– Team includes researchers from University College Dublin
– Data from I-LOFAR telescope in Birr, Co. Offaly used as part of the survey project
An international team of more than 200 astronomers from 18 countries, including researchers from University College Dublin (UCD), has today published the first phase of a major new sky survey at unprecedented sensitivity using the Low Frequency Array (LOFAR) telescope.
The survey reveals hundreds of thousands of previously undetected galaxies, shedding new light on many research areas including the physics of black holes and how clusters of galaxies evolve.
A special issue of the scientific journal Astronomy & Astrophysics is dedicated to the first twenty-six research papers describing the survey and its first results.
Radio astronomy reveals processes in the Universe that we cannot see with optical instruments. In this first part of the sky survey, LOFAR observed a quarter of the northern hemisphere at low radio frequencies. At this point, approximately ten percent of that data is now being made public. It maps three hundred thousand sources, almost all of which are galaxies in the distant Universe; their radio signals have travelled billions of light years before reaching Earth.
Associate Professor John Quinn, UCD School of Physics and his PhD student, Sean Mooney, who is supported through an Irish Research Council Government of Ireland Postgraduate Scholarship, are members of the LOFAR surveys key science project.
They are lead authors on one of the papers published today and contributed to several others. Their paper is focused on the jets from supermassive black holes that are pointed towards the Earth.
Professor Huub Röttgering, Leiden University, and principal investigator of the surveys team said, “If we take a radio telescope and we look up at the sky, we see mainly emission from the immediate environment of massive black holes. With LOFAR we hope to answer the fascinating question: where do those black holes come from?”
“What we do know is that black holes are pretty messy eaters. When gas falls onto them they emit jets of material that can be seen at radio wavelengths.”
Associate Professor John Quinn, UCD School of Physics said, “The LOFAR survey provides us with an unprecedented view of galaxies with supermassive black holes at their centers, and how they evolve. The sensitivity and resolution of this LOFAR survey is unparalleled at low frequencies, and the technological advancements required to make this possible are relatively recent.”
Sean Mooney, PhD student, UCD School of Physics said, “We’re interested in studying high-speed jets of plasma that are ejected from supermassive black holes, and the survey is a goldmine of information for us. Now that the data are public, it will surely prove to be a useful resource for many other astrophysicists around the world also.”
Find out more via this short video via ASTRON
Creating low-frequency radio sky maps requires significant computational resources. Much of the analysis has been done at a data centre at SURFsara in Amsterdam, which hosts over 20,000 terabytes of LOFAR data.
“It is the largest astronomical data collection in the world. Processing the enormous data sets is a huge challenge for scientists. What normally would have taken centuries on a regular computer was processed in less than one year using the high throughput compute cluster (Grid) and expertise”, said Dr Raymond Oonk, SURFsara, a member of the international team of researchers.
Machine learning algorithms are being used to automate parts of the analysis, with some of this work being done at UCD on powerful computing clusters.
The international LOFAR telescope consists of a European network of radio antennas, connected by a high-speed fibre-optic network spanning seven countries. LOFAR was designed, built and is now operated by ASTRON (Netherlands Institute for Radio Astronomy), with its core located in Exloo in the Netherlands.
The Irish station was installed in the grounds of Birr Castle, Co. Offaly in 2017, with support from Science Foundation Ireland, Enterprise Ireland, the Department of Business, Enterprise, and Innovation, Offaly County Council, the Department of Culture, Heritage, and Gaeltacht, UCD, TCD, Armagh Observatory, DCU, UCC, NUIG, DIAS, and AIT.
The 26 research papers in the special issue of Astronomy & Astrophysics were done with only the first two percent of the sky survey. The team aims to make sensitive high-resolution images of the whole northern sky, which will reveal 15 million radio sources in total.
“This sky map will be a wonderful scientific legacy for the future. It is a testimony to the designers of LOFAR that this telescope performs so well”, said Carole Jackson, Director General of ASTRON.
“Just imagine some of the discoveries we may make along the way. I certainly look forward to it”, she added.
The special issue of Astronomy & Astrophysics is titled LOFAR Surveys.
The paper which Sean Mooney and Associate Professor John Quinn are lead authors is entitled Blazars in the LOFAR Two-Metre Sky Survey First Data Release.
Dublin, Ireland, February 18, 2019: An international team of scientists from Trinity College Dublin, the University of Helsinki, and the Dublin Institute for Advanced Studies today announced a major discovery on the nature of solar storms in the journal Nature Astronomy (PDF available at Springer Nature SharedIt).
