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

older | 1 | .... | 28 | 29 | (Page 30) | 31 | 32 | .... | 71 | newer

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    © ASTRON & UCT copyright

    The atomic hydrogen gas (HI) in late-type galaxies usually extends well beyond their stellar disk. However, due to the low surface brightness of the gas in the external regions of the galaxies, many HI observations fail to map their full extent.

    The present galaxy is NGC 7424, a ~10^10 Msun galaxy located ~13 Mpc away and observable from the southern hemisphere. It is a candidate of the upcoming MHONGOOSE (MeerKAT HI Observations of the Nearby Galactic Objects: Observing Southern Emitters) survey, a survey that intends to make use of the upcoming MeerKAT telescope in South Africa to study galaxy evolution. This galaxy, along with 29 other nearby galaxies, will be observed to low column densities. The galaxy was observed using the seven-dish Karoo Array Telescope (KAT-7) in South Africa. Because of its short baselines, KAT-7 is an ideal tool to observe low column density gas in galaxies.

    The left panel of the figure shows the column density map of the galaxy overlaid on a DSS optical image. The resolution of the map is given in the lower left corner, along with the contour levels. The central part of the map shows a disturbed distribution of the gas in the inner region of the galaxy, consistent with previous observations with the australian compact array (ATCA). The gas extends out to more than twice the optical size of the galaxy. In the right panel, we show the velocity field of the galaxy. The top left side of the galaxy is the approaching end of the galaxy while the bottom right side is receding.


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    © ASTRON

    The APERTIF correlator will use 16 UniBoards to correlate the signals from 12 WSRT telescopes for all 37 beams over 300MHz bandwidth. These 16 UniBoards will be placed in two subracks. To enable this configuration, two new boards had to be made, OEB and CoBI.

    The Uniboard contains 8 FPGAs, only 4 of which have standard optical interfaces. To facilitate the other 4 with optical interfaces as well, the OEB (Optic to Electric Board) was designed. It contains optical connectors to receive 12 fibers from 12 telescopes (representing a single polarization). Each fiber link transports 10Gbps. On the EOB, the optical signals are converted to the electrical domain and demultiplexed to 48 streams of 3.125Gbps. These can be easily handled by a UniBoard, each of which will have one OEB.

    On the CoBI (Correlator Backplane Interface), eight UniBoards, eight OEBs and a PAC (Power and Clock) can be plugged. A CoBI has the same dimension as the backplane of the Apertif beamformer, so the same subrack can be used. With all boards placed in the subrack, CoBI will transport 1.2Tbps.

    The picture shows a Uniboard and PAC in the front, the OEB in the back and the CoBI that connects them in the middle. More information about the Correlator can be found in the daily image of 02-02-2015. (http://www.astron.nl/dailyimage/index.html?main.php?date=20150202)

    Sieds Damstra (layout CoBI), Sjouke Zwier (layout OEB), Daniel van der Schuur (firmware design) and Gijs Schoonderbeek (schematic design).


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    © JIVE

    My name is Zhigang Wen, and I am a Ph.D. student from Xinjiang Astronomical Observatory, China. This summer, I worked at JIVE on Fast Radio Bursts (FRBs) searching and localization with the European VLBI Network (EVN). I was honored very much to be under instruction of five supervisors: Zsolt Paragi, Aard Keimpema, Andrew Siemion, Sander ter Veen and Mike Garrett.

    FRBs are intense bursts of radio emission that have durations of milliseconds and exhibit the characteristic dispersion sweep of radio pulsars. The origin and progenitor of FRBs are unknown. They are generally thought to be extragalactic because of the very high observed dispersion measure. The EVN would be a powerful instrument to prove their extragalactic origin by precise localization, to ensure that FRBs can be used as cosmological probes.

