Daily Image

Click here or on the picture for a full size image.

Summer students 2012: Properties of faint sources in the LOFAR-EoR oberving windows

Submitter: Saavidra Perera
Description: The aim of this summer student project was to analyse the properties of extracted faint sources from LOFAR-HBA data taken of one of the EoR windows. This included building a sky model of this field (for flux densities greater than 6mJy) and comparing spectral properties to the image of this field of view. Often, the spectra were affected by the station beam model, proximity to bright sources and ionospheric effects. In addition, many bright sources would be counted as multiple by incorrectly identifying sidelobes as separate sources. Therefore, two data sets were taken exactly one week apart, one with 240 sources and the other with 222 sources. Once the unreliable targets were removed, the number of sources reduced to 214 (102 appearing in both data sets).

There were a couple of interesting spectra that could not be discounted by their location. One is of the source located at RA 8h 25m 32.07s, DEC 48d 17' 41.63", which is depicted in the above figure. The image displays the LOFAR data image (top left), LOFAR data spectra (top right), FIRST data image (bottom left) and an optical image taken from the Digital Sky Survey with contour plots from the LOFAR-HBBA data (green) and from the FIRST survey (white).

The LOFAR data showed an interesting parabolic shaped spectrum. The field of view image indicated
that it was a source. As a result, we looked at the FIRST survey and found there was diffuse emission around this source. From this it was hypothesised that the source could be a radio relic. As can be seen in the figure, there is a clear optical counterpart which could also indicate that it is a wide angle tailed radio galaxy. It is clear that the LOFAR image is not very conclusive and we would also need information about its magnetic field in order to be sure of the nature of this object.
Copyright: ASTRON/JIVE
  Follow us on Twitter
Please feel free to submit an image using the Submit page.