The Sun is the closest star to our planet in the Universe, and like many stars, it is far from quiet. Sunspots, many times the size of Earth, can appear on its surface and store enormous reservoirs of energy. And it is within these regions that huge explosions called solar storms occur.
Solar storms are spectacular eruptions of billions of tonnes of hot gas travelling at millions of kilometres an hour. If they impact the Earth, they can produce beautiful displays of the aurora, but they can also cause problems with communication and navigation systems and power grids.
In 1859, the largest solar storm ever observed – the so-called Carrington Event – erupted. Within hours, it generated displays of the aurora as far south as Italy and Cuba and caused interruptions in early telegraph systems in Europe and the US. In Ireland, it reportedly stopped London stock market prices being received in Dublin “due to a strange atmospheric phenomenon”.
Our society is now even more dependent on technology, and solar storms have the potential to cause significant effect on their performance. In 2003, transformers in South Africa were damaged, while Swedish air traffic control systems were closed down in 2015 for more than an hour due to effects associated with a solar storm. More recently, emergency response communications were interrupted during hurricane season in September 2017 in the Caribbean.
“We used data from the Low Frequency Array, LOFAR, together with images from NASA, NOAA and ESA spacecraft to work out where particles are accelerated by the particularly large solar storm on September 10, 2017, soon after we turned on the Irish LOFAR station”, said Dr Diana Morosan, the lead author on the publication, and affiliated with Trinity and the University of Helsinki.
“We built the Irish LOFAR station at Birr Castle to study how solar storms move and how they generate bursts of radio waves”, according to Professor Peter Gallagher of the Dublin Institute for Advanced Studies, who leads the I-LOFAR project on behalf of Trinity. “We used I-LOFAR to detect tiny radio bursts in coordination with the LOFAR core in the Netherlands to work out where the burst were coming from.”
“Our observations enabled us to work out that the solar storm created a huge shock wave as it erupted from the Sun, which then accelerated electrons that generated radio bursts. This gives us an amazingly detailed insight into how solar storms work, and may in the future help us to produce more accurate forecasts of when solar radio bursts occur and how they impact the Earth”, said Dr Morosan.
Speaking about the research, Professor Mark Ferguson, Director General of Science Foundation Ireland and Chief Scientific Adviser to the Government of Ireland, said: “Less than two years ago we officially launched the I-LOFAR radio telescope at Birr Castle, and it is fantastic to see the fascinating breakthroughs it has already made possible. It demonstrates the tangible rewards that arise from investing in cutting-edge infrastructure which facilitates collaborations between researchers and leads to exciting discoveries. I wish to congratulate the individuals from Trinity College Dublin, DIAS and University of Helsinki for their impressive work on solar storms, and I am confident that their future work with I-LOFAR will continue to provide us with invaluable insights.”
“These excellent results from I-LOFAR demonstrate the quality of the site in Ireland and the benefits of international collaboration in research and innovation. I am delighted to see such a return from the Government funding for I-LOFAR.” Minister of State for Training, Skills, Innovation, Research and Development, John Halligan T.D.
I-LOFAR is funded by Science Foundation Ireland and the Department of Department of Business, Enterprise and Innovation.
Access to PDF of the Nature Astronomy Publication
A PDF of the Nature Astronomy publication can be accessed free-of-charge at Springer Nature SharedIt.
I-LOFAR is owned and operated at Birr Castle by Trinity College Dublin on behalf of the I-LOFAR Consortium, which includes Trinity College Dublin, Dublin Institute for Advanced Studies, Armagh Observatory & Planetarium, University College Dublin, University College Cork, National University of Ireland, Galway, and Athlone Institute of Technology.
The I-LOFAR fibre link is sponsored by open eir.
Head of Irish LOFAR Consortium:
Professor Peter Gallagher
Trinity College Dublin and Dublin Institute for Advanced Studies
+353 87 656 8975
Lead author on Nature Astronomy paper:
Dr Diana Morosan
Trinity College Dublin and University of Helsinki
+358 50 317 5827
Fionn (11) and Luke (8) Teeling-Gallagher have been busy building an international LOFAR radio telescope in Minecraft. Click on the movie above to learn all about how it works.
A consortium including the Local Enterprise Office (LEO) Offaly, Offaly County Council and I-LOFAR has been awarded €458,240 from the Enterprise Ireland Regional Development Fund to establish “STREAM Creative Suite” in Birr Technology Centre.
