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Articles on this Page
- 10/28/14--17:00: _Dome Open Users Pla...
- 10/27/14--17:00: _LOFAR discovers lar...
- 10/30/14--17:00: _Calibratability Fun...
- 10/29/14--17:00: _Today's colloquium:...
- 11/02/14--16:00: _Tackling the puzzle...
- 11/03/14--16:00: _A Dwarf in Detail
- 11/04/14--16:00: _Another pretty pict...
- 11/05/14--16:00: _Today's Colloquium:...
- 11/06/14--16:00: _APERTIF successfull...
- 11/09/14--16:00: _MFAA analog beamfor...
- 11/10/14--16:00: _LOFAR station DE609...
- 11/12/14--16:00: _Today's colloquium:...
- 11/11/14--16:00: _Philae's landing - ...
- 11/13/14--16:00: _The Low Noise Tile'...
- 11/16/14--16:00: _SKA MFAA frontend...
- 11/17/14--16:00: _Today's colloquium:...
- 11/18/14--16:00: _Released version 15...
- 11/19/14--16:00: _The lonely life of ...
- 11/20/14--16:00: _The deepest look of...
- 11/21/14--16:00: _Sinterklaas, the Ch...
- 10/28/14--17:00: Dome Open Users Platform Event: where science and SME's meet
- 12.00 Arrival and lunch
- 13.00 Highlights of Dome R&D, plenary session (introduction and scientific update)
- 14.00 Three interactive parallel sessions (discussing specific issues, put forward by participants)
- 14.45 Coffee break
- 15.15 Again, three interactive parallel sessions
- 16.00 Plenary talk (summarizing results from interactive sessions), followed by drinks
- 10/27/14--17:00: LOFAR discovers largest carbon atoms outside our Milky Way
- 10/30/14--17:00: Calibratability Fundamentals (1): Apparent source statistics
- 11/02/14--16:00: Tackling the puzzle of pulsar emission with LOFAR
- 11/03/14--16:00: A Dwarf in Detail
- 11/04/14--16:00: Another pretty picture of LOFAR
- 11/06/14--16:00: APERTIF successfully passed its Critical Design Review
- 11/09/14--16:00: MFAA analog beamformer testboard
- 11/10/14--16:00: LOFAR station DE609 (Hamburg) extending the ILT
- 11/11/14--16:00: Philae's landing - today, live in the auditorium!
- 11/13/14--16:00: The Low Noise Tile's Reproducibility and averaged results
- 11/16/14--16:00: SKA MFAA frontend review meeting
- Current progress review of the overall front-end design task
- Deliverable review for the Front-End task and MFAA as a whole
- Clarify the work ahead for each front-end design task member
- Whole differential front-end design is in a good prospect
- Emerging technologies for AA
- Principle discussions for consensus on technology selection
- MFAA work towards PDR and beyond
- Forecasting the Mid-frequency science goals
We are keenly looking forward to next year's face-to-face meeting at KLAASA, in China!
- 11/18/14--16:00: Released version 15.0 of the LOFAR Imaging Cookbook
- 11/19/14--16:00: The lonely life of PSR J1745-2900
- 11/20/14--16:00: The deepest look of the WSRT
- 11/21/14--16:00: Sinterklaas, the Children's Friend
- There is no elaborate dinner, to be prepared and served by a harassed host/hostess.
- There are no multi-day gatherings to put a lethal strain on families.
- There are no pantomimes in which children are forced to perform.
- All presents are safely credited to Sinterklaas only, thus avoiding the emotional pitfalls of personal gifts.
- Presents are supposed to be accompanied by a short poem, which may gently poke fun at the recipient.
- Some presents may be hilarious fakes ("surprises"), to the delight of the smaller children.
- There is the healthy threat of some actual penalties beyond getting fewer presents. They range from mild corporeal punishment by means of a bundle of twigs (the "roe"), to being taken back to Spain in a sack.
Of course the Dutch economy cannot afford to ignore the consumptional opportunities of Christmas. But our parents, children and shopkeepers are united in the wish to preserve the unique charms of Sinterklaas as well.
