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A daily view of all the goings-on at ASTRON and JIVE.
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    © CC BY 4.0

    Recently, a team of ASTRON scientists has been working hard to get the so called "Image Domain Gridder" (IDG) working. IDG is an imaging technique invented by ASTRON's Bas van der Tol and Bram Veenboer, that allows extremely fast imaging of very wide field of views, and it is therefore well suited for imaging LOFAR data. For the SKA, fast imaging will be even more crucial. One of the major features of this imager is that it can undo some of the effects of the instrument while imaging. In particular, it can correct the (polarized) response of the beam as well as correct for the ionosphere. It can do this with an accuracy that was so far not possible.

    These images show the 3C 196 field in Stokes Q polarization as observed with LOFAR. From previous LOFAR observations it was discovered that the 3C 196 field, which is one of the fields targetted by the LOFAR Epoch of Reionization project, has intriguing linear polarized structures in the EoR field that as of yet are not well understood (see Jelić et al. 2015 and daily image 20151110). For testing IDG, a single subband of a 3C 196 observation was imaged and corrected for LOFAR's beam response.

    Both the left and right image were cleaned as deep as possible using WSClean's auto-masking cleaning strategy, with one important difference: IDG was used to produce the right image to correct for the beam, leading to a dramatic improvement of image quality. The left image shows strong artefacts from sources that are not polarized, but end up in the image because the instrumental leakage of LOFAR is not corrected for. In the IDG image, sources that are not polarized are 'cleaned' from the image, and the real polarized structure is much more clearly visible. This process is fully automated.

    IDG was developed by Bas van der Tol, Bram Veenboer, Tammo Jan Dijkema and André Offringa, with the help of several scientists that have tested the imager, and was recently published in A&A (Van der Tol, Veenboer & Offringa 2018) and IEEE (Veenboer, Petschow & Romein 2017).


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  • 12/10/18--16:00: Goodbye Ruud
  • © ASTRON

    Today we say goodbye to our colleague Ruud Overeem. Ruud worked at ASTRON for more than 15 years. He worked most of his time at ASTRON on the development of the control system for the LOFAR telescope. To be more precise: the "Monitoring And Control" and "Specification And Scheduling" system, better known by insiders as the MAC/SAS system of LOFAR. Later on, he used this expertise to design and develop the APERTIF software architecture. This led for APERTIF to the choice of a Service Oriented architecture with the usage of a messagebus for the communication.

    Ruud was also the one who took care of the development and effort necessary to start a real-time observation at Exloo, during the LOFAR opening by our Queen Beatrix at the 12th of June in 2010. Not known by many and finally revealed to the public the famous push on the golden button by the Queen led to the important action of Ruud to press "Enter" on his computer in order to start a live observation.

    Ruud requested to celebrate his goodbye low-profile and non-standard. He is a person who thinks different and preferred to give treats by himself during the coffee break today.

    We like to thank Ruud for all his efforts and being our colleague for such a long time. We wish you all the best and good luck in your new and interesting job.


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    © ASTRON

    On Thursday 22 November, Lankhorst Engineering enjoyed their return visit to ASTRON, as a follow up of the R&D outing earlier this year. During the visit, the team from Lankhorst learned about the institute, got a tour through the facilities, and visited the the Dwingeloo telescope, including a live pulsar observation.

    The tour ended with an informal Q&A session, while enjoying some drinks and snacks. The ASTRON staff involved got a very nice present from Lankhorst, to enjoy during the upcoming dark months...

    The Lankhorst staff was especially impressed by the enthusiasm and joy that the ASTRON staff showed during the tour. Clearly, we are very proud of the work we do at ASTRON.


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  • 12/08/18--16:00: Goodbye Ruud
  • © ASTRON

    Today we say goodbye to our colleague Ruud Overeem. Ruud worked at ASTRON for more than 15 years. He worked most of his time at ASTRON on the development of the control system for the LOFAR telescope. To be more precise: the "Monitoring And Control" and "Specification And Scheduling" system, better known by insiders as the MAC/SAS system of LOFAR. Later on, he used this expertise to design and develop the APERTIF software architecture. This led for APERTIF to the choice of a Service Oriented architecture with the usage of a messagebus for the communication.

    Ruud was also the one who took care of the development and effort necessary to start a real-time observation at Exloo, during the LOFAR opening by our Queen Beatrix at the 12th of June in 2010. Not known by many and finally revealed to the public the famous push on the golden button by the Queen led to the important action of Ruud to press "Enter" on his computer in order to start a live observation.

    Ruud requested to celebrate his goodbye low-profile and non-standard. He is a person who thinks different and preferred to give treats by himself during the coffee break today.

    We like to thank Ruud for all his efforts and being our colleague for such a long time. We wish you all the best and good luck in your new and interesting job.


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    © Pratika Dayal

    Galaxy formation in the first billion years mark a time of great upheaval in the history of the Universe: as the first sources of light, these galaxies ended the 'cosmic dark ages' and produced the first photons that could break apart the hydrogen atoms suffusing all of space starting the process of cosmic reionization. As the earliest building blocks, the galaxies that formed in the first billion years also determine the physical properties of all subsequent galaxy populations. I will start by introducing the reionization process and detail the reasons for which the history and topology of reionization remain debated. I will then show how cross-correlations of 21cm data with the underlying galaxy population, in the forthcoming era of 21cm cosmology, will yield tantalising constraints on the average intergalactic medium ionization state as well as the reionization topology. Time permitting, I will try to give a flavour of how the assembly of early galaxies, accessible with the forthcoming James Webb Space Telescope, can provide a powerful testbed for Dark Matter models beyond "Cold Dark Matter".