Orla Martin, Head of Enterprise in LEO Offaly explained that STREAM Creative Suite will be a natural extension to the I-LOFAR Project. The I-LOFAR radio telescope, situated in Birr Castle, is the Irish Station in the largest radio telescope in the world. There are 52 LOFAR Stations across Europe, generating 3 Gbps per station, over 150 Gigabits per second, more than 6 Petabytes per year.
Therefore, I-LOFAR provides a unique opportunity to access big data in real time. This data can be utilised for training purposes and for proving algorithms for many sectors. Professors and researchers of universities affiliated with the international LOFAR network together with Software Developers and Data Analysts from companies operating within or in cooperation with companies based in the Midland Region will have the opportunity to use the STREAM Creative Suite – either through regular hot desk usage or through the establishment of a base there.
The space will comprise an open plan work area for researchers, a training room and smaller office spaces. The programme will also include a residential/visiting researcher programme, support for workshops, summer internships, and training in Data Analytics and related topics. The funding will also support the salary costs of a manager who will be hired for 3 years to run the suite and develop future activities.
The Creative Suite will bring together researchers and practitioners in areas such as the visual arts, multi-media, technology and astronomy, who share a common interest in Big Data.
Offaly County Council Cathaoirleach Cllr. Danny Owens welcomed the news and acknowledged the collaborative efforts those who made the successful application: Offaly County Council’s Chief Executive, Ms. Anna Marie Delaney; Head of Enterprise, Ms. Orla Martin; Prof. Peter Gallagher, I-LOFAR Consortium and Mr. Joe Hogan, Founder of Openet.
We are delighted to launch a new engagement project in 2019 – the Astronomical Midlands or AstroLands for short – that uses the recently constructed Irish Low Frequency Array (I-LOFAR) and Education Centre at Birr Castle to connect with students, teachers and members of the public in rural communities in the Midlands.
Astronomical Midlands, funded by Science Foundation Ireland Discover Programme, will embark on three key initiatives:
o Space4Exploration: Create an engaging, inspirational and multi-use space in the I-LOFAR Education Centre.
o Space4Students: Launch day-long and week-long space camps at the Education Centre that run during school term and school holidays for students aged 10 to 14.
o Space4Teachers: Create CPD workshops for upper primary and lower secondary school teachers based around the National Junior Certificate themes of Earth and Space.
Astronomical Midlands is overseen by our Project Manager, Aine Flood and Project Scientist Prof Peter Gallagher. We will also recruit “Astronomical Ambassadors” to interact with visitors to Birr and to deliver space camps and teacher workshops.
Astronomical Midlands will open new conversations with groups that have had little involvement with STEM using our unique facility at Birr. Our project will allow people in the Midlands to discover opportunities for further education and careers in STEM and inspire the next generation of scientific explorers.
Astronomical Midlands is go for launch from February 2019!
Press Release from Offaly County Council:
Professor Gallagher received the award at a Civic Reception in Offaly County Council on Monday, 16th October 2018. The special event was attended by Professor Gallagher’s family, colleagues and guests from the worlds of science, academia, tourism, enterprise and local development. Among the guests were Lord and Lady Rosse, Lady Alicia Clements of Birr Castle, and Mr. Joe Hogan of Openet.
At the Civic Reception, Offaly County Council Cathaoirleach Cllr. Danny Owens informed the attendees that the decision to confer a Civic Recognition Award is a reserved function of Offaly County Council. It is an acknowledgement of a person’s outstanding contribution to the County.
The Civic Recognition Award acknowledges Professor Peter Gallagher’s outstanding contribution to the County; leading the €2m I-LOFAR project in Birr, developing the I-LOFAR Education Centre in conjunction with Offaly County Council, and for on-going work to develop collaborative research and discovery in Offaly.
Cathaoirleach Cllr. Danny Owens spoke of Birr’s rich astronomical heritage, a worldwide reputation that is a great source of pride for Offaly people. The selection of Birr as the location for the new I-LOFAR radio telescope marks a new chapter for scientific endeavour in Offaly.
I-LOFAR is the Irish Station in a European wide network of state-of-the-art radio telescopes. The telescope is used to study celestial objects such as the sun, black holes and magnetic fields.
In addition to the benefits of having a cutting-edge science project in Offaly, having the I-LOFAR telescope in Birr opens up new possibilities for research, jobs, tourism and science education.
