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

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    © E. Orru' on behalf of the Team Green

    Since May 2018 the Radio Observatory has started a new projected aimed at implementing state of the art calibration processing pipelines on production scales. These pipelines will allow the Radio Observatory to provide science-ready data to the full LOFAR community and external users.

    A dedicated team of developers, called Team Green, will do this project. The members of this team come partly from the in-kind GLOW contribution (D. Rafferty, A. Drabent and B. Adebhar) and partly from the Radio Observatory (E. Orru and J. Schaap).

    The project kicked off with a busy week in which the team members followed lectures and demos about the RO development methods and the specification, processing and archiving systems.

    The scrum methodology has been chosen for use in the project, with sprints of three weeks to build up system functionalities that will allow the RO to run among the most complex LOFAR calibration schemes available.

    The first milestone is to implement and offer to the users the HBA direction-independent pipeline (pre-factor). This pipeline not only will allow the user to dispose of pre-calibrated data, but, due to the compression, will also aid the data transfer between the LTA sites and the user's computational facilities.

    Further work will aim toward implementation of new pipelines or new releases of existing pipelines, for instance the new pre-factor pipeline suitable for HBA, LBA and international baselines. Other examples are the direction-dependent pipeline being currently developed by the CITT and polarisation and long-baseline pipelines.

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    © Jacki Gilmore / Stefan Wijnholds / Curtin University

    From May 28 to June 1, the URSI Atlantic Radio Science Conference (AT-RASC) was held in the pleasant place of Gran Canaria, Spain. This URSI flagship meeting was well attended with 578 registrants presenting about 700 papers.

    At its flagship meetings, URSI organises a very competitive Student Paper Competition (SPC) supported by funding from the United States National Committee of URSI. At the AT-RASC, the first prize was awarded to Jan-Willem Steeb, a PhD student from Stellenbosch University (SU) supervised by David Davidson (Curtin University, SU) and Stefan Wijnholds (ASTRON, SU) for his paper on "Mitigation of Non-Narrowband Radio Frequency Interference". This paper proposes two methods to deal with RFI that cannot be adequately represented (and therefore suppressed) by standard narrowband techniques. An example of such RFI are Digital Audio Broadcast (DAB) signals occupying the full width of a LOFAR subband.

    The photo kindly made by Jacki Gilmore (SU) shows Jan-Willem Steeb holding his certificate with his proud supervisor Stefan Wijnholds. The insets show the certificate and his equally proud other supervisor David Davidson, who, unfortunately, was not able to attend the conference himself.

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    © MPE

    The X-rays are amongst the wavebands where the sky is least well known. There exists only one shallow survey, made by the ROSAT satellite in the 1990s in the soft X-rays. This will change with the launch in March 2019 of the German eROSITA experiment on the Russian satellite Spectrum-X-Gamma. eROSITA will perform a four year long survey of the X-ray sky at energies up to 10keV, discovering a million new Active Galaxies, 100000 galaxy clusters, and a large number of other objects.

    In my talk I will summarize the scientific aims of eROSITA, describe the technology to be used, and I will discuss the use of the eROSITA in the context of other all sky surveys that will become available in the 2020s.

    Photo: eROSITA in the laboratory before shipment to Russia.

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  • 06/07/18--17:00: Taking the JIVE experience
  • © Ross Burns

    As part of efforts to develop radio astronomy operations expertise associated with African radio astronomy ahead of the SKA, JIVE and ASTRON are currently hosting two trainees on the LOFAR science operations training program, Bernard Asabere and Emmanuel Manful. The program included one week of training in VLBI operations and science at JIVE. During this week, trainees were walked through the processes of planning, scheduling, observing and processing VLBI observation data and were present during eVLBI and EVN test observations as part of the ongoing EVN session.

    Emmanuel and Bernard will be our trainees and welcomed guests until late July

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  • 06/10/18--17:00: Experiential learning!
  • © Astron

    From May 14th to 25th, 2018 two young Latvian engineers from Ventspils International Radio Astronomy Centre (VIRAC), which is the scientific institute of Ventspils University of Applied Sciences visited ASTRON for training within the framework of project 'Building on Advanced Lofar Technology For Innovation, Collaboration and Sustainability' (No. 692257 - BALTICS).

    The main goal of the training was to provide VIRAC staff experience in work with LOFAR antenna array hardware which will be necessary for daily operation of the upcoming International Lofar Telescope (ILT) station at VIRACs radio telescope site in Irbene, Latvia.

