2017A&A...598A..72M

Query : 2017A&A...598A..72M

2017A&A...598A..72M - Astronomy and Astrophysics, volume 598A, 72-72 (2017/2-1)

Galactic winds and the origin of large-scale magnetic fields.

MOSS D. and SOKOLOFF D.

Abstract (from CDS):

Context. Observations of dwarf galaxies suggest the presence of large-scale magnetic fields. However the size and slow rotation of these galaxies appear insufficient to support a mean-field dynamo action to excite such fields.
Aims. Here we suggest a new mechanism to explain large-scale magnetic fields in galaxies that are too small to support mean-field dynamo action. The key idea is that we do not identify large-scale and mean magnetic fields. In our scenario the magnetic structures originate from a small-scale dynamo which produces small-scale magnetic field in the galactic disc and a galactic wind that transports this field into the galactic halo where the large turbulent diffusion increases the scale and order of the field. As a result, the magnetic field becomes large-scale; however its mean value remains vanishing in a strict sense.
Methods. We verify the idea by numerical modelling of two distinct simplified configurations, a thin disc model using the no-z approximation, and an axisymmetric model using cylindrical r,z coordinates.
Results. Each of these allows reduction of the problem to two spatial dimensions. Taken together, the models support the proposition that the general trends will persist in a fully 3D model. We demonstrate that a pronounced large-scale pattern can develop in the galactic halo for a wide choice of the dynamo governing parameters.
Conclusions. We believe that our mechanism can be relevant to explaining the presence of the fields observed in the halos of dwarf galaxies, and maybe elsewhere. We emphasize that detailed modelling of the proposed scenario needs 3D simulations, and adjustment to the specific dynamo governing parameters of dwarf galaxies.

Abstract Copyright: © ESO, 2017

Journal keyword(s): galaxies: magnetic fields - galaxies: dwarf - dynamo

Simbad objects: 1

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Number of rows : 1
N Identifier Otype ICRS (J2000)
RA 		ICRS (J2000)
DEC 		Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2024 		#notes
1 NGC 2976 GiP 09 47 15.458 +67 54 58.97 11.77 11.03 10.16 9.51   ~ 673 1

Query : 2017A&A...598A..72M

Basic data :
NGC 2976 -- Galaxy in Pair of Galaxies
Origin of the objects types :

(Ref) Object type as listed in the reference "Ref"
(acronym) Object type linked to the acronym according to the original reference
() Anterior to 2007, before we can link the objet type to a reference, or given by the CDS team in some particular cases

