1. A2255 as seen by LOFAR Roberto Pizzo, Annalisa Bonafede, Reinout van Weeren, Giulia Macario

2. At 25 cmAt 85 cm FWHM ~ 15’’  Jy/beam FWHM ~ 1’  mJy/beam Relic Halo Bridge

3. THE OBSERVATION L2011_24627: 1-7 am of March 27 th 2011 The observation was supposed to cover the frequency range between 210-250 MHz, but due to a problem during scheduling only the frequencies between 225-250 MHz (SB000-070) could be used for the data reduction. We performed a few tests to understand what approach to follow for the data reduction

4. Cas A & Cyg A: subtraction in BBS Data averaged by a factor of 6 in frequency Models for Cas and Cyg extracted from the 74 MHz maps Test done on SB000 (225 MHz)

5. Cas A & Cyg A: demixing Data have not been averaged. Plots refer to SB000

6. WENSS model 230 components Data averaged to 10 sec and 2 channels SB064 Data clipped at 40 Jy dynamic range ~ 350

7. Pizzo’s model 750 components Data averaged to 10 sec and 2 channels Clipping at 40 Jy after calibration SB064 dynamic range ~ 330

8. Difference between Global solver and single-SB solver No big difference is seen in the noise level but the image with the global calibration looks better (i.e., the huge head-tail to the south of the cluster center is better visible).

9. The pipeline process Courtesy of R. Pizzo, R. van Weeren, A. Bonafede & C. Ferrari dynamic range ~ 2.500 SB00-025 excluded from the processing

10. Abell 2255 in HBA (225-250 MHz) 53 SBs, dynamic range ~ 2.500 Courtesy of R. Pizzo, R. van Weeren, A. Bonafede & C. Ferrari

11. Abell 2255 in HBA (225-250 MHz) 53 SBs, dynamic range ~ 2.500 Courtesy of R. Pizzo, R. van Weeren, A. Bonafede & C. Ferrari

12. Broad-band low-level RFI SB000

13. Broad-band low-level RFI SB010