2011ApJ...736...83H


C.D.S. - SIMBAD4 rel 1.7 - 2019.10.20CEST17:54:42

2011ApJ...736...83H - Astrophys. J., 736, 83 (2011/August-1)

Magnetic fields in large-diameter H II regions revealed by the Faraday rotation of compact extragalactic radio sources.

HARVEY-SMITH L., MADSEN G.J. and GAENSLER B.M.

Abstract (from CDS):

We present a study of the line-of-sight magnetic fields in five large-diameter Galactic H II regions. Using the Faraday rotation of background polarized radio sources, as well as dust-corrected Hα surface brightness as a probe of electron density, we estimated the strength and orientation of the magnetic field along 93 individual sight lines through the H II regions. Each of the H II regions displayed a coherent magnetic field. The magnetic field strength (line-of-sight component) in the regions ranges from 2 to 6 µG, which is similar to the typical magnetic field strength in the diffuse interstellar medium. We investigated the relationship between magnetic field strength and electron density in the five H II regions. The slope of magnetic field versus density in the low-density regime (0.8/cm3 < ne<30/cm3) is very slightly above zero. We also calculated the ratio of thermal to magnetic pressure, βth, for each data point, which fell in the range 1.01 < βth< 25. Finally, we studied the orientation of the magnetic field in the solar neighborhood (d < 1.1 kpc) using our data from five H II regions along with existing measurements of the line-of-sight magnetic field strength from polarized pulsars whose distances have been determined from their annual parallax. We identify a net direction for the magnetic field in the solar neighborhood, but find no evidence for a preferred vertical direction of the magnetic field above or below the Galactic plane.

Abstract Copyright:

Journal keyword(s): H II regions - ISM: magnetic fields - polarization - radio continuum: ISM

Simbad objects: 19

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Number of rows : 19

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2019
#notes
1 NGC 7822 HII 00 01 08.58 +67 25 17.0           ~ 112 3
2 V* V747 Cep Al* 00 01 46.8679211513 +67 30 25.102163893 11.6 11.38 10.07     O5.5V(n)((f)) 39 0
3 NGC 884 OpC 02 22 23 +57 07.5           ~ 436 0
4 NAME Heart Nebula HII 02 32.7 +61 27           ~ 271 1
5 SH 2-205 HII 03 52 14 +53 25.0           ~ 35 0
6 NGC 1499 HII 04 03 18 +36 25.3           ~ 150 0
7 * alf Cam s*b 04 54 03.0103983 +66 20 33.636467 3.47 4.34 4.29 4.18 4.18 O9Ia 633 1
8 Siv 3 HII 04 57.5 +65 29           ~ 6 0
9 Cl Collinder 69 OpC 05 35 06 +09 56.0     2.8     ~ 214 0
10 NAME lam Ori Molecular Ring HII 05 35.3 +09 56           ~ 63 1
11 NAME Car Arm PoG 10 00 -60.0           ~ 367 1
12 NAME Crux-Scutum Spiral Arm reg 12 30 -60.0           ~ 263 0
13 RCW 94 HII 15 40.8 -54 10           ~ 5 0
14 PSR B1604-00 Psr 16 07 12.1034 -00 32 40.830           ~ 197 0
15 GUM 51 HII 16 10.0 -49 08           ~ 21 1
16 LBN 006.00+24.73 HII 16 35 56.8 -12 43 05           ~ 51 0
17 * zet Oph Be* 16 37 09.5390545 -10 34 01.529471 1.73 2.58 2.56 2.46 2.50 O9.2IVnn 1705 2
18 PSR J1643-1224 Psr 16 43 38.15583 -12 24 58.7200           ~ 153 1
19 Ass Cyg OB 1 As* 20 17.8 +37 38           ~ 237 1

    Equat.    Gal    SGal    Ecl

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2019.10.20-17:54:42

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