably similar, even though our galaxy’s black hole is more than a thousand times smaller and less massive than the colossus pictured in 2019 and the physical conditions very different.

Piecing together the image of Sgr A* – even though it is much closer to us – was considerably more difficult because of the variations in the data. In comparison, M87* was an easier, steadier target, with nearly all images looking the same, that was not the case for Sgr A*. The image of the Sgr A* black hole is an average of the different images the team extracted, finally revealing the giant lurking at the centre of our galaxy for the first time.

“Despite all the experience with M87*, imaging Sgr A* has not been a stroll in the park. The rapid variability in the emission and a much more lively environment at the centre of the galaxy has forced us to develop new techniques for the analysis of the data and of the numerical simulations, said Professor Rezzolla. The end result is that we now have much more confidence on how black holes behave and can discard a number of theoretical models that do not fit observations.”

C.M. Fromm (University Würzburg, Germany), L. Rezzolla (University Frankfurt, Germany) and the EHT Collaboration

Large-scale 3D morphology of the jet and disk from simulation of a rapidly rotating black hole. The image shows the fast, dilute and highly magnetized out-flowing jet (blue) and the denser and weakly magnetized accretion disk (red). Magnetic field lines that spiral around the jet are plotted in yellow. The insets are magnifications of the large-scale image on the reported scales.

The effort was made possible through the ingenuity of more than 300 researchers from 80 institutes around the world that together make up the EHT Collaboration. Along with the US’s National Science Foundation, the European Research Council (ERC) has provided crucial support to the EHT though the €14 million BlackHoleCam project. Over the past two decades the EU also supported the development and upgrading of the large telescope infrastructure essential to the success of the EHT project, investing more than €30 million in RadioNet.

In addition to developing complex tools to overcome the challenges of imaging Sgr A*, the EHT team worked rigorously for five years, using supercomputers (some of which were fully funded by the ERC) to combine and analyse their data, all while compiling an unprecedented library of simulated black holes to compare with the observations. Scientists are particularly excited to finally have images of two black holes of very different sizes, which offers the opportunity to understand how they compare and contrast. They have also begun to use the new data to test theories and models of how gas behaves around supermassive black holes, and whether alternatives to black holes are compatible with the data. This process is not yet fully understood, but is thought to play a key role in shaping the formation and evolution of galaxies.

https://erc.europa.eu/news-events/magazine/Behind-the-scene-with-blackhole-scientists

https://erc.europa.eu/projects-figures/stories/astronomers-reveal-first-ever-image-black-hole

https://erc.europa.eu/news/eu-funded-scientists-unveil-first-ever-image-black-hole

https://www.youtube.com/watch?v=Dr20f19czeE

EHT press release

BlackHoleCam

Other ERC-funded research on black holes:

Launching, propagation and emission of relativistic jets from binary mergers and across mass scales (JETSET) https://cordis.europa.eu/project/id/884631
Mapping Magnetic Fields with INterferometry Down to Event hoRizon Scales (M2FINDERS) https://cordis.europa.eu/project/id/101018682

Today: Press conference at ESO on groundbreaking Milky Way results from the EHT Collaboration

Astrid Spiering — Thu, 12 May 2022 07:00:00 +0000

Today at 15:00 CEST, the Event Horizon Telescope (EHT) project will hold a press conference at the the European Southern Observatory (ESO) headquarters to present major results on the Milky Way.

The ESO Director General will open the press event. EHT Project Director Huib Jan van Langevelde and EHT Collaboration Board Founding Chair Anton Zensus will deliver speeches. A panel of EHT researchers will explain the result and answer questions.

The conference will be streamed online on the ESO website and the ESO YouTube channel. There will be simultaneous press conferences organized around the world, including in Washington D.C., Santiago de Chile, Mexico City, Tokyo, and Taipei.

Astronomers image magnetic fields at the edge of M87’s black hole (By ESO)

Amanda Schut — Wed, 24 Mar 2021 14:56:20 +0000

The Event Horizon Telescope (EHT) collaboration, who produced the first ever image of a black hole, has today revealed a new view of the massive object at the centre of the Messier 87 (M87) galaxy: how it looks in polarised light. This is the first time astronomers have been able to measure polarisation, a signature of magnetic fields, this close to the edge of a black hole. The observations are key to explaining how the M87 galaxy, located 55 million light-years away, is able to launch energetic jets from its core.

“We are now seeing the next crucial piece of evidence to understand how magnetic fields behave around black holes, and how activity in this very compact region of space can drive powerful jets that extend far beyond the galaxy,” says Monika Mościbrodzka, Coordinator of the EHT Polarimetry Working Group and Assistant Professor at Radboud University in the Netherlands.

On 10 April 2019, scientists released the first ever image of a black hole, revealing a bright ring-like structure with a dark central region — the black hole’s shadow. Since then, the EHT collaboration has delved deeper into the data on the supermassive object at the heart of the M87 galaxy collected in 2017. They have discovered that a significant fraction of the light around the M87 black hole is polarised.