    Training was carried in direct, hands-on fashion - apprentices had to troubleshoot, repair and test the three neglected LOFAR High Band Antenna (HBA) test tiles located in the backyard of ASTRON with help of recently developed V2 prototype of HBA-PC (HBA Portable Controller).This way apprentices not only gained valuable experience on LOFAR hardware maintenance in actual field conditions, but also contributed to HBA-PC development by introducing multiple improvements the most notable being the added functionality of single HBA tile satellite tracking. This demonstrates beamforming technology in a practical way, which could be used by ASTRON in future for introducing phased antenna arrays and beamforming to students.

    This training was further supplemented by actual maintenance visits at LOFAR core stations near Exloo and by spending a day at Westerbork radio telescope site which only further increased the competencies of VIRAC engineers.

    For more information see the staff exchange portfolio at link below:


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    © ASTRON

    Last Monday, 4 June, we were honored with the visit of Minister Van Engelshoven of the Ministry of Education, Culture and Science.

    The visit started with a tour at the LOFAR core. Here, the Minister got explained what LOFAR is and what we do with LOFAR. As you can see in the picture it was a little wet outside, luckily, we have our ASTRON boots. In the field, the visitors were impressed by the size of the LOFAR core.

    After the tour at the LOFAR core, the company travelled to Dwingeloo for a tour through the ASTRON building. At Dwingeloo the Minister got the learn, as much as possible during one visit, about ASTRON. Which is of course quite hard with all the great things that happen at ASTRON.

    At the end of the visit there was a press moment for the Gemini board. Paula and Gijs introduced the Gemini board to the Minister. The Minister was very impressed by all the capabilities of the Gemini board. As you can see in the images it was more crowded than normal in our digital lab, with journalists and visitors who wanted to know all about Gemini.

    We can look back on a successful visit.

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    © photo: Simone Kajuiter

    Since 2002, ASTRON has been organising three-day courses on applied Radio Frequency technology, also known as the RF course.

    Over the years, more than 350 engineers and scientists from industries and institutes attended the course. The course includes hands-on training using the most advanced radio engineering tools, like network and spectrum analysers.

    This week, we organised the 35th edition of the course and we will continue to do so. We should engage young and talented engineers in the wonderful world of creators of new systems. Systems which could only be built by using RF technology.

    After making her 30th(!) course happen, our Renate van Dalen unfortunately stops organising the courses. Therefore, we would like to express our many thanks for being the organiser of this great educational event. Renate, on behalf of the entire 'course team': Thank you very much!

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    © Sarka Wykes

    Light jet interacting with a 3 Gyr AGB star at its highest mass-loss rate. The jet plasma is flowing in from the left. The wake shows von Karman-like vortices, which in three dimensions would evolve into downstream turbulence.

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    © Channah Vogel

    On the 6th of June, most interns paid a visit to the Westerbork Radio telescope. Every nook and cranny of the area was explored, under the guidance of tour guide Jan-Pieter. The interns retuned after 6 hours with much more knowledge and a lot of pictures.

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  • 06/17/18--17:00: Arts Tabs First Light
  • © J Hargreaves

    On 9th May, the DESP group handed over a version of the ARTS firmware with Tied Array Beams (TABS) enabled to our astronomer colleagues for initial testing. We expected to get some feedback about packets-per-second, header-field errors and so on.

    It was a nice surprise when, within 30 minutes, Leon Oostrum had imaged a pulsar!

    Several new things had to work for that to happen: The TABs beamformer, adapted from the Apertif one by Daniel; A script written by Pieter to set and read back the weights; the packetizing firmware, extensively re-written during April to save FPGA resources; and of course the astronomy pipeline software running on the ARTS cluster.

    After a small cake celebration, we are continuing to test, debug and add features - always easier to do on a working system.

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    © ASTRON

    As part of the ASTRON/JIVE SOS traineeship programme in LOFAR Science Operations, there was a visit to SURFsara in Amsterdam on June 06, 2018. This was to introduce the trainees (Bernard and Emmanuel) and new SOS recruit (Thomas) to the largest long-term storage facility of the LOFAR Long-Term Archive (LTA), where about two-thirds of LOFAR's current incredible 32PB capacity data is stored. The Head of SOS, Dr. Roberto Pizzo, organised the visit. Onno Sweers (Data Storage Unit), Raymond Onno (newly-recruited Support Scientist) and Natalie Danezi (User Support Unit) of SURFsara gave us a guided tour of the infrastructure and facilities at the outfit. SURFsara is one of Netherlands' biggest National Supercomputing and Big Data Storage Facilities. During the tour we visited several systems including the HPC Cloud, Supercomputer Clusters (Cartesius, Lisa and Hadoop), the Grid Infrastructure, Data Ingest Service and the tape library technology Data Archive.

