2016A&A...588A.114B


Query : 2016A&A...588A.114B

2016A&A...588A.114B - Astronomy and Astrophysics, volume 588A, 114-114 (2016/4-1)

Radio polarization and magnetic field structure in M 101.

BERKHUIJSEN E.M., URBANIK M., BECK R. and HAN J.L.

Abstract (from CDS):

We observed total and polarized radio continuum emission from the spiral galaxy M 101 at λλ6.2cm and 11.1cm with the Effelsberg telescope. The angular resolutions are 2.5 (=5.4kpc) and 4.4 (=9.5kpc), respectively. We use these data to study various emission components in M 101 and properties of the magnetic field. Separation of thermal and non-thermal emission shows that the thermal emission is closely correlated with the spiral arms, while the non-thermal emission is more smoothly distributed indicating diffusion of cosmic ray electrons away from their places of origin. The radial distribution of both emissions has a break near R=16kpc (=7.4), where it steepens to an exponential scale length of L≃5kpc, which is about 2.5 times smaller than at R<16kpc. The distribution of the polarized emission has a broad maximum near R=12kpc and beyond R=16kpc also decreases with L≃5kpc. It seems that near R=16kpc a major change in the structure of M 101 takes place, which also affects the distributions of the strength of the random and ordered magnetic field. Beyond R=16kpc the radial scale length of both fields is about 20kpc, which implies that they decrease to about 0.3µG at R=70kpc, which is the largest optical extent. The equipartition strength of the total field ranges from nearly 10µG at R<2kpc to 4µG at R=22-24kpc. As the random field dominates in M 101 (Bran/Bord≃2.4), wavelength-independent polarization is the main polarization mechanism. We show that energetic events causing HI shells of mean diameter <625pc could partly be responsible for this. At radii <24kpc, the random magnetic field depends on the star formation rate/area, σSFR, with a power-law exponent of b=0.28±0.02. The ordered magnetic field is generally aligned with the spiral arms with pitch angles that are about 8° larger than those of H i filaments.

Abstract Copyright: © ESO, 2016

Journal keyword(s): galaxies: individual: M 101 - galaxies: magnetic fields - galaxies: star formation - radio continuum: galaxies - polarization - radiation mechanisms: non-thermal

VizieR on-line data: <Available at CDS (J/A+A/588/A114): list.dat fits/*>

Simbad objects: 14

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Number of rows : 14
N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2023
#notes
1 M 31 G 00 42 44.330 +41 16 07.50 4.86 4.36 3.44     ~ 12012 1
2 M 33 GiG 01 33 50.8965749232 +30 39 36.630403128 6.17 6.27 5.72     ~ 5568 1
3 IC 342 SBG 03 46 48.514 +68 05 45.98   10.5       ~ 1462 1
4 ICRF J052109.8+163822 Sy1 05 21 09.8855216664 +16 38 22.054553988   19.37 18.84 18.480   ~ 815 1
5 M 99 H2G 12 18 49.625 +14 24 59.36 10.45 10.44 9.87     ~ 856 2
6 M 51 GiP 13 29 52.698 +47 11 42.93   9.26 8.36 8.40   ~ 4137 4
7 3C 286 Sy1 13 31 08.2883506368 +30 30 32.960091564   17.51 17.25     ~ 4142 2
8 M 83 SBG 13 37 00.91920 -29 51 56.7400 8.85 8.11 7.52 7.21   ~ 2436 2
9 NAME M101 Group GrG 14 03 +54.3           ~ 96 1
10 M 101 GiP 14 03 12.583 +54 20 55.50   8.46 7.86 7.76   ~ 2751 2
11 NGC 5471 EmG 14 04 28.627 +54 23 52.84           ~ 236 1
12 NGC 5474 GiP 14 05 01.608 +53 39 43.95   11.28 10.79     ~ 419 1
13 NGC 6946 H2G 20 34 52.332 +60 09 13.24   10.5       ~ 2404 2
14 NAME Local Group GrG ~ ~           ~ 7832 0

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2022.11.28-10:26:15

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