“This work is a major milestone: the polarisation of light carries information that allows us to better understand the physics behind the image we saw in April 2019, which was not possible before,” explains Iván Martí-Vidal, also Coordinator of the EHT Polarimetry Working Group and GenT Distinguished Researcher at the University of Valencia, Spain. He adds that “unveiling this new polarised-light image required years of work due to the complex techniques involved in obtaining and analysing the data.”

Light becomes polarised when it goes through certain filters, like the lenses of polarised sunglasses, or when it is emitted in hot regions of space where magnetic fields are present. In the same way that polarised sunglasses help us see better by reducing reflections and glare from bright surfaces, astronomers can sharpen their view of the region around the black hole by looking at how the light originating from it is polarised. Specifically, polarisation allows astronomers to map the magnetic field lines present at the inner edge of the black hole.

“The newly published polarised images are key to understanding how the magnetic field allows the black hole to ‘eat’ matter and launch powerful jets,” says EHT collaboration member Andrew Chael, a NASA Hubble Fellow at the Princeton Center for Theoretical Science and the Princeton Gravity Initiative in the US.

The bright jets of energy and matter that emerge from M87’s core and extend at least 5000 light-years from its centre are one of the galaxy’s most mysterious and energetic features. Most matter lying close to the edge of a black hole falls in. However, some of the surrounding particles escape moments before capture and are blown far out into space in the form of jets.

Astronomers have relied on different models of how matter behaves near the black hole to better understand this process. But they still don’t know exactly how jets larger than the galaxy are launched from its central region, which is comparable in size to the Solar System, nor how exactly matter falls into the black hole. With the new EHT image of the black hole and its shadow in polarised light, astronomers managed for the first time to look into the region just outside the black hole where this interplay between matter flowing in and being ejected out is happening.

The observations provide new information about the structure of the magnetic fields just outside the black hole. The team found that only theoretical models featuring strongly magnetised gas can explain what they are seeing at the event horizon.

“The observations suggest that the magnetic fields at the black hole’s edge are strong enough to push back on the hot gas and help it resist gravity’s pull. Only the gas that slips through the field can spiral inwards to the event horizon,” explains Jason Dexter, Assistant Professor at the University of Colorado Boulder, US, and Coordinator of the EHT Theory Working Group.

To observe the heart of the M87 galaxy, the collaboration linked eight telescopes around the world — including the northern Chile-based Atacama Large Millimeter/submillimeter Array (ALMA) and the Atacama Pathfinder EXperiment (APEX), in which the European Southern Observatory (ESO) is a partner — to create a virtual Earth-sized telescope, the EHT. The impressive resolution obtained with the EHT is equivalent to that needed to measure the length of a credit card on the surface of the Moon.

“With ALMA and APEX, which through their southern location enhance the image quality by adding geographical spread to the EHT network, European scientists were able to play a central role in the research,” says Ciska Kemper, European ALMA Programme Scientist at ESO. “With its 66 antennas, ALMA dominates the overall signal collection in polarised light, while APEX has been essential for the calibration of the image.”

“ALMA data were also crucial to calibrate, image and interpret the EHT observations, providing tight constraints on the theoretical models that explain how matter behaves near the black hole event horizon,” adds Ciriaco Goddi, a scientist at Radboud University and Leiden Observatory, the Netherlands, who led an accompanying study that relied only on ALMA observations.

The EHT setup allowed the team to directly observe the black hole shadow and the ring of light around it, with the new polarised-light image clearly showing that the ring is magnetised. The results are published today in two separate papers in The Astrophysical Journal Letters by the EHT collaboration. The research involved over 300 researchers from multiple organisations and universities worldwide.

“The EHT is making rapid advancements, with technological upgrades being done to the network and new observatories being added. We expect future EHT observations to reveal more accurately the magnetic field structure around the black hole and to tell us more about the physics of the hot gas in this region,” concludes EHT collaboration member Jongho Park, an East Asian Core Observatories Association Fellow at the Academia Sinica Institute of Astronomy and Astrophysics in Taipei.

More information

This research was presented in two papers by the EHT collaboration published today in The Astrophysical Journal Letters:

“First M87 Event Horizon Telescope Results VII: Polarization of the Ring” (doi: 10.3847/2041-8213/abe71d)

“First M87 Event Horizon Telescope Results VIII: Magnetic Field Structure Near The Event Horizon” (doi: 10.3847/2041-8213/abe4de).

Accompanying research is presented in the paper

“Polarimetric properties of Event Horizon Telescope targets from ALMA” (doi: 10.3847/2041-8213/abee6a) by Goddi, Martí-Vidal, Messias, and the EHT collaboration, which has been accepted for publication in The Astrophysical Journal Letters.

The EHT collaboration involves more than 300 researchers from Africa, Asia, Europe, North and South America. The international collaboration is working to capture the most detailed black hole images ever obtained by creating a virtual Earth-sized telescope. Supported by considerable international investment, the EHT links existing telescopes using novel systems — creating a fundamentally new instrument with the highest angular resolving power that has yet been achieved.

