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

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    On Tuesday, September 20th, Rik Jongerius defended his PhD thesis entitled "Exascale Computer System Design: The Square Kilometre Array" at the University of Eindhoven.

    The day started with an excellent small symposium on the subject of Rik's thesis. He then preceded his defence by a clear 10 minute overview for a general audience, of the challenges of the next generation of giant radio telescopes, in particular limiting the power consumption by the data processing system. The committee then subjected him to some close questioning, but he stood firm as you can see in the picture above.

    Four years ago, Rik started as the first IBM-Dome PhD student, or predoc in IBM speak, at the ASTRON & IBM Center for Exascale Technology in Dwingeloo. Rik quickly became an important link between the technology at the IBM Zurich research labs, and the technical challenges faced by ASTRON in (co-) developing the Square Kilometre Array via contributions to the different SKA engineering consortia.

    With his easygoing and thorough style, he started to model and analyse the SKA designs in order to pinpoint those aspects that require the most processing, and thus electrical power, and thus cost. For a system that is "exascale", or in other words requiring up to operations per second, the answers certainly helped the engineers to improve their designs.

    His core contribution to SKA is the development of a tooling set, including an application-specific (SKA) model, and processor performance models. With this tooling set it is possible to very quickly assess the processing cost of many different SKA architectures. The holistic analysis tool itself is nearing its completion, and also has a big potential outside the SKA context. In addition to this, Rik also contributed to many other topics, such as taking part in the design of application-specific chips (ASICs) for the SKA station processors.

    A sizeable contingent of DOME and ASTRON colleagues had made the long journey to Eindhoven to cheer him on. We all congratulate Rik with this excellent personal and professional milestone.

    Editor's note: The robed gentleman with the magnificent chain on the right is Prof Bart Smolders, another ex-ASTRON employee who has risen high in the world.

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  • 09/25/16--17:00: APERTIF Milestone BBQ
  • © R.H. van den Brink

    Mid-September we celebrated several APERTIF milestones in the nice surrounding of the WSRT, an obvious location since that's where APERTIF is being installed. We have currently placed all hardware at Westerbork, including the correlator hardware. Most parts of the firmware are in place, and a large part of the software is finished as well. The whole team really did a great job to get to this point.

    Now we are in the challenging phase were everything has to come together. Issues pop up during testing and while creating the first Measurement Sets. Problems are being tackled while astronomers are eager to start using this magnificent instrument.

    So it was nice to see everybody together at the BBQ: the people who are involved in the design, deployment, implementation, testing, commissioning, and the people that can't wait to start using APERTIF.

    The weather was nicely planned, so let's make sure we can deliver APERTIF equally successfully!

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    © Helen Schat-Hansen

    On June 25 a group of Dutch Management Assistants, all members of EUMA, came from all over the country to ASTRON for a company-visit and their annual general meeting (AGM).

    After the well-known ASTRON lunch Marco de Vos gave a presentation, telling why ASTRON is here and what steps need to be taken to develop the innovative instruments like WSRT and LOFAR, that enable astronomers to make such beautiful pictures. To give an insight into those developments Jan Geralt bij de Vaate took the visitors for a tour through the R&D labs, while the group also went to the Dwingeloo Telescope for a presentation by CAMRAS.

    There was a lot of interaction between EUMA members and ASTRON colleagues. After the visit many members told me how extraordinary this company visit was, and how impressed they were by what we do.

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    © JvL/DK

    Recently, an apparently random traffic sign was placed in the Astronomy Group hallway. Its solidity, pointedness and slanted positioning have led some to claim it is a menace; and it recently disappeared as a safety precaution. What do you think?

    Joeri van Leeuwen, staff astronomer:

    The unsecured, loose signpost that was in front of my office cannot be tolerated. Think of the children! And what is it even about, did my tax guilders pay for that? If we give in, soon the building will be filled with signs! Where will old people have to walk?

    Derk Kuipers, senior facilitair medewerker gebouwen en logistiek:

    Oke Joeri. I will try to explain it in understandable language. Anyone with any sense will immediately see the sign depicts an astrophysical explosion of some kind! Very artistic and inspirational. The formulas beside quickly point to those Fast Radio Bursts we hear so much about, that ALERT on Apertif will find. An extremely motivational sign for any astronomer. Naysayers that claim otherwise have no imagination! Clear enough? Ok!

    Editor's note: There seem to be several subliminal messages hidden in this amusing text. Can you spot them? Big Prizes can be won.

