This animated image shows Stokes I 40×40 degrees images centered on the North Celestial Pole as seen by NenuFAR at four frequencies ranges: 29-41.5 MHz, 41.5 -54 MHz, 54-66.5 MHz, 66.5-82.1 MHz. For comparison, an AARTFAAC HBA image at 122.1 MHz produced by Bharat Gehlot (Large-scale 21-cm Cosmology with LOFAR and AARTFAAC, Chapter 5, Fig. 5.2) is also included. The current 400-meter maximum baseline of NenuFAR limits the resolution to 1.2 degrees at the lowest frequency and 0.5 degrees at the highest frequency, while the AARTFAAC image has a resolution of 0.2 degrees. The upcoming addition of remote mini-arrays to NenuFAR will push the resolution down to 4 arcmins at 85 MHz. The Field of View NenuFAR is set by the mini-array diameter (25 meters) which gives a primary-beam FWHM of 20 and 9 degrees at the lowest and highest frequency respectively (26 degrees for AARTFAAC HBA image at 122.1 MHz). Despite the very different resolution and Field of View, the similarities in the images are striking. The smallest baselines were included in making these images at which large-scale diffuse Galactic emission, clearly and consistently seen in these images, starts to dominate. Modeling and including this diffuse emission in the calibration sky-model can significantly enhance calibration of the instrument.

Credit : Florent Mertens