The individual telescopes involved are: ALMA, APEX, the Institut de Radioastronomie Millimetrique (IRAM) 30-meter Telescope, the IRAM NOEMA Observatory, the James Clerk Maxwell Telescope (JCMT), the Large Millimeter Telescope (LMT), the Submillimeter Array (SMA), the Submillimeter Telescope (SMT), the South Pole Telescope (SPT), the Kitt Peak Telescope, and the Greenland Telescope (GLT).

The EHT consortium consists of 13 stakeholder institutes: the Academia Sinica Institute of Astronomy and Astrophysics, the University of Arizona, the University of Chicago, the East Asian Observatory, Goethe-Universitaet Frankfurt, Institut de Radioastronomie Millimétrique, Large Millimeter Telescope, Max Planck Institute for Radio Astronomy, MIT Haystack Observatory, National Astronomical Observatory of Japan, Perimeter Institute for Theoretical Physics, Radboud University and the Smithsonian Astrophysical Observatory.

The Atacama Large Millimeter/submillimeter Array (ALMA), an international astronomy facility, is a partnership of ESO, the U.S. National Science Foundation (NSF) and the National Institutes of Natural Sciences (NINS) of Japan in cooperation with the Republic of Chile. ALMA is funded by ESO on behalf of its Member States, by NSF in cooperation with the National Research Council of Canada (NRC) and the Ministry of Science and Technology (MOST) and by NINS in cooperation with the Academia Sinica (AS) in Taiwan and the Korea Astronomy and Space Science Institute (KASI). ALMA construction and operations are led by ESO on behalf of its Member States; by the National Radio Astronomy Observatory (NRAO), managed by Associated Universities, Inc. (AUI), on behalf of North America; and by the National Astronomical Observatory of Japan (NAOJ) on behalf of East Asia. The Joint ALMA Observatory (JAO) provides the unified leadership and management of the construction, commissioning and operation of ALMA.

The BlackHoleCam research group was awarded the European Research Council €14 million Synergy Grant in 2013. The Principal Investigators are Heino Falcke, Luciano Rezzolla and Michael Kramer and the partner institutes are JIVE, IRAM, MPE Garching, IRA/INAF Bologna, SKA and ESO. BlackHoleCam is part of the Event Horizon Telescope collaboration.

Links

Originally published by ESO March 24, 2021

BlackHoleCam / EU EHT Meeting 2020

Amanda Schut — Tue, 11 Feb 2020 11:42:08 +0000

Address

Max-Planck-Institut für Radioastronomie, Bonn, Germany

BlackHoleCam / EU EHT Meeting 2020

General Information

General information

Dates: Wednesday, 6 May 2020, – Thursday, 7 May 2020.
Location: Max Planck Institute for Radio Astronomy, Bonn, Germany.

The meeting will start on Wednesday morning and close on Thursday evening.

The meeting is open to non-EHT members on Wednesday (“community day”), and will be EHT-members-only on Thursday (“EU-EHT day”).

SOC / LOC

Scientific Organizing Committee:

Ciriaco Goddi (Radboud University Nijmegen, NL) [Chair]

Heino Falcke (Radboud University Nijmegen, NL)

Ilse van Bemmel (JIVE, NL)

Oliver Port (University of Amsterdam, NL)

Luciano Rezzolla (Frankfurt University, Germany)

Michael Kramer (MPIfR, Bonn, Germany)

Eduardo Ros (MPIfR, Bonn, Germany)

Stefan Gillessen (MPE, Garching, Germany)

Gregory Desvignes (Observatoire de Paris, France)

Karl Schuster (IRAM, France)

Mariafelicia de Laurentis (Naples University, Italy)

Kazi Rygl (INAF, IT-ARC, Bologna, Italy)

Michael Lindqvist (Onsala Observatory, Sweden)

Ziri Younsi (University College London, UK)

Jose-Luiz Gomez (Instituto de Astrofísica de Andalucía, Granada, Spain)

Roger Deane (University of Pretoria, South Africa)

Local Organizing Committee:

Ciriaco Goddi (Radboud University Nijmegen, NL)

Amanda Schut (Radboud University Nijmegen, NL)

Mariya Halvadzhieva (MPIfR Bonn, Germany)

Registration

Logistics

Venue

The conference will take place at the Max-Planck-Institut für Radioastronomie.

The main meeting room is 0.02.

On Thursday, May 7th, we also have three breakout rooms available: TBD.

Free coffee, tea and cookies are available in the meeting rooms. Lunch will be served.

