2008A&A...486..191P


Query : 2008A&A...486..191P

2008A&A...486..191P - Astronomy and Astrophysics, volume 486, 191-208 (2008/7-4)

Resolving distance ambiguities towards 6.7 GHz methanol masers.

PANDIAN J.D., MOMJIAN E. and GOLDSMITH P.F.

Abstract (from CDS):

Distances to most star forming regions are determined using kinematics, through the assumption that the observed radial velocity arises from the motion of the source with respect to the Sun resulting from the differential rotation of Galaxy. The primary challenge associated with the application of this technique in the inner Galaxy is the kinematic distance ambiguity. In this work, we aim to resolve the kinematic distance ambiguity towards a sample of 6.7GHz methanol masers, which are signposts of the early stages of massive star formation. We measured 21cm HI absorption spectra using the Very Large Array in C and CnB configurations. A comparison of the maximum velocity of HI absorption with the source velocity and tangent point velocity was used to resolve the kinematic distance ambiguity. We resolved the distance ambiguity towards 41 sources. Distance determinations that are in conflict with previous measurements are discussed. The NE2001 spiral arm model is broadly consistent with the locations of the star forming complexes. We find that the use of vertical scale height arguments to resolve the distance ambiguity can lead to erroneous classifications for a significant fraction of sources.

Abstract Copyright:

Journal keyword(s): Galaxy: kinematics and dynamics - Galaxy: structure - HII regions

VizieR on-line data: <Available at CDS (J/A+A/486/191): table1.dat>

Simbad objects: 13

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Number of rows : 13
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 NAME Per Arm PoG 03 30 +45.0           ~ 1519 0
2 NAME Crux-Scutum Spiral Arm reg 12 30 -60.0           ~ 306 0
3 3C 286 Sy1 13 31 08.2883506368 +30 30 32.960091564   17.51 17.25     ~ 4351 2
4 NAME Car-Sgr Arm PoG 15 00 -40.0           ~ 518 1
5 NAME Galactic Center reg 17 45 39.60213 -29 00 22.0000           ~ 14463 0
6 NAME Sgr A* X 17 45 40.03599 -29 00 28.1699           ~ 4400 3
7 GAL 010.15-00.34 HII 18 09 21.5680 -20 19 27.720           ~ 74 0
8 RAFGL 2078 HII 18 09 25.9 -20 19 25           ~ 80 1
9 W 31 SFR 18 10 28.6 -19 55 51           ~ 261 0
10 SNR G030.8-00.0 SNR 18 47 32 -01 56.5           ~ 531 0
11 [KB94] 21 HII 18 52 20.3 +00 25 50           ~ 5 0
12 W 51 SNR 19 23 50 +14 06.0           ~ 1278 1
13 NAME Local Arm reg ~ ~           ~ 540 0

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