    It was interesting to see the Grid infrastructure, where some of the LOFAR data is processed, and the Tape Storage facility where LOFAR LTA is housed. The expandable 200PB capacity tape storage system currently hosts about 40PB of data, a half of which belongs to LOFAR. Amazingly, the SRON analysis Tropomi satellite, the Large Hadron Collider experiments, the gravity wave detectors (LIGO-Virgo), large-scale DNA analyses (BBMRI, Project MinE), dark matter experiments (Xenon1T), and other high-processing power and huge data storage demanding establishments are all affiliates of SURFsara.

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    © Authors, CC BY-SA

    Pulsars are rapidly rotating neutron stars, which produce intense beams of radio emission, like Galactic lighthouses. As the beam crosses a telescope, it produces a characteristic 'pulse', like the peaks in the plots on the left. The rotational stability of these cosmic flywheels often shows almost clock-like perfection.

    However, the pulsar J0922+0638 (B0919+06) is an atypical example which shows unexplained, anomalous variations of its rotation, where the pulse appears to episodically move to an earlier longitude for a few tens of rotations before reverting to the usual phase for several hundred to more than a thousand rotations. These events have been previously detected in observations from 300 to 2000 MHz. We present simultaneous observations from the Effelsberg 100-m radio telescope at 1420 MHz and the Bornim (Potsdam) station of the LOw Frequency ARray (LOFAR) at 150 MHz.

    The colour intensity diagrams on the furthest left show the received radio power (or flux) as a function of the rotational phase along the X-axis and the total observation time along the Y-axis, such that blue represents low power and red, the maximum. Note the narrow spikes protruding to the left between the black dashed lines. The coloured line-plots show the regions bounded by black dashed lines on the intensity diagram. Each line represents the flux over 10 seconds. The solid yellow lines denote the maximum 'swing' of the pulse longitude.

    We show the absence of the phase-shifting behaviour at 150 MHz. Instead, the observed intensity at the usual pulse-phase typically decreases, often showing a pseudo-nulling feature corresponding to the times when shifts are observed at 1420 MHz. The presence of weak emission at the usual pulse-phase suggests that these shifts may result from power being absorbed by material lying along the line of sight.

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    © Colloquium

    This talk aims to investigate three important phenomena in the study of active galactic nuclei: how AGN are triggered, how they vary throughout their lifetimes, and how they can effect their host galaxies through feedback.

    We search for evidence of triggering by mergers using MUSE-VLT data from the Close AGN Reference Survey (CARS). We compare stellar kinematics of our active galaxies and a comparison sample of inactive galaxies to measure the deviation from disk like rotation. We show that the AGN have a slight enhancement in large scale asymmetry. Many AGN are known to vary strongly throughout their lifetime. We observed known changing look AGN Mrk 1018 as part of CARS and found that the broad lines and continuum emission had dramatically changed for a second time. We attempt to explain the possible causes for this recent change, and discuss what such short timescale variability means for theories of AGN feedback. Finally, we show that outflows are prevalent in luminous local type 2 AGN using multiple component Gaussian emission line modelling to disentangle the kinematic and ionisation properties of emission lines. This allows us to show that shock-like emission is present in these galaxies, demonstrating that the outflows are directly impacting the surrounding ISM within the galaxies.

    The image shows a combined Stripe 82 image of changing look active galaxy Mrk 1018.

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    © JvL

    Kids with burning questions that want a different answer than "that's just the way it is" or "just because" can save them up for the annual Klokhuis Vragendag at NEMO. Two of the questions from the trailer are "Can you smell in space" and "Where does Wifi come from". Well, we know the answer to those two very well here.

    This year, over 500 kids submitted questions, and these were all answered by a team of about 40 scientists from various disciplines. Using models, laptops, and taking brains (still bloody) from jars.

    There was also the traditional Vraag Maar Raak show (at 3m30 in the Klokhuis episode). Here, a cognitive scientist, biologist, chemist, physicist and an astronomer had to answer 10 questions in 20 minutes. Kids wrote down questions when entering the theater, these were drawn from a large vat, and then it was up to the audience to decide whether the learned team had demonstrated and explained well enough. If we did not make it, we had to dance. If we did, we got high-fives. Given the many available props, some were doable (such as: "Why are there tides", explained above by dancing out an Earth-Sun-Moon system). Others were harder -- the worst one being "Why is there gravity". If I knew that .. Still we managed, and were paid with a few hundred high-fives.