Conference dinner

A social dinner is being planned for the evenings of May 6th, 2020, which will take place at

Restaurante Perú deputamare!
Graurheindorfer Straße 61
53111 Bonn

Hotel [TO BE UPDATED]

Hotel myPOPPELSDORF

Wallfahrtsweg 4

53115 Bonn

Reservations

Phone: +49 228 269 10

Email: info@mypoppelsdorf.com

https://www.ameronhotels.com/en/poppelsdorf-bonn

Details:

68 € governmental rate incl. breakfast for 4+7 March and 100 € for 5+6 March due to a trade fair: Please mention the Max Planck Institute for Radio Astronomy when booking via email or phone to get the special rate, thanks.
8 minutes by bus – line 631 – from MPIfR
Bus stop near hotel: Poppelsdorfer Platz, MPIfR bus stop: Immenburgpark (time schedule attached)

President Hotel

Clemens-August-Str. 32-36
53115 Bonn

Phone: +49 228 7250 0

Email: info@presidenthotel.de

https://www.presidenthotel.de/home.html

Details:

113 € including breakfast, no governmental rate available
8 minutes by bus – line 631 – from MPIfR
Bus stop near hotel: Poppelsdorfer Platz, MPIfR bus stop: Immenburgpark (time schedule attached)

Hotel Mozart

Mozart Straße 1

53115 Bonn

Phone: +49 228 41 00 14 0

E-Mail: info@hotel-mozart-bonn.com

http://www.hotel-mozart-bonn.com/

Details:

74 euros governmental rate incl. breakfast if you stay 3 nights or more. Please mention the Max Planck Institute for Radio Astronomy when booking via email or phone to get the special rate, thanks (we blocked 10 single rooms until 16 Feb)
Bus stop: Herwarthstraße, bus line 610, 611 (see attached)

Ibis Hotel

Vorgebirgsstrasse 33

53119 Bonn

Phone: +49 228 72660

Fax: +49 228 7266405

Email: H1441@accor.com

Details:

Approximately 100 € incl. breakfast, no governmental rate

Transportation

Transportation to/from the institute is your individual responsibility.

The closest airport is Cologne Bonn airport or alternatively Düsseldorf airport.

The distance from Cologne Bonn airport to the institute is 25 km.

The distance from Düsseldorf airport to the institute is 85km.

Information shared on the website of the institute:

By Car

Take the A565 autobahn. Exit at Bonn-Endenich and follow the signs for Euskirchen/Duisdorf. To reach the Institute, consult the map.

By Train

From Bonn Central Station (Bonn Hauptbahnhof), take a taxi to the Institute.
Alternatively, go to the adjacent bus station and take the no. 611 bus (heading for Lessenich) or the no. 610 (heading for Duisdorf). Alight at the bus stop Immenburgpark.

By Plane

The nearest airports are Cologne/Bonn (Köln/Bonn), Düsseldorf and Frankfurt. A taxi from Cologne/Bonn Airport will cost around EUR 40. There is a regular bus service from the airport to Bonn bus station (next to the railway station).To proceed, see “By Train”. Trains leave for Bonn every hour from Düsseldorf and Frankfurt Airports.
Only IC/EC trains (every 2 hours) go directly to Bonn Main station. Fast train ICE to Cologne Main station / change to Bonn or to stop Bonn/Siegburg / change to tramway No 66.

Participants

List of participants [TO BE UPDATED]

55 participants are currently registered.

First Name	Last Name	Institute
Rebecca	Azulay Romero	MPIfR
Amit	Bansod	MPIfR
Christiaan	Brinkerink	Radboud University
Thomas	Bronzwaer	Radboud University
Chiara	Ceccobello	Chalmers University of Technology
Weiwei	Chen	MPIfR
Jordy	Davelaar	Radboud University
Mariafelicia	De Laurentis	ITP/ Goethe University Frankfurt
Roger	Deane	University of Pretoria
Gregory	Desvignes	MPIfR
Jason	Dexter	MPE
Ralph	Eatough	MPIfR
Frank	Eisenhauer	MPE
Heino	Falcke	Radboud University
Raquel	Fraga-Encinas	Radboud University
Christian	Fromm	ITP/ Goethe University Frankfurt
Stefan	Gillessen	MPE
Ciriaco	Goddi	Radboud University
Roman	Gold	ITP/ Goethe University Frankfurt
Sara	Issaoun	Radboud University
Michael	Janssen	Radboud University
Ramesh	Karuppusamy	MPIfR
Andreas	Keil	European Research Council Executive Agency
Mark	Kettenis	Jive
Jonas	Köhler	ITP/ Goethe University Frankfurt
Katharina	Königstein	Radboud University
Michael	Kramer	MPIfR
Thomas	Krichbaum	MPIfR
Kira	Kühn	MPIfR
Claus	Laemmerzahl	ZARM, University of Bremen
Matthew	Liska	University of Amsterdam
Kuo	Liu	MPIfR
Rusen	Lu	MPIfR
Nicholas	MacDonald	MPIfR
Sera	Markoff	University of Amsterdam
Yosuke	Mizuno	ITP/ Goethe University Frankfurt
Monika	Moscibrodzka	Radboud University
Iniyan	Natarajan	Rhodes University
Hector	Olivares	ITP/ Goethe University Frankfurt
Prajwal	Padmanabh	MPIfR
Oliver	Pfuhl	Max-Planck-Institut fuer extraterrestrische Physik
Oliver	Porth	ITP/ Goethe University Frankfurt
Luciano	Rezzolla	ITP/ Goethe University Frankfurt
Freek	Roelofs	Radboud University
Eduardo	Ros	MPIfR
Helge	Rottmann	MPIfR
Alan	Roy	MPIfR
Salvador	Sanchez	IRAM
Karl	Schuster	IRAM
Lijing	Shao	MPIfR
Viola	Tegethoff	MPIfR
Remo	Tilanus	Radboud / Leiden Obs
Pablo	Torne	IRAM
Ilse	van Bemmel	Jive
Huib Jan	van Langevelde	Jive
Daniel	van Rossum	Radboud University
Jan	Wagner
Norbert	Wex	MPIfR
Robert	Wharton	MPIfR
Vojtech	Witzany	ZaRM, University of Bremen
Ziri	Younsi	ITP/ Goethe University Frankfurt
Shan-Shan	Zhao	Radboud University

