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A daily view of all the goings-on at ASTRON and JIVE.

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    © ASTRON

    A few weeks ago, the traditional ASTRON-JIVE Summer Student Garden Party was held - an opportunity for the students to relax with their supervisors and the many others that have supported the programme. A few special guests were also present, including Harry van der Laan, Hanny van Arkel and Board member Josee van Eijndhoven. The students also received special summer student T-shirts. The party was again blessed by good weather (well at least it was dry), and was rounded off with a generous helping of strawberries, chocolate cake and cream. A grand time was had by all!

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  • 07/09/13--17:00: 2013 Mountainbike afternoon
  • © MC/EK/AB/JvL

    On the lovely afternoon of Tuesday July 2, a somewhat rowdy but prepared-looking group of 32 ASTRON/JIVErs got together for the 2013 mountainbike outing. After fitting the rental bikes, these cyclists easily traversed the unpaved sandy terrain near the new building to get together for a group picture, while there was still little mud on everyone. We then split into three groups of varying speed, to tour the trails around the ASTRON building.

    The ages ranged from 65, and the experience from looking for fun, to sporty and seasoned. The latter got a taste of some of the off-track GPS trails that Eric had previously put together. After a break a little over half way, near Hotel Spier, the second half of the course sported a steep climb onto the new bank of the A28. Then past some nice, sandy, zigzagging forest single-track back to Astron, where the PV had prepared a spread of healthy drinks and snacks, that went down well after the warm afternoon.

    Thanks Alex B., Eric K. and Marja C. for co-organising.

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    © ASTRON

    Earlier this month, Trinity College Dublin (TCD) was home to the European Space Expo - a giant transportable dome in which visitors can learn all about the European space programme and engage with interactive exhibits for free. TCD solar physicist Prof. Peter Gallagher, PI of the I-LOFAR initiative, organised the Dublin Space Expo event, and on the final evening a special evening was held in order to highlight Ireland's ambition to build an international LOFAR station at Birr castle.

    Speeches were made by Peter, Lord Rosse, and Declan Kirrane, Director of ISC Intelligence in Science (coordinator of AERAP, together with the South African Mission to the EU). Lord Rosses' speech was particularly inspiring - he noted that the great telescope of Birr (the "leviathan") that first discovered the spiral nature of nearby galaxies, was also built during a very challenging period in Ireland's history. As part of the European Space Expo programme at TCD, Dr. Anna Scaife (a LOFAR KSP member, former post-doc at TCD and a recent ERC award recipient) gave a public lecture entitled Exploring the Radio Universe with LOFAR. Various large companies were also there to show their support, including IBM Ireland - Barry O'Brian (IBM Gov. Prog. Executive) is pictured together with the AJDI author.

    During the LOFAR evening event, there was a special message from Canadian astronaut Chris Hadfield who recently sprang to fame with his cover version of "Major Tom"� performed in space. Chris' daughter, Kristin Hadfield a student a TCD was present on his behalf. After the event finished, several of the participants retired to the nearby Irish pub scene, in order to consider the day's success and make plans for the future. Hopefully Peter Gallagher will visit ASTRON in the autumn, in order to continue discussions on LOFAR and to give a colloquium on some recent solar results.

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    © SKA

    From 29-31 May, five outreach officers convened at the SKA Organisations head office at Jodrell Bank Observatory in the UK for a 3-day meeting about the communication strategy for the Square Kilometre Array (SKA).

    The SKA will be the largest and most sensitive radio telescope in the world with a total collecting area of approximately one square kilometre. The SKA will be built in Southern Africa and in Australia. It is a global enterprise bringing together 11 countries from the 5 continents. The SKA is led by the SKA Organisation, a not-for-profit company with its headquarters at Jodrell Bank Observatory, near Manchester, UK.

    Of course, we want the whole world to know about this telescope, so this enormous project requires a well thought out communications strategy in which all participating countries play a role. The members of the SKA Communications and Outreach Working Group (SKACOWG, see photo) met face to face and discussed, in excellent collaborative spirit, upcoming communications opportunities such as big conferences and (outreach) events, important messages about the SKA that we want the public but also students, industry and governments to know, and the way the SKA is being branded.