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    © ASTRON Mechanical Department

    On Friday the 8th of June, the Mechanical Group took off for a road trip to Amsterdam. The destination for the day was our fellow department at ASTRONs sister NWO institute AMOLF.

    AMOLFs research programme consists mainly of nanophotonics, focusing on the achievement of spatio-temporal control of light at the smallest possible scale. The nanophotonics research program inspires many possible applications in solid-state lighting, functional materials and devices, and advanced materials fabrication and characterization.

    Our main goals were to achieve a clearer view of their mechanical pursuits and challenges within the field of nanophotonics. We were also granted a clear view of their mechanical strengths and possibilities, workshop equipment and CAD/CAM successes and challenges.

    At the end of the day, we returned back north with our heads filled with knowledge, creativity and ideas. Needless to say, we are more than pleased to return the favour and welcome our AMOLF colleagues for a visit to our department here at ASTRON.

    A big thanks to Marnix Verweij, mechanical engineer at AMOLF (second from right), for inviting and welcoming us at their facilities, and taking plenty of time being our guide for the day and answering our in-depth questions.

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    © Daria Dall'Olio

    Planets are common. Beyond the eight in our own solar system, thousands more have already been found orbiting other stars. Studies are now showing that almost every star must have at least one planet. Planets form in flattened, rotating structures that surround stars in their forming stages. Such a disk is initially composed of gas interspersed with tiny soot-like dust particles with sizes of about a micrometer (10-6 m). Planets are at least 107 m in size, so planet formation needs to cross a staggering 13 orders of magnitude in scale. The first step in this process is to coagulate the tiny grains into pebbles with sizes of millimeters to centimeters. Eventually, a few bodies will need to grow to kilometer size boulders, at which point their gravitational pull will be sufficient to attract and retain gas molecules from the protoplanetary disk. This is the proposed mechanism for the formation of giant gas planets, such as Jupiter and Saturn.

    In a publication that appeared in Nature Astronomy yesterday (Harsono et al. 2018), we present evidence of growing grains in a very young protoplanetary disk. Pointing the ALMA interferometer telescope at the protostar TMC1A in the Taurus constellation, we found a remarkable absence of carbon monoxide (13CO and C18O) gas emission in the inner part of its disk. By comparing the observed data with numerical models, we could demonstrate that millimeter sized pebbles (10-3 m, a factor 1000 larger than the initial grains!) must be responsible for blocking the CO gas emission. The size of the region with larger grains corresponds to the space encompassed by the orbit of Neptune in our Solar system.

    With the evidence for grain growth in such a young protoplanetary disk, we can now start to explain the formation of gas giant planets. All protoplanetary disks gradually, but inevitably lose their gas. Therefore, if there is to be enough gas present to build Jupiter-like planets, the first steps need to start this early.

    We look forward to finding the same tell-tale signs of planet formation around other young protostars with gas-rich disks. At the moment, ALMA -- with its dishes spread out to 16 km baselines -- is the only telescope capable of resolving dust and gas emission at scales where new planets are forming, matching the scales in our Solar system. In the future, similarly high resolution observations will be attained with the dishes of the Square Kilometre Array (SKA) to be built in South Africa. Compared with ALMA's millimeter wave detectors, the SKA will be sensitive to longer wavelengths (2 cm and above) and will therefore help to localize centimeter-sized grains. Once these are formed, the first four orders of magnitude will be behind us, on the way to building real planets.

    Image: Artist drawing of an embedded, gas-rich protoplanetary disk (left). In the central part of this disk, grains have grown to millimeter sizes (bottom), which is the first step toward building a planetary system (right). Image credit: Daria Dall'Olio.

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  • 06/26/18--17:00: RadoAstron in Dwingeloo
  • © Lavochkin Science and Production Association; JIVE

    From 25th-29th June 2018 ASTRON and JIVE are co-hosting the 31st RadioAstron International Science Council (RISC) and Science Working Groups’ meetings.

    RadioAstron, the international Space VLBI (SVLBI) mission, has been operating in orbit for almost seven years. Owing to its baseline comparable in length to the distance from the Earth to the Moon, RadioAstron has established a number of records in angular resolution in astronomy.

