Daily Image
01-06-2010
High resolution observations with LOFAR
| Submitter: | Olaf Wucknitz |
| Description: | Currently LOFAR is in a transition from a purely Dutch to a truly international telescope. Compared to the stations in the Netherlands, there will be only a small number of international stations so that the sensitivity of the array will be improved only marginally. However, the international stations add something unique, and that is long baselines and correspondingly much higher resolution. The image of today demonstrates how the long international baselines make an enormous difference. Shown are synthesis images of 3C196 in the frequency range 30-80 MHz (10-4m wavelength). The observations were taken over 6 hours in February using a total bandwidth of 31 MHz. The featureless blob shown in the left image was made by using only the five Dutch stations participating in this experiment. Because they are relatively close together, there are only short baselines. The resulting resolution of 30 arcsec (uniform weighting, circular PSF) is not sufficient to resolve any structure in this source. In contrast to this, the image on the right also includes data from three German LOFAR stations (the first international stations, in Effelsberg, Tautenburg and Unterweilenbach). These are much further away, and thus provide longer baselines. The resulting resolution is 1.5 arcsec, just enough to resolve the source into four main components, with some sub-structure. The colours are chosen to resemble what the human eye would see if it were sensitive to radiation at a wavelength ten million times larger than visible light. This map displays the highest resolution ever achieved in radio maps in this wavelength range. It constitutes a big step forwards towards Europe's first dedicated e-VLBI array. The data analysis was performed by Olaf Wucknitz (AIfA, Bonn). Efforts of many colleagues at the stations and at ASTRON were required to make this result possible. We particularly mention James Anderson (MPIfR), Annette Haas, Matthias Hoeft and Jochen Eisloeffel (TLS), Benedetta Ciardi (MPA), and George Heald and Antonis Polatidis (ASTRON). Unfortunately there is not sufficient space to mention all the engineers, software developers, astronomers, caterers etc. on whose work this result is based. |
| Copyright: | public domain |
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