Programme

The agenda for the meeting is as follows: TO BE UPDATED

Wednesday, May 6th, 2020
Time	Topic	Speaker	Location
11:00	Registration for the meeting opens		in front of the main meeting room
12:00 – 13:00	LUNCH		foyer – in front of the main meeting room
13:00 – 18:00	Updates from the EHTC WGs	Ciriaco Goddi (Chair)	Room: 0.02

13:15 – 14:00	Updates on WGA: Instrumentation
	Instrumentation: Update on IRAM	Salvador Sanchez	Room: 0.02
	Integration & Verification	Alan Roy	Room: 0.02
	Monitoring and Control	Daan van Rossum	Room: 0.02
	Discussion		Room: 0.02

14:00 – 15:00	Updates on WGB: Data Collection & Processing
	Proposal Coordination	Eduardo Ros	Room: 0.02
	Science Operations	Thomas Krichbaum	Room: 0.02
	Correlation	Jan Wagner	Room: 0.02
	Synthetic Data	Roger Deane	Room: 0.02
	Calibration & Error Analysis	Michael Janßen	Room: 0.02
	Discussion		Room: 0.02
15:00 – 15:30	COFFEE BREAK		foyer – in front of the main meeting room
15:30 – 16:20	Updates on WG3: Data Analysis
	Imaging	Sara Issaoun / Freek Roelofs	Room: 0.02
	Scattering	Christiaan Brinkerink	Room: 0.02
	Time Domain	Michael Kramer	Room: 0.02
	Discussion		Room: 0.02

16:20 – 17:30	Updates on WG4: Science Utilization
	Parameter Definition	Heino Falcke	Room: 0.02
	Theory & Simulation	Yosuke Mizuno	Room: 0.02
	Model Comparison & Feature Extraction	Christian Fromm	Room: 0.02
	Non-Horizon Science (AGN)	Thomas Krichbaum	Room: 0.02
	Pulsars	Michael Kramer	Room: 0.02
	Discussion		Room: 0.02

17:30 – 17:50	Updates on WG5: Software & Data Compatibility
	Software & Data Compatibility	Ciriaco Goddi	Room: 0.02
	Discussion		Room: 0.02
17:50 – 18:00	Wrap up	Ciriaco Goddi	Room: 0.02

18:30 – …	Social Dinner at the MPIfR		foyer – in front of the main meeting room

Thursday, May 7th, 2020
Time	Topic	Speaker	Location
Session I	Overview Talks
09:00 – 09:30	Review Talk on BHC	Heino Falke, Michael Kramer, Luciano Rezzolla	Room: 0.02
09:30 – 09:45	1mm VLBI array overview and update	Remo Tilanus	Room: 0.02
09:45 – 10:00	2017 mm-VLBI campaign with ALMA	Ciriaco Goddi	Room: 0.02

Session II	Simulations of black holes	Chair: Luciano Rezzolla
10:00 – 10:10	Simulations of black hole accretion	Oliver Porth	Room: 0.02
10:15 – 10:25	Modeling polarization of black holes	Monika Moscibrodzka	Room: 0.02
10:30 – 11:00	COFFEE BREAK		foyer – in front of the main meeting room
11:00 – 11:10	Ultra high resolution GRMHD simulations of (thin) accretion disks using H-AMR	Mathew Liska	Room: 0.02
11:15 – 11:25	Progress on Radiative Transfer around Black Holes	Ziri Younsi	Room: 0.02
11:30 – 11:40	Characterizing the relation between black-hole spin and image asymmetry for radiative models of accreting supermassive black holes	Thomas Bronzwaer	Room: 0.02
11:45 – 11:55	A new method for extending solutions to the self-similar relativistic MHD equations for black hole outflows	Chiara Ceccobello	Room: 0.02
12:00 – 12:10	Imaging highly relativistic non-black hole space-times: the case of boson stars	Hector Olivares	Room: 0.02
12:15 – 12:25	Orbitting black holes in Virtual Reality	Jordy Davelaar	Room: 0.02
12:25 – 13:30	LUNCH		foyer – in front of the main meeting room

