Daily Image
20-04-2009
Waste not, want not - a 327 MHz VLBA Survey
| Submitter: | Michael Garrett |
| Description: | The VLBA and a subset of the EVN antennas (including the WSRT), conduct VLBI observations at frequencies that are not so far removed from the top-end of the LOFAR HBA range (240 MHz). While most VLBI observations take place at centimetre wavelengths (where the sky noise is low and the coherence times are relatively long), VLBI observations at 327 MHz are also fairly routine. However, a trawl through the most popular refereed journals, reveals a disappointing number of publications. To address this issue, we recently began to automatically analyse VLBA 327 MHz archive data, observed by users of the VLBA over the last 5 years. Our aim was to draw-up an adhoc list of calibrators that might be useful for LOFAR, and in particular, the RadioAstron space VLBI mission (see http://www.astron.nl/dailyimage/main.php?date=20081210). The latter is also equipped with a 327 MHz receiver, and will attempt to detect sources on baseline lengths of up to 350000 km! Via a simple shell script in Classic AIPS, we automatically calibrated, fringe-fitted and imaged 44 different sources. 34 sources were detected on at least one baseline, and 30 of these had sufficient data for images to be made (see above for images of two of the most famous sources in our sample). Of the 30 sources imaged, 13 are detected on the very longest VLBA baselines (~ 9 Mega wavelengths). Some of these will hopefully make interesting initial targets for the RadioAstron mission. Some of the sources detected might also make suitable "in-beam" calibrators, permitting deep, wide-field studies of other faint sources in the same field of view (see http://www.astron.nl/dailyimage/main.php?date=20060821). The full paper (Rampadarath, Garrett & Polatidis, 2009) has recently been accepted by Astronomy and Astrophysics. For more details consult http://xxx.lanl.gov/abs/0904.0478v1 |
| Copyright: | ASTRON |
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