    During my summer internship, I reduced data of six pulsars and two Rotating Radio Transients (RRATs) obtained from phase-referencing VLBI observations. The positions were determined by imaging the single pulses. The pulsar test data showed that individual pulses could be localized at the few tens to 100 milliarcsecond accuracy level. We then imaged the brightest of the 7 pulses we found for RRAT J1819-1458. For the first time, we determined its position well below arcsecond accuracy using radio interferometry data. Our summer work provided technical and methodical preparation for FRBs searching and localization with EVN.

    The image shows two bursts at a DM of 196 pc/cm^3. The bottom panel shows the time-series after de-dispersion.

    I would like to thank my supervisors, fellow summer students and everyone else at ASTRON and JIVE for their kind help and making this summer experience incredible and unforgettable.


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    © ASTRON / LOFAR

    The Multifrequency Snapshot Sky Survey (MSSS) is LOFAR's first large-area imaging survey. A great deal of effort has gone into characterizing the survey performance and checking the quality of the resulting data products. Much of that work has been done using data from a 100-square-degree region of sky dubbed the MSSS Verification Field (MVF). That effort has now been described and made available to the astronomical community through the publication of the first MSSS paper, which is available here and has been accepted for publication in Astronomy & Astrophysics.

    Ultimately, all of the MSSS data will be made publicly available and we have started that process by releasing the MVF data through ASTRON's Virtual Observatory compliant data server, which is located here.

    Today's image illustrates the LOFAR sky in the MVF region, through a combination of the 16 images covering the huge frequency range (30-160 MHz) covered by MSSS. Different colors are used for the various frequencies; reddish colors are from the lowest frequencies, and bluish colors are from the highest frequencies.


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    © Keith Bannister

    A subset of compact quasars have exhibited peculiar, distinctive variations in their light curves, whose timescales are so short that they cannot be explained by intrinsic processes. This effect must be due to anomalous propagation through dense plasma lenses in our own Galaxy, which has given rise to the name `Extreme Scattering Event' (ESE). However, the densities required to produce such extreme lensing are wildly inconsistent with our current understanding of gas conditions in the Milky Way.

    I will introduce our systematic survey (ATESE) to discover and characterise these events using a novel frequency domain approach, which ideally suits the wideband capabilities of the Australia Telescope Compact Array (ATCA). This survey has already detected 2 candidates and we have triggered a variety of radio and optical followup. I will present the survey technique, our two candidates, and how we are constraining the models of the ESE phenomenon with our data.


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    © ICRAR/Curtin

    The first SKALA2 antenna has been deployed at the Murchison Radio-astronomy Observatory (MRO), the future site of SKA_Low. It will be operated as a standalone total-power instrument. The objectives of the deployment are:

  • to collect long-term data on the RF stability of the SKALA2;

  • to collect data on the RFI environment as seen by the candidate SKA_Low antenna element

    The SKALA has a modified LNA with RF coaxial outputs rather than RF-over-fibre. Its output will be connected to the digital processing of the BIGHORNS system. The spiral cone antenna that can be seen behind the SKALA2 is also connected to this system, as an RFI monitor.

    The BIGHORNS system is a spectrometer which splits the data into 4096 ~117 kHz frequency channels with fine time resolution. The integration time is configurable from ~10 ms up to several seconds. We intend to use an integration time of ~100ms, to capture the fine time structure of short duration RFI events while maintaining a manageable rate of the data sent from the MRO to Perth.

    Data are stored as dynamic spectra in standard astronomy format FITS files with approximately 1 minute of data per file. Basic metadata (time, frequency info) is included in the files such that they are self-contained.


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  • 09/14/15--17:00: Good night, sleep tight!
  • © ASTRON

    Advanced civilisations harnessing energies on galactic scales (so-called Kardashev Type III civilisations) are expected to be detectable in the mid-Infrared part of the spectrum via the emission of significant waste heat products. A team of astronomers led by Dr. Jason Wright (Penn State University, USA) have used a mid-IR all-sky survey (conducted by the WISE satellite) to draw up a list of interesting candidate galaxies (the so-called Ĝ [Glimpsing Heat from Alien Technologies] sample) that show the kind of mid-IR features that might be expected of a galaxy hosting an advanced civilisation. One of the images above, presents an advanced civilisation harnessing power from stars via Dyson swarms.

