Recombination-line and continuum observations of compact H II regions at 10.5 GHz

1976 ◽  
Vol 81 ◽  
pp. 512 ◽  
Author(s):  
M. R. Viner ◽  
J. N. Clarke ◽  
V. A. Hughes
Keyword(s):  
H Ii Regions ◽  
Recombination Line

scholarly journals A Survey of Recombination-line Abundances in Planetary Nebulae and H II Regions

2003 ◽  
Vol 209 ◽  
pp. 383-384 ◽  
Author(s):  
Y. G. Tsamis ◽  
M. J. Barlow ◽  
X.-W. Liu ◽  
I. J. Danziger
Keyword(s):  
Planetary Nebulae ◽  
Magellanic Cloud ◽  
H Ii Regions ◽  
Recombination Line ◽  
Large Aperture

We have derived C, N and O abundances, relative to H, using optical recombination lines (ORLs), for a number of galactic planetary nebulae and for three Magellanic Cloud PNe (LMC N66, N141, SMC N87) and compared them with the corresponding abundances derived from collisionally-excited lines (CELs). Our goal was to investigate the fact that PNe ORL abundances are in most cases larger than those obtained from CELs. Our scanning, long-slit observations were combined with large-aperture IUE, IRAS and ISO data to yield integrated abundances for more than half of our target objects.

scholarly journals Recombination Line Survey of Galactic H II Regions.

1967 ◽  
Vol 72 ◽  
pp. 824
Author(s):  
E. C., III Reifenstein ◽  
T. L. Wilson ◽  
B. F. Burke ◽  
P. G. Gomez
Keyword(s):  
H Ii Regions ◽  
Recombination Line ◽  
Line Survey

A hydrogen and helium radio recombination-line survey of galactic H II regions at 10 GHz

1979 ◽  
Vol 229 ◽  
pp. 524 ◽  
Author(s):  
S. M. Lichten ◽  
L. F. Rodriguez ◽  
E. J. Chaisson
Keyword(s):  
H Ii Regions ◽  
Recombination Line ◽  
Radio Recombination Line ◽  
Line Survey

scholarly journals UNTANGLING THE RECOMBINATION LINE EMISSION FROM H ii REGIONS WITH MULTIPLE VELOCITY COMPONENTS

2015 ◽  
Vol 810 (1) ◽  
pp. 42 ◽  
Author(s):  
L. D. Anderson ◽  
L. A. Hough ◽  
TREY V. Wenger ◽  
T. M. Bania ◽  
Dana S. Balser
Keyword(s):  
Line Emission ◽  
H Ii Regions ◽  
Recombination Line

scholarly journals G−0.02−0.07, the compact H ii region complex nearest to the galactic center with ALMA

2019 ◽  
Vol 71 (6) ◽  
Author(s):  
Masato Tsuboi ◽  
Yoshimi Kitamura ◽  
Kenta Uehara ◽  
Atsushi Miyazaki ◽  
Ryosuke Miyawaki ◽  
...  
Keyword(s):  
Shock Wave ◽  
Galactic Center ◽  
Emission Lines ◽  
Continuum Emission ◽  
Molecular Gas ◽  
H Ii Regions ◽  
Recombination Line ◽  
The Galaxy ◽  
H Ii Region ◽  
Absorption Features

Abstract We have observed the compact H ii region complex nearest to the dynamical center of the Galaxy, G−0.02−0.07, using ALMA in the H42α recombination line, CS J = 2–1, H13CO+J = 1–0, and SiO v = 0, J = 2–1 emission lines, and the 86 GHz continuum emission. The H ii regions HII-A to HII-C in the cluster are clearly resolved into a shell-like feature with a bright half and a dark half in the recombination line and continuum emission. The analysis of the absorption features in the molecular emission lines show that H ii-A, B, and C are located on the near side of the “Galactic center 50 km s−1 molecular cloud” (50MC), but HII-D is located on the far side of it. The electron temperatures and densities ranges are Te = 5150–5920 K and ne = 950–2340 cm−3, respectively. The electron temperatures in the bright half are slightly lower than those in the dark half, while the electron densities in the bright half are slightly higher than those in the dark half. The H ii regions are embedded in the ambient molecular gas. There are some molecular gas components compressed by a C-type shock wave around the H ii regions. From the line width of the H42α recombination line, the expansion velocities of HII-A, HII-B, HII-C, and HII-D are estimated to be Vexp = 16.7, 11.6, 11.1, and 12.1 km s−1, respectively. The expansion timescales of HII-A, HII-B, HII-C, and HII-D are estimated to be tage ≃ 1.4 × 104, 1.7 × 104, 2.0 × 104, and 0.7 × 104 yr, respectively. The spectral types of the central stars from HII-A to HII-D are estimated to be O8V, O9.5V, O9V, and B0V, respectively. These derived spectral types are roughly consistent with the previous radio estimation. The positional relation among the H ii regions, the SiO molecule enhancement area, and Class-I maser spots suggest that a shock wave caused by a cloud–cloud collision propagated along the line from HII-C to HII-A in the 50MC. The shock wave would have triggered the massive star formation.

scholarly journals Helium Abundances in Gaseous Nebulae

1989 ◽  
Vol 131 ◽  
pp. 211-211 ◽  
Author(s):  
R.E.S. Clegg ◽  
J. P. Harrington
Keyword(s):  
Planetary Nebulae ◽  
H Ii Regions ◽  
Type I ◽  
Quantum Calculation ◽  
Recombination Line ◽  
Metastable Helium ◽  
Gaseous Nebulae ◽  
The Mean

New collision strengths, from a 19-state quantum calculation for He I, are used to derive revised He/H ratios in planetary nebulae (PN). Empirical formulae are given, for the correction of He I recombination line fluxes for collisional effects, and for the calculation of the population of metastable helium (He I 23S) in gaseous nebulae. The revised He abundances for PN, for four samples of published line fluxes, show a mean ratio He/H = 0.100 ±0.007 if nebulae with neutral He and Type I PN are excluded. The mean reduction due to collisional effects is only 10% for Galactic PN. It is shown that the hypothesis, that He/H should be independent of nebular temperature and density, is better satisfied when collisional effects are allowed for. The new He abundances indicate that there is very little He enrichment in Galactic PN of Types II, III, and IV, and that the enhancement of Type I PN in He over H II regions is reduced from earlier values by one third.

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