    Besides this group, the SKA Communications and Outreach Network (SKACON) exists, that includes outreach officers of all SKA partner countries. Both groups have regular teleconferences to keep each other up to date and to share ideas about how we can pass on our enthusiasm for the project to the outside world.

    The image shows the members of the SKACOWG, from left to right around the table: Sam Rametse (SKA South Africa), Femke Boekhorst (ASTRON), Jerry Skinner (SKA Australia), Eric Chisholm (National Research Council, Canada) and William Garnier (SKA Organisation). On the phone was also Shui Min (Ministry of Science and Technology, China).

    Want to know more about the SKA? Check out the website at or like the Facebook pages at

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    © ODIN

    On June the 7th, a group of students from the electrical engineering faculty of the Technical University of Eindhoven visited the Westerbork telescopes and ASTRON.

    The group was welcomed and started off with a tour at the old control room and the impressive radiotelescopes at Westerbork.

    Then there was a tour at ASTRON. The students were informed about JIVE and NOVA and they had the opportunity to see the R & D labs and the control room. There were also models of the new generation of radio telescopes, such as LOFAR (designed and developed by ASTRON) and SKA in which ASTRON plays one of the leading roles.

    As an unexpected extra we also visited the old Dwingeloo telescope next door, responsible for the discovery of two galaxies.

    See also:

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    © Astron

    A key feature of galaxy formation is that progressively smaller galaxies find it harder and harder to convert their gas into stars. This leads to the question whether there is a minimum galaxy mass below which no gas is converted into stars: could there be starless objects ('dark galaxies') that are only detectable through their cold gas. Such dark galaxies have become some kind of Holy Grail for HI astronomers; many Quests have been undertaken to find one, but so far no convincing case has been discovered.

    This may change. Last year, a mysterious gas cloud (called GBT1355+5439) with absolutely no stellar counterpart was found near the galaxy M101 by Chris Mihos and coworkers using data taken with the Greenbank telescope. GBT1355+5439 immediately caught the attention of the HI community, because you never know... Tom Oosterloo, George Heald and Erwin de Blok used the WSRT to have a closer look to see whether this cloud could be a dark galaxy.

    The outcome turned out to be more interesting than expected. The conclusion is that it is very unlikely that GBT1355+5439 is a dark companion galaxy of M101. It would be loo large and too massive to be consistent with the theory of dark galaxies. However, it is not inconceivable that instead it is a (much less distant and much smaller) dark galaxy companion of our own Milky Way that happens, by coincidence, to be in the same part of sky as M101, but that has nothing to do with that galaxy. GBT1355+5439 seems to have similar properties as the objects from the population of small HI clouds recently discovered with Arecibo by, among others, Betsey Adams (who will join ASTRON after the summer as a postdoc) and that are interesting candidates for being dark (or almost dark) galaxies in the vicinity of the Milky Way. It is quite possible that GBT1355+5439 belongs to this group of objects; it would be the first one to be imaged in HI and to be studied in detail.

    All this, and more, is written down in a Letter that recently appeared in A&A:

    The figure shows the HI contours of GBT1355+5439 on top of its optical image

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  • 07/15/13--17:00: AARTFAAC Hardware Tests
  • © ASTRON

    Recently, the AARTFAAC hardware required in the LOFAR superterp stations has been produced: 24 URI (UniBoard Ring Interface) boards(*), 12 UniBoards (2 per station) and 12 XGBs (10 Gigabit extension boards). All units are being evaluated thoroughly by Gijs Schoonderbeek and Sjouke Zwier.

    The goal of the AARTFAAC project is to correlate all (288) LBA dipoles on the superterp with each other, giving 288x288/2=41.472 correlation products. With a bit of software, this represents a highly sensitive all-sky detector for transient phaenomena, i.e. astronomical sources that change in brightness (or polarization) on a relatively short time-scale.

    In addition, 6 URI boards have been made for Oxford University, for their single-station correlator.

    (*) URI: boards that bend data instead of spoons.

