A2255 as seen by LOFAR
Roberto Pizzo, Annalisa Bonafede, Reinout van Weeren, Giulia Macario
At 25 cmAt 85 cm
FWHM ~ 15’’Jy/beam
FWHM ~ 1’mJy/beam
Relic
HaloBridge
THE OBSERVATION
• L2011_24627: 1-7 am of March 27th 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
Cas A & Cyg A: subtraction in BBS
• Data averaged by a factor of 6 in frequency
• Models for Cas and Cyg extractedfrom the 74 MHz maps
• Test done on SB000 (225 MHz)
Cas A & Cyg A: demixing
Data have not been averaged. Plots refer to SB000
WENSS model
• 230 components• Data averaged to 10 sec and 2 channels
SB064
Data clipped at 40 Jy
dynamic range ~ 350
Pizzo’s model
• 750 components• Data averaged to 10 sec and 2 channels
Clipping at 40 Jy after calibration
SB064
dynamic range ~ 330
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).
The pipeline process
Courtesy of R. Pizzo, R. van Weeren, A. Bonafede & C. Ferraridynamic range ~ 2.500
SB00-025 excluded fromthe processing
Abell 2255 in HBA (225-250 MHz)
53 SBs, dynamic range ~ 2.500Courtesy of R. Pizzo, R. van Weeren,
A. Bonafede & C. Ferrari
Abell 2255 in HBA (225-250 MHz)
53 SBs, dynamic range ~ 2.500Courtesy of R. Pizzo, R. van Weeren,
A. Bonafede & C. Ferrari
Broad-band low-level RFI
SB000
Broad-band low-level RFI
SB010