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    © A.-K. Baczko et al. 2016, A&A, 593, A47

    An international team of astronomers including ASTRON have measured the magnetic field in the vicinity of a supermassive black hole and pinpointed its location in the nearby active galaxy NGC1052. This has been made possible with an observation of the Global mm-VLBI Array which operates at a high frequency of 86GHz and uses a network of radio telescopes in Europe, the USA and East Asia.

    The bottom panel shows the two highly symmetric jets emanating from a compact, bright central feature of only 57 microarcseconds or 2 light-days in size. This marks the position of the black hole and the region, where the jets are initially formed (middle panel). Based on its high brightness, the magnetic field close to the black hole can reach values between 0.02 and 8.3 Tesla (top panel). Such strong values are consistent with theoretical models of jet launching through the extraction of magnetic energy from a rapidly spinning supermassive black hole. The combination of powerful twin jets and close proximity (only 60 million light years), makes NGC1052 an ideal target for future observations of nearby powerful galaxies in the new era of VLBI due to the availability of ALMA, the Atacama Large Millimetre Array.

    The study is published in the recent issue of Astronomy & Astrophysics (A.-K. Baczko, R. Schulz, M. Kadler et al., 2016; ; ) and a press release was issued by the Max Planck Institute for Radio Astronomy ( )

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  • 09/29/16--17:00: Dwingeloo-1 revisited
  • © Albert van Duin

    The Dwingeloo 1 galaxy (a.k.a. PGC100170) was discovered with the venerable Dwingeloo Radio telescope in 1994 while performing the Dwingeloo Obscured Galaxy Survey (DOGS), which searched for neutral hydrogen (HI) radio emissions at the wavelength of 21 cm from objects in the so-called Zone of Avoidance. This is the region of sky where dust of our own Galaxy obscures much of the visible light from objects behind it. Only red and infrared light and radio waves will penetrate this dust. So Dwingeloo 1 was discovered in radio emission, but it is (just) detectable in visible light too! Although Dwingeloo 1 seems very faint, it is actually very nearby, only 10 million lightyears away from us.

    The image above is a stack of 17 red-filtered integrations of 600s each, made with a cooled CCD camera mounted on a 0.4m telescope in Beilen. I will try to acquire some more images using different filters to create an L-RGB colour image. This photo-negative representation shows the shape of these faint galaxies a bit better. The barred spiral Dwingeloo 1 with faintly visible spiral arms is in the middle of the image, the faint blob a bit lower is another galaxy: PGC166069.

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  • 10/02/16--17:00: Never too Young for Science
  • © P.M.Fusiara

    One of the advantages of living in the vicinity of the WSRT is that you can pack your kids into a bike trailer, hop on the bike yourself and enjoy the autumn breeze of the nearby forest within minutes.

    Those of you who are familiar with the cycling paths in the Holmers-Halkenbroek area, know that there is a watchtower. Not only you can train your muscles while climbing it, but also you will be rewarded with a very nice view once you have reached the top.

    My almost 5-year-old daughter is fascinated by the stars and enjoys looking up in the sky and spotting stars, the moon and airplanes flying by. During one of the trips to the forest I showed her the watchtower and she immediately started climbing the stairs. At the top she shouted to me:

    "Mommy, mommy! Look, it's your work over there!! You must see it, look! There are the telescopes! Can we go there and watch some stars please?"

    She reached for the camera and took a photo. Then she turned around, looked at me and said:

    "Mom..., when I'm a big girl, I want to build rockets [sic] and telescopes, just like you do!"

    The seed of curiosity has been sown ... :)

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    © Betsey Adams

    Ultra-compact high velocity clouds (UCHVCs) are isolated HI clouds detected in the ALFALFA HI survey with no optical counterpart in current optical surveys. They are intriguing objects because they are good candidates to represent gas-rich dark matter halos with a negligible stellar content. In order to address this hypothesis, an international team led by Betsey Adams and including Tom Oosterloo, observed twelve UCHVCs at higher angular resolution with the Westerbork Synthesis Radio Telescope (WSRT). The WSRT observations revealed that two objects, with a potential third, are the good galaxy candidates. The other UCHVCs are likely clouds of gas associated with our own Milky Way. The best galaxy candidates had the highest column density values in the ALFALFA data; this lesson will be used to select the best UCHVCs for further studies.