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    © ASTRON & SKA

    The SKA Organisation is expanding rapidly, in order to gear up for the pre-construction phase. A wide variety of new positions are currently being advertised with a deadline of 19 July. The goal is to appoint 20 new recruits over the summer, including several senior positions. For more information consult:

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    © Diana Morosan, Trinity College Dublin

    With the arrival of summer here in the Netherlands, and weather which is providing us with more than the annual requirement of five continuous hours of sunshine, it is good to take a look and see what the Sun looks like through LOFAR.

    In February we started trialling a "snapshot" imaging mode of the Sun using the multi-beam capabilities of LOFAR. Using the core stations it is possible to form up to approximately 200 Tied-Array Beams which can be formed into concentric "rings" around the central observing direction (lower left picture - blue circle represents the Sun for comparison). These can be used to map out an area of sky, including on and around the Sun and it's corona. The advantage of using this mode to effectively image the Sun is that we can get much higher time resolution than the usual one second with interferometry, though possibly at the cost of some spatial resolution, and that a dynamic spectrum can be formed easily from the data of each tied-array beam. Having the dynamic spectra is particularly useful for identifying the type of radio burst(s) being observed.

    In this observation we observed a succession of Type-III radio bursts, which are very short duration (a few seconds) bursts commonly associated with flare activity. These can be seen in the dynamic spectrum (lower right image for beam 24) as the bursts progressing rapidly from higher to lower frequency with time as they drift out through the corona. This drifting is illustrated in the top three images which were created from averages over 5 MHz in frequency and a third of a second in time, progressing from 50-55 MHz on the left to 30-35 MHz on the right. The central circle illustrates the Sun's location, the outer circle is a radius of four solar radii from the Sun for illustration purposes, and the small square to the lower left of the Sun illustrates the location of beam 24.

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  • 07/21/13--17:00: Who knows what LOFAR is?
  • © ASTRON

    Who indeed? The heart of the International LOFAR Telescope is located near the municipality of Borger-Odoorn, in Drenthe, The Netherlands. But strangely enough, if you ask an inhabitant or tourist what LOFAR is, there's a big chance you will be none the wiser(*). Fortunately, this is about to change.

    The foundation LofarTafel, a group of entrepreneurs in Exloo, Drenthe, is very eager to inform inhabitants and visitors about the telescope. Among other things, they organize the yearly LOFAR days in cooperation with foundation Het Drentse Landschap (owner of the nature reserve where LOFAR is located, and ASTRON.

    On Saturday 13 and Sunday 14 July, the LOFAR days took place in Exloo, Borger-Odoorn. Visitors participated in many activities, ranging from excursions to the telescope, previews of a theater performance about the LOFAR telescope called the LOFAR Expedition (to be premiered on 2 August), to operating a small robot made by students from the Hanze Institute of Technology.

    In the field where the telescope is located, kids participated in various interactive activities to introduce them to the telescope and its technology. In addition, visitors experienced a journey through the sky in the mobile planetarium, and satisfied their hunger with "heavenly" dishes at a market with local produce. Everything was accompanied by (live) music and great weather!

    Of course, the press was also there. Check out coverage on: naar lofar gebied

    (*) LOFAR is a next-generation giant radio telescope that consists of thousands of small antennas and is spread over most of north-western Europe.

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    © ASTRON

    Over the past decade it has become clear that the growth and evolution of galaxies is strongly tied to that of the central supermassive black hole. This is generally attributed to feedback mechanisms which, according to simulations, often take the form of outflows of gas, quenching star formation in the host galaxy and halting accretion onto the central black hole. While there are a number of plausible ways that outflows could be produced, recent results have shown that in some cases, radio jets could be responsible for driving fast outflows of gas. One such example is the nearby radio galaxy 3C293.

    While fast outflows have previously been detected in this object using Westerbork (see Morganti et al., 2003), the spatial resolution of these observations was too low to accurately determine the location of the outflow. Using observations from the recently upgraded VLA we detect a fast outflow (~1200 km/s) of neutral gas approximately 0.5 kpc from the central core, suggesting that it is being driven by the radio jet. The image on the left shows the Westerbork radio continuum image of 3C293 overlaid on an optical image depicting the host galaxy. On the right is the new VLA observations where we detect the inner radio lobes on arcsec scales (middle panel) and the corresponding position-velocity diagram highlighting the broad HI absorption (top panel). A higher resolution VLBI image from Beswick et al., 2004 is shown at the bottom for comparison. The horizontal red line marks the axis along which the position-velocity diagram was extracted and the vertical red line indicates the position of the core taken from the VLBI image.