Offaly County Council’s Chief Executive Ms. Anna Marie Delaney acknowledged Professor Gallagher’s willingness to collaborate and work with Offaly County Council and others to harness the economic potential of I-LOFAR. Ms. Delaney outlined a number of projects where Professor Gallagher had generously given of his time, including the development of the I-LOFAR Education Centre and a field trip to ASTRON (the Netherlands Institute for Radio Astronomy).
Professor Gallagher then gave an informative and engaging presentation on the I-LOFAR project and the opportunities for further development. Elected Members Cllr. John Carroll and Cllr. John Clendennen commended Professor Gallagher’s enthusiasm, work to date and drive to develop scientific discovery in Offaly.
Offaly County Council Cathaoirleach Cllr. Danny Owens then presented Professor Gallagher with a framed scroll and a specially commissioned piece of art to commemorate the Civic Recognition. The commissioned piece was designed and produced by LEO Offaly client Michelle O’Donnell of Glasshammer Studios. Radio images generated from the I-LOFAR telescope were used as inspiration for the piece.
MC and Director of Services Mr. Frank Heslin thanked all present and invited all to join the Members for refreshments in the Council atrium.
I-LOFAR is operated by Trinity College Dublin on behalf of the I-LOFAR Consortium. It is supported by Science Foundation Ireland, the Dept of Business, Enterprise and Innovation, Offaly Co Co, and many others.
LOFAR station is a wide-band radio receiver, which operates at the frequency range from 10 MHz to 240 MHz. The full reception band is divided into low band (10 MHz – 90 MHz) and high band (110 MHz – 240 MHz). The frequencies in between low band and high band are not used due to RFI from FM radio transmitters.
The station signal processing has been originally designed assuming that three different antenna arrays would be used. These arrays would have been the low-band-low (LBL) antenna array, the low-band-high (LBH) antenna array, and the high-band antenna (HBA) array. However, the present standard stations do not have the LBL antennas, and the LBH antenna array is thus referred to as the low-band antenna (LBA) array.
Antennas used in LOFAR stations are briefly introduced in following two sections. Notice that the antenna array configurations are configurations of full antenna arrays. It is always possible to manually select only a subset of a full antenna array to be used e.g. in beamforming. Positions of individual antenna elements and antenna array definitions of a station are stored in station configuration files.
2. Receiver Control Units (RCUs)
The analogue signals from LBA elements and HBA tiles are transferred in coaxial cables to a LOFAR station cabinet, where each of the cables is connected to a receiver unit. A RCU performs input selection, followed by amplification and filtering of the analogue input signal. The conditioned analog signal is sampled with a 12-bit A/D converter. The A/D converter produces real signal samples at either 200 MHz or 160 MHz sampling frequency. Combinations of filter passband and sample clock frequency are selected so that the selected frequency band always aliases around zero frequency, without frequency aliasing inside the passband. With one of the available combinations the signal spectrum will be inverted, but it can be inverted back in subsequent processing steps.
The receiver units are numbered starting from zero. X-polarisation cables are connected to even-numbered RCUs and Y-polarisation cables are connected to odd-numbered ones. The only deviation from this rule is the LBA outer field, whose X-polarisation cables are connected to odd-numbered RCUs and Y- polarisation cables to the even-numbered ones. A receiver unit has three inputs: LBL, LBH, and HBA. The LBL and LBH connectors have an 8 V bias voltage. The HBA X-polarisation connectors have the 48 V bias voltage for power supply. The HBA Y-polarisation connectors have a 3.3 V bias voltage only when communicating with the HBA tiles.
A core station or a remote station with 96 LBA elements and 48 HBA tiles has 96 RCUs. The LBA inner array is connected to the LBH inputs and the LBA outer array to the LBL inputs. Despite the naming convention in RCUs, both LBA inner and LBA outer use the same kind of antenna elements. The HBA tiles are connected to the HBA inputs.
Due to their larger number of HBA tiles, international stations have 192 RCUs. The 96 LBA elements of an international station are connected to the LBH inputs of the RCUs, and the 96 HBA tiles are connected to the HBA inputs. In a basic installation of an international station the LBL inputs are left empty, thus facilitating later installation of an additional antenna array.
After frequency band selection and A/D conversion in the RCUs, the received signals are transferred to remote station processing boards. The RSP boards perform all digital signal processing that is done at the station, and send data to central processor (CEP).
The discrete signal samples arriving from a RCU to a RSP board are first buffered in a FIFO buffer. In order to compensate for differences in signal delays in the coaxial cables, buffer length can be adjusted independently for each individual RCU. The buffer is followed by a polyphase filter, which divides the wide band input signal into so-called subbands.
