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

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    © -

    On 20 October, a group of high school students from around the country visited ASTRON and CAMRAS to do their own observations with the Dwingeloo telescope. Independently, these students had discovered the Dwingeloo Live program. In that program, students do their own observation with the Dwingeloo telescope, and afterwards perform the data reduction through a web front-end. With their analysis, they find the period and dispersion measure of a pulsar, after which they fold the data to get a nice profile.

    Until now, Dwingeloo Live was mainly used with pulsar B0329+54, which is very bright. However, some of the students had a particular interest in the Crab nebula. Therefore, we decided to do a crab pulsar observation as well. For astronomical reasons, this observation was scheduled at 8:30 AM.

    With the help of Cees Bassa, we managed to catch some nice data of the Crab pulsar. The pulse profile is shown at the bottom of this image. (In principle, the telescope back-end by Paul Boven can work with higher time resolution, but even the 32 bins for the 3.3 ms period show the pulse and interpulse.) We even caught some giant pulses. The data and some more plots are available here.

    Apart from the pulsar observations, the students were also treated to lectures from Paul Boven and Vanessa Moss. We look forward to seeing some of these students back as colleagues when they have further progressed in their careers.


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  • 11/19/17--16:00: How to serve a dozen dishes
  • © ASTRON

    ALTA, The Apertif Long Term Archive system, has reached an important milestone. On 24 October, the hardware for the online storage system hosted in Dwingeloo was 'racked and stacked' in the basement of the ASTRON building. The core of the system is formed by two hundred and forty 10 terabyte hard disk drives which were one by one laid comfortably in their drawers, a dozen disks in each drawer. From these warm and safe beds, they will store and serve almost countless bits of scientific data to the astronomical community. The coming months the team will continue to work hard on the installation and configuration of the ALTA system and prepare it to serve the exquisite meals that the twelve Apertif dishes will bring us.

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    © Open University and Standard YouTube Licence

    ASTERICS and The Open University have created a short series of videos about collaborative science. The animations can be found on the OpenLearn channel of The Open University:

    Citizen Science (1/3) - https://youtu.be/fQqkbH4h6YM

    Messengers from Space (2/3) - https://youtu.be/VMxVkTyLnUE

    Multi-Messenger Science (3/3) - https://youtu.be/i2IpTuULJ1E

    "How do you become a scientist or contribute to a great discovery?

    We've all heard of Einstein, Newton and Hawking but did you know that even people without a PhD with some complicated sounding title can play an integral role in exploring and understanding our world?

    Citizen science gives everyone the opportunity to engage with cutting edge science and make a difference in the world, whether that be sifting through images from space, detecting intergalactic particles with your phone or investigating radio bursts.

    In these 3 short animations narrated by David Mitchell we look at the ways the general public of all ages are contributing to scientific discoveries and show you ways in which you can also help out." (OpenLearn from The Open University, YouTube.com)


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  • 11/21/17--16:00: Combining X-ray and HI
  • © Copyright: Radio spectrum of B2 0035+22 and NH-NHI plot: Ostorero et al. 2017 (ApJ, 839, 34; http://iopscience.iop.org/article/10.3847/1538-4357/aa8ef6; https://arxiv.org/abs/1709.08404); X-ray spectrum of PKS 0500+019: after Guainazzi et al. 2006 (A&A, 446, 87).

    The youngest radio galaxies - compact radio sources with a GHz-peaked spectrum (GPS) as well as those with Compact Symmetric Object (CSO) morphology - are fully contained in the inner regions (few thousand light years) of their host galaxies. They are in the process of expanding, and may grow grow to the size of an adult radio galaxy. They are complex systems where many different phenomena and different phases of the gas are present. Astronomers (including the authors of this Daily Image!) are still struggling to build a picture of the gaseous medium around these objects.

    Thanks to the sensitivity of the X-ray telescopes XMM-Newton and Chandra, more and more of such sources have been detected in the X-ray domain, suggesting the presence of large amounts of hot gas whose physical properties are still unknown. They are also often detected in HI absorption, suggesting that significant quantities of cold gas is present. Can these two phases of the gas coexist and be part of the same structure?

    Comparing the properties of the absorbing gas derived from spectral observations in the radio band (as shown in Fig. 1) with those of the absorbers detected in X-ray observations (as shown in Fig. 2) can help to statistically constrain the location of the absorbers, even with the use of low-angular-resolution observations. This, in turn, can shed light on the X-ray factory of these sources.

    To this aim, we investigated the relationship between radio (N_HI) and X-ray (N_H) column densities in a sample of GPS/CSOs, by combining literature data and new radio data we acquired with the WSRT through an observing plan conceived at ASTRON during a Helena Kluyver female visitor programme. The results are now presented in the paper Ostorero et al. 2017 (ApJ, 839, 34; https://arxiv.org/abs/1709.08404 ).

    We found that N_H and N_HI display a significant correlation (shown in Fig. 3 for the detections indicated with black symbols). This correlation tells us that GPS/CSOs with increasingly large X-ray absorption have an increasingly larger probability of being detected in HI absorption observations, and suggests that the gas responsible for the X-ray and radio absorption may be part of the same, possibly unsettled, hundred-parsec scale gas distribution. Such a scenario would imply that either parsec-scale dusty tori are not present in compact radio galaxies, or that the dominant contribution to the X-ray emission of GPS/CSOs does not originate in the accretion disc, but rather in the larger-scale jets or mini-lobes.


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    © Katharina Immer

    The life and death of high-mass stars are crucial for the evolution of galaxies, influencing their energy budgets via strong winds, jets, outflows and supernova explosions and enriching their interstellar media with heavy elements. Although of great importance, little is known about the formation of these high-mass stars since they are rarer than their low-mass counterparts, often located at larger distances and seldom form in isolation. In this talk, I take the opportunity to introduce my work by presenting four of my current and future projects: parallax and proper motion measurements in the framework of the BeSSeL survey, gas motion studies at the center of our Galaxy via VLBA maser observations, a line survey of the high-mass star forming complex Sgr B2(N) with the APEX telescope and a study of N2H+/CS ratios in W33 to identify possible chemical clocks.

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    © LOFAR Surveys Key Science Project

    The LOFAR Two-metre Sky Survey (LoTSS) is a deep 120-168 MHz imaging survey that will eventually cover the entire Northern sky. Each of the 3170 pointings will be observed for 8 hrs, which, at most declinations, is sufficient to produce ~6" resolution images with a sensitivity of ~100 micro-Jy/beam and accomplish the main scientific aims of the survey which includes studying magnetic fields and particle acceleration mechanisms in clusters of galaxies. In this talk I will overview the present status of the survey with a specific focus on galaxy cluster science.

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    © ASTRON/Heesen

    LOFAR was from the beginning expected to provide beautiful images of the diffuse and faint radio emission in radio galaxies. And indeed, it has kept this promise! In the image above, the red, twisting structure shows the radio emission traced by LOFAR at 145 MHz of a famous and well-studied radio galaxy known as 3C31. This is superposed to an optical image (white objects which trace regions with stars) of the field. Straightaway, one can see the huge extent of the radio emission compared to the optical size.

    The new LOFAR 145-MHz map shows that 3C 31 has a larger physical size than previously known, reaching 1.1 Mpc (4 million light-years!). This means 3C31 now falls in the class of giant radio galaxies.

    However, the 145-MHz LOFAR image is not only beautiful, but also very useful for understanding how such huge objects like 3C31 evolve. To do this, the LOFAR HBA image has been combined with LOFAR LBA data (60 MHz) and with observations by other radio telescopes (VLA, GMRT and WSRT). The analysis revealed that the plasma flow in the jets must decelerate while expanding into the intergalactic medium. This would suggest an age of the radio galaxy of about 190 Myr, implying supersonic expansion of the tails of plasma.

    The results are presented in Heesen, V. et al. 2017 “ LOFAR reveals the giant: a low-frequency radio continuum study of the outflow in the nearby FR I radio galaxy 3C 31”, published in Monthly Notices of the Royal Astronomical Society and available on https://arxiv.org/abs/1710.09746


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  • 11/26/17--16:00: Sunset
  • © Marjan Timmer

    An early sunset, seen from the office.

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    © AENEAS / IAA

    In October, the AENEAS (Advanced European Network of E-infrastructures for Astronomy with the SKA) project had the first all-hands meeting in Granada, Spain. The project runs for three years and started January 2017. The objective of the AENEAS project is to develop a concept and design for a distributed, federated European Science Data Centre (ESDC) to support the astronomical community in achieving the scientific goals of the Square Kilometre Array (SKA). AENEAS brings together all the European member states currently part of the SKA project as well as potential future EU SKA national partners, the SKA Organisation itself, and a larger group of international partners including the two host countries Australia and South Africa. Aeneas is funded by a EU H2020 grant.

    At the meeting first results were shown on requirements survey from astronomical users and potential resource providers (networking, storage and compute). Also initial testing of data transport methods were shown.

    The photo shows the participants of this meeting.

    More information on the meeting can be found at http://indico.astron.nl/event/AENEAS-Granada.


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  • 11/28/17--16:00: Combining X-ray and HI
  • © Copyright: Radio spectrum of B2 0035+22 and NH-NHI plot: Ostorero et al. 2017 (ApJ, 839, 34; http://iopscience.iop.org/article/10.3847/1538-4357/aa8ef6; https://arxiv.org/abs/1709.08404); X-ray spectrum of PKS 0500+019: after Guainazzi et al. 2006 (A&A, 446, 87).

    The youngest radio galaxies - compact radio sources with a GHz-peaked spectrum (GPS) as well as those with Compact Symmetric Object (CSO) morphology - are fully contained in the inner regions (few thousand light years) of their host galaxies. They are in the process of expanding, and may grow grow to the size of an adult radio galaxy. They are complex systems where many different phenomena and different phases of the gas are present. Astronomers (including the authors of this Daily Image!) are still struggling to build a picture of the gaseous medium around these objects.

    Thanks to the sensitivity of the X-ray telescopes XMM-Newton and Chandra, more and more of such sources have been detected in the X-ray domain, suggesting the presence of large amounts of hot gas whose physical properties are still unknown. They are also often detected in HI absorption, suggesting the presence of large amounts of gas whose physical properties are unknown.

    They are also often detected in HI absorption, suggesting that significant quantities of cold gas is present. Can these two absorbing gaseous media be part of the same structure?

    Comparing the properties of the absorbing gas derived from spectral observations in the radio band (as shown in Fig. 1) with those of the absorbers detected in X-ray observations (as shown in Fig. 2) can help to statistically constrain the location of the absorbers, even with the use of low-angular-resolution observations. This, in turn, can shed light on the X-ray factory of these sources.

    To this aim, we investigated the relationship between radio (N_HI) and X-ray (N_H) column densities in a sample of GPS/CSOs, by combining literature data and new radio data we acquired with the WSRT through an observing plan conceived at ASTRON during a Helena Kluyver female visitor programme. The results are now presented in the paper Ostorero et al. 2017 (ApJ, 839, 34; https://arxiv.org/abs/1709.08404 ).

    We found that N_H and N_HI display a significant correlation (shown in Fig. 3 for the detections indicated with black symbols). This correlation tells us that GPS/CSOs with increasingly large X-ray absorption have an increasingly larger probability of being detected in HI absorption observations, and suggests that the gas responsible for the X-ray and radio absorption may be part of the same, possibly unsettled, hundred-parsec scale gas distribution. Such a scenario would imply that either parsec-scale dusty tori are not present in compact radio galaxies, or that the dominant contribution to the X-ray emission of GPS/CSOs does not originate in the accretion disc, but rather in the larger-scale jets or mini-lobes.


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    © NSF/LIGO/Sonoma State University/A. Simonnet

    Since 2015, Advanced LIGO and Advanced Virgo have been detecting gravitational wave signals from binary black hole mergers. Here I focus on the recent discovery of a binary neutron star coalescence, which was also seen by electromagnetic means. Shortly after having been recorded by the gravitational wave detectors, it was observed as a gamma ray burst (GRB), corroborating the origin of short, hard GRBs as the results of binary neutron star mergers. Thanks to the concurrent observation of gravitational waves and gamma rays, the speed of gravity was establish to be equal to the speed of light to one part in 10^15. Due to the availability of three interferometers (the two LIGOs and Virgo), a reasonably accurate sky location could be provided, which enabled optical astronomers to find an afterglow to the event.

    This "kilonova", which emitted in X rays, ultraviolet, optical, infrared, and radio, had an evolving spectrum consistent with the creation of heavy elements, confirming the long held suspicion of their origin. The gravitational wave observation allowed for a measurement of tides on the neutron stars, which represents a first step towards constraining the elusive neutron star equation of state.

