2011A&A...535A..64S


Query : 2011A&A...535A..64S

2011A&A...535A..64S - Astronomy and Astrophysics, volume 535A, 64-64 (2011/11-1)

New λ6 cm and λ11 cm observations of the supernova remnant CTA 1.

SUN X.H., REICH W., WANG C., HAN J.L. and REICH P.

Abstract (from CDS):

We attempt to study spatial variations in the spectrum and rotation measures (RMs) of the large-diameter, high-latitude supernova remnant (SNR) CTA 1. We conducted new λ6cm and λ11cm observations of CTA 1 using the Urumqi 25-m and Effelsberg 100-m telescopes. Data at other wavelengths were included to investigate the spectrum and polarisation properties. We obtained new total intensity and polarisation maps at λ6 cm and λ11 cm with angular resolutions of 9.5' and 4.4', respectively. We derived a spectral index of α=-0.63±0.05 (Sν∝να) based on the integrated flux densities at 408MHz, 1420MHz, 2639MHz, and 4800MHz. The spectral index map calculated from data at the four frequencies shows a clear steepening of the spectrum from the strong shell emission towards the north-western breakout region with weak diffuse emission. The decrease of the spectral index is up to about Δα=0.3. The RM map derived from polarisation data at λ6cm and λ11cm shows a sharp transition between positive RMs in the north-eastern and negative RMs in the south-western part of the SNR. We note a corresponding RM pattern of extragalactic sources and propose the existence of a large-diameter Faraday screen in front of CTA 1, which covers the north-eastern part of the SNR. The RM of the Faraday screen is estimated to be about +45rad/m2. A RM structure function of CTA 1 indicates a very regular magnetic field within the Faraday screen, which is stronger than about 2.7µG for a distance of 500pc. CTA 1 is a large-diameter shell-type SNR located out of the Galactic plane, which makes it an ideal object to study its properties without suffering confusion. The previous detection of the rare breakout phenomenon in CTA 1 is confirmed. We identify a Faraday screen partly covering CTA 1 with a regular magnetic field in the opposite direction to the interstellar magnetic field. The detection of Faraday screens in the Galactic plane is quite common, but is difficult at high latitudes where the polarisation angles of weak polarised background emission are rotated. Additional RMs from extragalactic sources are needed for this purpose, although the number density of the extragalactic RMs that have been measured remains small despite significant observational progress.

Abstract Copyright:

Journal keyword(s): ISM: supernova remnants - polarization - radio continuum: general - methods: observational

Simbad objects: 11

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Number of rows : 11
N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2022
#notes
1 SNR G119.5+10.2 SNR 00 06.6 +72 47           ~ 242 1
2 NGC 40 PN 00 13 01.0170097248 +72 31 19.033338720   11.63 11.46     [WC8] 604 2
3 PSR B0105+68 Psr 01 08 29.500 +69 05 52.63           ~ 27 0
4 SNR G132.6+01.5 SNR 02 17 40 +62 45.0           ~ 171 0
5 SNR G156.2+05.7 SNR 04 58 51.300 +51 50 28.00           ~ 123 1
6 SNR G166.0+04.3 SNR 05 26 30.000 +42 56 00.00           ~ 172 0
7 SNR G180.0-01.7 SNR 05 39 00.000 +27 50 00.00           ~ 235 2
8 3C 286 Sy1 13 31 08.2883506368 +30 30 32.960091564   17.51 17.25     ~ 4119 2
9 3C 295 Sy2 14 11 20.467 +52 12 09.52   22.34 20.80 18.54   ~ 948 5
10 SNR G065.2+05.7 SNR 19 33.0 +31 10           ~ 94 0
11 NAME Cyg Loop SNR 20 51.0 +30 40           ~ 873 0

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2022.10.05-13:24:20

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