2011A&A...529A..94C


C.D.S. - SIMBAD4 rel 1.7 - 2020.01.26CET00:56:06

2011A&A...529A..94C - Astronomy and Astrophysics, volume 529A, 94-94 (2011/5-1)

Magnetic fields in local group dwarf irregulars.

CHYZY K.T., WEZGOWIEC M., BECK R. and BOMANS D.J.

Abstract (from CDS):

We wish to clarify whether strong magnetic fields can be effectively generated in typically low-mass dwarf galaxies and to assess the role of dwarf galaxies in the magnetization of the Universe. We performed a search for radio emission and magnetic fields in an unbiased sample of 12 Local Group (LG) irregular and dwarf irregular galaxies with the 100-m Effelsberg telescope at 2.64GHz. Three galaxies were detected. A higher frequency (4.85GHz) was used to search for polarized emission in five dwarfs that are the most luminous ones in the infrared domain, of which three were detected. Magnetic fields in LG dwarfs are weak, with a mean value of the total field strength of <4.2±1.8µG, three times lower than in the normal spirals. The strongest field among all LG dwarfs of 10µG (at 2.64GHz) is observed in the starburst dwarf IC10. The production of total magnetic fields in dwarf systems appears to be regulated mainly by the star-formation surface density (with the power-law exponent of 0.30±0.04) or by the gas surface density (with the exponent 0.47±0.09). In addition, we find systematically stronger fields in objects of higher global star-formation rate. The dwarf galaxies follow a similar far-infrared relationship (with a slope of 0.91±0.08) to that determined for high surface brightness spiral galaxies. The magnetic field strength in dwarf galaxies does not correlate with their maximum rotational velocity, indicating that a small-scale rather than a large-scale dynamo process is responsible for producting magnetic fields in dwarfs. If magnetization of the Universe by galactic outflows is coeval with its metal enrichment, we show that more massive objects (such as Lyman break galaxies) can efficiently magnetize the intergalactic medium with a magnetic field strength of about 0.8nG out to a distance of 160-530kpc at redshifts 5-3, respectively. Magnetic fields that are several times weaker and shorter magnetization distances are expected for primordial dwarf galaxies. We also predict that most star-forming local dwarfs might have magnetized their surroundings up to a field strength about 0.1µG within about a 5kpc distance. Strong magnetic fields (>6µG) are observed only in dwarfs of extreme characteristics (e.g. NGC4449, NGC1569, and the LG dwarf IC10). They are all starbursts and more evolved objects of statistically much higher metallicity and global star-formation rate than the majority of the LG dwarf population. Typical LG dwarfs are unsuitable objects for the efficient supply of magnetic fields to the intergalactic medium.

Abstract Copyright:

Journal keyword(s): galaxies: evolution - galaxies: magnetic fields - galaxies: dwarf - galaxies: irregular - Local Group - radio continuum: galaxies

Simbad objects: 25

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Number of rows : 25

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2020
#notes
1 NAME WLM Galaxy G 00 01 57.9 -15 27 50   11.50 11.10 10.93   ~ 562 2
2 IC 10 G 00 20 23.16 +59 17 34.7   13.6 9.5     ~ 988 0
3 M 31 G 00 42 44.330 +41 16 07.50 4.86 4.36 3.44     ~ 10674 1
4 NAME SMC G 00 52 38.0 -72 48 01   2.79 2.2     ~ 9184 1
5 NAME Pisces I G 01 03 56.6 +21 53 41   16.18 14.3     ~ 353 0
6 IC 1613 GiC 01 04 54.2 +02 08 00   10.42 10.01 9.77   ~ 1090 2
7 M 33 GiG 01 33 50.904 +30 39 35.79 6.17 6.27 5.72     ~ 5052 1
8 NAME Magellanic Clouds GrG 03 00 -71.0           ~ 5451 1
9 NGC 1569 IG 04 30 49.186 +64 50 52.52 11.72 11.86 11.03     ~ 1141 3
10 ICRF J052109.8+163822 Sy1 05 21 09.88592749 +16 38 22.0517668   19.37 18.84 18.480   ~ 730 1
11 NAME LMC G 05 23 34.6 -69 45 22     0.4     ~ 14476 1
12 M 81 Sy2 09 55 33.17306143 +69 03 55.0609270   7.89 6.94     ~ 3916 5
13 NAME Leo Dwarf Irregular Galaxy G 09 59 26.46 +30 44 47.0 14.08 13.54 13.26 13.33   ~ 540 0
14 NAME Sextans B H2G 10 00 00.8201300945 +05 20 09.572530884 12.77 12.25 11.89 11.71   ~ 457 0
15 NAME Sex A H2G 10 11 00.5 -04 41 30 12.48 12.13 11.93 11.78   ~ 642 2
16 M 99 H2G 12 18 49.625 +14 24 59.36 10.45 10.44 9.87     ~ 743 2
17 NGC 4449 EmG 12 28 11.118 +44 05 36.81 10.11 9.98 9.64 9.45   ~ 1001 1
18 UGC 8091 H2G 12 58 40.1930291852 +14 13 00.737117016 15.24 15.16 14.98 14.81   ~ 434 0
19 3C 286 Sy1 13 31 08.2885060664 +30 30 32.960825108   17.51 17.25     ~ 3649 1
20 NAME UMi Galaxy G 15 09 11.34 +67 12 51.7   13.60 10.6     ~ 1152 0
21 NAME Sgr dIG G 19 29 59.0 -17 40 41   15.5 13.6     ~ 271 1
22 NGC 6822 G 19 44 56.199 -14 47 51.29   18 8.1     ~ 1415 0
23 NAME Aquarius Dwarf G 20 46 51.7 -12 50 54 15.75 15.18 14.83 14.46   ~ 387 1
24 NAME Peg Dwarf Irregular Galaxy G 23 28 35.2 +14 44 35 13.85 13.16 12.52     ~ 413 1
25 NAME Local Group GrG ~ ~           ~ 6764 0

    Equat.    Gal    SGal    Ecl

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2020.01.26-00:56:06

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