Other object types: 		GiP (), G (2014AJ,HIJASS,...), Rad (BWE,GB6,...), GiG (2007ApJ,[CHM2007]), IR (IRAS,PSCz), AG? (2020MNRAS), Opt (SDSS)
Syntax of coordinates is : "ra dec (wtype) [error ellipse] quality bibcode" :
  • ra dec : right ascension and declination (unit and frame defined according to your Output Options)
    Grey values are increasing the original precision due to the computation of frame transformations
  • (wtype) : wavelength class for the origin of the coordinates (Rad, mm, IR, Optical, UV, Xray, Gam)
  • [error ellipse] : measurement uncertainty, on (ra,dec) if the positional angle is 90 degrees, on (majaxis,minaxis) otherwise (in mas at defined epoch in the original catalogue),
    position angle (in degrees North celestial pole to East)
  • quality : flag of quality
    • E ≥ 10"
    • D : 1-10" (and some old data)
    • C : 0.1-1"
    • B : 0.01-0.1" + 2MASS, Tyc
    • A : VLBI, Hipparcos
  • bibcode : bibcode of the coordinates reference
ICRS coord. (ep=J2000) : 		09 47 15.458 +67 54 58.97 (Infrared) [ ] C 2006AJ....131.1163S
Syntax of coordinates is : "ra dec (wtype) [error ellipse] quality bibcode" :
  • ra dec : right ascension and declination (unit and frame defined according to your Output Options)
    Grey values are increasing the original precision due to the computation of frame transformations
  • (wtype) : wavelength class for the origin of the coordinates (Rad, mm, IR, Optical, UV, Xray, Gam)
  • [error ellipse] : measurement uncertainty, on (ra,dec) if the positional angle is 90 degrees, on (majaxis,minaxis) otherwise (in mas at defined epoch in the original catalogue),
    position angle (in degrees North celestial pole to East)
  • quality : flag of quality
    • E ≥ 10"
    • D : 1-10" (and some old data)
    • C : 0.1-1"
    • B : 0.01-0.1" + 2MASS, Tyc
    • A : VLBI, Hipparcos
  • bibcode : bibcode of the coordinates reference
FK4 coord. (ep=B1950 eq=1950) : 		09 43 09.838 +68 08 52.58 [ ]
Syntax of coordinates is : "ra dec (wtype) [error ellipse] quality bibcode" :
  • ra dec : right ascension and declination (unit and frame defined according to your Output Options)
    Grey values are increasing the original precision due to the computation of frame transformations
  • (wtype) : wavelength class for the origin of the coordinates (Rad, mm, IR, Optical, UV, Xray, Gam)
  • [error ellipse] : measurement uncertainty, on (ra,dec) if the positional angle is 90 degrees, on (majaxis,minaxis) otherwise (in mas at defined epoch in the original catalogue),
    position angle (in degrees North celestial pole to East)
  • quality : flag of quality
    • E ≥ 10"
    • D : 1-10" (and some old data)
    • C : 0.1-1"
    • B : 0.01-0.1" + 2MASS, Tyc
    • A : VLBI, Hipparcos
  • bibcode : bibcode of the coordinates reference
Gal coord. (ep=J2000) : 		143.914428 +40.902510 [ ]
Syntax of radial velocity (or/and redshift) is : "value [error] (wavelength) quality bibcode"
  • value : radial velocity or/and redshift (Heliocentric frame) according to your Output Options
    (redshift may be not displayed if the data value is <0 and the database inside value is a radial velocity)
  • [error] : error of the corresponding value displayed before
  • (wavelength) : wavelength range of the measurement : Rad, mm, IR, Opt, UV, Xray, Gam or  '∼'(unknown)
  • quality : flag of quality ( A=best quality -> E=worst quality, ∼=unknown quality)
  • bibcode : bibcode of the value's origin
Radial velocity / Redshift / cz : 		V(km/s) 3 [~] / z(spectroscopic) 0.000010 [~] / cz 3.00 [~]
   (Rad) D 2020ApJ...902..145K
Syntax of morphological type is : mtype quality bibcode
  • mtype : Hubble morphological class (spirals, ellipticals, etc)
  • quality : flag of quality (A=best quality -> E=worst quality, {� } =unknown quality)
  • bibcode : bibcode of the morphological type reference
Morphological type: 		SA C 2019MNRAS.488..590B
Syntax of angular size is : "maj-axis min-axis angle (wtype) quality bibcode"
  • maj-axis : major axis size (arc minutes)
  • min-axis : minor axis size (arc minutes)
  • angle : orientation angle (in degrees)
  • (wtype) : wavelength class for the origin of the angular size (Rad, mm, IR, Opt, UV, Xray, Gam)
  • quality : flag of quality of the angular size values ( A=best quality -> E=worst quality, {� } =unknown quality)
  • bibcode : bibcode of the angular size reference
Angular size (arcmin): 		5.89 3.02 143 (Opt) D 2003A&A...412...45P
Syntax of fluxes (or magnitudes) is : "filter-name (System) flux-value [error] quality MultVarFlags bibcode"
  • filter-name : U, B, V, R, I, G, J, H, K, u, g, r, i, z
  • (System) : may be AB (default is Vega)
  • flux-value : value of flux or magnitude
  • [error] : error value
  • quality : flag of quality of the flux value ( A=best quality -> E=worst quality, {� } =unknown quality)
  • MultVarFlags : Mult is zero or one char (J) for joined photometry ; Var can be zero or two chars (V[0-4])
  • bibcode : bibcode of the flux reference
Fluxes (12) :
U (AB) 11.77 [0.03] C 2014MNRAS.445..881C
B (AB) 11.03 [0.03] C 2014MNRAS.445..881C
V 10.16 [0.13] D 2007ApJS..173..185G
R (AB) 9.51 [0.03] C 2014MNRAS.445..881C
J 8.345 [0.020] C 2006AJ....131.1163S
H 7.722 [0.023] C 2006AJ....131.1163S
K 7.524 [0.030] C 2006AJ....131.1163S
u (AB) 13.560 [0.005] C 2009ApJS..182..543A
g (AB) 12.410 [0.002] C 2009ApJS..182..543A
r (AB) 11.719 [0.002] C 2009ApJS..182..543A
i (AB) 11.385 [0.002] C 2009ApJS..182..543A
z (AB) 11.088 [0.002] C 2009ApJS..182..543A
SIMBAD within arcmin
', {sourceSize:12, color:'#30a090'})); aladin.on('objectClicked', function(object) { var objName=object.data.MAIN_ID; aladin.showPopup(object.ra,object.dec,'',''+ objName+''); });" title="Show Simbad objects"> Overlay Simbad points in this preview
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The search radius has to be specified by the user. It is currently limited to a maximum of 30 arcsec. It depends mostly on the precision or quality of the coordinates (SIMBAD and VizieR catalogs), the resolution of the images from which the sources were extracted, source extent, and source crowding.
Suggestions are: crowded field: 0.5 to 1.5 arcsec, 3 arcsec otherwise; uncertain coordinates (SIMBAD quality E or coordinates without reference): 5 to 30 arsec (risky!). sed-help-icon
Some important notes on this object about identifications and objects associations.
notes:

Hierarchy : number of linked objects
whatever the membership probability is (see description here ) :

: 6
The count displayed here is the number of children objects.
The list obtained by clicking the button may be larger, as some children may be linked with different references or probability.

%This number is the number of distinct objets linked, by using this button, you will obtain all links (may be more than one) from that object to his children

: 11 		: 53 Display criteria :

The link on the acronym of the identifiers give access to the information for this acronym in the dictionary of nomenclature.
Identifiers (26) :
An access of full data is available using the icon Vizier near the identifier of the catalogue

NGC 2976 KUG 0943+681 SPB 108 [CHM2007] LDC 842 J094715.45+6754589
BWE 0943+6808 LEDA 28120 TC 516 [CHM2007] HDC 552 J094715.45+6754589
GB6 B0943+6809 2MASX J09471545+6754589 UGC 5221 [M98c] 094310.0+680843
87GB 094307.5+680848 2MASXI J0947167+675449 UZC J094715.3+675500 [MI94] Sm 42
HIJASS J0947+67 MCG+11-12-025 Z 312-23 [VDD93] 95
IRAS 09431+6809 PSCz Q09431+6809 Z 0943.1+6809
IRAS F09431+6809 SDSS J094715.30+675500.1 [B93] 9

References (673 between 1850 and 2024) (Total 673)
Simbad bibliographic survey began in 1850 for stars (at least bright stars) and in 1983 for all other objects (outside the solar system).
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Collections of Measurements


velocities : 12    distance : 12   

   

Observing logs


herschel : 12   

   

External archives :

Data at NED - NASA/IPAC Extragalactic Database : NGC 2976

Link by name to the catalogue in VizieR :

NGC 2976 BWE 0943+6808 IRAS 09431+6809 IRAS F09431+6809 KUG 0943+681
2MASX J09471545+6754589 SDSS J094715.30+675500.1 UGC 5221

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