Session III	VLBI/Interferometric Observations	Chair: Eduardo Ros
13:30 – 13:45	Sagittarius A* at 3mm: first results from GMVA+ALMA	Sara Issaoun	Room: 0.02
13:45 – 14:00	First look at polarized emission variability of Sgr A*	Christiaan Brinkerink	Room: 0.02
14:00 – 14:15	Polarimetric VLBI observations of M87 and 3C84 at short millimeter wavelengths	Jae-Young Kim	Room: 0.02
14:15 – 14:30	Coreshift of SgrA*	Raquel Fraga-Encinas	Room: 0.02
14:30 – 14:45	Imaging the event horizon of Sagittarius A* from space	Freek Roelofs	Room: 0.02

Session IV	Interfacing simulations and observations	Chair: Heino Falcke
14:45 – 15:00	MeqSilhouette refactored: now with wide-user base capability	Roger Deane	Room: 0.02
15:00 – 15:15	THEMIS – A parameter estimation framework for the EHT: Overview & first results	Roman Gold	Room: 0.02
15:15 – 15:30	ipole + Themis: Fitting new ray-tracing code with EHT observations	Shan-Shan Zhao	Room: 0.02
15:30 – 16:00	COFFEE BREAK		foyer – in front of the main meeting room
16:00 – 16:15	Radiative signatures of parsec-scale jets	Christian Fromm	Room: 0.02
16:15 – 16:30	Testing no-hair theorem with pulsars around Sgr A* BH	Lijing Shao	Room: 0.02

Session V	*Spacetime around Sgr A using stellar and pulsar orbits**	Chair: Michael Kramer
16:30 – 16:45	Gravity	Stefan Gillessen	Room: 0.02
16:45 – 17:00	Test-particle dynamics in general spherically symmetric black hole spacetimes	Mariafelicia De Laurentis	Room: 0.02
17:00 – 17:15	Measurements of the magneto-ionic properties of the Galactic Centre with PSR J1745-2899	Ralph Eatough	Room: 0.02
17:15 – 17:30	Update on BHC-related progress at the IRAM 30-m observatory	Pablo Torne	Room: 0.02
17:30 – 17:45	Observing pulsars with a Phased ALMA	Kuo Liu	Room: 0.02
17:45 – 18:00	Searching for Galactic Center Pulsars with the Very Large Array	Robert Wharton	Room: 0.02


18:30 – …	Social Dinner at Restaurant Peru		Restaurante Perú deputamare! Graurheindorfer Straße 61 53111 Bonn

DELETE
Time	Topic	Speaker	Location
09:00 – 09:30	Organization of the discussion sessions	Ciriaco and PIs	Room: 0.02
09:30 – 10:30	Discussion I (breakout) – Theory	Moderator: Luciano Rezzolla	Room: 0.01
09:30 – 10:30	Discussion II (breakout) – EHT data calibration and synthetic data	Moderators: Roger Deane, Ciriaco Goddi	Room: 3.25
10:30 – 11:00	COFFEE BREAK		foyer – in front of the main meeting room
11:00 – 12:00	Discussion I (breakout) – Theory	Moderator: Luciano Rezzolla	Room: 0.01
11:00 – 12:00	Discussion II (breakout) – EHT data calibration and synthetic data	Moderators: Roger Deane, Ciriaco Goddi	Room: 3.25
12:00 – 12:30	Reports from Discussion I and II (Plenary)	Moderators of the discussions I & II	Room: 0.02
12:30 – 13:30	LUNCH		foyer – in front of the main meeting room
13:30 – 15:00	Wrap-up, outlook	Heino Falke, Michael Kramer, Luciano Rezzolla	Room: 0.02
15:00 – 18:00	Discussion III,IV,V (optional Breakouts)
	Breakout III	Public outreach	Rooms: 0.01, 0.02, 3.25 or 2.05
	Breakout IV	AGNs projects
	Breakout V	Observations proposals
	Collaboration work	Various topics

Abstracts

These are the abstracts submitted in random order:

Freek Roelofs, Radboud University Nijmegen

Imaging the event horizon of Sagittarius A* from space

It has been proposed that Very Long Baseline Interferometry (VLBI) at sub-millimeter waves will allow us to image the shadow of the black hole in the center of our Milky Way, Sagittarius A* (Sgr A*), and thereby test basic predictions of the theory of general relativity. In this work, the imaging prospects of a new Space VLBI (SVLBI) mission concept have been investigated. An initial design study of the concept has been performed for the purpose of the Event Horizon Imager (EHI). The concept may be suitable for imaging Sgr A* at high frequencies (up to ~690 GHz), which has significant advantages over performing ground-based VLBI at 230 GHz. The setup investigated here consists of two satellites with either 3-meter or 6-meter dishes in polar or equatorial circular Medium-Earth Orbits (MEOs) with slightly different radii. This setup will result in a dense spiral-shaped uv-coverage with long baselines (up to ~60 G\lambda), allowing for extremely high-resolution and high-fidelity imaging of radio sources. We simulate observations of a general relativistic magnetohydrodynamics (GRMHD) model of Sgr A* for the proposed configuration and noise calculated from model system parameters. Even though the resulting signal-to-noise ratio on individual measurements may be low, gridding the uv-plane and averaging visibilities in the same grid cell accumulated over multiple months of observations will be sufficient to obtain a strong signal, even at the long baselines. Our simulations show that with this method, images of the black hole shadow of Sgr A* with a resolution of 4 uas (about 8% of the shadow diameter) could be reconstructed within a few months of observing time. The concept may be of high scientific value. The black hole shadow could be measured much more precisely than with ground-based VLBI, allowing for stronger tests of General Relativity and accretion models.