    One potential problem with this approach is that some astrophysical processes can also produce similar features via natural processes associated with thermal emission from dust.

    One way to weed out these "false-postives" is to apply the well known infrared/radio correlation to the Ĝ sample.

    It turns out that the vast majority of the galaxies in the Ĝ sample do indeed follow the mid-IR/radio correlation - this implies that their mid-IR emission almost certainly arises from natural astrophysical processes. The presence of radio emission at the levels expected from the correlation, suggests that the mid-IR emission is not heat from alien factories but more likely emission from dust � for example, dust generated and heated by regions of massive star formation or a central AGN.

    There are a handful of candidates with very high values of q (log L_MIR/L_Radio) as might be expected if a advanced civilisation was present in these particular galaxies (see one of the images above). However, these systems also seem best explained via a standard astrophysical explanation e.g. nascent star formation. Nevertheless, there are few objects that have not yet been studied in any detail, and these require further multi-wavelength observations to be made.

    In short, our of a list of 100000 resolved objects in the WISE survey, only a handful of galaxies appear to remain as viable Kardashev Type III candidates, and even these are most likely to be best explained via natural astrophysical interpretations. The conclusion drawn is that advanced civilisations are rare or entirely absent in the local Universe. Why this should be is not at all clear - there are several possibilities - perhaps technological civilisations are very short lived, perhaps advanced civilisations have found ways of reducing their waste heat emissions or perhaps we really are alone in the Milky Way and the rest of the Universe. In any case, and at the risk of tempting fate, alien invasion seems unlikely - good night, sleep tight!

    These results will be presented this week as a letter in the European journal Astronomy & Astrophysics - Garrett 2015, A&A 581, L5 - see also: http://arxiv.org/abs/1508.02624


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    © Minnie Mao,

    Our business is Radio Aperture Synthesis, in which Fourier Transforms play an important role. Of course this is a very serious business, but in our lighter moments we sometimes play little games with the tools of our trade.

    We started with regular images of two well-known JIVE leaders, whom we will call Bob and Alice, as is customary in this kind of demonstration. Both images were artificially blurred by removing the high spatial frequencies (i.e. the sharp features). The resulting fuzzy images, which only contain low spatial frequencies, were then subtracted from the originals to obtain images with only the sharp features(*). The six small images show the results.

    The large hybrid image was then made by combining the high spatial frequencies of Bob (or Alice) with the low spatial frequencies of Alice (or Bob). We leave it to the reader to figure out which combination was actually used.

    When you are close to the hybrid image, you can see the small details of the high-frequency components, and thus you recognize the person whose sharp features were used. But when you are further away, you are not sensitive to the high-frequency components so you recognize the one whose blurred image was used. Try it.

    (*) In aperture synthesis, the sharp details are measured by the long baselines, while the short ones are sensitive to large fuzzy features. They are combined by means of the Fourier Transform.


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  • 09/15/15--17:00: It happens all the time...
  • © Madroon Community Consultants (MCC)

    It happens distressingly often with temporary staff. They work here for a few years, and just before they leave, one discovers that they are actually rather interesting, and one is sorry to see them go.

    This appears to be the case more often with people from outside the dominant culture. As V.S.Naipaul observed(*), such people need to be more multi-faceted because they have to prove themselves in a different (and sadly complacent) environment. But since the effort tends to make them somewhat reserved, their extra facets are more difficult to spot. Fortunately, this barrier may be breached by the refreshing directness of the Dutch, for which they are loved (or rather appreciated, or at least tolerated) around the globe. It just requires a little effort, and the rewards are definitely rewarding.

    The picture was taken at the recent Goodbye Borrel for Peeyush Prasad (in yellow clogs), who is busily arranging his well-wishers just so. In his case we get a second chance, because he will remain involved with ASTRON from Amsterdam(**). Let's use it well.