    The image above shows one of the good galaxy candidates (left) compared to one of the objects that is likely associated with our own Milky Way (right). The top and bottom rows are at two different angular resolutions. The contours indicate the distribution of HI gas and the colors the velocity motion of the gas. The good galaxy candidates have a smooth distribution of gas at higher angular resolution and show ordered velocity motion. This velocity motion indicates that the gas could be rotating in a dark matter halo. For a range of plausible distances, the candidate galaxies have rotation velocities of 8-15 km/s, HI masses of 0.6-50 x 10^5 Msun, HI radii of 0.3-2 kpc, and dynamical masses of 2-20 x 10^7 Msun. Future surveys with Apertif, a new phased array feed for WSRT, will produce data like that pictured above, allowing the properties of these marginal galaxies to be studied.

    You can find more details in Identifying galaxy candidates in WSRT HI imaging of ultra-compact high velocity clouds Elizabeth A. K. Adams, et al. 2016, A&A in press,

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    © ASTRON

    Today we say goodbye to our old radiolab, which is being completely refurbished. The old lab has served us well during 20 years of building and testing instruments (1996-2016). Numerous famous projects and instruments were born here. To name a few: MFFE, OSMA, THEA, LOFAR, EMBRACE, LFAA Photonic links, APERTIF and the new MFAA tile development.

    Having a good lab is really the glue that connects all competences. In the development process, all our thoughts and ideas come together in the hardware and software we design. A well-designed and equipped radio lab makes it possible to build and test the result.

    The newly refurbished lab is almost ready for use. We expect to be very happy with our new place to develop the next generation of radio telescopes. We will be ready for it.

    (The picture shows Michel Arts performing a last-minute measurement before closing down the old lab. He is analyzing the electromagnetic performance of a new material for the housing of a MFAA tile.)

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    © astron

    In this talk, I present 1D cosmic ray transport models, numerically solving equations of pure advection and diffusion for the electrons and calculating synchrotron emission spectra. As a study in case, we apply these model to a small survey of 12 late-type edge-on galaxies and to low-frequency LOFAR observations of the nearby FRI radio galaxy 3C31. We measure advection speeds, diffusion coefficients and magnetic field scale heights and lengths, which allow us to study magnetic field strengths without the assumption of "local" energy equipartition.

    We find that our galaxies are either diffusion dominated (no outflow) or advection dominated (outflow), where the cosmic-ray electrons can partially leave the galaxy (non-calorimetric halo) and the advection speed is similar to the escape velocity, indicative of a galactic wind. In the FRI galaxy we extend the known source size by 15 per cent to 1 Mpc, so that advection speeds of 2000-3000 km/s result in a dynamical age of 250 Myr.

    Our models show the existence of non-calorimetric haloes in star-forming galaxies that can explain global energy equipartition, as suggested by models of the radio-SFR(FIR) relations. For radio galaxies, these models result in improved estimates of the source age and energy, important to quantify the AGN feedback in the Universe.

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    © (c) Astron 2016

    In 2015 we used LOFAR station RS509, close to the Eemshaven, to investigate the effect of windmills on LOFAR data. We observed radio frequency interference (RFI) associated with TenneT's 380 kV Eemshaven-Oudeschip facility. Most of the signal was direct, but some of it was scattered by the rotors of nearby wind turbines, picking up their time modulation. Agentschap Telecom measured that the RFI was too severe, and TenneT engineered a solution.

    Because one does not simply decouple more than a GigaWatt from the national grid, it took from July 4 until end of September to upgrade the entire installation. The horizon images show that the 380 kV station (right white bar) has improved already after the first modifications on the LOFAR-facing side, and is now no longer detectable in one second of single sub band data. The remaining intermittent RFI comes from the direction of RWE's Eemshavencentrale (left white bar). This does not necessarily mean that it is the interference's source: it might just be reflecting signals from the environment, or the RFI may even belong to a wind turbine in between the powerplant and the LOFAR station. We currently do not know. In any case, the excessive interference's disappearance enables further research into windturbine-caused RFI at the Eemshaven wind farm.

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    © Gert Kruithof

    At the beginning of September, the head of the ASTRON lab Gert Kruithof visited the Observatorio de Yebes (IGN) in Spain. IGN is a very interesting institute with�beautiful surroundings. Our old friend Paco Colomer (top right) and Jos� Antonio Lopez were the hosts and they showed Gert around during his two-day visit to Yebes.

    The activities of Observatorio de Yebes are complementary in many ways to those of ASTRON and JIVE. We�had the opportunity to take a look�at their facilities, the fast moving dish with the many receivers and large mirrors; very impressive.

