© Dome, original design by Freepik

During this afternoon's event, the Van de Hulst auditorium is the setting for plenary sessions. You may also spot some interactive sessions in the Muller, JIVE, Hooghoudt and former control room. After lunch, there will first be an update on novel technologies and new computing approaches that are being developed within DOME. For more information on the Dome research streams, please click here http://www.dome-exascale.nl/oupe2014/index.php

This plenary session will be followed by some interactive subsessions. We have challenged a number of SME's to analyse where the opportunities lie that may enhance their business and could benefit our economy as a whole. We are curious to see what IT-related constraints they are facing when it comes to developing products and services, and which of those the Dome team could help solve. If there is a viable match with one or more of the Dome research streams, the aim would be to proceed with R&D on a collaborative basis.

© Leah Morabito (Background Image credit: J. Gallagher, M. Mountain, and P. Puxley)

Carbon atoms are about half a million times smaller than the average thickness of a human hair, but in very cold and sparse gas they can be up to a billion times larger(*). The weak spectral signature of these very large atoms can be observed at very low radio frequencies.

In the past most radio telescopes have either not been sensitive enough or not been tuned to the right frequencies to be able to detect these lines outside of our own Galaxy. However, the LOFAR radio telescope, that stretches from the northeast of the Netherlands across Europe, is perfect for these kind of observations because of its wide frequency range and excellent sensitivity.

The LOFAR study of the nearby starburst galaxy M82 has now, for the first time, been able to detect the spectral signature from large carbon atoms outside of our own Milky Way. These observations, in combination with future measurements, present us with a new tool to study the properties of the cold and sparse gas in M82 and what role this gas plays in evolution of this galaxy.

(*) Such large atoms are called Rydberg atoms (see e.g. wikipedia).

© Stefan Wijnholds

This will be an issue for the new generation of giant radio telescopes. Certainly for the SKA, but already for specific LOFAR observations. In order to analyse the problem, we first have to understand the "apparent source statistics", i.e. the statistics of sources that will be visible in the field-of-view of a particular telescope.

To get some feeling for this, we assumed a primary beam with the shape of an Airy pattern, the theoretical power beam pattern of a homogeneously illuminated circular aperture(**). The Airy pattern for a 15-m aperture at 1 GHz is shown in the left panel. We then used this to filter the known source statistics at the observing frequency of 1 GHz, to obtain the apparent source statistics shown in the right panel. The vertical line gives a rough indication of the 1-sigma limit for the SKA dish system after 1000 hours of integration over 1 MHz. Note that the same limit holds for 100 hours over 10 MHz and 10 hours over 100 MHz.

The various curves indicate the total number of sources brighter than a given apparent flux, for various lobes of the primary beam. They show that almost all (over 85%) visible sources typically reside in the main lobe, with most of the others located in the first two sidelobes. The number in the far (>2nd) sidelobes is typically less than 1%.

All this is encouraging, because calibration is easier in the main lobe. However, it should be noted that this ratio will be different for different primary beams, and after subtracting as many sources as possible. Unfortunately, the problem will be exacerbated for the new telescopes, since they are sensitive to hitherto invisible source populations that cause the density of sources to increase more steeply with decreasing flux.

In a future AJDI, we will present a useful plot(***) that makes it easy to determine the extent of the problem for various existing and proposed radio telescopes. It indicates how low the PSF sidelobe level has to be for a given nominal sensitivity, and how many sources have to be subtracted.

(*) Point Spread Function

(**) PSF sidelobes are higher for unfilled apertures

(***) This plot was presented at the recent URSI GA in Beijing

© C. Ng (MPIfR), et al.

To discover more pulsars we have begun the High Time Resolution Universe (HTRU) survey: a blind survey of the northern sky with the 100-m Effelsberg radio telescope in Germany, and a twin survey of the southern sky with the 64-m Parkes radio telescope in Australia. The HTRU survey uses multi-beam receivers and backends constructed using recent advancements in technology, providing unprecedentedly high time and frequency resolution to probe deeper into the Galaxy than ever before. Observations from Parkes have recently been completed, and it is thus a suitable moment to review the success of the survey.