    This result is presented in a paper by Elizabeth Mahony, Raffaella Morganti, Bjorn Emonts, Tom Oosterloo and Clive Tadhunter that has been accepted for publication in Monthly Notices of the Royal Astronomical Society. The preprint is also available at .

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    © DB

    Last month I spent a few days in a vault-like room near the JIVE computers. I leafed through thousands of documents, mostly the records of meetings that happened decades ago. Sound dull? Most of it was. But from these pages, I got a look at the development of ASTRON and its predecessor SRZM, which is in fact a very interesting story as well as a crucial part of my research project: a history of the Dutch astronomical community in the twentieth century.

    J.C. Kapteyn, the great astronomer, once described his work as "grinding huge masses of fact into law". My work can best be described as "grinding huge masses of historical record into one coherent story", which admittedly sounds less catchy. Luckily, not all of the records that I need reside in windowless basements. In addition, I talk to active and retired astronomers and science administrators, besides which I also read more general books to get a better idea of the (national and international) scientific, political, cultural and economic sides of the world in which Dutch astronomers worked.

    It was great to spend a few days in Dwingeloo, experiencing the atmosphere at ASTRON and in the guest house. Those are things that can't be learned from archives, but are nevertheless relevant for the story that I want to tell. If all goes well, a Dutch-language book will appear next year. An English-language book will follow.

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  • 07/24/13--17:00: HI in HO: a myth debunked
  • © Astron/HST Heritage

    One of the gems of the sky is Hoag's Object (HO). Discovered by Art Hoag in 1950 as a very unusual galaxy, its full beauty, as a red galaxy surrounded by a peculiar very blue ring, really became apparent with the Hubble image (shown above) taken 52 years later. The peculiar beauty of HO inspired several people to peculiar explanations of this peculiar object. For example, Hoag himself suggested that 'his' object could be a case of gravitational lensing (it would be a perfect Einstein ring), but later observations ruled out this hypothesis because it would require the central object to be at least 100 times more massive than any other galaxy.

    So is HO a strange object or are appearances deceiving? One way to explore the nature of a galaxy is to study the properties of the neutral hydrogen (HI) in and around it. HI has a long memory: the timescales on which the HI structures around a galaxy change are long and the HI can be used as a tracer of things that happened long ago. This is not a new idea and Noah Brosch (Tel Aviv University) used the WSRT in 1982 to try to detect the HI in HO in an attempt to unravel the nature of HO. Unfortunately, in 1982 the WSRT was not sensitive enough to detect the HI and the mystery of the nature and origin of HO was not solved.

    Napoleon has told us that "la victoire appartient aux plus perse've'rants", so 30 years later, Brosch did a new attempt with, obviously, a much improved WSRT. And indeed, in the new observations the HI in HO was clearly detected. One of the key results of the new observations is that, although HO looks peculiar in the optical, from the HI point of view HO is a fairly normal galaxy.

    The data show that the nice blue ring is very gas rich while the red central galaxy has no gas. The fact that the HI seems to peak at the E and W side of the ring is an observational effect due to the elongated shape of the WSRT beam at these declinations (bottom left). The HI extends slightly beyond the blue ring; in these outer regions the HI ring warps slightly from the plane of the inner ring. The HI in the ring of HO shows no signs of any recent (i.e. less than 1 Gyr) event that could have created the blue ring, consistent with earlier studies of the stellar population in the ring (Finkelman). However, there are some shreds of HI floating around, far away from HO, that may have to do something with the origin of the ring, many Gyr ago.

    All these HI characteristics are observed in many early-type galaxies and the conclusion of the WSRT observations is that HO may look special, but it really isn't.

    The observations and their discussion are written in the paper 'HI in HO: Hoag's Object revisited' by Brosch, Finkelman, Oosterloo, Jozsa and Moiseev that has been accepted for publication in the Monthly Notices of the Royal Astronomical Society. A copy of this paper can be found at .