Ralph Eatough, MPIfR Bonn

Measurements of the magneto-ionic properties of the Galactic Centre with PSR J1745-2900

PSR J1745-2900 — a radio loud magnetar that lies close to Sgr A* — is a unique probe of the interstellar environment toward the Galactic Centre. Atypically for magnetars, it has remained active in the radio band for close to five years since its discovery. Because PSR J1745-2900 also displays a rapid proper motion, it has enabled measurements of the Faraday Rotation and Dispersion Measure along multiple lines of sight. In this talk I will present results on the Galactic Centre environment near PSR J1745-2900 from radio monitoring observations with a suite of European telescopes.

Robert Wharton, MPIfR Bonn

Searching for Galactic Center Pulsars with the Very Large Array

The Karl G. Jansky Very Large Array (VLA) is an extremely sensitive and versatile instrument that is particularly well suited for searching for pulsars in the Galactic center. I will give a brief overview of the different types of pulsar observing possible with the VLA and then discuss how we are using these new pulsar modes for Galactic center pulsar searches. Finally, I will give some preliminary results and discuss applications for next generation pulsar surveys.

Pablo Torne, IRAM

Update on BHC-related progress at the IRAM 30-m observatory

The IRAM 30-m telescope (a.k.a Pico Veleta) is an important facility for the Event Horizon Telescope array and for the surveys searching for pulsars closely orbiting Sgr A*. This telescope has undergone significant upgrades in the last year, in particular related to backends, finally reaching the specifications of the project: a 64-Gbps recording system on a IF of 5-9 GHz. Additionally, the BHC-funded dedicated pulsar backend has recently been upgraded to a large bandwidth of 8 GHz. With this latest equipment, the upcoming observations for the imaging of black holes and AGNs, and for searching and studying pulsars at millimetre wavelengths, will be carried out with a very high sensitivity. We will review these last technical upgrades, and discuss the status of the Galactic Centre pulsar survey carried out from the IRAM 30-m at wavelengths between 3 and 2 mm (~87 to 140 GHz).

Michael Kramer, MPIfR Bonn

BHC and Pulsar work within the EHT

This talk will introduce the activities around the BHC pulsar work envisioned for the EHT and how, apart from science questions, it can also lead to informed decisions in other areas.

Kuo Liu, MPIfR Bonn

Observing pulsars with a Phased ALMA

Observing pulsars with an interferometer is possible, when it can be operated as a phased array. While it is relatively easy to achieve phasing at low frequencies, keeping stable phasing at high radio frequencies requires regular readjustments which are typically inconsistent with pulsar observing modes. A particular case is ALMA, where the phasing is re-done every 10 sec. In order to investigate the impact on pulsar observations, the Vela pulsar has been observed in January 2017. I will present the results so far, i.e. integrated pulse profile of Vela obtained by folding the data with a known ephemeris. I will also present the polarisation properties of the detection at multiple frequency bands. Additional tests made with VLBI data on Sgr A* indicate some systematics that we did not seen in Vela. We present those and discuss their impact for future pulsar observations and other observing modes.

Shan-Shan Zhao, Radboud University Nijmegen

ipole + Themis: Fitting new ray-tracing code with EHT observations

Ipole is a new public ray-tracing code for covariant, polarized radiative transport. Themis is a framework for performing analyses of the EHT observations. By coupling ipole and Themis, we can use MCMC sampler to traverse the whole parameter space and find out the best fit model parameters by fitting EHT observations under Bayesian statistical frame. This talk will show the latest progress of the work.

Roger Deane, University of Pretoria

MeqSilhouette refactored: now with wide-user base capability”

I’ll update the collaboration on the significantly refactored version of MeqSilhouette, an effort that was motivated by the desire to empower the user. MeqSilhouette can now be run in several different ways other than from source, including Docker and in a Jupyter Notebook. I’ll demonstrate the usability, new features, the discuss the more immediate applications with respect to EHT synthetic data generation.

Luciano Rezzolla, Goethe University Frankfurt

BHC theory: a report from Frankfurt.

I will report on the theoretical efforts carried out in Frankfurt within the scientific scopes of BHC. In particular, I will briefly review those topics that will be discussed more in detail in subsequent talks, namely, simulations of dilaton black holes, parameterised test-particle dynamics, and various code developments.

