Daily Image
14-06-2007
Where is Cygnus?
| Submitter: | Sarod Yatawatta and Jan Noordam |
| Description: | In earlier images made with LOFAR/CS1 (e.g. see yesterday, 13/6), we managed to remove the brightest source in the sky (Cas A) completely, but the last 2% of the next brightest source (Cygnus A) always remained as an ugly (albeit interesting) artefact. The reason was that this source gets quite close to the horizon during the observation, where its signal-to-noise ratio (SNR) was then too low for accurate calibration. For the present image, the 48-dipole station in the CS1 array (for explanation, see 13/6) was pointed at Cygnus, rather than Cas. This raised the SNR on this source sufficiently to allow us to subtract it completely. The brightest source in the image above is now Tycho (above Cas A). It shows fewer sources than the one of 13/6, because it is made of only a single 24 hr observation, and a total bandwith of 2 Mhz rather than 6. Note the resulting difference in PSF. The sky to the right seems more empty, because it was below the horizon for a substantial part of the observation. |
| Copyright: | LOFAR |
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