    The figure shows the HST image of HO with the HI intensity contours drawn on top.

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    © astron

    Astronomer Vibor Jelic' (Kapteyn Astronomical Institute, University of Groningen (RuG)/ASTRON), has been awarded a Veni grant of 250 000 EUR by the Netherlands Organisation for Scientific Research (NWO). With this grant, Jelic' will study complicated radio emission from our own Galaxy that obscures the view towards the first stars and the early Universe. His work will also play a crucial role for the success of the Epoch of Reionization (LOFAR-EoR) key science project of the world-leading radio telescope LOFAR (the Low Frequency Array), designed and built by ASTRON, the Netherlands Institute for Radio Astronomy. The LOFAR-EoR project is led by scientists from the Kapteyn Astronomical Institute of theRuG and ASTRON.

    Using the LOFAR radio telescope, scientists are expecting to detect cosmological radiation emitted billions of years ago, from the time of the first stars. This pivotal period in the history of the Universe is called the Epoch of Reionization (EoR). This era is key to understanding structure formation and the evolution of the Universe, and thus represents a missing piece of the puzzle in our current knowledge of the Universe. However, the faint cosmological radiation from the EoR is swamped by the foreground emission of our Galaxy and other extragalactic radio sources. Without removing the foreground emission from the data, the project team will not be able to detect the cosmological radiation and understand the EoR.

    Jelic' will exploit the innovative technology and capabilities of the LOFAR radio telescope in order to conduct a first detailed study of the foreground emission below 250 MHz. A special focus will be given to the (astro)physics of the Galactic foreground emission, e.g., the peculiar polarized structures of our Galaxy and the properties of its magnetic field. The study of the foregrounds not only constitutes a very interesting and exiting field of study in its own right, but the gained knowledge will also be used to develop foreground removal techniques, helping LOFAR in the race to be the first in probing the Epoch of Reionization.

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    © ASTRON

    On Thursday 25 July late at night, the first try-out of the theater production 'The LOFAR Expedition' kicked off. From 25 July to 25 August, the theater group 'the PeerGroup' plays 'the LOFAR Expedition', a cosmic journey into the unknown, with astronaut/ comedian Vincent Bijlo as your professional guide.The performance is played in the core of the LOFAR telescope and in the surrounding nature area of foundation 'Het Drentse Lanschap', between the villages of Exloo and Buinen.

    The night started off with some heavy rain and thunder storms, which unfortunately caused a 1-hour delay. However, after the rain stopped, visitors enjoyed a fun and humourous show led by Vincent Bijlo and his 'students'. His ability to relate cosmic events to aspects in everyday life, makes the LOFAR Expedition an interesting, fun and fascinating experience. Accompanied by a live band, made up of the PeerGroup members themselves, a light show and numerous cosmic 'props', visitors were hopefully left in awe of the universe and everything that surrounds them.

    LOFAR stands for Low Frequency Array and is a network of thousands of sensitive sensors spread over the northeastern parts of the Netherlands and in Germany, England, Sweden and France. One of the main projects for which scientists use the LOFAR telescope is to map the very beginning of the universe, when the first stars and galaxies were formed.

    In 'the LOFAR Expedition', we travel to the origins of our universe. Vincent Bijlo thinks he has found the fastest route to the Big Bang. On the way, he makes many exciting cosmic adventures that will shed new light on our existence.

    With a lot of music, humour and fantasy, the PeerGroup brings the seemingly infinte universe closer. Black holes, curved spaces and supernovas:everything becomes clear. In over an hour we travel lightyears back and who knows, maybe we'll even hear the Big Bang....


    Performance dates:

    Thursday 25 - Sunday 28 July at 8.30 pm (try-out)

    Thursday 1 August - 8.30 pm (try-out)

    Friday 2 August - 8.30 pm Premi�re

    Sat 3 & Sun 4 August - 8.30 pm

    Thurs 8 - Sun 11 August - 8.30 pm

    Thurs 15 - Sun 18 August - 8.30 pm

    Thurs 22 - Sun 25 August - 8.30 pm

    More information and tickets:

    Location: LOFAR base, Exlo�rweg 13, Buinen (Gemeente Borger-Odoorn).