    The 10-meter space-borne radio telescope of the RadioAstron mission on board the spacecraft “Spektr-R” conducts observations at four standard VLBI frequency bands, while virtually all earth-based radio telescopes able to conduct VLBI observations at the RadioAstron frequency bands are involved. The European VLBI Network plays a prominent role and RadioAstron SVLBI data is correlated at the Astro-Space Center, Moscow, the Max-Planck-Institut für Radioastronomie, Bonn and JIVE, Dwingeloo.

    To date the mission has successfully detected extremely high brightness temperatures in Active Galactic Nuclei (AGN) and exceptionally compact maser spots in Galactic and extragalactic hydroxyl (at 18 cm) and water vapour (1.35 cm) masers. Pulsar observations at 92 cm have revealed unexpected complexity of the Galactic interstellar medium, while observations of both pulsars and quasars on interferometric baselines exceeding the Earth’s diameter by an order of magnitude, indicated manifestation of the elusive refracting scattering in the interstellar medium. Finally, as a “non-radio astronomy” bonus, the RadioAstron’s on-board H-maser enabled researchers to attempt to verify the cornerstone of the fundamental physics, the Einstein Equivalence Principle.

    The RadioAstron mission is led by the Astro-Space Center of the Russian Academy of Sciences and Roscosmos (the Russian State Corporation). Many partners in Europe, Australia, Canada and USA are actively involved in the RadioAstron endeavour.

    This week RISC are reviewing the current operational status of the mission, its scientific results and planning for the next operational year. The Space VLBI endeavour continues.

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    © Colloquium

    According to co-evolutionary scenarios, nuclear activity and star formation play relevant roles in the early stages of galaxy formation. I will show how it is possible to exploit high-resolution and high-sensitivity X-ray, millimeter and radio-wavelength data to confirm the presence or absence of star formation and nuclear activity in high redshift galaxies and describe their relative roles in shaping the spectral energy distributions and in contributing to the energy budgets of the galaxies.

    I will present the data, model, and analysis in the X-ray and millimeter (mm) bands for two strongly lensed galaxies, SDP.9 (HATLAS J090740.0-004200) and SDP.11 (HATLAS J091043.1-000322), selected in the Herschel-ATLAS catalogs for their excess emission in the mid-IR regime at redshift ≳1.5. This emission suggests nuclear activity in the early stages of galaxy formation. We observed both of them with Chandra ACIS-S in the X-ray regime and analyzed the high-resolution mm data that are available in the ALMA Science Archive for SDP.9 (see the figure). By combining the information available in mm, optical, and X-ray bands, we reconstructed the source morphology.

    By taking advantage of the lensing magnification, we identify weak nuclear activity associated with high-z galaxies with high star formation rates. This is useful to extend the investigation of the relationship between star formation and nuclear activity to two intrinsically less luminous high-z star-forming galaxies than was possible so far. Given our results for only two objects, they alone cannot constrain the evolutionary models, but provide us with interesting hints and set an observational path toward addressing the role of star formation and nuclear activity in forming galaxies. We plan to complement the multi-band investigation for a larger sample of objects with the radio band information on the AGN activity. I will present preliminary results obtained with ATCA and archival data for the FIR-radio correlation in lensed galaxies and discuss the possibilities that will be offered by SKA to constrain the galactic evolutionary scenario.

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    © Cees Bassa

    The 2018 ASTRON/JIVE summer students have arrived!

    This year we are hosting six summer students from all around the world. From left to right on the picture are Daysi (Ecuador), Alexander (Russia), Anshu (India), Amy (United Kingdom), David (Ireland), and Iuliana (Romania). Please give them a warm welcome.

    A brief description of the projects the students are working on can be found at

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    © CC-BY-4.0 Tammo Jan Dijkema

    The latest version of the (free, open source) planetarium program Stellarium has the great new feature of showing surveys in the HIPS format.

    HIPS (Hierarchical Progressive Surveys) is a standard developed by CDS but adopted as a standard by the International Virtual Observatory Alliance (IVOA) in 2015. This standard also allows Aladin to render various surveys in a responsive way.

    Many many surveys are available, notably WENSS, the Westerbork Northern Sky Survey, and LAB, the Leiden-Argentina-Bonn Galactic HI survey (Kalberla et al 2015). The latter was used to show the galactic hydrogen above ASTRON, as measured by the Dwingeloo Telescope. This uses the custom Stellarium background that is freely available.

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