© ASTRON

This technique has been extensively applied to data obtained by the Westerbork Synthesis Radio Telescope in the PhD work of Katinka Gereb (Daily Image 08-10-2014, see also Daily Image 26-11-2013 and 20-08-2014).

The latest results on the characterization of the atomic neutral hydrogen (HI) content of a sample of about 1600 galaxies (with redshift up to z

We find that the HI content is more dependent on colours, with a decreasing amount of gas going from so-called "blue cloud", i.e. galaxies dominated by relatively young stars, to "green valley" and only an upper limit for the "red sequence" where only old stars are present, and less on ionization properties of the gas in the galaxies. This is illustrated in the plot on the left. This means that regardless of the presence of an optical active nucleus (based on optical ionization line diagnostics), green-valley galaxies always show HI, whereas red galaxies only produce an upper limit (as illustrated in the plot on the right). These results suggest that "feedback" from optical active nuclei, the so called "feedback", is not the (main) reason for depleting the large-scale gas reservoirs and quench star formation.

We also find that the radio emission in galaxies bright in infrared (IR), stems from enhanced star formation, in agreement with the finding that this group is detected in HI. However, IR early-type galaxies lack any sign of HI gas and star formation activity, suggesting that radio AGN are likely to be the source of radio emission in this population.

This study has been used as test case and to set up the necessary software and explore the possibilities in preparation to the surveys that will be done by Apertif.

© ASTRON

The roll out of the first 6 APERTIF Phased-Array Feeds is already well underway, and is expected to be complete by the end of this year. The remaining systems will be rolled out in the spring/summer of 2016. With the full system deployed, the survey speed of the WSRT for HI surveys will be an order of magnitude better than the current performance obtained from the current MFFE single-pixel receivers. The main scientific impact of APERTIF will be in the fields of galaxy evolution, transients and pulsars. The system will also eventually be available as a very sensitive phased-up element of the European VLBI Network.

The Board's decision represents an important milestone for the APERTIF project, and we celebrate this with the image presented above. This digital artwork was created by Dutch artist, Danielle Futselaar, in collaboration with ASTRON. See http://www.daniellefutselaar.com/ for more of Danielle's illustrations, including several she has prepared for ASTRON, the SETI Institute and NASA.

© Natasha Maddox (ASTRON)

The first quasar selection was based at radio wavelengths, but we now know that only ~10% of quasars are radio loud. Quasars can also be bright at X-rays, but if the central engine is surrounded by gas and dust, the X-rays are absorbed. The SDSS has used optical light to construct a catalogue of more than 200,000 quasars at redshift up to 5, but it is still missing quasars located in dusty galaxies, and quasars with unusual spectral properties.

The near-infrared (NIR) is able to see through dust in galaxies to find quasars that would otherwise be missed by optical selection. It is also able to find quasars with strange properties, that may not look like quasars at first. Combining optical and NIR imaging, we have designed an algorithm to search through large amounts of imaging data to find quasar candidates that were missed by other search algorithms. Spectroscopy of the candidates was recently performed at the 4.2m William Herschel Telescope on La Palma, and 140 previously unknown quasars were discovered. Images of four of the new quasars and their spectra are shown in the image. Among the newly found quasars is one of the most luminous known, along with quasars with unusual spectra.

© ASTRON

Since such principles have to be carried by each member of the group, they cannot simply be imposed top-down. Therefore we organized a "day on the heath" at an external retreat, to establish the ingredients for the group mission. It was an intensive day, with a lot of discussions and laughter. We talked about who our customers are, what needs we endeavour to satisfy, and what technology to use for that lofty purpose. But also how to distinguish ourselves, and which values and beliefs are essential in our work. Basically, the questions are "who gives us existence?" "why are we here?" and "what business are we in?". Every member of the group had a say, and continues to do so.

We did a lot of exercises. First we held a mirror up to ourselves personally, and then to the group as a whole. This process has led, in early 2015, to the DESP Mission reproduced below. As a by-product, we also formulated some Statutes, which outline the ways in which we strive to work within the DESP group.

The DESP Mission

Unveiling the mysteries of the universe through the use of advanced digital systems.

The Digital and Embedded Signal Processing group delivers digital systems to radio astronomers for retrieving astronomical information from data. With these systems we provide the optimal balance between quality and time to science.

Involvement and focus on customers are key values for us. We communicate with each other and our customers in an open way. We are a team.

The picture was taken by Bastiaan Spijk of HRM, who contributed significantly to the process. It shows all the members of the DESP group, clutching the Mission and the Statutes. We have already started to live by them.

© Ronald Halfwerk

At first glance it seems an odd collaboration: a steel producer that works together with astronomers. Yet this collaboration is more logical than it seems at first sight. TATA Steel produces, processes and distributes high-quality steel products. The company is the fifth largest steel company in the world and uses the latest technologies. TATA Steel is looking for solutions to automatically detect very small (0.01mm) defects and contaminants in large surface areas of steel. These steel sheets are rolling of the production line at high speed.