A polyphase filter is a novel FFT-based implementation of a bandpass filter bank, which divides the real input signal into 1024 complex subband signals. Because the real input contains two identical (mirrored) copies of the signal spectrum – one at positive and the other at negative frequencies – the lowest 512 subbands are complex conjugates of the 512 highest ones. The whole receiver passband is thus covered by the 512 lowest subbands, which are used in further processing. Depending on sample clock frequency, subband width is either 200 MHz/1024 = 195.3125 kHz, or 160 MHz/1024 = 156.250 kHz.
After the polyphase filter the signal bandwidth is small enough to facilitate phased-array beamforming1, which produces beamformed subband signals called beamlets. Although 512 subbands are produced in the polyphase filter, only 244 beamlets can be formed by the station signal processing. Subbands used in beamforming are selected immediately after the polyphase filter. The beamforming is performed in a ring, where a process handling signal from one RCU receives a partial beamforming result, adds the contribution from its own RCU, and passes the result forward to the process handling signal from the next RCU. In order to facilitate the beamforming, the RSP boards of a LOFAR station are connected together as a ring. After a full cycle in the ring, the beamformed sample is complete and ready to be transmitted to central processing.
The beamforming ring is divided into four separate lanes, each of which has its start and end point in a different RSP board. Beamformed data are output from those RSP boards that are endpoints of the beamforming lanes. In core stations the beamforming lanes can be split into two halves, allowing independent beamforming with the HBA0 and HBA1 arrays. Because 244 beamlets can be formed with both arrays, the splitting allows core stations to form 488 beamlets simultaneously, but each of them with only 24 HBA tiles. Four additional output RSP boards are defined in the split mode, i.e. data are being output from eight RSP boards simultaneously.
In addition to the beamforming, the RSP boards can calculate so-called subband statistics , beamlet statistics , and array covariances (crosslet statistics) . Likewise the beamlets, the co- variances are also formed in the ring of RSP boards, and their calculation is divided into four lanes. All these crosslet lanes start from and end to the same RSP board, which also outputs the data. The crosslet output board is usually different from the beamlet output boards. The RSP boards can also send either raw A/D converter samples or subband data to ring buffers in transient buffer boards.
An RSP board has four antenna processors (AP). Each AP processes two orthogonal polarisations from its connected antenna. Each RSP board thus has 8 digital inputs for the signals from the RCUs, which defines the number of RSP boards in a station: core stations and remote stations have 12 RSP boards, whereas international stations have 24 RSP boards.
4. Transient Buffer Boards (TBBs)
Transient buffer boards are not part of the main signal processing chain, but their function is to store a short period of raw voltage data in a ring buffer. Writing to the buffer can be stopped when a triggering event is detected, after which the data can be read from the buffer.
TBBs are physically connected to the RSP boards, which provide the raw data that is buffered to the boards. Two kinds of data can be buffered: in ”transient” mode real signal samples are copied to TBBs immediately after the FIFO buffers in RSP boards, whereas in ”subbands” mode complex subband data produced by the polyphase filter are copied to the TBBs. TBB memory is divided into pages, which are large enough for 1024 12-bit data samples in ”transient” mode. Because the subband data is in 16-bit format, only 487 of the 512 subbands can be recorded in ”subbands” mode.
One TBB is capable of recording data from 16 RCUs, and each TBB is thus connected to two RSP boards. Core stations and remote stations thus have 6 TBBs, whereas international stations have 12 TBBs.
5. Local Control Unit (LCU)
Local Control Unit (LCU) is a computer running the Redhat Linux OS. All station control happens via the LCU, which runs a number of control processes that communicate with the different processing boards of the station. LCU also receives station clock signals from GPS and a rubidium standard. Users can log on to the LCU via a ssh connection, and control the whole station from the command line. Single-station control is covered in more detail in Section 3, and relevant commands are listed in the command reference.
TURN ON YOUR television, or your radio, and tune it to an empty station where you can’t receive any signal. See all those black and white dots scattering around the screen, or hear that faint hiss in the background? A part of that is a radio signal from the universe, namely the Cosmic Microwave Background radiation, the heat energy left over from the Big Bang itself.
Light at radio-wavelengths is emitted by all kinds of celestial bodies: stars, galaxies, planets, and more. Visible light that we use “normal” telescopes for only gives us part of the picture, whereas radio astronomy opens up an entire new spectrum of the universe we are otherwise blind to.
The full article can be read here.