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Alma Mater Studiorum Universit`a degli Studi di Bologna ... - Inaf

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112 6. Faraday rotation in two extreme environments<br />

IMAGE: 07_PSPC_CONVL_AS_1.3_OGEOM.FITS<br />

CNTRS: 07_1.3_I_4.FITS<br />

0 0.0002 0.0004 0.0006 0.0008<br />

37 49 00<br />

50 kpc<br />

DECLINATION (J2000)<br />

37 48 00<br />

37 47 00<br />

37 46 00<br />

37 45 00<br />

07 58 40<br />

07 58 30<br />

RIGHT ASCENSION (J2000)<br />

07 58 20<br />

Figure 6.1: Overlay of the X-ray emission (ROSAT PSPC) around 0755+37 on ra<strong>di</strong>o contours at<br />

1.385 GHz at 4.0 arcsec resolution.<br />

Table 6.3: Frequencies, bandwidths and angular resolutions used in the RM and Burn law k<br />

images. Details of the 0755+37 dataset are given in the Appen<strong>di</strong>x.<br />

source ν ∆ν beam<br />

[MHz] [MHz] [arcsec]<br />

0755+37 1385.1 12.5 1.3-4.0<br />

1464.9<br />

4860.1 100<br />

M 87 4635.1 50 0.4<br />

4735.0<br />

4835.1<br />

4935.0<br />

8085.1<br />

8335.1<br />

8535.1<br />

8785.1<br />

by G.B. Taylor. The RM maps were calculated only at pixels with polarization angle uncertainties<br />

≤10 ◦ at all frequencies. The RM maps have not been corrected for the Galactic contribution. For<br />

0755+37, this is estimated to be negligible (-1±2 rad m −2 ; Simard-Norman<strong>di</strong>n et al. 1981). For<br />

M 87, the value is less well-determined, but the source is at very high Galactic latitude, and the<br />

associated RM must be very small compared with the measured values (see below). Values of<br />

σ RM integrated over the maps are not corrected for the fitting errorσ RMfit ,<br />

I produced Burn law k images at the same resolutions and using the same frequencies as the<br />

RM maps. Weighted least-squares fits were made to the fractional polarization maps ln p(λ) as a<br />

112

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