2001ApJ...550..799B


Query : 2001ApJ...550..799B

2001ApJ...550..799B - Astrophys. J., 550, 799-816 (2001/April-1)

Very large array H I Zeeman observations toward the W49 complex.

BROGAN C.L. and TROLAND T.H.

Abstract (from CDS):

We report Very Large Array (VLA) H I Zeeman observations toward the W49A star-forming region and the supernova remnant W49B. Line-of-sight magnetic fields (Blos) of 60-300 µG at 25" resolution were detected toward W49A at velocities of ∼4 and ∼7 km.s–1. The Blos values measured toward W49A show a significant increase in field strength with higher resolution, especially for the ∼4 km.s–1 H I component. The H I gas in the velocity range -5-25 km.s–1 toward W49A shows good agreement both kinematically and spatially with molecular emission intrinsically associated with W49A. On the basis of comparisons with molecular data toward W49A, we suggest that the ∼4 km.s–1 H I component is directly associated with the northern part of the H II region ring, while the ∼7 km.s–1 H I component seems to originate in a lower density halo surrounding W49A. We estimate that the W49A North core is significantly subvirial (2T/{mid}W{mid}∼0.2) and that the total kinetic+magnetic energies amount to less than (1)/(3) of the total W49A North gravitational energy. These magnetic field results suggest that W49A North is unstable to overall gravitational collapse, in agreement with evidence that the halo is collapsing onto the W49A North ring of H II regions. The majority of the H I column density toward W49B comes from Sagittarius arm clouds along the line of sight at ∼40 and ∼60 km.s–1. No significant magnetic fields were detected toward W49B. Comparison of the spectral distribution of H I gas toward W49A and W49B suggests that evidence placing W49B 3 kpc closer to the Sun (i.e., at 8 kpc) than W49A is quite weak. Although we cannot place W49B at the same distance as W49A, we find the morphology of a ∼5 km.s–1 H I component toward the southern edge of W49B suggestive of an interaction.


Abstract Copyright:

Journal keyword(s): ISM: Clouds - ISM: individual (W49A, W49B) - ISM: Magnetic Fields - Radio Lines: ISM

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 - 2021
#notes
1 W 3 MoC 02 27 04.10 +61 52 27.1           ~ 984 3
2 NAME M 17 SW SFR 18 20 23.1 -16 11 43           ~ 258 0
3 NGC 6618 OpC 18 20 47 -16 10.3           ~ 1526 0
4 [DJW84] W49 Q HII 19 10 10.51 +09 05 11.9           ~ 12 1
5 [DJW84] W49 BB Rad 19 10 10.62 +09 05 45.6           ~ 4 0
6 [DJW84] W49 CC Rad 19 10 11.72 +09 06 33.5           ~ 5 0
7 [DJW84] W49 S HII 19 10 11.73 +09 05 27.2           ~ 11 1
8 [DJW84] W49 A HII 19 10 12.93 +09 06 11.9           ~ 31 0
9 W 49n HII 19 10 13.2 +09 06 12           ~ 425 3
10 [DJW84] W49 G HII 19 10 13.57 +09 06 12.9           ~ 25 0
11 [DJW84] W49 GG Rad 19 10 13.67 +09 06 50.0           ~ 3 0
12 [DJW84] W49 I HII 19 10 13.73 +09 06 24.9           ~ 11 0
13 [DJW84] W49 J HII 19 10 14.14 +09 06 15.4           ~ 13 0
14 [DJW84] W49 HH Rad 19 10 14.21 +09 05 52.8           ~ 3 0
15 [DJW84] W49 L HII 19 10 14.54 +09 06 18.9           ~ 11 0
16 [DJW84] W49 II Rad 19 10 14.86 +09 06 44.0           ~ 2 0
17 W 49a SFR 19 10 15.7 +09 06 05           ~ 268 2
18 [DJW84] W49 O Rad 19 10 16.34 +09 06 07.1           ~ 8 0
19 [DJW84] W49 JJ Rad 19 10 18.54 +09 06 09.0           ~ 3 0
20 W 49 SFR 19 10 20 +09 07.7           ~ 529 1
21 NAME W 49A South HII 19 10 21.6 +09 05 03           ~ 51 2
22 [DJW84] W49 LL Rad 19 10 22.87 +09 04 14.4           ~ 2 0
23 [DJW84] W49 MM Rad 19 10 23.34 +09 06 04.3           ~ 3 0
24 W 49b SNR 19 11 09.000 +09 06 24.00           ~ 416 1
25 [DJW84] W49 DD HII ~ ~           ~ 5 0

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2021.09.21-16:43:27

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