© Dome, original design by FreepikToday, ASTRON is hosting a special Dome event where a select group of entrepreneurs and knowledge institutes will challenge the Dome team to help them overcome technological restraints, thus paving the road for new and interesting business opportunities though collaborative R&D. Dome is the research project in which ASTRON and IBM have joined forces to create new technology in order to handle the huge amounts of data that will be generated by the Square Kilometre Array (SKA).
During this afternoon's event, the Van de Hulst auditorium is the setting for plenary sessions. You may also spot some interactive sessions in the Muller, JIVE, Hooghoudt and former control room. After lunch, there will first be an update on novel technologies and new computing approaches that are being developed within DOME. For more information on the Dome research streams, please click here http://www.dome-exascale.nl/oupe2014/index.php
This plenary session will be followed by some interactive subsessions. We have challenged a number of SME's to analyse where the opportunities lie that may enhance their business and could benefit our economy as a whole. We are curious to see what IT-related constraints they are facing when it comes to developing products and services, and which of those the Dome team could help solve. If there is a viable match with one or more of the Dome research streams, the aim would be to proceed with R&D on a collaborative basis.
© Leah Morabito (Background Image credit: J. Gallagher, M. Mountain, and P. Puxley)An international team of astronomers, led by Leah Morabito (Leiden Observatory) and involving ASTRON astronomer Raymond Oonk, has for the first time discovered the largest carbon atoms outside our Milky Way in the nearby galaxy M82. This discovery was carried out with the LOFAR radio telescope. In the future astronomers will be able to use these large Carbon atoms to measure how cold and how dense the gas around these atoms is. The results are published in the journal Astrophysical Journal Letters on 28 October.
Carbon atoms are about half a million times smaller than the average thickness of a human hair, but in very cold and sparse gas they can be up to a billion times larger(*). The weak spectral signature of these very large atoms can be observed at very low radio frequencies.
In the past most radio telescopes have either not been sensitive enough or not been tuned to the right frequencies to be able to detect these lines outside of our own Galaxy. However, the LOFAR radio telescope, that stretches from the northeast of the Netherlands across Europe, is perfect for these kind of observations because of its wide frequency range and excellent sensitivity.
The LOFAR study of the nearby starburst galaxy M82 has now, for the first time, been able to detect the spectral signature from large carbon atoms outside of our own Milky Way. These observations, in combination with future measurements, present us with a new tool to study the properties of the cold and sparse gas in M82 and what role this gas plays in evolution of this galaxy.
(*) Such large atoms are called Rydberg atoms (see e.g. wikipedia).
© Stefan WijnholdsThere is a convenient rule-of-thumb that says that, when the sensitivity of a (radio) telescope increases with a factor n (e.g. n=10), roughly n times more sources become visible above the noise. Since all these faint sources will be convolved with the telescope PSF(*), their cumulative sidelobes can increase the noise to the level where it nullifies the (very expensive) nominal sensitivity of the telescope.
This will be an issue for the new generation of giant radio telescopes. Certainly for the SKA, but already for specific LOFAR observations. In order to analyse the problem, we first have to understand the "apparent source statistics", i.e. the statistics of sources that will be visible in the field-of-view of a particular telescope.
To get some feeling for this, we assumed a primary beam with the shape of an Airy pattern, the theoretical power beam pattern of a homogeneously illuminated circular aperture(**). The Airy pattern for a 15-m aperture at 1 GHz is shown in the left panel. We then used this to filter the known source statistics at the observing frequency of 1 GHz, to obtain the apparent source statistics shown in the right panel. The vertical line gives a rough indication of the 1-sigma limit for the SKA dish system after 1000 hours of integration over 1 MHz. Note that the same limit holds for 100 hours over 10 MHz and 10 hours over 100 MHz.
The various curves indicate the total number of sources brighter than a given apparent flux, for various lobes of the primary beam. They show that almost all (over 85%) visible sources typically reside in the main lobe, with most of the others located in the first two sidelobes. The number in the far (>2nd) sidelobes is typically less than 1%.
