scholarly journals Observations of 23 Planetary Nebulae at 408 MHz

1969 ◽  
Vol 22 (4) ◽  
pp. 545 ◽  
Author(s):  
AE Le Marne
Keyword(s):  
Planetary Nebulae ◽  
Radio Flux ◽  
Recombination Line ◽  
Hydrogen Recombination

Various observers (e.g. Slee and Orchiston 1965; Davies et al. 1967; Hughes 1967; Thompson and Colvin 1967; Thompson, Colvin, and Stanley 1967; Kaftan-Kassim 1968) have so far detected nearly 100 planetary nebulae a.t high radiofrequencies (~3 GHz). In this range, the nebulae have been shown to be optically thin, their spectra being almost flat. Wherever possible, the radio flux densities have been compared with hydrogen recombination line observations.

Recombination Line versus Forbidden Line Abundances in Planetary Nebulae

2005 ◽  
Vol 157 (2) ◽  
pp. 371-395 ◽  
Author(s):  
Mark Robertson‐Tessi ◽  
Donald R. Garnett
Keyword(s):  
Planetary Nebulae ◽  
Recombination Line

scholarly journals Probing Sagittarius A* accretion with ALMA

2016 ◽  
Vol 11 (S322) ◽  
pp. 21-24
Author(s):  
Elena Murchikova
Keyword(s):  
Galactic Center ◽  
Accretion Rate ◽  
Recombination Line ◽  
Ionized Gas ◽  
X Ray ◽  
Sagittarius A ◽  
Hydrogen Recombination ◽  
Unique Probe ◽  
Cool Gas

AbstractThe submm Hydrogen recombination line technique can be used as a probe of the Galactic Center. We present the results of our H30α observations of ionized gas from within 0.015 pc around SgrA*. The observations were obtained on ALMA in cycle 3. The line was not detected, but we were able to set a limit on the mass of the cool gas (T~ 104 K) at 2 × 10−3M⊙. This is the unique probe of gas cooler than T ~106 K traced by X-ray emission. The total amount of gas near SgrA* gives us clues to understanding the accretion rate of SgrA*.

scholarly journals Determination of Element Abundances in Planetary Nebulae from Recombination Line Spectra

1993 ◽  
Vol 155 ◽  
pp. 573-573
Author(s):  
A.A. Nikitin ◽  
A.F. Kholtygin ◽  
A.A. Sapar ◽  
T. Kh. Feklistova
Keyword(s):  
Planetary Nebulae ◽  
Recombination Line ◽  
Element Abundances

Carbon, nitrogen and oxygen abundances have been found from the recombination lines for 63 planetary nebulae.

scholarly journals Millimetre observations of Planetary Nebulae

1997 ◽  
Vol 180 ◽  
pp. 266-266
Author(s):  
L.-Å. Nyman ◽  
G. Garay ◽  
H. E. Schwarz
Keyword(s):  
Planetary Nebulae ◽  
Recombination Line

We have observed a sample of 16 PNe of different morphological classes (from stellar to bipolar) in the mm-region, using the 15m Swedish-ESO Submillimetre Telescope (SEST). Continuum observations at 230 GHz were made with the SEST bolometer, and recombination line and continuum observations at 99 GHz (H40α) and 147 GHz (H35α) were made with SIS receivers.

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 ALMA observations of the submillimetre hydrogen recombination line from the type 2 active nucleus of NGC 1068

2016 ◽  
Vol 459 (4) ◽  
pp. 3629-3634 ◽  
Author(s):  
Takuma Izumi ◽  
Kouichiro Nakanishi ◽  
Masatoshi Imanishi ◽  
Kotaro Kohno
Keyword(s):  
Recombination Line ◽  
Active Nucleus ◽  
Hydrogen Recombination ◽  
Ngc 1068

Element abundances in planetary nebulae from recombination line spectra

1994 ◽  
Vol 3 (1-2) ◽  
pp. 112-123
Author(s):  
A.A. Nikitin ◽  
A.F. Kholtygin ◽  
A. Sapar ◽  
T. Feklistova
Keyword(s):  
Planetary Nebulae ◽  
Recombination Line ◽  
Element Abundances

scholarly journals In-depth study of the hypercompact H II region G24.78+0.08 A1

2019 ◽  
Vol 624 ◽  
pp. A100 ◽  
Author(s):  
R. Cesaroni ◽  
M. T. Beltrán ◽  
L. Moscadelli ◽  
Á. Sánchez-Monge ◽  
R. Neri
Keyword(s):  
Massive Star ◽  
Physical Structure ◽  
Continuum Emission ◽  
Expansion Velocity ◽  
Recombination Line ◽  
Hydrogen Recombination ◽  
Lyman Continuum ◽  
Depth Study ◽  
Region Size ◽  
The Continuum

Context. The earliest phases of the evolution of a massive star are closely related to the developement of an H II region. Hypercompact H II regions are the most interesting in this respect because they are very young, and hence best suited to study the beginning of the expansion of the ionised gas inside the parental core. Aims. We have analysed the geometrical and physical structure of the hypercompact H II region G24.78+0.08 A1, making use of new continuum and hydrogen recombination line data (H41α, H63α, H66α, H68α) and data from the literature (H30α, H35α). Methods. We fit the continuum spectrum with a homogenous, isothermal shell of ionised gas at 104 K and derive the size of the H II region and the Lyman continuum luminosity of the ionising star. We also fit the recombination line spectra emitted from the same shell with a model taking into account expansion at constant speed. Results. The best fits to the continuum and line spectra allow the derivation of the Lyman continuum luminosity of the ionising star, H II region size, geometrical thickness of the shell, and expansion velocity. Comparison between the 5 cm and 7 mm brightness temperature distributions demonstrates that a thin layer of ionised gas of a few 1000 K at the surface of the H II region is necessary to reproduce the morphology of the continuum emission at both wavelengths. Conclusions. We confirm that the G24 A1 hypercompact H II region consists of a thin shell ionised by an O9.5 star. The shell is expanding at a speed comparable to the sound speed in the ionised gas. The radius of the H II region exceeds the critical value needed to trap the ionised gas by the gravitational field of the star, consistent with the observed expansion.

On the radio and near-infrared hydrogen recombination-line emission from M82

1980 ◽  
Vol 238 ◽  
pp. 41 ◽  
Author(s):  
L. F. Rodriguez ◽  
E. J. Chaisson
Keyword(s):  
Near Infrared ◽  
Line Emission ◽  
Recombination Line ◽  
Hydrogen Recombination

Observations of infrared hydrogen recombination line emission from external galaxies

1984 ◽  
Vol 279 ◽  
pp. 563 ◽  
Author(s):  
S. C. Beck ◽  
S. Beckwith ◽  
I. Gatley
Keyword(s):  
Line Emission ◽  
Recombination Line ◽  
Hydrogen Recombination ◽  
External Galaxies
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