    Finally, compact binary mergers offer a novel way of measuring distances in the Universe, bypassing the "cosmic distance ladder". These observations open up a new field at the intersection of physics, astronomy, and cosmology.

    I will end with plans for future observations with novel gravitational wave observatories, such as LISA and Einstein Telescope.


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    © Grange, Shulevski, Molenaar

    As part of the European Open Science Cloud (EOSC) pilot project, the LOFAR prefactor pipeline has been reimplemented in the Common Workflow Language (CWL). This is a language in which workflows and pipelines can be described independently of the software system used to run them.

    The implementation was written by Gijs Molenaar. The goal of the project is to demonstrate how we could make our pipelines available for non-expert users, for example in the European Open Science Cloud. Using a standard like CWL to describe pipelines offers the opportunity to use different methods to manage running pipelines and workflows by any user, while making it easier to adapt the pipeline for expert users.

    The image shows a visualisation of the first part of the prefactor pipeline - which takes care of calibration using a calibrator source, simplified and based on the pipeline written in CWL and parsed with the standard CWL viewer.

    The time runs from top to bottom. The blue blocks represent the pipeline in- and outputs. Each block is either a file or a configurable value. Each yellow block represents one processing step and each arrow in or out of the box corresponds to an in- or output data product of that box.

    For more information, please visit (one of) the following pages:

    the cwl pipeline

    The same pipeline in the standard CWL viewer

    CWL

    EOSC pilot


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  • 12/03/17--16:00: First Light!
  • © astropix.nl

    After nearly a year of building and testing, first light was finally achieved at my new remote observatory. An animation of the assembly can be seen in an earlier DailyImage:

    http://www.astron.nl/dailyimage/index.html?main.php?date=20170613

    Last week, the weather was good enough for a few hours to allow the first remote test. This image of NGC891 is a combination of 10 integrations of 10 minutes, 1 each for RGB and 7 for Luminance. The signal to noise ratio is already better than that of a 4.5 hour integration at the telescope's previous location in Beilen!

    After the test, it started raining again, so it was a relief to watch the dome shutter close after the test. Otherwise a nightly 110km drive to Germany would have been needed to save the observatory.

    There is still some distortion in the star images due to a misalignment of the camera (chip not at right angles to the optical axis of the telescope), but that has been corrected last week.

    Now confidence is building to allow the observatory to operate fully autonomous, controlled by a software package called ACP Scheduler.


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    © ASTRON

    Place holder

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    © AENEAS / IAA

    In October, the AENEAS (Advanced European Network of E-infrastructures for Astronomy with the SKA) project had the first all-hands meeting in Granada, Spain. The project runs for three years and started January 2017. The objective of the AENEAS project is to develop a concept and design for a distributed, federated European Science Data Centre (ESDC) to support the astronomical community in achieving the scientific goals of the Square Kilometre Array (SKA). AENEAS brings together all the European member states currently part of the SKA project as well as potential future EU SKA national partners, the SKA Organisation itself, and a larger group of international partners including the two host countries Australia and South Africa. Aeneas is funded by a EU H2020 grant.

    At the meeting first results were shown on requirements survey from astronomical users and potential resource providers (networking, storage and compute). Also initial testing of data transport methods were shown.

    The photo shows the participants of this meeting.

    More information on the meeting can be found at http://indico.astron.nl/event/AENEAS-Granada.


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    © Cristiana Spingola

    On November 22-23 JIVE hosted a scaled down version of the first successful CASA VLBI workshop held in October. This smaller version catered to Dutch and local astronomers, taught them the ropes of processing VLBI data in CASA, and served to identify problems and missing functionality. A major milestone was reached: Cristiana Spingola (Kapteyn Institute, University of Groningen) produced the first image of a VLBI science target which was fully processed with the new CASA tools.

    The image is of a gravitational lens with emission from four images of the lensed source (A through D) and from the lensing galaxy. The data were obtained with the VLBA at L-band, in a 12 hour run. The data was amplitude calibrated, phase calibrated with the new fringe fitter, imaged and cleaned fully in CASA.

    The new CASA VLBI tools consist of a newly implemented fringe fitting task, upgrades of existing tasks to handle VLBI data, and a collection of scripts to ensure proper handling and import of the meta-data. The new fringefit task is based on the AIPS FRING task. The development of the CASA VLBI tools was started for the ERC BlackHoleCam project, with financial support from SKA-NL. It currently continues under the RadioNet RINGS JRA, with help from the CASA developers at NRAO, Socorro.

    Further testing and development is still ongoing, e.g. prototyping a dispersive delay fit has started, and a next step will be the handling of discontinuous frequency bands. The current plan is to provide a beta-version of the VLBI tools in CASA 5.3.


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  • 12/04/17--16:00: An Influential Friend
  • © Madroon Community Consultants (MCC)

    It is of course a pity when a valuable colleague leaves ASTRON for greener pastures. But the upside is that we gain an influential friend somewhere else in our small radio-astronomical world.

    The image shows Prof Oleg Smirnov, surrounded by members of the South African Radio Astronomy Techniques and Technology group (RATT). It was taken in Cape Town, where many of his students participated in the yearly African SKA Bursary Conference. The screen in the centre shows the rest of his students at Rhodes University in Grahamstown.

    Your editor has been privileged to participate in the lively activities of Oleg's group in various ways. First there was a visit by Thorsten Ensslin and his students from MPI Garching, to discuss 4th Generation Calibration (4GC). Then there was a Meerkat Data Processing workshop, where the details of the various Large Survey Programs were discussed. Obviously, the RATT software played an important role. After that, at the Bursary Conference, the many students and young postdocs connected with the African SKA effort got a chance to present their work and discuss it with each other. And finally to Grahamstown for a Busy Week. All very stimulating and impressive.


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    © Nik Szymanek and Ian King

    WEAVE is the next-generation wide-field survey facility for the William Herschel Telescope (WHT). WEAVE will provide the instrument required for full scientific exploitation of the Gaia, LOFAR, and APERTIF surveys in the Northern Hemisphere. WEAVE is a multi-object and multi-integral-field-unit (IFU) facility utilizing a large, new 2-degree-diameter prime focus corrector at the WHT with a pick-and-place fibre positioner system hosting nearly 1000 multi-object fibres or 20 mini-IFUs for each observation, or a single wide-field IFU. The fibres are fed into a dual-beam spectrograph located in the GHRIL enclosure on the WHT's Nasmyth platform. The spectrograph - built by NOVA in Dwingeloo - records nearly 1000 spectra simultaneously at a resolution of R~5000 over an instantenous wavelength range of 366-959 nm or at a resolution of R~20000 over two more-limited wavelength ranges. WEAVE will be on sky by early 2019 to provide complete phase-space coordinates of more than 5 million stars in the northern sky selected with ESO's Gaia satellite, distances and properties of galaxies selected from the low-frequency radio-wave surveys being conducted with LOFAR, "three-dimensional" spectroscopy of galaxies selected from surveys using the new Apertif focal plane array at WSRT, and deep surveys of galaxy clusters and moderate-redshift galaxies.

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    © Astron

    The heart of the SKA LOW correlator, in development at CSIRO and ASTRON, is the Gemini LRU. To find the best cooling solution for the Xilinx FPGA (Field Programmable Gate Array) on Gemini, the DESP group is working together with the Mechanical group.

    The image shows Sjouke Kuidersma testing a water block. For the measurements, Sjouke has made a setup wherein 130W can be generated and cooled by different water blocks. By measuring the temperature of the heat-plate, the liquid in- and outlet, and the liquid flow, the efficiency of the water block can be calculated. By carefully designing the pattern of the channel on the inside of the block, the optimal heat transfer from the FPGA to the liquid can be found.


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  • 12/10/17--16:00: One of the Apertif heroes
  • © ASTRON

    Imagine: you have been on a business trip to Australia and a few days after your return to the Netherlands, you are still suffering from a jetlag. In that case you decide to get up early and to start your working day at ASTRON at a time only a few people will be there, too.

    If you were at ASTRON on the early morning of November 29th (7.00 a.m.) you would have noticed that Boudewijn already started his highly appreciated work for Apertif. On the picture, it may be a little difficult to notice but in the middle of the Apertif room at the first floor you see Boudewijn working on the commissioning.

    I hope you already have recovered from your jetlag, Boudewijn?


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