Yosuke Mizuno, Goethe University Frankfurt

On the Present Ability to Test Theories of Gravity via BH Shadows

Upcoming sub-millimetre VLBI images of Sgr A* carried out by the EHT Collaboration are expected to provide critical evidence for the existence of this supermassive black hole. In this work we assess our present ability to use EHTC images to determine if they correspond to a Kerr black hole as predicted by Einstein’s theory of general relativity or to a black hole in alternative theories of gravity. To this end, we perform GRMHD simulations and use GRRT calculations to generate synthetic shadow images of a magnetised accretion flow onto a Kerr black hole. In addition, and for the first time, we perform GRMHD simulations and GRRT calculations for a dilaton BH, which we take as a representative solution of an alternative theory of gravity. Taking into account the configuration of the VLBI observing array from the 2017 EHTC campaign, we find that it could be extremely difficult to distinguish between black holes from different theories of gravity, thus highlighting that great caution is needed when interpreting BH images as tests of general relativity.

Ziri Younsi, Goethe University Frankfurt

Progress on Radiative Transfer around Black Holes

In this talk, I will give an overview of the progress made in Frankfurt in the past 12 month with respect to general-relativistic radiative transfer calculations. I will discuss the recent developments of the radiative transfer code, BHOSS, as applied to perform high-accuracy GRRT calculations of electromagnetic radiation from astrophysical plasmas in BH environments, as well as some of our future intended directions of scientific application, in particular with respect to Sgr A*.

Roman Gold, Goethe University Frankfurt

THEMIS – A parameter estimation framework for the EHT: Overview & first results

I will present recent work in developing THEMIS, a modular, extensible parameter estimation framework for the Event Horizon Telescope. Specifically, I will demonstrate the validity of this new tool by reproducing known results of fitting Gaussian, crescent and RIAF models to old Event Horizon Telescope data. I will highlight some new capabilities such as fitting simultaneously visibility magnitude and closure phase data, yielding new non-trivial results even with the old data set. Finally, I will give an outlook of what the next steps in this general framework could be.

Christian Fromm, Goethe University Frankfurt

Radiative signatures of parsec-scale jets

Using state-of-the-art relativistic magneto-hydrodynamical simulations and ray-tracing algorithms we model the dynamics of jets along with their radiation microphysics, investigating the impact of magnetisation on the jet dynamics and the observed emission. During the post-processing procedure we account for the properties of the observing array (sparse uv-plane) and the imaging algorithm, enabling a more direct comparison between simulations and ground or space-based VLBI observations.

Hector Olivares, Goethe University Frankfurt

Imaging highly relativistic non-black hole space-times: the case of boson stars

General relativistic magneto-hydrodynamic (GRMHD) simulations and radiative transfer (GRRT) calculations are powerful tools to study a variety of accretion scenarios potentially observable by the Event Horizon Telescope, some of them involving extensions to General Relativity. In this talk, we first describe new additions to the GRMHD code BHAC, namely Upwind Constrained Transport algorithms for the evolution of the magnetic field and adaptive mesh refinement procedures compatible with them, which allow a significant speed-up while satisfying the solenoidal constraint of the magnetic field at machine precision. Then, we discuss an application of this code to simulate accretion onto a boson star, an object appearing as a consequence of some dark matter models and models of particle physics derived from string theory. The mass and compactness of some boson stars, as well as their lack of a hard surface makes them similar to supermassive black holes, despite the absence of an event horizon. By comparing the dynamics of plasma accreting from a magnetized torus onto a Schwarzschild black hole and onto a non rotating boson star and analysing GRRT images obtained from radiation transport calculations using the code BHOSS, we discuss the possibility of using shadow images to distinguish a black hole from a boson star, and more generally, to infer the presence of an event horizon.

Mariafelicia De Laurentis, Goethe University Frankfurt

Test-particle dynamics in general spherically symmetric black hole spacetimes

To date, the most precise tests of general relativity have been achieved through pulsar timing, albeit in the weak-field regime. Since pulsars are some of the most precise and stable “clocks” in the Universe, present observational efforts are focused on detecting pulsars in the vicinity of supermassive black holes (most notably in our Galactic Centre), enabling pulsar timing to be used as an extremely precise probe of strong-field gravity. In this paper a mathematical framework to describe test-particle dynamics in general black hole spacetimes is presented, and subsequently used to study a binary system comprising a pulsar orbiting a black hole. In particular, taking into account the parameterization of a general spherically symmetric black hole metric, general analytic expressions for both the advance of the periastron and for the orbital period of a massive test particle are derived. Furthermore, these expressions are applied to four representative cases of solutions arising in both general relativity and in alternative theories of gravity. Finally, this framework is applied to the Galactic Centre S-stars and four distinct pulsar toy models. It is shown that by adopting a fully general-relativistic description of test-particle motion which is independent of any particular theory of gravity, observations of pulsars can help impose better constraints on alternative theories of gravity than is presently possible.

Oliver Porth, Goethe University Frankfurt

Simulations of black hole accretion

In this contribution I will provide an update on ongoing development and current projects with the BlackHoleAccretionCode. BHAC is an oct-tree adaptive mesh refinement general relativistic magnetohydrodynamics code which now features staggered mesh constrained transport and thus conserves divergence of the magnetic field to machine precision. Recent additions are the resistive physics module, the updated particles module as well as the ability to incorporate nuclear equations of state. First science cases have been published or submitted. Finally, I will summarise the GRMHD code comparison project of the EventHorizonTelescope collaboration.