NOVA, the Dutch Research School for Astronomy, develops scientific instruments that monitor the night sky constantly, looking for very small changes. When astronomers observe a change, they investigate further with different types of telescopes. They unravel the light which is coming from an object, which reveals a lot of information about the chemical composition of stars and planets. Techniques used in astronomy are also useful in terrestrial applications. For example, you can detect contaminants or defects with the aid of the polarization of light.

NOVA and Tata Steel will examine whether the techniques developed in astronomy also offer a solution for the challenges in steel production. This applies not only to the extremely sharp look, but also the super-fast processing of large amounts of data.

In the picture from left to right: Ramon Navarro, head of the NOVA optical- infrared instrumentation division, Theo Henrar, CEO of TATA Steel Netherlands and Minister Henk Kamp of Economic Affairs.

Science for Competitiveness is a key topic for the Netherlands 'Nationale Wetenschapsagenda'.

© don't worry

Many thanks to Tom Oosterloo, Wilfred Frieswijk, Erwin de Blok, Bob Campbell, Paul Boven, Sander ter Veen, Marco Iacobelli, Wim van Cappellen, Johan Pragt for giving the presentations. And special thanks to Leah Morabito for herding the students through the day and in fact the semester.

© ASTRON

In typical ASTRON fashion, the summer students had no sooner finished their pancakes before they were immediately put to work helping start a colleague's car. When asked for volunteers to help push, our new crew of summer students immediately and unanimously offered to help. With this kind of team spirit and work ethic, no doubt we can expect to see some great radio astronomy projects this summer.

© Rik ter Horst

Originaly the images were made with a Minolta camera on 400 ISO film (slides), the location was Assen-noord. Photoshop was used to make the animated GIF.

The Aurora Borealis show of 1989 was one of the most spectacular ever, with reports coming even from the south of France.

© astron

As is common on such occasions, the mood was reflective and grateful for all the good things the telescope has brought in the last 15 years. Many of the attendants expressed gratitude for the privilege to have been part of it all. It was a wonderfull instrument.

Although the 'departure' of the MFFE's, the DZB and the IVC marks the end of an amazing era, and many of us feel slightly sad about this, the actual reason to 'turn off' the WSRT is that now we can install phased-array feeds on the WSRT dishes and change the WSRT into Apertif. This will change the type of science the WSRT will be doing and will ensure it will rermain a relevant telescope in the times that we prepare for SKA....

You should expect the first data of the new system in August.. Stay tuned... It will be fun!!

© University of Cape Town

The short baselines and low system temperature of the telescope make it, despite the fact that it consists of only seven 12-m dishes, very sensitive to large-scale, low-surface-brightness emission. The KAT-7 observations of NGC 253 detected 33% more flux than previous Very Large Array observations. As can be seen in the figure, HI can be found at large distances perpendicular to the plane out to projected distances of ~10 kpc away from the nucleus and ~14 kpc at the edge of the disc.

The observations show that a large amount of HI is found outside the disk of NGC 253. The kinematics of this extra-planar gas suggests that it consists of gas blown out from the disk by the central starburst occurring in NGC 253 and by the galactic fountains in the outer parts. Analysis of the near-IR WISE data, shows clearly that the star formation rate is compatible with the starburst nature of NGC 253.

The results of these observations we recently published in the Monthly Notices of the Royal Astronomical Society (HI observations of the nearest starburst galaxy NGC 253 with the SKA precursor KAT-7 by Lucero, D.M., Carignan, C., Elson, E.C., Randriamampandry, T.H., Jarrett, T.H., Oosterloo, T.A. and Heald, G.H.; see http://arxiv.org/abs/1504.04082 )

© Roelie

This recent picture shows her taking her regular break outside, enjoying a quiet cigarette with anyone who would join her. With her characteristic voice, she was always ready to discuss the complexities (and occasional hardships) of keeping our working environment clean and happy.

Thank you, Henny, and goodbye. We will really miss you.

© ASTRON

In his spare time, he was closely connected to the checkers club HDC Hoogeveen as member and treasurer. Even when his health deteriorated, he continued visiting the club evenings.

After his retirement Cees continued to attend the outings of the ASTRON/JIVE Personeelsvereniging, and kept on coming to the Christmas High Tea.

Our thoughts are with his family and friends.

© Kelley Hess

The grey-scale image from the Widefield Infrared Space Explorer (WISE) shows the stellar content of the Antlia Cluster (as well as many foreground Milky Way stars). The colored contours correspond to HI detected galaxies by the KAT-7 telescope in South Africa.

