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Articles on this Page
- 11/17/16--16:00: _The Rise of ILOFAR
- 11/21/16--16:00: _Radio jets in IC 50...
- 11/20/16--16:00: _Inter-FPGA communic...
- 11/22/16--16:00: _Revision of the Wes...
- 11/23/16--16:00: _Today's Colloquium:...
- 11/24/16--16:00: _The LOFAR Two-metre...
- 11/27/16--16:00: _Dome Seminar Design...
- 11/28/16--16:00: _Leah Morabito succe...
- 11/29/16--16:00: _Dutch Embassies vis...
- 11/30/16--16:00: _Today's Colloquium:...
- 12/01/16--16:00: _Telescooploop 2016
- 12/04/16--16:00: _The Terrors of Sint...
- 12/05/16--16:00: _Discovery of five l...
- 12/06/16--16:00: _Sjouke's Golem
- 12/07/16--16:00: _Welcome to JIVE, La...
- 12/08/16--16:00: _The LOFAR search fo...
- 12/11/16--16:00: _Replacing the LOFAR...
- 12/12/16--16:00: _APERTIF busy weeks
- 12/13/16--16:00: _Unboxing New RFI sh...
- 12/14/16--16:00: _MFAA development - ...
- 11/17/16--16:00: The Rise of ILOFAR
- 11/20/16--16:00: Inter-FPGA communication with Compaan
- 11/22/16--16:00: Revision of the Westerbork Synthesis Radio Telescope 2013-2016
- 11/24/16--16:00: The LOFAR Two-metre Sky Survey (LoTSS) preliminary data release
- 11/27/16--16:00: Dome Seminar Design for Testability, November 17th
- 11/28/16--16:00: Leah Morabito succesfully defends her PhD thesis
- 11/29/16--16:00: Dutch Embassies visit ASTRON
- 12/01/16--16:00: Telescooploop 2016
- 12/04/16--16:00: The Terrors of Sinterklaas
- 12/06/16--16:00: Sjouke's Golem
- 12/07/16--16:00: Welcome to JIVE, Latvia!
- 12/11/16--16:00: Replacing the LOFAR station Control Units (LCUs)
- 12/12/16--16:00: APERTIF busy weeks
- 12/13/16--16:00: Unboxing New RFI shielding cans
- 12/14/16--16:00: MFAA development - system integration test
© School of Physics, Trinity College, Dublin, IrelandIn unseasonably favourable weather, the footprint for the latest LOFAR station (IE613) emerges from the ground at Birr Castle, Ireland. The ground levels are being raised by local contractors, Conneeley Building & Civil Engineering, to counter risks to the arrays posed by flooding. Deployment of the antennas is scheduled to commence in spring 2017 after a pause for winter. IE613, when operational, will extend the LOFAR baseline to ~1950kms. Commissioning is expected to be completed in early autumn of 2017.
The build can be followed at http://www.lofar.ie and http://www.twitter.com/i_lofar
Image by Joe McCauley, 10 Nov. 2016
© Dasyra et al/AstronThe enigmatic nearby Seyfert galaxy IC 5063 was the first galaxy known (Morganti+ 1998) to harbour a fast outflow of atomic hydrogen driven by the radio jets and later observations showed that also optical and near-infrared line emitting gas participates in this outflow. The molecular counterpart, observed in the CO J=2-1 line, of this outflow was first detected by Astron astronomers Raffaella Morganti, Tom Oosterloo and Raymond Oonk with APEX and subsequently mapped by them in detail with ALMA. However, with only one CO transition it is not possible to say anything reliably about the conditions (and hence the mass involved) of this molecular gas and therefore more observations were done with ALMA.