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    © Image credits: Gyula I. G. Jozsa, Peter Kamphuis, Rich Rand, George Heald and the HALOGAS consortium.

    In the HALOGAS project we have observed 22 spiral galaxies with the WSRT, each galaxy for 120 hours. The goal is to characterise the faint, neutral gas component. It is thought that a lot more infalling gas than is observed in spiral galaxies is required to maintain star formation at the observed rates. It is therefore important to know whether the visible gas (neutral hydrogen) shows any signs of infall, and whether this correlates with other characteristics of the galaxies.

    Getting a good overview means including galaxies in the sample that at a first glance seem to not be exceedingly exciting. NGC 5023 does not form many stars, and it is not interacting. However, careful kinematical modeling showed that the galaxy appears rather asymmetric. Assuming a symmetric disk, we would deduce a rather strong decline of the rotation velocity with height above the disk - a parameter that is thought to provide information about the connection between the galaxy and its atmosphere. But introducing spiral arms in our models (a possibility in the modelling software TiRiFiC), we achieve a brilliant fit, and the decline in the rotation velocity becomes much more modest.

    The little animation shows first the stellar component of the galaxy, to blend with our deep WSRT observation of the neutral hydrogen. Then the modeled neutral-hydrogen component is shown (notice the good match!). We then sharpen our view to finally make the galaxy artificially opaque and to turn it around. We can visualise the (typical) spiral pattern that we believe is present in the galaxy, despite the fact that it is not immediately evident in the observed edge-on view. We are hence using the velocity information in our very deep observation to conduct a galaxy tomography.

    The results are described in a paper by Peter Kamphuis et al., soon to appear in the Monthly Notices of the Royal Astronomical Society (MNRAS).

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    © Hiddo Hanenburg

    As the spider's web is deployed to catch the flies in the heather, the Dwingeloo telescope is poised to capture the stars in the sky.

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  • 08/06/13--17:00: Field of Dreams (II)
  • © ASTRON

    On Thursday (weather permitting) the second Softball match will be held at de Boerken hotel in Lhee. This is another activity organised by Bob Campbell for the summer students, other summer visitors and ASTRON & JIVE staff. If you want to play, please let Bob know ( Meanwhile, the images above show some of the all-stars in action.

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  • 08/05/13--17:00: Pictures LOFAR Expeditie
  • © H.J. Stiepel

    On Saturday 3th of August a group of ASTRON colleagues visited a performance of "De LOFAR expeditie". They were very positive about it. Comedian Vincent Bijlo explains (radio) astronomy very well in combination with jokes and humour.

    Pictures can be found at:

    An evening very well spent. N.B. It is still possible to attend! Performance dates:

    Thurs 8 - Sun 11 August - 8.30 pm

    Thurs 15 - Sun 18 August - 8.30 pm

    Thurs 22 - Sun 25 August - 8.30 pm

    More information and tickets:

    Location: LOFAR base, Exloerweg 13, Buinen (Gemeente Borger-Odoorn).

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  • 08/04/13--17:00: High Fidelity pays off!
  • © Parisa Noorishad

    Last month, Parisa Noorishad successfully defended her thesis at Groningen University proudly watched by promotores Prof. Thijs van der Hulst and Prof. Arnold van Ardenne.

    Called "Optimization for High Fidelity Imaging with Aperture Array Telescopes", the thesis addressed some key and fundamental issues relevant for the success of aperture arrays. She presented a fresh look on (limits of) redundancy in aperture arrays like LOFAR and activities toward their use in the SKA, suggested solutions of constrained self-calibration and optimal modelling for extended sources aiming to improve to high fidelity imaging. This is very relevant as the wide field potential of these arrays and the inevitable intense processing required, can only result in good imaging after fully understanding where we are in algorithmic speech, and what need to be done next and therefore the thesis is an excellent basis for further work. See

    Dr Noorishad is now working on processing software in the TARGET centre in Groningen tackling Big Data visualization issues. We wish her all the best in this emerging and also for radio astronomy, highly relevant field!

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