All this is encouraging, because calibration is easier in the main lobe. However, it should be noted that this ratio will be different for different primary beams, and after subtracting as many sources as possible. Unfortunately, the problem will be exacerbated for the new telescopes, since they are sensitive to hitherto invisible source populations that cause the density of sources to increase more steeply with decreasing flux.
In a future AJDI, we will present a useful plot(***) that makes it easy to determine the extent of the problem for various existing and proposed radio telescopes. It indicates how low the PSF sidelobe level has to be for a given nominal sensitivity, and how many sources have to be subtracted.
(*) Point Spread Function
(**) PSF sidelobes are higher for unfilled apertures
(***) This plot was presented at the recent URSI GA in Beijing
© C. Ng (MPIfR), et al.The extreme conditions found in and around pulsars make them fantastic natural laboratories, providing insights into a rich variety of aspects of fundamental physics and astronomy.
To discover more pulsars we have begun the High Time Resolution Universe (HTRU) survey: a blind survey of the northern sky with the 100-m Effelsberg radio telescope in Germany, and a twin survey of the southern sky with the 64-m Parkes radio telescope in Australia. The HTRU survey uses multi-beam receivers and backends constructed using recent advancements in technology, providing unprecedentedly high time and frequency resolution to probe deeper into the Galaxy than ever before. Observations from Parkes have recently been completed, and it is thus a suitable moment to review the success of the survey.
In my talk I will discuss the discovery highlights such as the magnetar, two 'planet-pulsar' binaries and the Fast Radio Bursts (FRBs) from cosmological distances. The HTRU low-latitude data promises to provide the deepest large-scale search ever of the Galactic plane region. I have already discovered 60 new pulsars from processing 50% of the Galactic plane data.
I will present an innovative segmented search technique, which aims to increase our chances of discoveries of highly accelerated relativistic binary systems, including the potential pulsar-black-hole binaries. I will provide an overview of the northern survey with Effelsberg and present an update on the survey status.
© MPWe analyzed LOFAR observations of a sample of 100 radio pulsars (Pilia et al., submitted to A&A). LOFAR offers the unique capability of observing pulsars in a mostly unexplored range of frequencies: the 10-240 MHz range with large fractional bandwidth. We produced the cumulative pulse profiles of 100 pulsars in the 120-167 MHz range as well as the 15-63 MHz profiles for 25 of these pulsars. We performed a multi-frequency study of the profiles comparing the LOFAR observations with higher-frequency archival data, and following the profile evolution from 1400 MHz down to 15 MHz, where possible. We determined the relationship between this evolution and the geometry and astrometric parameters of the pulsar, or the external effects that alter the signal traveling towards us, which are prominent at lower frequencies.
We followed the evolution of the full profile width and that of its single components, in case of multiple peaks; also in case of multiple peaks we traced the evolution of the ratio of the amplitudes of the two most prominent peaks.
We found that the profile evolution with decreasing radio frequency does not follow a specific trend but, depending on the geometry of the pulsar, new components can enter into, or be hidden from, view. Nonetheless, in general our observations confirmed the widening of pulsar profiles at low frequencies, as expected from radius-to-frequency mapping or birefringence theories. We found good agreement of our data with the empirical core + cones model from Rankin (1983+) and the phenomenological model from Karastergiou and Johnston (2007).
Credits: M. Pilia, J.W.T. Hessels, B.W. Stappers, J. van Leeuwen and LOFAR Pulsar Working Group
© Erwin de BlokA few months ago the AG organised a workshop on making pretty pictures from astronomical data. This workshop was given by Jayanne English from the University of Manitoba and who used to be part of the Hubble Heritage team, famous for its colourful Hubble telescope pictures.
As a result of this workshop, Erwin de Blok from ASTRON used his multi-wavelength data, along with other archival data, of nearby Local Group dwarf galaxy to make false-colour image shown here.