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  • 10/10/16--17:00: Harry turns 80
  • © Madroon Community Consultants (MCC)

    Last week we celebrated the 80st birthday of Harry van der Laan with a mini-symposium in the old Sterrewacht in Leiden. A glittering list of speakers highlighted his many contributions to the development of (inter)national modern astrophysics. Apart from running (and revitalizing) the Sterrewacht for almost 20 years, he reorganized SRZM (later called NFRA and now ASTRON) for operating the WSRT, he initiated the UK/NL collaboration on La Palma and Hawaii, and reorganized ESO for building the VLT. He also helped to launch EVN/JIVE, and to secure the funds for LOFAR.

    The image shows Harry and his Renate, surrounded by the speakers (except Vincent Icke) and the organizers of the symposium. The event was attended by his extended family, which included not only his children and grandchildren, but also many of his "spiritual" children who have benefited from his vision and encouragement. Fond memories (and some anecdotes) were exchanged about Harry's years at the helm.

    Harry was particularly pleased by being compared to a bulldozer by one of the speakers, and pointed out that this was always his mandate. He acknowledged that there might be situations that could require more diplomacy, but his brand of gentle firmness was needed when things actually had to be done. Of course we all raised our glass to that.

    Congratulations, Harry, and thank you.

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  • 10/11/16--17:00: Summer student map 2016
  • © ASTRON

    The final event for the 2016 ASTRON/JIVE summer student programme was a BBQ at the guesthouse, organized by Fritz Moller.

    At the BBQ, the students presented a gift of a world map with their names and home countries marked on it. The gift was accepted on behalf of the summer student programme organization team by Cees Bassa and Natasha Maddox from the Astronomy Group, pictured here with the students (L-R Floor, Yuping, Anoj, Aarthi, Anjali and Xiaoxi) , while the photo was taken by Zsolt Paragi from JIVE. The international nature of the programme is highlighted by the diversity of countries represented.

    The summer programme has many traditions, including the welcome pancake party, the visit to ESTEC, wadloping, wednesday bridge, and the tour of Westerbork and LOFAR. We hope that ASTRON/JIVE will continue to welcome students from all over the world, and that future summer students will continue this new tradition of marking their home countries on the map.

    The map is located in the Minnaert Kamer. It is bound to become more and more valuable with time.

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    © ASTRON

    In 2016, no less than six people at the R&D department celebrated their 12.5 anniversary of employment at ASTRON. The reason for this little wave is that about 12.5 years ago the preparations for LOFAR were in full swing, and a lot of work had to be done. So new people were hired. Renate van Dalen was one of them.�

    In her part-time job as one of the R&D secretaries, Renate lends support to the Bureau for Technology Transfer (BTT) and she is involved in the organization of the Techno- and Software Lunches. Together with the other R&D secretaries she takes care of planning appointments, organising meetings and making travel arrangements. Her attitude is modest and friendly and she is always striving for a high service level.

    During a�recent surprise�lunch at the nearby Bospub, Renate was presented with a beautiful bouquet of flowers which she gladly accepted. She told us that she very much likes her job as R&D secretary. Her most challenging and pleasant task is organizing the RF course(*). In the beginning she was involved with this at a low level, but now she takes care of almost everything that has to be organized and prepared�for this course. Renate, thank you very much and congratulations with this anniversary!

    (*) The RF course is a yearly event in which ASTRON shares its expertise in analog electronics at radio frequencies. It lasts a week, and is very popular as a refresher course with the technical staff of small and medium-sized companies.

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    © FAME team

    At the SPIE conference - Astronomical Telescopes and Instrumentation - in Edinburgh last June 2016 we proudly showcased our FAME demonstrator. We presented the latest achievements in several papers, but more importantly were able to show the real hardware in the Dutch pavilion at the exhibition.

    This has been the fantastic result of a collaboration between the NOVA - Optical Infrared Instrumentation Group, LAM (F), ATC (UK) and Konkoly (H). Through the hard work and sheer determination of the team the demonstrator made its appearance at the conference.

    The demonstrator consists of freeform mirror which has a very high quality surface with a shape accuracy of less than 5 micrometre rms. With active actuation the as-built demonstrator mirror shape will be within 100 nanometre rms of the as-designed optical surface. The fun part of the project starts now, which is the characterisation of the element, which will be followed by updating the design such that it can be used in a vacuum and at cryogenic temperatures.