The new ALMA CO J=4-3 observations, in a study led by Kalliopi Dasyra (National and Kapodistrian University of Athens) and including Morganti, Oosterloo and Oonk, show that the CO J=4-3 emission from the regions affected by the radio jet is much brighter than the CO J=2-1 emission. Combining these results with the previous CO J=2-1 information, a much better estimate of the mass of the outflowing molecular gas can be made. The data show that the outflowing molecular gas in IC 5063 is warm and dense, and also that it is optically thin. This implies that the mass of the outflowing molecular gas may be even an order of magnitude lower than previously estimated. Earlier estimates indicated that, by far, most of the gas in the outflow is molecular, but the new result suggests that there is roughly a 50-50 balance between molecular and atomic hydrogen. The minimum outflowing mass indicated by the new observations is 2*10^6 solar masses. The regions unaffected by the jet, in the larger-scale gas disk, show normal levels of the CO J=4-3 to J=2-1 emission, thus indicating the existence of regular cold, quiescent molecular gas here.
This investigation shows that radio loud AGN do not only expel cold gas, but also heat this gas, thereby preventing it from partaking in star formation. Knowledge of the total outflowing mass, and other properties of the gas, is very important for our understanding of the role that AGN and their radio jets play in the evolution of galaxies. The very bright emission observed in IC 5063 for the higher CO transition is also interesting for future studies of higher redshift sources, as it shows that these important transitions may be more easily detected than previously expected.
The image shows the radio emission, as observed with ALMA, of the radio jet and its hot spots, while the contours show the bright CO emission, nicely wrapping around the radio jet, indicating a close connection between the two. The spatial resolution of this image is about 0.5 arcsec. An animation illustrating the results in IC 5063 can be found here https://www.youtube.com/watch?v=sopEHuZeOgY. In this animation, the jet is shown as a red beam propagating through the galaxy. The white, dense clouds form the disk of the galaxy. The results are based on observations collected with the Atacama Large Millimeter Array (ALMA) and are now published in A&A (Dasyra et al.). They can also be found here: https://arxiv.org/abs/1609.03421
© ASTRONFor the last few months, Bas Priest from Stenden University in Emmen has been working on expanding the board support package of UniBoard for Compaan. Compaan software can be used to port "normal" software algorithms onto FPGAs. Furthermore, Compaan can be used to find parallelism in the code, and map this onto multiple FPGAs. Compaan and Astron have been cooperating for over a year now.
The main goal of Bas was to enable the use of the communication links between multiple FPGAs on the UniBoard for the Compaan tooling. Adding this functionality to the board support package allows Compaan to utilize the full capacity of a Uniboard. The picture shows Bas, together with his mentor Hajee Pepping (right), giving a demonstration of a design generated by Compaan and using the communication between two nodes (FPGAs) of the UniBoard. A test--script has been made in which data is constantly written and checked. Over a million datasets are written without any failure.
In the last weeks of Bas's graduation work at ASTRON he will expand the demo, so that all nodes on a UniBoard are used. This will result in a proof-of-concept showing that the Compaan software can use the communication links in between the nodes successfully.
This activity is conducted in the context of the Dome project, a collaboration between ASTRON and IBM.
© Jan-Pieter de ReijerSince 1996 the WSRT has successfully operated with the Multi Frequency Front End antenna and the IVC, DZB, TADU and PuMa back end electronics.
In order to be fully prepared for the coming APERTIF era, all telescopes are completely overhauled.
The telescope steering control system ( frequency converters, cables, encoders and software) has been redesigned.
All telescopes now have 144 glasfibers to the main building, for data and control.
The telescopes are cleaned and painted. Bolts damaged by rust were replaced.
In the 12 APERTIF telescopes, 128 coax cables were installed, to the focus box.
In the 2 remaining telescopes, 4 new coax cables were installed, for VLBI and test measurements with the MFFE receiver.
The APERTIF electronics (beamformer) are housed in a shielded container, under the telescope. An extra roof protects the container from extensive sun load.
Bearings were replaced in all declination- and hourangle gearboxes.
The power distribution (3kV transformers and cables) has been updated to meet the actual regulations.
We are confident that the WSRT again faces a new successful future.
© Jacqueline HodgeStudies of star formation in the distant universe have made substantial progress over the last decade. While the initial progress relied largely on deep fields in the rest-frame optical and UV, the advent of new radio/millimeter telescopes is allowing dramatic advances in our understanding of the molecular gas and dust-obscured star formation in distant galaxies. I will present recent progress in detecting and mapping the star-forming
interstellar medium and dusty star formation in high-redshift galaxies, including a detailed case study of a z~4 submillimeter galaxy. I will then discuss our current efforts with the Atacama Large Millimeter Array (ALMA) to expand the sample size beyond one. I will end with a discussion of future prospects for using such long-wavelength studies to understand the nature of high-redshift star formation and, consequently, how today’s galaxy population developed through cosmic time.
© Timothy ShimwellOne of the main goals of LOFAR is to characterise the low-frequency emission from the northern sky in unprecedented detail. With this aim the LoTSS team is working towards mapping the 120-160 MHz sky at a sensitivity of ~100 microJy/beam at a resolution of ~5arcsec. Recently the team have made an important first step towards realising this aim with a preliminary data release of images that span 350 square degrees in the region of the HETDEX Spring Field (right ascension 10h45m00s to 15h30m00s and declination 45d00m00s to 57d00m00s). These images reach a noise level of less than 0.5mJy/beam at a resolution of 25arcsec, they characterise over 44,000 sources, and are significantly more sensitive than those produced by any other large-area low-frequency survey.
This work could not have been done without the incredible efforts of members of the Surveys Key Science Project, many additional collaborators, and the observatory. The recent LoTSS results are described in Shimwell et al. 'The LOFAR Two-metre Sky Survey - I. Survey Description and Preliminary Data Release' Astronomy & Astrophysics in press ( https://arxiv.org/abs/1611.02700 ) and the mosaics and catalogs can be downloaded from http://lofar.strw.leidenuniv.nl/doku.php .
The LoTSS team is now preparing to demonstrate that the survey can be fully realised and that the ambitious observational targets of routinely imaging the sky with ~100 microJy/beam sensitivity at a resolution of ~5arcsec can be met. A large number of people at institutes across the globe are contributing to the huge steps that are being made in this area and the infrastructure is in now place to rapidly turn raw LOFAR data into the required high quality continuum images using multiple computational facilities to execute the excellent calibration and imaging pipelines that have been developed.
© H.J.Stiepel / ASTRONElectronic printed circuit board (PCB) designs nowadays may contain over 20 layers, may be very densely packed with components, operate at high clock frequencies, and may include components having over 2000 connections. Even with a carefully balanced design and thought-through test strategy it is not always easy to test and debug these systems. Small systems often are not simple either and even simple systems may pose challenges if these need to be produced at a scale of millions.
In order to address these challenges, the ASTRON & IBM Centre for Exascale Technology in Dwingeloo organised a one-day seminar on design for testability, including talks and demonstrations. This was done together with Variass, Batenburg, Transfer, and JTAG technologies, companies active in the field of electronics production, design, testing and tooling. During the day, a series of talks were given addressing the "why", the "what", and the "how" of testing. Possibilities and limitations of different testing approaches were explained, and practical experience in testing was reported on. These included for example optical inspection (AOI) to check the presence of misplaced components, X-ray tests to check soldering of the connections under a chip (for example the so-called ball grid array), electrical probes ("flying probe") to check connections electrically, and JTAG boundary scan to probe the system from within chips that support the IEEE Standard 1149.1-1990.
The talks gave a very nice overview of the coverage of the different testing approaches and techniques for each of the design and production phases. Not surprisingly there is no "silver bullet" fitting all designs, and for each design and application a tradeoff must be made between testability, lead time and cost. Indeed, in the summary session all parties agreed that he mantra of the day had been "early involvement" of the design and production companies in order to get an optimal result. With this message we all went home after a very interesting day.
© H.J. van LangeveldeOn September 13th Leah Morabito, successfully defended her PhD thesis in Leiden. The thesis on "Radio Emission Galaxies at Low Frequencies: high spatial and spectral resolution studies with LOFAR", was supervised by Huub Rottgering and George Miley.
The picture shows Leah proudly presenting her doctorate. Congratulations! For the occasion she created a special dress in the spirit of her thesis, showing how she boldly and successfully used the LOFAR Low Band Antennas (LBA: displayed on the hem of the dress) to observe both the nearby universe (M82: displayed on the sleeves) and the far-away universe (4C 43.15: displayed on the collar)
Leah's thesis focused on detecting the lowest-frequency radio emission from radio galaxies. In the nearby universe she observed the famous nearby starburst galaxy M82 in the 48-64 MHz range and made the first extragalactic discovery of carbon radio recombination lines ( http://www.astron.nl/dailyimage/pictures/20141028/drawing2.jpg ). These spectral lines provide an excellent tracer of the physical conditions in the cold neutral medium and had sofar only been observed in our own Milky Way. With the increased sensitivity and resolution offered by LOFAR she has shown that it is now possible to detect these lines in other galaxies and potentially out to very large distances.
Her next step was to go out and observe the continuum morphology on arcsecond-scales in far-away, radio galaxies. For this she had to use the full international capabilities of LOFAR and succesfully mapped the enigmatic FRII radio source source 4C 43.15 ( http://www.astron.nl/dailyimage/pictures/20160812/combined.png ) on 0.9 arcsec by 0.6 arcsec scales at 55 MHz! This is first sub-arcsecond resolution image below 100 MHz. Combination of the LOFAR image with higher frequency VLA data shows that the ultra-steep radio lobes of this galaxy have a break at low frequencies, and implies that distant radio galaxies are fundamentally the same as their local counterparts. Along the way Leah contributed greatly to improving the calibration of the international baselines for LOFAR.
During her PhD work Leah was a frequent guest at ASTRON. She has now moved to Oxford to continue her work with LOFAR as a Postdoc at the University of Oxford.
Good luck for your future career, full of exciting LOFAR results!
© ASTRONInterest for ASTRON's activities from all over the world, this time�from Dutch Embassies in several countries in Europe, Africa and Asia. On 3 November, a group of around 20 representatives of the Ministry of Foreign Affairs�visited Drenthe.
In the morning, Gert Kruithof welcomed them at ASTRON and gave a presentation on ASTRON's activities and the challenges with regard to big data. He concluded his presentation with the following 'take home message':
-�Our society evolves�towards a 'smart and connected world'
- Data is raw material in a production process of information
- Data is an asset; it represents value, delivers competitive edge
- 'Edge computing': process data at the source of generation
- Big data is a solution as well as problem in sustainability
- Attention needs to be paid to privacy aspects
- Scientific and industrial organisations in the Netherlands can provide valuable expertise on: algorithms, models, artificial intelligence, architectures, computing technology, sensors
After the presentation from Gert, the Dutch Embassies had a tour through the labs of ASTRON. Afterwards, Marco Bosch of Sustainder in Emmen, demonstrated their smart public lighting hub.
It was a perfect day with great weather and the sun highlighted the autumn colours in the beautiful surroundings of ASTRON, which they really enjoyed. Along the foot path to the Dwingeloo telescope, many mush rooms (agarics), were 'calling for attention'. So not only pictures were taken of the Dwingeloo telescope.... They continued their trip for a visit to Health Hub in�Roden.
Just before leaving Lysianne Katier, of the Ministry of Foreign Affairs, spoke a few words of thanks to�ASTRON for the hospitality and handed over a 'Haagse Kakker' to Gert who,�born in The Hague, was not familiar with this kind of flat raisin bread filled with almond paste.�With regard to the visit she stated:�"The visit was very interesting. For our colleagues, it was good to hear and see ASTRON's activities. This knowledge is very useful for the various Embassies in supporting Dutch companies doing business abroad."
© Aritra BasuThe Antennae galaxies are the nearest spiral galaxies undergoing a major merger. The magnetic field orientations in this merging system are shown as the yellow line segments. The magnetic field is well aligned along the tidal tail in the south, making it the largest detected coherent magnetic field structure on galactic scales. The coherent field extends more than 20 kpc towards the south-east of the main bodies of the galaxies. The colour image traces various stages of star-formation activity in the Antennae galaxies with GALEX FUV shown in blue (tracing stars 100 Myr old) and HST narrow band H-alpha in red (tracing stars
© Ger van Diepen, Eric Kooistra, Betsey AdamsOn November 10th the Personeelsvereniging organised the 3rd Telescooploop, a run or walk from the telescope in Westerbork to the telescope in Dwingeloo, a distance of 24.3 km. People who thought 24.3 km a bit too much, could step in later and do 15.3 or 8.5 km.
