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