    The aim of FAME is to combine extreme freeforms and deformable mirrors using standard optics in order to provide a stable integrated system solution that can be used in future instrumentation, regardless of the environment (cryogenics or otherwise). The goal is to illustrate that it is possible to reduce complexity, mass, volume and cost, while improving the performance of the overall system.

    The work concentrated on:

    - Optical design solutions and design optimization flows for freeform based optical designs.

    - Identification of several compact, fast, wide-field optical designs working in the visible, with diffraction limited performance.

    - Optimization of the lay-out and required number of actuators.

    - A novel method for surface shaping with very high quality through hydroforming and stress polishing.

    - The design of an active array to control the mirror shape dynamically.

    - Novel actuator designs and control system.

    This research forms part of the OPTICON program and is supported by the European Commission's FP7 Capacities program (Grant number: 312430).

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    © ASTRON, University of Manchester, CISCO, NOKIA

    Last week, colleagues from Manchester university, NOKIA and CISCO have performed emission measurements in the EMC facility at ASTRON. The goal was to assess the emission levels of the latest 100 GB switch and transmission equipment from different manufacturers up to a RF frequency of 20 GHz. This class of equipment is investigated for possible use for science data transport in the SKA telescope arrays.

    Since the spurious emission is to be measured up to 20 GHz, a straightforward test setup would not be adequate. Therefore a special setup was made to load the equipment with 100G Ethernet traffic, and to configure it to represent operation in a SKA dish pedestal environment.

    The RF measurement setup was pushed to its limits. Two standard gain antenna's and extra low noise gain amplifiers were used to cover the frequency range, and to improve the signal to noise ratio. By using these 'known' antennas and the calibration data, the effective field strength radiated from the Unit under Test could be calculated back during post-processing.

    We built the RF setup together, calibrated it and processed the measured data. At the end of the week all the planned EMC tests were finalized successfully.

    (The insert shows hardware to be tested)

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    © 2016 Rob Millenaar

    Having the MeerKAT array in my back yard (relatively speaking) doesn't make night-time photography there any easier. Selecting a moon-less night in good weather conditions when there is no observing done (now that observing operations have started and any camera interference is to be prevented) is challenging.

    Yet, l recently I managed to do so, and here is just one of the many images I brought home. Of course the MeerKAT dish is the main star of the image, but the Milky Way backdrop is perfect for it. A simple head-lamp allowed me to light-paint the dish.

    For this image I took three shots, 25 seconds exposure each and stitched them together vertically. On the lower left another telescope is visible, as a black outline in the light from the building complex behind Losberg hill.

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  • 10/18/16--17:00: Terrestrial visit
  • © Astron

    The Lofar stations are rolled out all over the northern part of the country, usually in remote and quiet locations. This is certainly the case with the station near Nieuwolda. Far away from humans, and close to a lake with lots of birds and fish, this is a perfect habitat for predators.

    One of these, probably a marten (bottom left) or a polecat (bottom right), did take a fancy to one of our HBA tiles, using it for shelter, dining room, bedroom and toilet. And whenever he was bored, he had lots of fun playing around with the styrofoam structure that supports the HBA antennas, putting his teeth into the soft material again and again.

    Although the construction did get weaker and weaker over time, the electronic parts kept working. Yes, the animal did chew on some cables, but this had only minor effect on the performance (yet). But eventually, this antenna tile had to be exchanged for a brand new one. In this image you see this exchange in action, and especially the impressive mess made by our little friend. Obviously, we are contemplating eco-friendly measures to discourage this kind of thing in future.

    Henri, Martijn, Peter, Lute and Jan-Pieter

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    © Kadler M, Krauss F et al., Nature Physics 12, 807

    Active galaxies harbor a supermassive black hole at their center. They often show perpendicular outflows of matter, called jets, which might contribute to the observed cosmic rays and neutrinos. The IceCube collaboration has detected an extraterrestrial neutrino flux with the most significant signal in the southern sky at PeV energies.

    We show that AGN jets are able to produce the observed neutrino flux using multiwavelength data. We further find that a major outburst of a single blazar is in spatial and temporal consistency with the 2 PeV IceCube neutrino event. The energy output of PKS B1424-418 alone can explain the neutrino event, indicative of a physical association. We further studied simultaneous radio to gamma-ray SEDs from the TANAMI sample.

    This large data set allows us to address key questions in AGN jet physics like the blazar sequence, jet-emission models and the fundamental plane of black hole masses.

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