This year a new element was added: from the Superterp of the LOFAR telescope via the WSRT to Dwingeloo, a distance of 48 km.
About 16 people took part in the event, a bit less than at previous events as business trips and injuries prevented some keen people from taking part. Several brave men and women did the full 24.3 km: three runners and two walkers. The young and energetic Bram Veenboer set a new record: 1 hour and 50 minutes. Two people ran 15.3 km and six did the 8.5 km. Three diehards, including the almost-71-year-old Arie Doorduin, walked all the way from LOFAR to Dwingeloo. Breaks included, it took them a bit more than 9 hours.
The circumstances were pretty good: no rain and only a very light wind from the NE, but it was cold (a maximum of 3 degrees) without hardly any sunshine. Gloves were definitely necessary!
The landscape was very nice and varying. Through the woods of Westerbork, the fields around Zwiggelte, the beautiful heath and lakes of the Terhorsterzand and the familiar woods of Dwingeloo. The leaves of many trees had turned yellow making the woods very colourful.
For the 24km run, the last third through the Dwingelderveld is always the toughest - you're tired and it feels familiar, like you should be almost done, but there's still quite a distance to go. It was very enjoyable despite the aching muscles towards the end.
The stretch from LOFAR to WSRT was great as well. The start was before 7 o'clock in the pitch dark at the Superterp. Vaguely a HBA field next to the road could be seen. Without a GPS it would have been hard to find the way. But soon it became lighter, so walking in the woods below Borger was very pleasant. The stretch from Schoonloo to WSRT went through the woods over a beautiful, old cobblestone path. Telescope C and D could be spotted before Wim Brouw and Jan Pieter de Reijer gave a hearty welcome at the WSRT office with coffee and some pieces of applecake. Between Zwiggelte and Terhorst the walkers took a slightly different route to have a tea break in Beilen.
The Personeelsvereniging has done another wonderful job. It was very well organized with plenty of drinks and food along the way and in the canteen at the end. Nobody got lost, so the signs were certainly clear enough. Many thanks to the organisers, Eric Kooistra and Sjouke Zwier, and the volunteers, Monique Sluiman and Pieter Jager.
© PVIt can be rather terrifying for young believers to be called forward to face Sinterklaas during his yearly visit to our institutes. Not only do they tremble for the Big Red Book and the accompanying homily, but they may also be called upon to sing a quavering song. In order to make it easier for them, the GoodHolyMan called them forward in sibling pairs, possibly backed up by a reassuring parent. And of course they were ultimately sustained by the lively expectation of a present.
What the children do not realize is that Sinterklaas himself may be equally terrified, even after many years of practice. In this picture, his desperate concentration on his multiple roles causes his face to appear dark and threatening. Fortunately, the old man is soothed and sustained by the gleaming eyes of the accompanying mothers.
Despite all the turmoil in the outside world, the Personnel Club, ably helped by Femke Hoogenraad, managed to organize another joyful Sinterklaas party for the younger children of our multi-national employees. The single Piet (Michel Arts, in smudged pink) was an unmissable presence, and secured the help of the somewhat older children for dispensing presents and pepernoten. A great time was had by all.
© S. ParkFor her summerstudent project Songyoun Park (Department of Astronomy, Yonsei, Korea) visited JIVE to work with ASTRON and JIVE astronomers Raymond Oonk, Jun Yang (now at the Onsala Space Observatory, Sweden) and Zsolt Paragi on a radio VLBI project to study the continuum emission from radio galaxies in the center of the Perseus galaxy cluster. In particular she focused on the red-and-dead, elliptical galaxy NGC 1277 and how it compares with its peers in the dense environment at the center of the Perseus Galaxy cluster. According to optical observations, an over-massive black hole resides within NGC 1277 (van den Bosch et al. 2012).
Westerbork Synthesis Radio Telescope (WSRT) observations show that NGC 1277 and other nearby ellipticals emit radio emission, but the observations lack the spatial resolution to pinpoint the origin of this emission. Songyouns summer project consisted of analyzing high resolution very long baseline interferometric observations, conducted with the EVN, of these sources. She selected five (incl. NGC 1277) in the central 10 arcminute region of the Perseus cluster, imaged them with a resolution of about eight milliarcseconds and detected all of them at 1.4 GHz. They show non-variable, compact structure and brightness temperatures above 10 million K, implying that the radio emission is non-thermal. Ongoing nuclear star formation is also ruled out.
Songyoun concludes that these VLBI-detected radio sources are parsec-scale jets associated with supermassive black holes in low luminosity active galactic nuclei (LLAGNs), although there are no clear signs of this nuclear activity observed in the optical and infrared bands. Using the fundamental plane relation in black holes, we find no significant evidence for or against an extremely massive black hole hiding in NGC 1277. The work by Songyoun shows that VLBI observations are an excellent tool to disentanle the nature of radio emission in nearby galaxies. The results have been accepted for publication in MNRAS and are also available here: http://adsabs.harvard.edu/abs/2016arXiv161105986P
The picture shows the combined image of the radio-optical emission with the compact radio sources detected from the EVN observation on milliarcsecond scale. The EVN maps of our five early-type galaxies and the phase-reference check source (J0320+412) are presented on the top and left-hand side. The contour levels on the VLBI images are powers of two times the 3 sigma noise level. The green contours represent the 1.4 GHz WSRT radio continuum (Sijbring 1993) which is overlaid on a SDSS g band image.
© Madroon Community Consultants (MCC)In Jewish folklore, a Golem (/ˈɡoʊləm/ GOH-ləm; Hebrew: גולם) is an animated anthropomorphic being that is magically created entirely from inanimate matter (specifically clay or mud, i.e. Silicon Oxide). There are many tales differing on how the Golem was brought to life and afterwards controlled (Wikipedia).
At 14 November Sjouke Zwier retired. In his farewell speech he was wondering and contemplating if he would be forgotten. He wanted to make sure that was not going to happen. Therefore, he made a piece of art together with Gijs Schoonderbeek. The material used consists of the electronic boards (lots of Silicon) developed by him and others from the digital and embedded signal processing group during all those years. It has become a real masterpiece and eyecatcher in front of the digital lab, that makes everybody smile.
Sjouke was right in saying "during tours through the building, they cannot deny it". Since his retirement, a tour through the building takes 5 minutes longer because we have to explain the masterpiece to visitors before we can enter the digital lab.
The impact is perhaps even more severe than he had thought. The masterpiece stands around a corner and every morning when I walk to my office it scares me because I think a person is standing there. So, every day we are remembering Sjouke Zwier and what a special person he is.
© VentA/VIRAC/JIVEThe JIVE family has expanded again: after a process of negotiations that spanned more than three years, and in accord with other important radio astronomy developments on the national arena, Latvia has become a member of the Joint Institute for VLBI - European Research Infrastructure Consortium.
The views of the recently refurbished Irbene 32-m antenna, located some 25 km northeast of Ventspils, featured in the ASTRON and JIVE Daily Image more than once over the past several years (search with keyword "Latvia" in the AJDI archive). The recent appearance on 14.11.2016 has marked an important milestone: joining of the EVN by the Ventspils International Radio Astronomy Center on 26 October 2016.
But that day marked yet another milestone: exchange of letters between the JIV-ERIC Council, represented by the JIVE Director Huib Jan van Langevelde, and the Latvian Ministry of Education and Science, represented by Ms. Diana Laipniece, Deputy Director of the MoES Department of Innovation, on the Latvian's membership in JIV-ERIC (on the photo).
Later, in its semi-annual meeting in Dwingeloo on 15 November 2916, the JIV-ERIC Council has approved the new membership. From 1 January 2017, the Latvian flag will be proudly displayed together with the five flags of other JIV-ERIC members and logos of four JIVE-ERIC participating organisations. Laipni ludzam JIVE, Latvija!
© Beams and sensitivity plots: K. Mikhailov. Background images of nearby galaxies: CDS PortalThe diverse populations of radio pulsars and rotating radio transients are only known in and close to the Milky Way. To investigate whether other galaxies host similar populations, deep pulsar and transient searches are required. For pulsars in other galaxies, the discovery would set a guide for the source birth rate, population synthesis (as a result of star-formation rate and mass-energy distribution), the spatial and flux density distributions. The subsequent timing would probe scintillation and scattering tails, profile variations, interstellar medium (ISM) in host galaxies as well as intergalactic medium (IGM), an important quantity to distinguish Fast Radio Bursts (FRBs).
Several attempts have been made in the past to capture periodic and single pulse signals from nearby galaxies, with different telescopes: Arecibo, Parkes, GBT, and WSRT (covered frequency range: 328-1440 MHz). None of them, however, discovered new sources. Only among relatively close stellar overdensities - globular clusters and nearest neighbour galaxies of the Local Galactic Group, the Small and Large Magellanic Clouds - pulsar discoveries have been made.
With LOFAR HBA antennas, it is possible to track several nearby galaxies at the wavelengths where the pulsar flux density distribution peaks. The large bandwidth, high core gain, and multi-beaming functionality allow for efficient, deep integrations.
We performed 4-h radio observations of nearby galaxies M33, M81 and M82 with LOFAR. We coherently combined at most 23 LOFAR HBA stations to completely cover M33, and both M81 and M82.
The search did not result in any new pulsars or transients from M33, M81 or M82. To compare against our knowledge from the Milky Way, we virtually put all Galactic pulsars at the distances to M81/M82 and M33. Figure 2 shows the expected flux density versus pulse period, for those assumed populations. The LOFAR sensitivity curves are drawn for several DMs, however only the most realistic (highest) DM for M33/M81/M82 shows the error contour. The most luminous Galactic pulsar, PSR J1305-6455, is denoted with a star. Panel (a) shows that our survey was sensitive enough to detect almost the entire, actual Galactic pulsar population. Panel (b) demonstrates our sensitivity if these same pulsars are put at the distance to M82/M81 (left y-axis) and M33 (right y-axis).
Our conclusion is that, compared to the Milky Way population, there are no extragalactic pulsars shining toward Earth that are brighter by only a factor of a few in M33, and by an order of magnitude in M81 or M82.
The results are presented in A&A (in print: ) by Klim Mikhailov and Joeri van Leeuwen, and can also be found here: https://arxiv.org/abs/1605.04165
© ASTRONThe oldest LOFAR stations have been operational since end2009/early 2010. These stations still use the original server control systems which are therefore more than 6 six years old by now. Therefore, a replacement project was started at the end of 2015 with sufficient budget to purchase 55 new server systems and ensure careful preparation and execution of the replacement. We decided to upgrade to a much newer 64-bit OS and to upgrade the WinCC station monitoring software, as well.
The systems were ordered and delivered in the first half of 2016. Initial testing of the new systems with all required software modifications started in the LOFAR test lab in Dwingeloo early July. Finally, a first test with a new LCU in a real LOFAR station, CS302, was started on Sep 30th. Meanwhile, plans were made for the replacement campaign itself. The intention was to keep telescope downtime to a minimum.
All systems had been prepared by Reinoud Bokhorst and Teun Grit in the basement of the ASTRON building using the powerful combination of XCAT and Ansible. Then, on Nov 15th, we had four teams of 2 persons each in the field: Teun Grit, Klaas Stuurwold, Jan Pieter de Reijer, Peter Gruppen, Lute van de Bult, Henri Meulman, Menno Norden en Richard Blaauw. On this grey and rainy morning, they succeeded in replacing the LCUs in all Core Stations and a fair fraction of the Remote stations. The following day, the remaining remote stations were visited. While the people in the field were doing the hard labour, Arno Schoenmakers quickly checked each system after replacement and took care to finish the setup and configuration from the LOFAR control room. We finished well in time for the upcoming observations of that night and the new systems have been working flawlessly ever since.
We also need to replace the LCUs at the international stations. All systems for these stations have been prepared and shipped to our international partner institutes who will do the replacement with their own staff. We agreed with all international stations to replace the LCUs on Dec 6th.
The slides show some impressions of the preparations in the ASTRON basement, the work done in the fields and the shipment of LCUs for the international stations. The LCU replacement campaign has been a great success so far, thanks to many people involved over the duration of this project.
© R.H. van den BrinkTwo APERTIF Busy Weeks were initiated in 2016, which gave the team the opportunity to have a dedicated focus on APERTIF without distractions from other projects and to have great and fast interaction between different disciplines.
The first BusyWeek was at the end of September and focused on effort from all disciplines in order to achieve full field of view. There were challenges within all groups from hardware to software, but also on the interaction between the various fields of expert. Although we did not completely succeed in reaching all goals, we made great progress in all parts of APERTIF. Also the outcome of the BusyWeek nicely revealed parts that needed focus and attention in order to book progress and gave direction.
The second BusyWeek at the end of November, did not had one major goal as a driver, but two subgoals which concentrated on software and firmware. The computing group put in all effort for being able to use all controllers. This will also help and speedup further technical and science commissioning. The DESP group in parallel worked on getting the system more robust and set up various validation tests to validate changes made after feedback from commissioning steps.
The message bus infrastructure and scripts to automatically setup the routing structure were successfully tested. As were all the controllers separately.
- DirectionControl, controlling the pointing of the dishes
- SignalControl, controlling all the hardware at the telescope: LOG, DCU, ADU, PAC, NoiseSource, and (Beam-former) UniBoards
- CorrelatorControl, controlling the correlator: PAC, and (correlating) UniBoards
- DatawriterControl, controlling the data writers that write the raw visibilities to a number of Measurement Sets.
All controllers also worked together, each doing its own thing, while keeping an eye on the correct timing of the execution of the commands.
A number of encountered issues could be solved right away. Some will take more time, and will be addressed in the coming weeks.
Both weeks were intense and with high ambition. We look back with satisfaction, because nice progress was made and it takes us a step closer up till the delivery of the APERTIF system. Well done!
© ASTRON Mechanical GroupTwo neatly packed boxes arrived yesterday. What is their content? Each box contains 25 pieces of one of the two proto designs of new RFI shielding cans for the latest LNA for the MFAA tile.
Straight away from the factory, shining bright and looking great like a piece of jewelry. Do not wear it though, it contains Nickel ;-)
Ladies and Gents, unboxing and holding the first can in my hands does feel special in a way because this is my 'very first' end-product I designed at ASTRON, which was produced externally by VECO precision metal.
At the first glance the photo-etched cans look very similar. However, the snag is in details. One design is folded entirely from 1 piece of sheet metal, and the other is made of 2 sheet metal parts which are folded and spot welded.
These little babies are now in the hands of the Radio Group and are waiting to be soldered to the LNA PCB and tested. Keep your fingers crossed!
© ASTRONWithin the MFAA front-end project we wanted to know if several separate modules would work nicely together. We had already built Vivaldi antennas as well as the LNA modules which will be mounted on the antenna elements. We just finished the construction of two beamformer boards, which combine the signals from multiple LNA modules. To test these boards, we had constructed a controller which consists of a microcontroller and switches to route the data to the desired beamformer board. So, all in all we had the parts ready and functioning separately, and we would like to know if they would work in a system.
We decided that the easiest and quickest way to test the integration was to measure the noise temperature of an array. Therefore we attached 16 LNA modules to a large array of antenna elements, connected them to the beamformer boards, controlled those with the controller, crossed our fingers, and measured the output with a spectrum analyzer. The result of the measurement can be seen in the images above.
The system performed as expected with constant gain over the operating frequency bandwidth and no strange artifacts in the noise temperature measurement.
NB: The measurements have been performed with old LNA modules and many unconnected antenna elements. Both factors had a significant influence on the noise temperature of the array. Currently our new LNA modules are being characterized and a new noise temperature measurement is being planned. This measurement will show the true potential of dense connected arrays.