    (*) Naipaul actually said that writers from outside London (especially himself, but also e.g. the Irish) were better because they had had to fight their way in. In the Netherlands we have the Belgian writers in a similar role.

    (**) Peeyush is bridging the gap between builder and user for LOFAR/AARTFAAC and WSRT/APERTIF.


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    © Swinburne

    The mergers of binary compact objects (black holes, neutron stars, white dwarfs) are amongst some of the most violent events in the Universe. The physics driving these events in strongly curved spacetimes are extremely complex and rich, but still remain elusive. These cosmic laboratories present us now with both a challenge and an opportunity. The challenge is to explain the physics at play in strong-field gravity in Universe. The opportunity is to detect the accompanying electromagnetic and gravitational radiation jointly for the first time with a suite of time-domain telescopes and newly upgraded gravitational wave (GW) detectors. In this pivotal new era of strong-field gravity astronomy, the most compelling astrophysical sources are neutron star binary mergers, which should emit both in electromagnetic (EM) and GWs.

    I will first review the most recent advances in this blossoming field of EM + GW astronomy, which combines two active disciplines: time-domain astronomy and general relativity. I will discuss the promises of this new convergence by illustrating the wealth of astrophysical information that a combined EM+GW measurement would immediately bring. I will then outline the main challenges that lie ahead for this new field in pinpointing the sky location of and characterising neutron star mergers using GW detectors and optical and radio wide-field synoptic surveys.


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    © JIVE and ESA (for Mars, Phobos and MEX images)

    PRIDE (Planetary Interferometry and Doppler Experiment), a project led by the Joint Institute for VLBI - ERIC (JIVE), aims for ultra-precise determination of spacecraft state vectors (i.e. position, velocity, etc). By state vectors determination, PRIDE has already produced results on the atmospheres of Titan, Venus, and Mars.

    My summer student project focused on PRIDE observations of ESA's Mars EXpress (MEX) spacecraft during a close (58 km) flyby of Phobos, one of the two small moons of the planet Mars. We used the bright radio source J1232-0224 (top right) as a phase reference, applying its calibration solutions to MEX. In this manner, we produced some 200 images of the spacecraft, a subset of which can been seen at the top left.

    We fitted Gaussians to these images to find the position of MEX as a function of time. The uv-coordinate plot (bottom right) shows the coverage achieved by the 30 radio telescopes all over Europe that were involved in the 26 hours of observations. All of the processing has been done in AIPS (Astronomical Image Processing System) controlled via ParselTongue, a python wrapper for AIPS created at JIVE.

    The project focused on the technical aspect of the experiment. Pascal Rosenblatt (PI of the observations) will include our data in his dynamical modelling of the Phobos flyby. Using this model, one can constrain the structure of Phobos' gravitational field. The latter will give information about the moon's interior. By determining the interior composition we hope to constrain the possible origin scenarios, and determine whether Phobos was formed in situ, or whether it is a captured asteroid.


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  • 09/20/15--17:00: AG to the Efteling
  • © Cees Bassa, Kelley Hess, Marjan Tibbe, Vanessa Moss, Gemma Janssen

    On Tuesday 8 September the Astronomy Group travelled south for a long-awaited group outing. After a voting process to define our plans, The Efteling was chosen. This amusement park near Kaatsheuvel is the largest one in The Netherlands and known for its variety: from thrill-rides to easy-going themed rides and a fairy-tale enchanted forest.

    "Pride comes before the fall"

    One of the favourite rides of the day for the thrill-seekers was the "Baron 1898", a spectacular new rollercoaster based on the story of a gold mine where the owner was too greedy. He promised the workers lots of gold but didn't count on the witte wieven that protect the mine. After a couple of seconds of suspense hanging from the top, the miners experience the 37-meter free fall followed by Immelmann and Zero-G roll loopings. The movies show this ride is definitely not for the weak-hearted:

    video showing Sarrvesh, Cees, Klim and Nina (front row from the right).

    Water waves

    The weather was quite nice in Kaatsheuvel, and when the sun started shining some of us decided to take the risk in the Wild-water-ride Pirana. Several of us got splashed big time, to great amusement of those on the other side of the boat... and then the next wave came.