In my talk I will discuss the discovery highlights such as the magnetar, two 'planet-pulsar' binaries and the Fast Radio Bursts (FRBs) from cosmological distances. The HTRU low-latitude data promises to provide the deepest large-scale search ever of the Galactic plane region. I have already discovered 60 new pulsars from processing 50% of the Galactic plane data.

I will present an innovative segmented search technique, which aims to increase our chances of discoveries of highly accelerated relativistic binary systems, including the potential pulsar-black-hole binaries. I will provide an overview of the northern survey with Effelsberg and present an update on the survey status.

© MP

We followed the evolution of the full profile width and that of its single components, in case of multiple peaks; also in case of multiple peaks we traced the evolution of the ratio of the amplitudes of the two most prominent peaks.

We found that the profile evolution with decreasing radio frequency does not follow a specific trend but, depending on the geometry of the pulsar, new components can enter into, or be hidden from, view. Nonetheless, in general our observations confirmed the widening of pulsar profiles at low frequencies, as expected from radius-to-frequency mapping or birefringence theories. We found good agreement of our data with the empirical core + cones model from Rankin (1983+) and the phenomenological model from Karastergiou and Johnston (2007).

Credits: M. Pilia, J.W.T. Hessels, B.W. Stappers, J. van Leeuwen and LOFAR Pulsar Working Group

© Erwin de Blok

As a result of this workshop, Erwin de Blok from ASTRON used his multi-wavelength data, along with other archival data, of nearby Local Group dwarf galaxy to make false-colour image shown here.

The optical background is made of a combination of B, V and R images from the Local Group Survey by Massey et al (2007, AJ, 133, 2392). The blue stars have been enhanced using near-UV data from GALEX (Hunter et al 2010, AJ, 139, 447). The red emission shows the H alpha distribution as published in de Blok et al (2006, AJ, 131, 363), and finally the distribution of the neutral hydrogen (HI) is taken from Australia Telescope Compact Array observations described in de Blok et al (2000, ApJ, 537, L95).

Note how the bluest (youngest) stars can be found near holes in the HI. The origin of the large hole in the bottom-left (south east) is not clear. It could be caused by star formation, but there is no clear evidence for a remnant population. Alternatively, NGC 6822 could be interacting with an even smaller dwarf (visible as the cloud in the top-right), with the hole (and the tail that can be seen going off towards the bottom left) being the result of a tidal interaction.

NGC 6822 is only 0.5 Mpc away from us and is the closest gas-rich dwarf galaxy outside the Large and Small Magellanic clouds. The image measures about 0.7 by 0.7 degrees - NGC 6822 therefore has an apparent size about that of the moon!

© Madroon Community Consultants (MCC)

© Heino Flacke

© ASTRON, 2014

To independently assess the system and to minimize the risk that something has been overlooked, a Critical Design Review (CDR) was organized. A strong international panel of experts was invited to review whether the APERTIF system fulfills the science and system requirements and whether all major risks were identified. The review panel consisted of the following members: Mark Bowen (CSIRO, chair), Erwin de Blok (ASTRON), Hans van der Marel (ASTRON), Lister Staveley-Smith (UWA/ICRAR), Ravi Subrahmanyan (Raman Research Institute), Gundolf Wieching (MPIfR) and Victor Pankratius (MIT Haystack Observatory). The APERTIF team supplied them with an extensive set of documentation, describing every detail of the design and initial commissioning results. During a face-to-face meeting the highlights and issues were discussed. And of course the panel went for a tour to the WSRT to see the ALPHA-3 system in action.

We are excited to report that the panel was very impressed by the quality of the documentation and the presentations and was unable to identify any significant risk that was not already reflected in the risk register. The panel concluded that, as designed, APERTIF promises to make the WSRT a world class facility for the next decade. We are eagerly looking forward to start rolling out APERTIF in the coming year.

© ASTRON

The chip is designed to form two beams by means of phase-shift and amplitude control. The integrated circuit includes many differential functions such as low noise amplifiers, switches, polyphase filters, variable gain attenuators and a SPI/I2C interface for the digital control of all settings.

This BFC has 16 equally distributed phase steps of 22,5 degrees. Amplitude control of 4.5 dB with 8 equally distributed steps is implemented to accomplish a phase-dependent amplitude variation of less than +/- 0.5 dB. The total power consumption of the BFC is

The testboard has been designed by our own Sieds Damstra, whereas all soldering has been done by Anne Koster. PCB manufacturing by our in-house pcb facility, operated by Albert van Duin Great work!

© Nico Ebbendorf

This new LOFAR site is located north of the city of Hamburg, in a small town called Norderstedt. In the last 4 weeks, a total of 96 Low Band Antennas (LBA), 96 High Band Antennas (HBA) have been installed, and a large cabinet for the back-end electronics.

With this new addition, the International LOFAR Telescope (ILT) will consist of a total of 38 stations in the Netherlands, 6 in Germany, and one each in France, the United Kingdom and Sweden. More will follow.

The data collected from all LOFAR stations is processed and stored in Amsterdam, Groningen and Julich (Germany), and coordinated by Astron. International stations (i.e. stations located outside NL) can also operate in stand-alone mode, acting as a single telescope.

© David A. Hardy/AstroArt.org

We computed synthetic light curves that demonstrate that SN 2005ek could be explained by our model. We argue that the second explosion in some double neutron star systems (for example, the double pulsar PSR J0737-3039B) was likely associated with an ultra-stripped Type Ic SN. New results of an ongoing systematic investigation of the progenitors of electron capture SNe versus Fe CCSNe in close binaries are discussed.

The second topic of this talk is focused on the possibility of forming neutron stars via the accretion-induced collapse (AIC) of a massive ONeMg white dwarf, illustrated in the picture above. Both observational evidence and theoretical computations are discussed.

© ESA / ASTRON

The probe is expected to continue to operate until March 2015 - at that point the comet will be much closer to the sun, and the probe will be threatened by rising temperatures and increasing activity on the comet's surface. Meanwhile the orbiting Rosetta spacecraft will continue to monitor the comet all the way through perihelion (August 2015), giving us a remarkable ring-side seat in which to view the various outgassing processes.

An animation of today's landing is available at: http://youtu.be/szKZ77MbF9Q

© ASTRON

Measurements were done at four different azimuthal positions of the array, spaced at 45 degrees. Noise measurement results for the individual positions, as well as their average are presented, showing mean values below 45 K, with a standard deviation of 1-2 K.

Furthermore, we present results on the reproducibility of noise measurements with the experimental 60-element Medium Sized Tile (MST), for one polarization of its 5x6 array. Seven measurements were done at one hour intervals during the day, between 9:30 and 15:30. Results of the individual measurements and their average show values below 45 K, with a standard deviation smaller than 1 K. As may be observed from the concerning noise plot, results for some of the measurements between 1150MHz and 1250 MHz that were strongly affected by RFI, have been omitted. These frequencies showed large noise temperature peaks in a number of measurements during the day, with much larger standard deviations.

In the present results for the MST we observe a 5 K noise temperature increase, compared to the results in the AJDI of 26-05-2014. A possible explanation for this difference is the influence of low level RFI on the measurements, which is subject of further investigation.

The third noise plot shows a comparison of the averaged noise temperatures for the 1 m2 tile and the MST. The results are quite close to each other, indicating that the measurements on the smaller MST with respect to the 1 m2 tile, give a good indication of the noise performance of a larger array. This allows lower cost and easier handling for this type of array experiments.

© UMAN

During the meeting, all three workpackage partners (KLAASA, UMAN, ASTRON) presented their progress, focussing mainly on the antenna and LNA designs. Additional material was presented by University of Cambridge, Observatoire de Nancay and Stellenbosch University.

In addition to all the technical fun, which included lively discussions among all engineers present, the SKA Office treated us to their latest view on SKA2 science goals.

David Zhang (UMAN), the LOC chair, summarized the meeting with an impressive list of the main achievements:

© Picture courtesy of Matt Schmachtenberg, from JMU's 'The Breeze'

© Roberto Pizzo

The first version of the manual was published more than 4 years ago, when the first LOFAR commissioners met together during the commissioning Busy Weeks to test and validate the new reduction software regularly becoming available for processing LOFAR data.

Since 2010, the manual has developed significantly. Its content has become very comprehensive of all the data reduction steps needed to achieve outstanding LOFAR imaging results. The topics covered range from data inspection to flagging, calibration, imaging, and source extraction. More recently, important chapters have been included on advanced methods to remove the A-team signal from the visibilities, advanced tools to inspect the calibration solutions, the automated self-calibration algorithm, and a description of the new LOFAR CEP 3 cluster - which inspired the release of this new version of the manual.

The LOFAR Imaging Cookbook is edited by Roberto Pizzo, who coordinates the large group of experienced LOFAR commissioners in charge of updating the chapters of the manual: G. van Diepen, T. J. Dijkema, G. Heald, F. de Gasperin, M. Iacobelli, J. McKean, M. Mevius, A. Offringa, E. Orru ́, D. Rafferty, C. Tasse, B. van der Tol, V. Vacca, N. Vilchez, R. van Weeren, W. Williams and S. Yatawatta, on behalf of the Lofar commissioning team.

© Bower, O'Leary et al.

A major breakthrough came in 2013, with the discovery of the magnetar PSR J1745-2900, separated from the supermassive black hole by just a fraction of light-year in projection. Magnetars are relatively rare, highly magnetised neutron stars which are unfortunately not well suited to the kind of tests we would like to perform at the Galactic Centre. It did serve, however, as the bearer of bad news: the scattering of pulses originating from pulsars at the Galactic Centre was not nearly as bad as suspected. On first glance, this sounds positive: easier to observe the target pulsars! But it begs the question: if they weren't being hidden by scattering, where *are* all these other pulsars? If our expectations are wrong and there are actually few pulsars at the Galactic Centre, then we may never find one suitable to make the precise tests of general relativity.

To help answer this question, we observed PSR J1745-2900 over a period of a year with the Very Long Baseline Array plus the phased VLA, tracking its motion in the plane of the sky. The tiny motion observed was equivalent to seeing an ant crawl across a leaf from a distance of 1,000 km! The pulsar velocity is shown in the image in red, along with the velocity of a sample of other massive stars which orbit Sgr A* in a compact disk in black. By simulating the stellar population, we were able to show that PSR J1745-2900 is almost certainly bound to Sgr A*, and likely originated in the disk of stars shown in the image. We postulate that the lack of observed radio pulsars could be due to a time-variable star formation rate at the Galactic Centre, which has recently increased significantly after a long dip; older radio pulsars from previous periods of high star formation have faded away, and new ones are only just now being generated. "Millisecond" radio pulsars with much longer lifetimes would still be present in droves, but even the relatively limited amount of scattering we observe means they would still have been missed by previous surveys. Future, wide bandwidth surveys, and potentially those with the Square Kilometre Array, may still detect these fast pulsars. More details are given in our recently accepted paper.

© Astron

The results from these observations were presented in Morganti, Garrett, et al. 2004, A&A, 424, 371 (ArXiv:0405418) while follow up with VLBA and submillimeter SCUBA were presented by Wrobel et al. (including Mike Garrett and Raffaella Morganti) 2004, AJ, 128, 103 (ArXiv:0404007) and Frayer et al. (again including Mike Garrett and Raffaella Morganti) 2004, ApJS, 154, 137 (ArXiv:0406351) respectively.

© ASTRON PV

Just like his offshoot Santa Claus, Sinterklaas brings presents for all the children who have been good during the past year. But the older benefactor has the more gruelling schedule: not only does he deliver the goods on a single evening into millions of chimneys, seated on a presumably sure-footed white horse, but in the days and weeks before the 5th of December he also makes thousands of personal appearances like the one to our institute today. And although he does not have to do it all by himself, and has fewer households to serve, it is no wonder that his style is somewhat less jolly than Santa's: no "ho-ho-ho" from an exhausted Sinterklaas.

Despite the obvious similarities (which are driven by globalisation), there are significant differences between the two traditions. The most important is that Sinterklaas is much more intimate, aimed at the inner family: