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Articles on this Page
- 10/01/15--17:00: _ASTRON/JIVE Open Da...
- 10/13/15--17:00: _Calibratability fun...
- 10/12/15--17:00: _Remnant radio galax...
- 10/11/15--17:00: _Excellent AAVS1 LIN...
- 10/08/15--17:00: _Sorama visiting Astron
- 10/07/15--17:00: _Today's Colloquium:...
- 10/14/15--17:00: _WEAVE Spectrograph ...
- 10/15/15--17:00: _The spectacular hal...
- 10/18/15--17:00: _ASTRON/JIVE Open Da...
- 10/19/15--17:00: _Klokhuis "Universe"...
- 10/20/15--17:00: _Goodbye to Rob (and...
- 10/21/15--17:00: _Real-time recording...
- 10/22/15--17:00: _The Existence of Ex...
- 10/25/15--17:00: _E-ELT from LEGO bricks
- 10/24/15--17:00: _Heel Nederland Kijk...
- 10/26/15--17:00: _searching for cool ...
- 10/27/15--17:00: _LOBOS mini survey -...
- 10/29/15--17:00: _Alternative uses fo...
- 10/28/15--17:00: _Today's Colloquium:...
- 10/31/15--17:00: _Bus of stiltemeter ...
- 10/01/15--17:00: ASTRON/JIVE Open Day (Dwingeloo) and LofarDag (Exloo)
- 10/13/15--17:00: Calibratability fundamentals (4): psf sidelobe noise in LOFAR
- 10/12/15--17:00: Remnant radio galaxies in the LOFAR sky
- 10/11/15--17:00: Excellent AAVS1 LINFRA progress in Australia
- A run-in trench was dug outside the CPF compound to facilitate the introduction of the AAVS1 trunk fibre cables into the existing underground fibre routing infrastructure.
- A conduit was installed under the main MRO access road to create a crossing point for the AAVS1 trunk fibre cables that are running from the AAVS1 site to the CPF.
The next step will be fibre deployment. Currently we are investigating whether a commercial contractor should be entrusted with this, or whether it is feasible for the local LINFRA team to do it themselves.
- 10/08/15--17:00: Sorama visiting Astron
- 10/14/15--17:00: WEAVE Spectrograph Production started
- 10/15/15--17:00: The spectacular halos of spiral galaxies
- 10/18/15--17:00: ASTRON/JIVE Open Day great success!
- 10/19/15--17:00: Klokhuis "Universe" series: every Wednesday in November
- 10/20/15--17:00: Goodbye to Rob (and Janni) Millenaar
- 10/21/15--17:00: Real-time recording of IVS R1 observations
- 10/25/15--17:00: E-ELT from LEGO bricks
- 10/24/15--17:00: Heel Nederland Kijkt Sterren 2015
- 10/26/15--17:00: searching for cool neutral meduim in UCHVCs
- 10/27/15--17:00: LOBOS mini survey - challenging the LOFAR system
- 10/29/15--17:00: Alternative uses for the LOFAR LBA
- 10/28/15--17:00: Today's Colloquium: A Multi-Wavelength View of Nearby Galaxies
- 10/31/15--17:00: Bus of stiltemeter put schools to work
© ASTRONASTRON and JIVE Open Day
On Sunday 4 October, from 12:00 to 17:00, at the Dwingeloo Observatory, everybody will be welcomed again in the world of Radio Astronomy!
There will be a wide range of activities, from making pulsars to treasure hunting! Our astronomers will answer almost all your questions about Radio Astronomy and the Universe.
The 25m Dwingeloo Radio telescope will be open to the public, and CAMRAS will organise various activities around it.
In addition, on the same day, the LofarTafel will organise its own Open Day at LOFAR, the largest radio telescope in the world, in Exloo. This will also be from 12:00 to 17:00.
As in Dwingeloo, there will be a lot of activities in Exloo. Not only will the LOFAR telescope be explained, but also the Nature surrounding it.
Do you find it hard to make a choice between the two Open Days? Why not go to both? It's only 30 minutes apart.
See you on Sunday!
© ASTRONIn our previous image in this series, we demonstrated the importance of low psf sidelobes to prevent weak sources from drowning in the psf sidelobe noise (PSN) generated by the plethora of other weak sources in the image. This immediately begs the question: how low should our psf sidelobes be? Today, we address this question for LOFAR after 300 hours of integration with 1 MHz bandwidth, typical values for a single frequency slice of an EoR observation.
The curves shown in the image above show the PSN levels as function of the flux of the brightest unsubtracted source (we assume that all brighter sources have been properly removed, including their sidelobes, by source subtraction) for different values for the RMS psf sidelobe level (SLL). Ideally, we want the PSN to be lower than the thermal noise in our image, i.e., we want to get the PSN below the horizontal line marked with "1-sigma noise level".
As long as the PSN is higher than the thermal noise level, we need more source subtractions to remove more psf sidelobe responses from the image. Unfortunately, we cannot continue doing this forever, since we need to be able to properly estimate flux and position of the brightest source in the image to subtract it. Since PSN and calibration errors may add to the effective noise in the image, we assumed a 10-sigma thermal detection limit (indicated by the vertical line) to ensure at least a 5-sigma detection of the brightest source assuming that the effective noise is no more than two times the thermal noise in the image. Since we cannot work our way down the curves by source subtractions further than this limit, this means that the curves have to get below the thermal noise level before hitting the vertical line. In other words, the RMS psf SLL needs to be low enough that the corresponding curve goes through the rectangle in the bottom right of the plot. The relevant parts of the curves are indicated with a thick line.
The curves are derived from observed source statistics while the density of sources below 0.08 mJy are extrapolations. For the LOFAR EoR regime we need to subtract sources weaker than the knee around 2 mJy where the RMS decays slowly and the number of sources increases steeply. As a result source finding and subtracting is far more tedious than at higher fluxes.
From this analysis, we can conclude that LOFAR needs an RMS psf SLL of at most -36 dB, and then (as we will see in a future image) requires many more than 20,000 subtractions. This requires a nicely filled visibility plane, which LOFAR can only provide in the core area. Fortunately, that is the part of the array that will be used for the EoR analysis. If the RMS psf SLL can be lowered further by appropriate weighting of the visibility data, the PSN gets below the thermal noise after fewer source subtractions. Fewer source subtraction provide a significant computational benefit as will be demonstrated in a future image.
© ASTRON - LOFARThe active phase of the radio AGN can last several tens of Myr after which the nuclear activity stops and the source starts to fade away. In this period, that we term the "remnant" phase, the core and the jets disappear and only low-surface brightness lobes remain visible radiating their energy away. The spectral study of this ageing plasma is of undoubted importance if we want to constrain the timescale of activity of radio galaxies.
Because of preferential cooling of high-energy electrons, the synchrotron spectrum of ageing plasma develops an exponential break at high frequency. The particles also suffer adiabatic losses, which can cause the fossil lobes to fade rapidly. This makes remnant AGNs very rare and difficult to identify and therefore their luminosity evolution remains largely unconstrained.
Thanks to its high sensitivity at MHz-frequency and the variety of spatial resolutions, LOFAR has initiated a new era in the search for these objects. BLOB1 is a 700-kpc remnant radio galaxy that we serendipitously discovered with LOFAR at 150 MHz. By combining LOFAR data with follow-up Westerbork observations and archival data at higher frequencies we investigated the source morphology and the spectral properties from 116 to 4850 MHz.
Our analysis suggests that the nuclear engine is currently switched off or, at most, active at a very low-power state. The host galaxy (z=0.051) is interestingly located outside a cluster and it is currently interacting with a companion galaxy. This interaction may have played a role in triggering and/or shut down the radio jets.
Unlike the majority of the previously identified remnant sources, BLOB1 does not have a very steep spectrum at low frequency. This result has also significant implications in the systematic selection of remnants AGNs in the LOFAR Tier-1 survey that we are now starting.
You can read more details about these findings in a paper now accepted for publication in Astronomy & Astrophysics: "LOFAR discovery of a 700-kpc remnant radio galaxy at low redshift" by M. Brienza, L. Godfrey, R. Morganti et al. (as part of the LOFAR survey KSP)
© ICRAR/CurtinThe Local Infrastructure work package (LINFRA, lead: ICRAR/Curtin) of the SKA Low Frequency Aperture Array (LFAA) has been making impressive progress on several fronts. This daily image reports on the trunk fiberoptic cable installation.
As the AAVS1 system will use RF over Fibre (RFoF) technology, we need to make sure that the antennas are connected via a stable fibre link to the digitisers in the Central Processing Facility on the MRO site (which also holds the ASKAP and MWA processing racks)
As can be seen on the pictures, the route between the AAVS1 station locations and the CPF offers several challenges:
© Sorama B.V.Sorama will be visiting ASTRON today. For a brief introduction of Sorama see this previous Daily Image. Current topics within Sorama are:
Smart City Audio Sensing
Sorama′s latest developments in smart-city applications include the new Beamforming 64-channel microphone-arrays Listener64. The new array boasts the state of the art Xilinx Zynq platform which includes an FPGA with an integrated dual-core ARM processor. The first stage in the audio processing, the decimation of the sigma-delta signals, is performed in the FPGA. The resulting audio signals are transferred over a single gigabit-Ethernet connection, using custom software running in the on-board Linux environment. Multiple Listener64′s can be coupled together using Ethernet synchronisation protocols such as NTP (Network Time Protocol) for millisecond synchronisation accuracy, or even PTP (Precision Time Protocol) for sample-level synchronisation accuracy. This highly accurate synchronisation between the microphone-arrays, allow for the construction of arbitrarily sized beamforming arrays.
Sorama at Eindhoven light festival GLOW2015
Two years ago, Sorama and the TU Eindhoven teamed up to develop one of the most popular attractions at an alternative route of the Eindhoven light festival. Waves, is how this piece of light art is called, is an interactive visualisation of the sound produced by visitors who walk through the setup. This piece of light art has returned from an international tour to Eindhoven for GLOW2015. Whistle, clap, shout and sing and see how the sounds you produce, create different patterns.
The Sorama Cam64 is the first affordable sound measurement instrument with an astonishing 64 channels. It uses the microphone which are also integrated in high-end smartphones.
Compared to a regular Sound Level meter the 64 channels improve the Signal to Noise ratio and allow to localise sound sources in 3D. With this device it is possible to see the spectrum with an incredible accuracy.
© Carl FerkinhoffThis year marks the 40th anniversary of the first far-infrared fine-structure line detection, the [OIII] 88 micron line by the NASA Learjet in 1975. Additional pioneering work through the early 90's revealed the astrophysical importance of the full suite of far-IR lines and demonstrated their power as probes of the physics conditions in the interstellar medium (ISM). While inaccessible from ground at their rest wavelengths, they begin falling into the short submillimeter telluric-windows (~200 to 500 micron) from high-z systems at z~1.
Over the past one and half decades ISO, Herschel and now SOFIA have provided detailed studies of the lines in the local universe while ground based observations made the first detections of the lines from the early universe. These first detections in the high-z universe demonstrated the lines' utility for studying high redshift systems. This includes the ability to constrain the size of star-forming regions, quantity of ionized gas, age of the starburst, and gas phase abundances to name a few. Now in the ALMA era, studies using the fine-structure lines have the potential to dramatically increase our understanding of early galaxies, both in their formation and evolution. Much work is required, however, to fully realize this potential.
In this talk I will seek to answer two questions in regards to the far-IR fine-structure lines: Where are we and where do we need to go? In answering these questions I will summarize the current state of fine-structure line studies--both locally and in the distant universe--while highlighting some of my recent work with ALMA cycle-0 observations of the [NII] 122 micron line and an explanation the "[CII] deficit".
In the last part of the talk I will discuss future multi-wavelength studies, such as radio continuum observations, that will help realize the full scientific potential of the FIR fine-structure lines for studying the early universe.
© NOVA Optical IR Instrumentation Group, Rijksuniversiteit Groningen, Isaac Newton Group of Telescopes (ING)The picture shows a part for the WEAVE Spectrogaph. The mechanical production is started and this is one of the first part. It is a mechanical holder for a VPH (Volume Phased Hologram) Grating. A VPH-Grating acts like a prism, but exist of a flat plate with vertical lines and creates a large dispersion. The part is measured at our CMM and correct. Next step is a black coating.
The first VPH-Grating will be delivered by INAF (Italy) early next year. Also optics and electronics production is started and more pictures to come.
WEAVE is a new multi-object survey spectrograph for the 4.2-m William Herschel Telescope (WHT) at the Observatorio del Roque de los Muchachos, on La Palma in the Canary Islands.
For more information see:
The Spectrograph team is a collaboration between NOVA Optical IR Instrumentation Group at ASTRON (Optomechanical Design and Production, Management), RAL in the UK (Optical Design), JMU Liverpool in the UK (Detectors), IAC at Tenerife Spain (Control Hardware), ING at La Palma Spain (Control Software), INAF Italy (VPH Gratings and Control Software).
Dutch PI is Scott Trager, Kapteyn Astronomical Institute, RUG.
© Jayanne English and the CHANG-ES collaborationThe "Continuum Halos in Nearby Galaxies - an EVLA Survey" (CHANG-ES) project has been highlighted here twicebefore. Now, this detailed study of edge-on spiral galaxies has revealed that "halos" of cosmic rays and magnetic fields above and below the galaxies' disks are much more common than previously thought.
The CHANG-ES collaboration is an international team of astronomers including ASTRON scientist George Heald. The survey made use of the Karl G. Jansky Very Large Array (VLA) to study 35 edge-on spiral galaxies at distances from 11 million to 137 million light-years from Earth. The study took advantage of the ability of the VLA, following completion of a decade-long upgrade project, to detect radio emission much fainter than previously possible.
Spiral galaxies like our own Milky Way have the vast majority of their stars, gas, and dust in a flat, rotating disk with spiral arms. Most of the light and radio waves seen with telescopes come from objects in that disk, although we know that careful observations with the venerable WSRT can reveal the low-density gaseous outskirts of a broad range of galaxies.
To see how extensive a "typical" radio continuum halo is, the CHANG-ES team scaled their images of 30 of the galaxies to the same diameter, then Jayanne English, of the University of Manitoba in Canada and a previous honored guest at ASTRON, combined them into a single image which is highlighted as today's Daily Image. The result, said project PI Judith Irwin (from Queen's University in Canada), is "a spectacular image showing that cosmic rays and magnetic fields not only permeate the galaxy disk itself, but extend far above and below the disk."
The CHANG-ES collaboration is now also making their first batch of survey images available online for other researchers. The data are available at this website.
The NRAO has released a press release on this spectacular image, and it can be found here.
© ASTRONDaily image
ASTRON/JIVE Open Day great success!
Now everything is finally behind us, we have had some time to look back at the ASTRON/ JIVE open day.
On 4 October everyone was welcome at ASTRON & JIVE to take a closer look into radio astronomy and all related organisations and projects and learn a great deal. From 12.00h till 17.00h many employees of ASTRON, JIVE and NOVA helped explain the wonders of the world of radio astronomy and what JIVE, NOVA and ASTRON do.
An astonishing, close to, 3000 people visited the ASTRON/JIVE Open Day, with lots of activities for the kids as well as interesting information for adults. An action-packed day with fun experiments like making your own exploded star, shooting a rocket in the sky and coding a Minecraft figure. Lectures were given on various topics. All over the building and outside, demonstrations took place. NOVA, JIVE and DOME set up booths to provide information and demonstrations. Huge tents provided a place for the crafting workshops. Kids made their own supercool aliens and pulsars or they soldered a computer board. The winners of the make your own alien competition have been announced. You can check it here: http://www.astron.nl/winnaars-maak-een-alien-bekend (Dutch).
The shows consisted of a Teslacoil, the comets show, the JIVE correlator tour and the photonics lab. The projects Dome and SKA were also present at the open day. In short: too much to mention. Next time just drop by and see for yourself.
© NTRThe Dutch-spoken kids show Klokhuis will feature a "Universe" series that airs starting 4 November, for 7 Wednesdays in row, on NPO 3, 18u25. Nienke and I put on our space suits and flew through the Solar System all the way out to the edge of the visible Universe. Recorded at Westerbork and in front of the studio green screen. After TV, the episodes will appear on Uitzending Gemist and the Klokhuis web site.
The series will premiere on Cinekid, the youth Film en TV Festival, on Wed Oct 21, in Amsterdam. We will show two episodes, plus two demonstrations and a game show by the presenter and myself. All in Dutch. In the autumn school break, so you're welcome to come out.
© ASTRONThis special AJDI supersedes the regular one for a few hours. However, do not miss the televison program Heel Nederland kijkt Sterren tonight, at 21:25 on NPO1
Today we mark the official retirement of Rob Millenaar, who has devoted more than 40 years to helping ASTRON to fulfill its Mission Statement. Of course he will not really disappear, since he has been snached up by our strategic partner in South Africa to work towards the giant SKA radio telescope for a few years.
The picture depicts just a minute slice trough his long career of building cutting-edge instruments for radio astronomy. It shows Rob in the early 80's (in his early 30's), working on a multiplexer of the Digital Continuum Backend (DCB) in the shielded environment at the Westerbork Observatory. In this context he contributed to the world's first small-sized Printed Circuit Board!
He obvious enjoyed his work, first on essentially all correlators for the WSRT, and later also on the first autocorrelator for the JCMT on Mauna Kea. He actually lived on Hawaii for several years to commission various instruments.
During the last decade or so he greatly contributed to the international SKA project, first by assessing the radiofrequency (interference) environment at putative SKA locations around the globe, and then to figure out the optimal configuration of the array of SKA stations at the chosen sites in Australia and South Africa.
In his spare time he not only pursued some unusual hobbies like sky-diving and flying gliders, but he did it at an unusual level. In sky-diving he participated in the more complicated art of formation flying, and he competed in gliding races at national level. (His son Peter, starting early, rose to dizzying heigths in international gliding, using the family glider to great effect).
Of course all this frenetic activity was only possible because the home fires were kept burning by his lovely Janni, who also worked for ASTRON (then SRZM/NFRA) as Office Manager in the 70's and 80's.
Thank you, Rob and Janni, for all you have done for the ASTRON family, and we wish you all the best and a great time in South Africa!
© Simone Bernhart (Institute of Geodesy and Geoinformation, Bonn University), Stuart Weston (Auckland University of Technology) and Harro Verkouter (JIVE)The International VLBI Service (IVS) conducts bi-weekly global geodetic VLBI observations (simultaneous S and X band) to measure the earth orientation parameters (EOPs). The recorded data of the Monday rapid sessions (R1) are uploaded to Bonn (*) for correlation after the observations have finished. The aim is timely distribution of post-correlation analysis results, e.g. the group delay.
In an attempt to shorten the time-to-product, first steps were undertaken to make a real-time copy of the 12m Warkworth (New Zealand) dish's data (see image), as it is being recorded on its Mark5 VLBI data recorder. The copy is transferred in real-time over high-speed international research and education networks (REANNZ of New Zealand and GEANT in Europe) onto servers in Bonn (Germany). This recording mode is in direct contrast to e-VLBI, where, if something goes awry with the real-time transfer, science data is immediately lost. In this mode the recorded science data can always be re-transferred at a later time.
To support this mode a program to modify an R1's observing schedule was written. It inserts commands to set-up and tear-down the real-time transfer at both ends (e.g. opening a file with the correct scan name in Bonn, configuring the network, starting to transmit when the recording starts etc). Once modified the schedule runs autonomously.
On August 24th/25th R1709 was observed in this mode at 256 Mbps data rate (see network throughput plot). The recorded data was transferred separately after the observation, to be able to compare the real-time data with the recorded data. The 'fourfit' program was run on correlations with both data sets and found the same group delay of 120ps, see the attached plots.
This special observing mode, where a copy of the data a Mark5 recorder can be siphoned off and transferred in parallel, is made possible by software created at JIVE. The 'jive5ab' software, produced under the succesful EXPReS and NEXPReS projects(**), exploits functionality offered by the MIT Haystack Mark5 VLBI recorder hardware. Having its roots in e-VLBI it implements several network protocols for real-time data transfer. In this case the UDT protocol was used: a reliable protocol over UDP/IPv4.
(*) Thursday's R4 session is uploaded to and correlated at USNO's Washington D.C. correlator facility
(**) European Commission funded projects to make e-VLBI a production observing mode
© Andre van EsOn October 8th, Andre van Es graduated as Master of Philosophy at the University of Groningen, with a thesis titled: The Existence of Extra-Terrestrial Intelligence, The Idea Behind SETI. Andre pursued his Philosophy degree in his spare time while working for ASTRON and now for the SKA Office at Jodrell Bank (UK).
Inspired by Michael Garrett, Andre executed an impressive literature study on the concept of extra-terrestrial intelligence throughout written history, leading to an analysis of the basis for the famous Drake Equation. Andre challenges the logic of this equation: Since determinism is a fallacy, it is important to search for better models, especially for the sociological and cultural factors of the equation.
He concludes that The future of SETI is not to intensify the search, but it should be turned into an actual research discipline, where optimal use is made of synergies between different disciplines that influence the parameters of the Drake Equation. As SETI spans the whole of science from astronomy, biology, chemistry, mathematics, technology, philosophy, history, sociology and art, it is the ideal scientific endeavor for a synergetic approach.
In response to a question about what this means for our SKA plans, Andre commented that future telescopes should definitely pursue the search for the unknown.
The picture shows Andre's tutors Dr. F.A. Keijzer and Prof. B.P. Kooij. Prof. Mike Garrett completed the examination committee.
© NOVALEGO is a great tool to attract the attention of a broad audience. This Picture of the Day shows ESO's European Extremely Large Telescope (E-ELT), as built entirely from LEGO bricks. It is on a 1:150 scale, contains over 5200 pieces and includes all the 798 mirror segments exactly as the real one. The model was designed by NOVA-and-University Leiden astronomer Frans Snik, who used dedicated LEGO CAD software for designing it.
Six astronomical instrument fanatics needed altogether 10 hours for assembling it. The model includes all proposed instruments for the E-ELT, among them MICADO and METIS for which the NOVA Optical IR Instrumentation Group will develop important contributions (of course related to the real telescope). The very first model built by Snik was donated to ESO's Director General Tim de Zeeuw, and stands now in his office.
The shown model of the E-ELT was on display at the ASTRON open day early this month, generating much excitement among the younger visitors (and their parents). Also recently, the same model played a dominant role at the signing of the NOVA-ESO agreement for the construction of the METIS instrument, of which NOVA will be the PI institute, on September 28 in Leiden.
For LEGO freaks: an instruction how to build this telescope yourself, together with a part list, can be downloaded from the ESO website: http://www.eso.org/public/announcements/ann14071/
Construction of the full size E-ELT started in June 2014, in the Chilean Atacama desert, and will take about 10 years for completion.
Photo courtesy Jan Noordam & ASTRON
© ASTRON / NPO / MaxTonight at 21:25, "Heel Nederland Kijkt Sterren" on NPO1 will be one the shows to open the new TV season, which traditionally starts in Fall. As the name suggests, this show aims to inform the general Dutch audience. It is positioned to be self-contained, without needing much existing knowledge to still be enjoyable to watch. Dutchies may sense the link to shows like "Heel Holland Bakt", which indeed has some overlap in editorial crew (!).
In 2014, HNKS was broadcast live from Westerbork, and, thanks to the hard work of many at ASTRON, drew a amazing 1.3 million viewers. This year the show comes live from the Oude Sterrenwacht in Leiden, with a report from LOFAR. That report was recorded on a very wet day but came out well. Note, in the image top-left, the simulated mobile app that shows the sky as LOFAR sees it, through the clouds that hide it from our eyes in optical. Bottom right shows a demonstration on distance and look-back time. The report uses great images from Sarod Yatawatta, John McKean & Michael Wise, and Francesco De Gasperin. Thanks to you all for taking the effort to convert your science image into a pretty picture; other readers of this daily image are encouraged to post their best LOFAR/WSRT/.. images on the ASTRON pretty astronomical picture page, and reach an audience of over a million.
© Bahar BidaranThe lack of observed dwarf galaxies compared to predictions for numerous low-mass dark matter halos is a well-known cosmological problem, often referred to as the missing satellites problem. Ultra-compact high velocity clouds (UCHVCs) identified in the ALFALFA HI survey have been presented as potential low mass galaxy candidates in the Local Group due to their single-dish HI properties. We observed some of the UCHVCs with the Westerbork Synthesis Radio Telescope (WSRT) to understand them as potential galaxies. By using the HI kinematics from the WSRT observations, we can constrain the underlying mass distribution, addressing the question of whether these systems represent gas in dark matter halos. We can also study the state of the interstellar medium (ISM) on spatially resolved scales, including searching for the presence of a cool neutral medium (CNM) component, addressing the potential of these systems to form stars and be recognized as ' bona-fid ' galaxies.
To accomplish this aim we have written a code to retrieve kinematical information by fitting both single and double component Gaussians to the resolved HI gas. As a test case, we focused on AGC 249525, which is interesting for showing ordered velocity motion, similar to another good galaxy candidate AGC 198606 (see Daily Image from 19-12-2014). We produced WSRT HI data cube at a resolution of 210" (matched to the Arecibo beam) with a velocity resolution of 4 km/s. We fit Gaussians to the data cube, to produce velocity fields (picture on the left). This velocity field reveals ordered velocity motion with a gradient of ~15 km/s. This can be interpreted as rotation with amplitude of ~12 km/s.