    Flying Dutchman

    Another of the favourite rides was the "Flying Dutchman" based on the story of a stubborn Dutch VOC captain that sailed on Easter, with no fear and despite a heavy storm. From that moment the ship was damned and had to sail until the end of time as a ghost ship.

    A small part of the group left the thrill-seekers to their adventures and enjoyed the other beautiful side of this park: various exposures of well-known fairytales in het Sprookjesbos, embedded in a well-kept natural park environment.

    All in all everyone had a great day, and we are looking forward to continuing the reinstated tradition of a yearly AG-outing!


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    © ASTRON

    The starburst/Seyfert galaxy NGC 3079 is a very famous object, hosting a spectacular outflow of hot, ionised gas driven by a starburst in the centre. Because of this, NGC 3079 has been the target of many studies at all possible wavelengths.

    Nevertheless there was more to discover in this object and our observations of the neutral hydrogen (HI) with the Westerbork Synthesis Radio Telescope have revealed previously unknown components in the galaxy and its environment that show that NGC 3079 is clearly going through a hectic phase in its evolution!

    The HI disk appears much more extended than previously observed and is morphologically and kinematically lopsided on all scales with evidence for strong non-circular motions in the central regions. The data also reveal prominent gas streams encircling the entire galaxy suggesting strong interactions with its neighbours. A 33-kpc long HI bridge is detected between NGC 3079 and MCG 9-17-9, likely caused by ram-pressure stripping of MGC 9-17-9 by the halo of hot gas of NGC 3079. The cometary HI tail of the companion NGC 3073, earlier discovered by Irwin et al., extends about twice as long in our data, while a shorter, second tail is also found. This tail is likely caused by ram-pressure stripping by the strong, starburst driven wind coming from NGC 3079. We also detect, in absorption, a nuclear HI outflow extending to velocities well outside what expected for gravitational motion. This is likely an atomic counterpart of the well-studied outflow of ionised gas present in this galaxy. This may indicate that also large amounts of cold gas are blown out of NGC 3079 by the starburst/AGN. Our estimates of the jet energy and kinetic power suggest that both the AGN and the starburst in NGC 3079 are powerful enough to drive the atomic outflow.

    The details of the work can be found in the paper now accepted for publication in the Monthly Notice of the Royal Astronomical Society "The "shook up" galaxy NGC 3079: the complex interplay between HI, activity and environment" by N. Shafi, T. Oosterloo, R. Morganti, S. Colafrancesco, R. Booth.

    The paper is available at http://arxiv.org/abs/1509.00350 .


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  • 09/22/15--17:00: Local gas, global meeting
  • © astron

    During the first week of September, about 100 astronomers from (almost) all over the world (see inset) gathered in Dwingeloo to attend a meeting called Life-cycle of gas in galaxies: A Local Perspective.

    The aim of the meeting was to discuss the latest developments relating to studies on the atomic hydrogen gas in nearby galaxies. Gas is a crucial component of galaxies and it is impossible to understand the structure and evolution of galaxies without knowing their gas properties, how galaxies consume their gas through star formation, and how they acquire fresh gas by accretion. Only in the local Universe one can study all these processes in the highest detail.

    This meeting was timely because the surveys planned for the SKA pathfinders, such as Apertif, ASKAP and MeerKat, are about to begin, and they will soon cause a breakthrough in our understanding of the cold gas properties of galaxies. They will provide, for the first time, a complete and detailed census of the HI properties of galaxies in the local Universe. Many exciting results were presented and discussed, clearly showing that the community is getting geared up for the avalanche of new data that will come from the pathfinders and that they are eagerly waiting for the first data sets coming from Apertif.


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    © Ewine van Dishoeck

    Editor's note: Do not miss this opportunity to hark(*) the next President of the IAU!

    Protoplanetary disks are the birthplaces of planets, but the spatial resolution at long wavelengths has so far been insufficient to resolve the critical 5-30 AU region where they are formed. ALMA now allows us to zoom in to nearby disks and probe the physical and chemical structure associated with planet formation.

    This talk will provide an overview of recent work by our group and colleagues on observations and models of protoplanetary disks around young stars in various stages of evolution. Early ALMA results include evidence for rotationally supported disks in the deeply embedded stage, the detection of organic molecules (including sugar) and water in forming disks, and the first images of the CO snowline in mature disks.

    Special attention will be given to transitional disks, which are a subset of disks with evidence for sharp-rimmed cavities (gaps or holes) in their inner part but with otherwise normal outer disks. These disks are called 'transitional' because they are thought to represent the evolutionary phase from the gas-rich protoplanetary disk to the gas-poor debris disk stage. They are the best candidate sources for harboring just-formed giant planets.

    ALMA allows imaging of both the gas and dust in these disks, with gas cavities found to be significantly smaller than those of the dust, providing constraints on the properties of the young planets. The surprising discovery of huge asymmetric dust traps ('planetesimal or Kuiper-Belt factory') will be highlighted.

    (*) To hark: To listen attentively to


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    © Niall Gaffney/TACC

    The Texas Advanced Computing Center (TACC) has been at the forefront of High Performance Computing for over a decade. During this time, many researchers have entered the era of "Big Data". While not entirely new in astronomical environments, the scale, diversity, and fluid nature of data research have created many challenges in supporting these research areas. TACC has created a diverse environment to support the needs of the computationally diverse data fields. In addition to computational and storage resources, we have also developed several components to enable data research and computations for user environments ranging from data gateways and portals to integration within languages more familiar to data researchers such as R and Python. In this talk, I will give a high level overview of the systems at TACC, including Stampede, the number 8 HPC system in the world, and Wrangler, a data system leveraging a 600 TB NAND Flash based storage system to accelerate analytics. I will also discuss how these systems are integrated to create a powerful and flexible environment for data research, and how rich APIs, such as the iPlant developed Agave API, acts as the foundation of many data systems at TACC to create powerful computational portals and gateways that enable data research across the wide spectrum of research projects at TACC.

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    © NOVA Optical Infrared Instrumentation group at ASTRON

    This morning, the European Southern Observatory ESO and the consortium of institutes for the design and construction of METIS, will sign the agreement for the construction at a ceremony at the Science Faculty Club of Leiden University in the Netherlands. The signing will be done by H.W. (Willem) te Beest, Vice-President Executive Board, Leiden University, on behalf of the consortium, and Tim de Zeeuw, ESO Director General, and in attendance of Bernhard Brandl, the Principal Investigator of METIS, as well as all co-Investigators and all project managers of partner institutes in the consortium.

    METIS, the infrared camera and spectrograph for the European Extremely Large Telescope (E-ELT), is one of the first-light instruments and led by NOVA - The Netherlands Research School for Astronomy. It will offer imaging and medium-resolution spectroscopy over a wavelength range from 3-19 microns, and high-resolution integral field spectroscopy over a wavelength range of 3-5.3 microns. METIS is the only E-ELT first light instrument to work at these longer mid-infrared wavelengths and complements the MICADO camera and HARMONI spectrograph.

    The METIS instrument, in conjunction with the huge light collecting power and resolution of the E-ELT, will allow many advances in a wide range of astronomical topics. These include the study of proto-planetary discs and the formation of planets, detailed investigations of the properties of exoplanets and, closer to home, the formation and history of the Solar System. METIS will also probe the growth of supermassive black holes as well as study star-forming galaxies in the early Universe.

    METIS will be the largest instrument ever built by NOVA, and it will take a decade for realization. At ASTRON, the NOVA Optical Infrared Instrumentation Division will build several core elements.


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    © NOVA

    Yesterday, at the Science Faculty Club of Leiden University, Tim de Zeeuw, ESO Director General of the European Southern Observatory ESO and H.W. (Willem) te Beest, Vice-President Executive Board, Leiden University, signed the agreement for the construction of METIS, one of the three first light instruments for the 39-m European Extremely Large Telescope E-ELT, which currently is being realized on top of Cerro Armazones in de Atacama desert in Northern Chile.

    METIS, the only infrared first-light instrument and offering imaging and medium-resolution spectroscopy over a wavelength range from 3-19 microns and high-resolution integral field spectroscopy from 3-5.3 microns, will be built by a consortium of institutes around Europe, and is led by NOVA - The Netherlands Research School for Astronomy. Next to NOVA, the consortium consists of the Max-Planck-Institut fuer Astronomie (MPIA) (Germany), the UK Astronomy Technology Centre (UKATC, United Kingdom), the Katholieke Universiteit Leuven (Belgium), CEA Saclay (France), ETH Zuerich (Switzerland) and Universitaet Wien on behalf of the A* consortium (Austria), all being present at the ceremony.

    In Greek mythology, Metis was the first wife of Zeus and mother of Athena, goddess of wisdom. The METIS instrument, in conjunction with the huge light collecting power and resolution of the E-ELT, will allow many advances in a wide range of astronomical topics, including the study of proto-planetary discs and the formation of planets, detailed investigations of the properties of exoplanets and, closer to home, the formation and history of the Solar System. METIS will also probe the growth of supermassive black holes as well as study star-forming galaxies in the early Universe.

    METIS will complement the HARMONI spectrograph and MICADO imager, the latter also having Dutch contributions. All first light instruments will take a decade for realization, and at ASTRON several core elements will be built by the NOVA Optical Infrared Instrumentation group.

    Straight after the signing ceremony, the METIS kick-off consortium started, settling the beginning of design phase B.


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  • 09/29/15--17:00: The DRAGN is breathing fire
  • © Vikram Singh

    Radio-loud galaxies are a subset of AGN that show enormous regions of radio emission outside the visible extent of the host galaxy. In the nearby universe, these double-lobed radio emissions have almost invariably been associated with elliptical galaxies. It has long been theorized (and supported by observations) that elliptical galaxies are formed by the merger of smaller galaxies and that such mergers provide the mechanism for the infall of gas into the accreting regions of the nucleus. It has also been proposed that such mergers are what result in the launching of kiloparsec-scale radio-loud jets from the central AGN by spinning up the supermassive black hole.

    0313-192 was the first confirmed double-lobed radio source hosted by a late-type galaxy and is the archetype for the Spiral DRAGN (Double Radio sources associated with Active Galactic Nuclei) phenomenon. The image above shows the preliminary results from the reduction of S-band (13cm) data obtained from the VLBA (Very Large Baseline Array, USA). It confirms beyond doubt that the radio source associated with 0313-192 is not a chance alignment. The angle of the milli-arcsecond scale jet seen matches (within error) with previously obtained images from the VLA and VLBA (3.6cm, X-band). A comparison with the X-band image yields a core spectral index of α = -0.46 confirming that the core is optically thick (very dense) and that synchrotron self-absorption is taking place at these frequencies. The next step for the team is to reduce L-band (21 cm) data from the VLBA to study the HI absorption in the galaxy.


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    © ASTRON

    After many successful years of MFFE-IVC-DZB observations, we were given the opportunity for a thorough upgrade. For the coming era of APERTIF and VLBI observations, all 14 telescopes have been modified, extensively.

    All coax and power cables have been replaced. The new APERTIF antenna uses 121 coax cables to the container. The old PVC power cables had become brittle and porous, and have been replaced. The telescope steering electronics of all 14 RTs (uP, frequency converter, relays, encoders) have been modified. Design, testing and software all by Pieter Donker (as was the 1996 version). Power distribution and 3kV transformers for 9AB and CD have been revised. All 14 telescopes now have a 144 fiber cable to the building, for data, control and monitoring.

    Jan-Pieter de Reijer

    Pieter Donker

    Peter Gruppen

    Lute van de Bult

    Cottus: Jack, Arie, Jeroen, Richard, Kevin


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