The optical background is made of a combination of B, V and R images from the Local Group Survey by Massey et al (2007, AJ, 133, 2392). The blue stars have been enhanced using near-UV data from GALEX (Hunter et al 2010, AJ, 139, 447). The red emission shows the H alpha distribution as published in de Blok et al (2006, AJ, 131, 363), and finally the distribution of the neutral hydrogen (HI) is taken from Australia Telescope Compact Array observations described in de Blok et al (2000, ApJ, 537, L95).
Note how the bluest (youngest) stars can be found near holes in the HI. The origin of the large hole in the bottom-left (south east) is not clear. It could be caused by star formation, but there is no clear evidence for a remnant population. Alternatively, NGC 6822 could be interacting with an even smaller dwarf (visible as the cloud in the top-right), with the hole (and the tail that can be seen going off towards the bottom left) being the result of a tidal interaction.
NGC 6822 is only 0.5 Mpc away from us and is the closest gas-rich dwarf galaxy outside the Large and Small Magellanic clouds. The image measures about 0.7 by 0.7 degrees - NGC 6822 therefore has an apparent size about that of the moon!
© Madroon Community Consultants (MCC)To be downloaded, e.g. for inclusion in your presentations. Just right-click the image.
© Heino FlackeBlack holes are supposed to power the nuclei of galaxies. The best place to test this paradigm is the Galactic center. Here a compact radio source, Sgr A*, with a mass of 4 Million solar masses marks the very center of our Galaxy. Numerical magnetohydrodynamic simulations and semi-analytic models seem to converge towards a combined jet-disk model producing radiation from radio to X-rays to explain the emission. Interestingly, radio interferometry and timing observations are now probing the smallest scales of this object, directly confirming that the high-frequency radio emission indeed comes from event-horizon scales. This allows one to study basic astrophysical processes such as jet formation and accretion physics. Precise measurements of NIR-emitting stars and potentially even radio pulsars in the Galactic Center help us to constrain mass and possibly spin of the black hole reliably. Using future mm-VLBI experiments it should be possible to even image the elusive event horizon of a black hole for the very first time. All this we address within the framework of a new ERC-funded project, BlackHoleCam, which seeks to turn Sgr A* into a fundamental laboratory for precision black hole astrophysics.
© ASTRON, 2014Over the last couple of years, the detailed design of APERTIF was performed. Several challenges have been overcome, such as the design of very low-noise room temperature amplifiers, the hostile RFI environment at the WSRT and the massive amount of digital data (9.8 Tbps) that must be processed in real-time. To validate the design, prototypes have been built and installed in 3 WSRT dishes. This prototype system, known as ALPHA-3, confirmed the expected performance of APERTIF.
To independently assess the system and to minimize the risk that something has been overlooked, a Critical Design Review (CDR) was organized. A strong international panel of experts was invited to review whether the APERTIF system fulfills the science and system requirements and whether all major risks were identified. The review panel consisted of the following members: Mark Bowen (CSIRO, chair), Erwin de Blok (ASTRON), Hans van der Marel (ASTRON), Lister Staveley-Smith (UWA/ICRAR), Ravi Subrahmanyan (Raman Research Institute), Gundolf Wieching (MPIfR) and Victor Pankratius (MIT Haystack Observatory). The APERTIF team supplied them with an extensive set of documentation, describing every detail of the design and initial commissioning results. During a face-to-face meeting the highlights and issues were discussed. And of course the panel went for a tour to the WSRT to see the ALPHA-3 system in action.
We are excited to report that the panel was very impressed by the quality of the documentation and the presentations and was unable to identify any significant risk that was not already reflected in the risk register. The panel concluded that, as designed, APERTIF promises to make the WSRT a world class facility for the next decade. We are eagerly looking forward to start rolling out APERTIF in the coming year.
© ASTRONPresented here is a testboard, hosting the 2013 Mid Frequency Aperture Array (MFAA) beamformer-chip (BFC), designend by Obs. de Nancay, France. NXP in Caen(Fr), provided the QUBIC4Xi bchip process. The latter is qualified as a high-performance technology to design a RF ASIC in the frequency band [400 MHz - 1600 MHz].
