2014A&A...562A.136S


C.D.S. - SIMBAD4 rel 1.7 - 2020.11.25CET08:59:14

2014A&A...562A.136S - Astronomy and Astrophysics, volume 562A, 136-136 (2014/2-1)

3D global simulations of a cosmic-ray-driven dynamo in dwarf galaxies.

SIEJKOWSKI H., OTMIANOWSKA-MAZUR K., SOIDA M., BOMANS D.J. and HANASZ M.

Abstract (from CDS):

Star-forming dwarf galaxies can be seen as the local proxies of the high-redshift building blocks of more massive galaxies according to the current paradigm of the hierarchical galaxy formation. They are low-mass objects, and therefore their rotation speed is very low. Several galaxies are observed to show quite strong magnetic fields. These cases of strong ordered magnetic fields seem to correlate with a high, but not extremely high, star formation rate. We investigate whether these magnetic fields could be generated by the cosmic-ray-driven dynamo. The environment of a dwarf galaxy is unfavourable for the large-scale dynamo action because of the very slow rotation that is required to create the regular component of the magnetic field. We built a 3D global model of a dwarf galaxy that consists of two gravitational components: the stars and the dark-matter halo described by the purely phenomenological profile proposed previously. We solved a system of magnetohydrodynamic equations that include an additional cosmic-ray component described by the fluid approximation. We found that the cosmic-ray-driven dynamo can amplify the magnetic field with an exponential growth rate. The e-folding time is correlated with the initial rotation speed. The final mean value of the azimuthal flux for our models is on the order of few µG and the system reaches its equipartition level. The results indicate that the cosmic-ray-driven dynamo is a process that can explain the magnetic fields in dwarf galaxies.

Abstract Copyright:

Journal keyword(s): magnetohydrodynamics (MHD) - dynamo - galaxies: magnetic fields - galaxies: dwarf - methods: numerical

Simbad objects: 7

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Number of rows : 7

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2021
#notes
1 IC 10 G 00 20 23.16 +59 17 34.7   13.6 9.5     ~ 1017 0
2 IC 1613 GiC 01 04 54.2 +02 08 00   10.42 10.01 9.77   ~ 1117 2
3 NGC 1569 IG 04 30 49.186 +64 50 52.52 11.72 11.86 11.03     ~ 1160 3
4 NAME LMC G 05 23 34.6 -69 45 22     0.4     ~ 15051 1
5 NGC 4449 EmG 12 28 11.118 +44 05 36.81 10.11 9.98 9.64 9.45   ~ 1028 1
6 NGC 6822 G 19 44 56.199 -14 47 51.29   18 8.1     ~ 1445 0
7 NAME Local Group GrG ~ ~           ~ 7108 0

    Equat.    Gal    SGal    Ecl

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2020.11.25-08:59:14

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