The presence of HI reveals which galaxies have most recently arrived to the harsh cluster environment, and the observations show that Antlia Cluster galaxies are already gas deficient when they reach 600 kpc from the cluster center. This suggests that either the cold gas is already beginning to be stripped out of the galaxies at large cluster radii, or the gas has been 'pre-processed' in smaller gravitationally-bound collections of galaxies called groups. In fact, it appears that galaxies are being accreted on to Antlia asymmetrically from the surrounding environment, and may be coming from a filament of galaxies that connects the Antlia Cluster to the Hydra Cluster about 18 Mpc away.

The results of these observations were recently accepted for publication in Monthly Notices of the Royal Astronomical Society (KAT-7 Science Verification: Cold Gas, Star Formation, and Substructure in the Nearby Antlia Cluster by Hess, K.M., Jarrett, T.H., Carignan, C., Passmoor, S.S., Goedhart, S.)

© Astron

For POLFAR, we assembled and tested 18 subracks in total. In parallel we are also preparing three ILT containers for the Polish LOFAR stations at Baldy, Borowiec and Lazy. The plan is to ship the first container at the end of this month. It is an intensive, but also an exciting period, and only made possible by the dedication and effort of the POLFAR team members, the DESP and TSG groups, and our external contractor Germon Offereins.

© NASA/DOE/Fermi LAT Collaboration

In this presentation I will review recent results from pulsar observations with the Fermi LAT, and discuss some implications stemming from these observations.

The image above shows a map of the entire sky at energies larger than 1 GeV based on five years of Fermi Large Area Telescope (LAT) data. To date, the LAT has uncovered more than 3000 gamma-ray sources, including more than 1000 that have no known associations.

© JIVE, IMAPP, MIT

The participants traveled from all over the world to talk about calibration, fringe finding, sparse imaging algorithms, and many more essential topics. Any effect that occurs between the source and the astronomer has to be understood in intricate detail to study the physics of mm-VLBI radio sources. This made instrument simulations a crucial topic of the workshop.

The official programme consisted of short talks, discussion session and interactive tutorials. The fabulous infrastructure of the room encouraged an unofficial programme of informal and wide-ranging information exchange.

The workshop ended with a discussion of future work. The participants unanimously declared that it is essential for the field of mm-VLBI to have a coherent organizational structure in place to disseminate the (currently rather fragmented and very globally distributed) knowledge of best practices in this field, and to work towards opening the field up for non-experts.

The workshop programme and talks are accessible on the workshop website.

© Astron

The LBA damage is somewhat worse than we expected, probably due to a more complex lightning discharge pattern than we assumed in our models. In total, we had to replace 54 LBA (antennas) and 4 RCU boards. For the LBA we found open, short or clipping circuits in the X or Y polarisation. For LBA-33 (direct impact) we found that the PCB track before the Gas Discharge Tube had been vaporized on the connected RCUs. Two other RCUs had a broken transistor switch for selecting LBL or LBH input. On the positive side, none of the 288 coax cables was damaged, and this is very good news.

Intriguingly, the signal delay communication for three HBA tiles had also failed. It was found that the modem program in the EEPROM had been erased due to high induction voltage. After re-progamming, these three RCUs worked as before!

We will continue to study the vulnerabilities in the LBA design, also for the benefit of future radio telescopes. Part of our new knowledge and technology is already included in SKA-LFAA prototype designs.

© ASTRON

The measured antennas are patch antennas using foam as a substrate. The patches and microstrip lines are cut from conductive copper tape. The measurements are performed in the near field antenna measurement room. The measured near field is transformed to the far field by software. Michel Arts prepared the antenna measurement system in order to do the measurements and performed them.

After the measurements Mark showed the students the ASTRON-facilities and the Dwingeloo Radio Telescope. They also went to Westerbork to see the WSRT.

© ASTRON

Andreas Doering presented his experience with designing the highly compact Dome microserver board; Klaus Flesch shared design considerations based on his 30+ years of experience with several SME companies. Hubert Harrer presented best practices from the IBM Server Group, and Gijs Schoonderbeek discussed his experience with designing the highly complex 18-layer UniBoard2.

The presentations and discussions made clear that several steps can be taken to increase the quality of the designs, these include careful communication, making checklists, and having a clear strategy on component library management. The discussions also concluded that the complexity of new high-end designs is enormous. This does not make it easy to reach high quality, but there are ways to get there, as the current state of the art designs show of course.

© Steve Torchinsky

The picture above shows (the majority of) the attendees, in front of the EMBRACE@Nancay array.

During the meeting we discussed several items, covering all aspects of the frontend work by all partners. These developments include antenna and LNA designs, analogue beamforming, receiver, receiver control and power supply for the front-end components.

The main goal of FED task is to design, build and verify a dual polarisation tile which demonstrates that AA technologies are ready for PDR. A tile forms the key building block for the antenna array for mid SKA frequencies. It provides all available FoV of an MFAA station which may be limited further on by processing or the available digital station output bandwidth.

It is not required to build a full size MFAA station to predict its behavior. From EMBRACE it is known that a down scaled array consisting of 9 to 16 tiles can provide the required evidence for the behavior of a full scale array.