The chip is designed to form two beams by means of phase-shift and amplitude control. The integrated circuit includes many differential functions such as low noise amplifiers, switches, polyphase filters, variable gain attenuators and a SPI/I2C interface for the digital control of all settings.
This BFC has 16 equally distributed phase steps of 22,5 degrees. Amplitude control of 4.5 dB with 8 equally distributed steps is implemented to accomplish a phase-dependent amplitude variation of less than +/- 0.5 dB. The total power consumption of the BFC is
The testboard has been designed by our own Sieds Damstra, whereas all soldering has been done by Anne Koster. PCB manufacturing by our in-house pcb facility, operated by Albert van Duin Great work!
© Nico EbbendorfThe construction of the 9th international LOFAR station, known as DE609-Hamburg is nearing completion. After an extended period of looking for a suitable location, and some negotiation with the land owner, construction work started at the beginning of October.
This new LOFAR site is located north of the city of Hamburg, in a small town called Norderstedt. In the last 4 weeks, a total of 96 Low Band Antennas (LBA), 96 High Band Antennas (HBA) have been installed, and a large cabinet for the back-end electronics.
With this new addition, the International LOFAR Telescope (ILT) will consist of a total of 38 stations in the Netherlands, 6 in Germany, and one each in France, the United Kingdom and Sweden. More will follow.
The data collected from all LOFAR stations is processed and stored in Amsterdam, Groningen and Julich (Germany), and coordinated by Astron. International stations (i.e. stations located outside NL) can also operate in stand-alone mode, acting as a single telescope.
© David A. Hardy/AstroArt.orgMass transfer from a helium star to a compact companion in a close binary can produce an ultra-stripped core (in some cases an almost naked metal core, barely above the Chandrasekhar-mass limit), which undergoes an iron-core collapse supernova (Fe CCSN). The resulting explosion leads to ejection of only 0.05-0.20 M☉ of material and produces a low-mass neutron star, as well as an extremely fast and faint Type Ic SN light curve.
We computed synthetic light curves that demonstrate that SN 2005ek could be explained by our model. We argue that the second explosion in some double neutron star systems (for example, the double pulsar PSR J0737-3039B) was likely associated with an ultra-stripped Type Ic SN. New results of an ongoing systematic investigation of the progenitors of electron capture SNe versus Fe CCSNe in close binaries are discussed.
The second topic of this talk is focused on the possibility of forming neutron stars via the accretion-induced collapse (AIC) of a massive ONeMg white dwarf, illustrated in the picture above. Both observational evidence and theoretical computations are discussed.
© ESA / ASTRONToday (12 November 2014) the Philae spacecraft will attempt a landing on the Comet 67P/Churyumov-Gerasimenko - the image above shows the prime landing site, "Agilkia" and landing timeline. The landing phase window will open at 1622 CET with the exact time of contact being dependant on the release and landing trajectory flown by the mothership, Rosetta. The best estimate is that touchdown will occur around 1700 CET +/- 15 minutes - this also takes into account the 28 minute light travel time of the radio signal from the spacecraft to Earth. If the timing holds up, we plan to start streaming a live video feed from ESOC in the van der Hulst auditorium, starting sometime in the mid-afternoon as Philae makes its final approach. The first panoramic images from the surface are expected at ESOC around 1800 CET.
The probe is expected to continue to operate until March 2015 - at that point the comet will be much closer to the sun, and the probe will be threatened by rising temperatures and increasing activity on the comet's surface. Meanwhile the orbiting Rosetta spacecraft will continue to monitor the comet all the way through perihelion (August 2015), giving us a remarkable ring-side seat in which to view the various outgassing processes.
An animation of today's landing is available at: http://youtu.be/szKZ77MbF9Q
© ASTRONIn our series of daily images on the progress of the Low Noise Tile (LNT) project (also see the AJDI of 21-03-2014 and that of 26-05-2014), we now present the results for a tile of one square meter (m2), equipped with 48 of the new LNT elements.
Measurements were done at four different azimuthal positions of the array, spaced at 45 degrees. Noise measurement results for the individual positions, as well as their average are presented, showing mean values below 45 K, with a standard deviation of 1-2 K.