In addition, studying the velocity dispersion on spatially resolved scales allows us to understand the star formation (SF) potential of these systems. The velocity dispersion traces the temperature structure of the gas. We are searching for a cool neutral medium (CNM) component that has the potential to collapse and form stars. A single Gaussian fit (or traditional moment 2 map) reveals no evidence for a CNM component (picture on the right). We are involved in an ongoing work to fit 2 Gaussian components to search robustly for a CNM component.
© LOFAR Radio ObservatoryLOBOS is a LOFAR commissioning project (PI N. Jackson) meant to search for calibrator sources for the HBA observations using the International stations. It is a mini survey that plans to cover in a relatively short amount of time (96 hours) approximately 40000 pointings. The amount of data products archived in the LTA will reach about 1.5 million.
This project has challenged the LOFAR system in various aspects. An ad-hoc script was developed to automatically generate the settings for observations and processing in order to optimise the telescope time. This resulted in a single file containing all the settings for 24 hours of observation and proved too big to be handled by the specification system. Therefore it was split into separate blocks of 6 hours each. The observations were scheduled and processed without particular problems, but the process of ingesting the data into the LTA was more difficult.
The top left corner of the image shows a screenshot of the one LOBOS 24 hours run as seen by the Control Room Scheduling system. The LOBOS data products are made of many small files, which adds substantial overheads to the ingest process. The ingest job could not be initiated once per block due to a safety limitation of about 50.000 files per ingest. This meant that each 6-hour block had to be further split into at least 4 blocks. Since the LTA-LOFAR system often experiences instability over long periods of time due to maintenance, failing network connections or other spurious problems, the ingest process required way more than 4 attempts to finish the ingest.
The right part of the image shows a screenshot of Mom with the ingest tentatives. The data of only 48 hours represent a significant fraction of the small size LTA data products if we consider that this a single project (96 hours) while the rest includes the total amount of data products present in the LTA since the beginning of LOFAR Cycle0 (from December 2012 until now).
In the bottom left corner of the image, two istograms present the total number of the LTA data products before (left panel) and after LOBOS (right panel).
© 'This image shows an alternative use for decommissioned LBA antennas.
© Liese van ZeeI will present the results of several recent studies investigating the gaseous and stellar distributions of nearby galaxies, utilizing observations obtained from the ultraviolet to the radio. The primary focus of my talk will be results from the Extended Disk Galaxy Exploration Science (EDGES) Survey, a deep imaging survey with the Spitzer Space Telescope that was designed to identify and measure the faint stellar populations around nearby galaxies.
In addition to the exquisite deep near-infrared data set, we have obtained complementary optical, ultraviolet, and radio observations of various sub-sets of the EDGES sample in order to explore the growth and stability of nearby galaxies.
I will highlight the results of these studies and discuss the implications for the formation and evolution of structure in a hierarchical universe.
© Dagmar Bij de Vaate"Pimp the bus", a creative contest
Hidden deep in the forests of the Dwingelderveld stands the bus of Fryqens Zonderling, the "stiltemeter" from "Het logboek". Through years of standstill the bus has lost many of its old glory. The colours are faded by the sun and downpours have left their marks. About time to pimp the bus!
Children's book week 2015 "Raar Maar Waar" was marked by inventions, technology and science. "Strange But True" that is exactly the theme of the adventure that Anke den Duyn has written last year to arouse children's interest in radio astronomy. Time for a creative contest!
Many teachers were pleasantly surprised by this challenge and activated their pupils to create a colourful bus, using pencils, old packaging materials or fabrics.
Also a number of libraries in Drenthe has paid attention to the contest and furnished a collection point within its walls. Four weeks later pimped buses have arrived Lhee from all directions.
It will be a difficult job for the jury to select the most original and inventive vehicle. This Sunday we'll know the winner of the "VIP Logboek Adventure". This lucky kid will follow the track of Luna, Cas and Merel, accompanied by three of its friends. After a visit to the Dwingeloo Radio Telescope where the writer and a colleague of "Oude Willem" will welcome them, they will be treated with pancakes in de Bospub, which was a model for "het Woudcafe".
Let's wish them a great time!
Last year ASTRON donated "Het logboek" to all primary schools in Drenthe. On the occasion of the Children's book week 2015, all libraries in the four northern provinces have received a copy as well.
The winner will be announced on the website on Sunday the 1st of November.