Furthermore, we present results on the reproducibility of noise measurements with the experimental 60-element Medium Sized Tile (MST), for one polarization of its 5x6 array. Seven measurements were done at one hour intervals during the day, between 9:30 and 15:30. Results of the individual measurements and their average show values below 45 K, with a standard deviation smaller than 1 K. As may be observed from the concerning noise plot, results for some of the measurements between 1150MHz and 1250 MHz that were strongly affected by RFI, have been omitted. These frequencies showed large noise temperature peaks in a number of measurements during the day, with much larger standard deviations.
In the present results for the MST we observe a 5 K noise temperature increase, compared to the results in the AJDI of 26-05-2014. A possible explanation for this difference is the influence of low level RFI on the measurements, which is subject of further investigation.
The third noise plot shows a comparison of the averaged noise temperatures for the 1 m2 tile and the MST. The results are quite close to each other, indicating that the measurements on the smaller MST with respect to the 1 m2 tile, give a good indication of the noise performance of a larger array. This allows lower cost and easier handling for this type of array experiments.
© UMANOn 5 and 6 Nov, the SKA Mid Frequency Aperture Array (MFAA) consortium organised its second face-to-face FrontEnd Workpackage design review meeting (the first was a year ago at ASTRON, as part of the MFAA all-hands meeting). We very much enjoyed our stay at the University of Manchester (the workpackage lead).
During the meeting, all three workpackage partners (KLAASA, UMAN, ASTRON) presented their progress, focussing mainly on the antenna and LNA designs. Additional material was presented by University of Cambridge, Observatoire de Nancay and Stellenbosch University.
In addition to all the technical fun, which included lively discussions among all engineers present, the SKA Office treated us to their latest view on SKA2 science goals.
David Zhang (UMAN), the LOC chair, summarized the meeting with an impressive list of the main achievements:
© Picture courtesy of Matt Schmachtenberg, from JMU's 'The Breeze'Pulsars are some of astrophysics' most exotic objects. We currently know of about 2300 pulsars in our Galaxy, but a small subset of them, the millisecond pulsars (MSPs), are truly remarkable. These systems are notoriously hard to detect, yet their numbers have more than doubled in the past 4 years via surveys using the world's most sensitive telescopes. Specialized 'timing' observations of these new systems as well as much improved monitoring of previously known MSPs are providing fantastic results. Some examples include unusual aspects of binary and stellar astrophysics, the nature of matter at supra-nuclear densities, and the direct detection of gravitational waves, possibly within the next five years.
© Roberto PizzoOn November 4 2014, version 15.0 of the LOFAR Imaging Cookbook has been released.
The first version of the manual was published more than 4 years ago, when the first LOFAR commissioners met together during the commissioning Busy Weeks to test and validate the new reduction software regularly becoming available for processing LOFAR data.
Since 2010, the manual has developed significantly. Its content has become very comprehensive of all the data reduction steps needed to achieve outstanding LOFAR imaging results. The topics covered range from data inspection to flagging, calibration, imaging, and source extraction. More recently, important chapters have been included on advanced methods to remove the A-team signal from the visibilities, advanced tools to inspect the calibration solutions, the automated self-calibration algorithm, and a description of the new LOFAR CEP 3 cluster - which inspired the release of this new version of the manual.
The LOFAR Imaging Cookbook is edited by Roberto Pizzo, who coordinates the large group of experienced LOFAR commissioners in charge of updating the chapters of the manual: G. van Diepen, T. J. Dijkema, G. Heald, F. de Gasperin, M. Iacobelli, J. McKean, M. Mevius, A. Offringa, E. Orru ́, D. Rafferty, C. Tasse, B. van der Tol, V. Vacca, N. Vilchez, R. van Weeren, W. Williams and S. Yatawatta, on behalf of the Lofar commissioning team.
© Bower, O'Leary et al.Radio pulsars are born in the supernova explosions that dramatically mark the death of massive stars. The Galactic Centre environment is teeming with massive stars, which means it should also be teeming with pulsars; an important fact, because a radio pulsar in the vicinity of the supermassive black hole at the Galactic Centre (Sgr A*) could be used to make unbelievably precise tests of general relativity. Finding these pulsars, however, has been frustrated by the presence of some very turbulent ionised gas somewhere between us and the Galactic Centre which scatters radio waves and smears out the characteristic radio pulsations - especially at the low frequencies where pulsars are bright.
A major breakthrough came in 2013, with the discovery of the magnetar PSR J1745-2900, separated from the supermassive black hole by just a fraction of light-year in projection. Magnetars are relatively rare, highly magnetised neutron stars which are unfortunately not well suited to the kind of tests we would like to perform at the Galactic Centre. It did serve, however, as the bearer of bad news: the scattering of pulses originating from pulsars at the Galactic Centre was not nearly as bad as suspected. On first glance, this sounds positive: easier to observe the target pulsars! But it begs the question: if they weren't being hidden by scattering, where *are* all these other pulsars? If our expectations are wrong and there are actually few pulsars at the Galactic Centre, then we may never find one suitable to make the precise tests of general relativity.
To help answer this question, we observed PSR J1745-2900 over a period of a year with the Very Long Baseline Array plus the phased VLA, tracking its motion in the plane of the sky. The tiny motion observed was equivalent to seeing an ant crawl across a leaf from a distance of 1,000 km! The pulsar velocity is shown in the image in red, along with the velocity of a sample of other massive stars which orbit Sgr A* in a compact disk in black. By simulating the stellar population, we were able to show that PSR J1745-2900 is almost certainly bound to Sgr A*, and likely originated in the disk of stars shown in the image. We postulate that the lack of observed radio pulsars could be due to a time-variable star formation rate at the Galactic Centre, which has recently increased significantly after a long dip; older radio pulsars from previous periods of high star formation have faded away, and new ones are only just now being generated. "Millisecond" radio pulsars with much longer lifetimes would still be present in droves, but even the relatively limited amount of scattering we observe means they would still have been missed by previous surveys. Future, wide bandwidth surveys, and potentially those with the Square Kilometre Array, may still detect these fast pulsars. More details are given in our recently accepted paper.
© AstronToday's Daily Image represents one of the posters submitted to the Astronomy Pretty Poster Pageant 2014 (see 1-Aug-2014, 12-Sep-2014, 15-Sep-2014, 30-Sep-2014 and 17-Oct-2014). It shows the image obtained with the Westerbork Synthesis Radio Telescope (WSRT) of an area of 1 degree^2, centred on the First Look Verification Strip of the Spitzer satellite (FLS). The WSRT image has a noise level of 8.5 uJy/beam and is the deepest WSRT image made to date. Over a thousand sources are detected in this image.
The results from these observations were presented in Morganti, Garrett, et al. 2004, A&A, 424, 371 (ArXiv:0405418) while follow up with VLBA and submillimeter SCUBA were presented by Wrobel et al. (including Mike Garrett and Raffaella Morganti) 2004, AJ, 128, 103 (ArXiv:0404007) and Frayer et al. (again including Mike Garrett and Raffaella Morganti) 2004, ApJS, 154, 137 (ArXiv:0406351) respectively.
© ASTRON PVToday is the traditional St Nicolas (Sinterklaas) party for the children of ASTRON, JIVE, NOVA and DOME employees.
Just like his offshoot Santa Claus, Sinterklaas brings presents for all the children who have been good during the past year. But the older benefactor has the more gruelling schedule: not only does he deliver the goods on a single evening into millions of chimneys, seated on a presumably sure-footed white horse, but in the days and weeks before the 5th of December he also makes thousands of personal appearances like the one to our institute today. And although he does not have to do it all by himself, and has fewer households to serve, it is no wonder that his style is somewhat less jolly than Santa's: no "ho-ho-ho" from an exhausted Sinterklaas.
Despite the obvious similarities (which are driven by globalisation), there are significant differences between the two traditions. The most important is that Sinterklaas is much more intimate, aimed at the inner family: