scholarly journals Deuterium Balmer Emission from Nebulae

2000 ◽  
Vol 198 ◽  
pp. 238-239
Author(s):  
Guillaume Hébrard ◽  
Daniel Péquignot ◽  
Alfred Vidal-Madjar ◽  
Jeremy R. Walsh ◽  
Roger Ferlet
Keyword(s):  
Optical Spectroscopy ◽  
Molecular Cloud ◽  
Planetary Nebula ◽  
H Ii Regions ◽  
Orion Nebula ◽  
Excitation Mechanism ◽  
Upper Limit ◽  
Balmer Lines ◽  
Low Metallicity ◽  
H Ii Region

We report on the detection and first identification of the deuterium Balmer lines dα and dβ, observed in emission in the Orion Nebula (M 42). The excitation mechanism is UV fluorescence from the Lyman(D i) lines at the interface between the H ii region and the molecular cloud. These lines may open the possibility to measure D/H in galactic H ii regions and, e.g., low-metallicity extragalactic H ii regions, using optical spectroscopy. Fluorescence provides an extremely sensitive way to detect deuterium. Thus, the non-detection of dα and dβ in the planetary nebula NGC 6572 leads to the stringent upper limit (D/H)ngc 6572 less than the order of 1 × 10−7.

The Deuterium Balmer Series

2005 ◽  
Vol 13 ◽  
pp. 811-812
Author(s):  
Guillaume Hébrard
Keyword(s):  
Spectral Resolution ◽  
Magellanic Clouds ◽  
High Spectral Resolution ◽  
Excitation Mechanism ◽  
Balmer Series ◽  
Detection And Identification ◽  
Balmer Lines ◽  
Low Metallicity ◽  
Resolution Data ◽  
Narrow Emission

AbstractThe first detection and identification of deuterium Balmer lines were recently reported in H ii regions, using high spectral resolution data secured at CFHT and VLT. The Di lines appear as faint, narrow emission features in the blue wings of the H i Balmer lines and can be distinguished from high-velocity Hi emission. The identification as deuterium and the excitation mechanism as fluorescence are both established beyond doubt. The deuterium Balmer series might lead to a new, optical method of deuterium abundance measurement in the interstellar medium. This may be the only way to observe atomic deuterium in objects like the Magellanic Clouds or low metallicity blue compact galaxies.

scholarly journals New line-blanketed model atmospheres and their impact on synthesis models

2003 ◽  
Vol 212 ◽  
pp. 604-611
Author(s):  
Linda J. Smith ◽  
Richard P.F. Norris ◽  
Paul A. Crowther
Keyword(s):  
Model Atmosphere ◽  
Evolutionary Synthesis ◽  
H Ii Regions ◽  
Single Star ◽  
New Model ◽  
New Models ◽  
Low Metallicity ◽  
H Ii Region ◽  
Basic Code ◽  
Photo Ionization

A new grid of ionizing fluxes for O-type and Wolf-Rayet stars is presented for use with evolutionary synthesis codes and analyses of single star H ii regions. A total of 230 expanding, non-LTE, line-blanketed model atmospheres have been calculated for five metallicities (0.05, 0.2, 0.4, 1 and 2 Z⊙). We have used the wm-basic code of Pauldrach et al. (2001) for O-type stars and the cmfgen code of Hillier & Miller (1998) for WR stars. The stellar wind parameters are scaled with metallicity for both O-type and WR stars. The ionizing fluxes of the new models, incorporated into the evolutionary synthesis code STARBURST99 (Leitherer et al. 1999), are compared with the predictions of the original starburst99 and Schaerer & Vacca (1998) for an instantaneous burst. We find large changes in the output ionizing fluxes as a function of age, especially below the He+ edge. In contrast to previous studies, nebular He ii λ4686 will be at, or just below, the detection limit in low metallicity starbursts during the WR phase. The new models have lower fluxes in the He i continuum for Z ≥ 0.4 Z⊙ and ages ≤ 7 Myr because of the increased line-blanketing. The accuracy of the new model atmosphere grid is tested by constructing photo-ionization models for an H ii region where the ionizing flux is provided by an instantaneous burst. The new models occupy the same region in nebular diagnostic diagrams as the observational data of Bresolin et al. (1999), particularly during the WR phase. The new model grid and updated starburst99 code can be downloaded from http://www.star.ucl.ac.uk/starburst.

scholarly journals Upper Limit to the Deuterium Abundance in Planetary Nebulae

2003 ◽  
Vol 209 ◽  
pp. 371-371
Author(s):  
G. Hébrard ◽  
D. Péquignot ◽  
J. R. Walsh ◽  
C. Morisset ◽  
A. Vidal-Madjar ◽  
...  
Keyword(s):  
Molecular Clouds ◽  
Planetary Nebulae ◽  
Observational Evidence ◽  
H Ii Regions ◽  
Balmer Series ◽  
Upper Limit ◽  
Balmer Lines ◽  
Atomic Interface

We recently reported the first detection of the deuterium Balmer series in emission in H II regions, performed at the CFHT (Hébrard et al. 2000a) and at the VLT (Hébrard et al. 2000b). These narrow lines are excited by UV continuum fuorescence and arise at the atomic interface between H II regions and molecular clouds.Following this discovery, we used the CFHT with the Gecko spectrograph to observe Balmer lines in planetary nebulae. The non-detection of the deuterium Balmer lines in planetary nebulae represents the first observational evidence that this isotope was, as expected, destroyed in the parent stars.

The primordial helium abundance determination using multicomponent photoionization modelling of low-metallicity H II regions

2018 ◽  
Vol 8 (1) ◽  
pp. 16-23
Author(s):  
I. Koshmak ◽  
B. Melekh
Keyword(s):  
Chemical Compositions ◽  
H Ii Regions ◽  
Helium Abundance ◽  
Rotating Stars ◽  
Chemical Abundances ◽  
Free Expansion ◽  
Outer Component ◽  
Low Metallicity ◽  
H Ii Region ◽  
Primordial Helium

The method for the multicomponent photoionization modelling (MPhM) of low-metallicity H II regions surrounding the starburst region was developed. The internal structure of the H II region has been determined using the evolutionary modelling of the superwind bubble surrounding the star-forming region. Models of Chevalier and Clegg (1985) and Weaver et al. (1977) have been used to determine the radial distribution of the gas density, the velocity of gas layers, and the temperature within internal components (the region of the superwind free expansion and the cavity, respectively). The chemical abundances in region of the superwind free expansion were obtained from the evolutionary population synthesis with including of rotating stars. The chemical abundances within cavity were defined by averaging over mass the chemical compositions of mixture of the abundances of gas from superwind and ones within outer component, because of gas evaporation from external component into the cavity. External components of our models describe a high-density, thin shell of gas formed by superwind shock and a typical undisturbed hydrodynamically H II region, respectively. Evolutionary grids of multicomponent low-metallicity models are calculated. A comparative analysis of the results of their calculation with the observed data has been carried out. The ionic abundances averaged over modelling volume as well as chemical composition assumed in models were used to derive the new expressions for ionization-correction factors that were used to redetermine the chemical compositions of 88 H II regions in blue compact dwarf galaxies. It must be noticed that we used for this propose the ionic abundances obtained by Izotov et al. (2007). In result the primordial helium abundance and its enrichment during stellar chemical evolution of matter were determined.

scholarly journals 13CO(J = 1-0) Observations of the Orion Molecular Cloud

1987 ◽  
Vol 115 ◽  
pp. 149-150
Author(s):  
K. Sugitani ◽  
Y. Fukui
Keyword(s):  
Millimeter Wave ◽  
High Velocity ◽  
Molecular Cloud ◽  
High Velocity Resolution ◽  
H Ii Region ◽  
Co Emission

We present new 13CO(J = 1-0) measurements of the Orion molecular cloud. The data were taken with the 4-m millimeter-wave telescope of Nagoya University with a beamwidth of 2.7′. The high velocity resolution of 0.1 km s−1 employed has revealed significant details of the 13CO emission toward the H II region.

scholarly journals On the Nature of R 136, the Central Object of 30 Dor. A Comparison by the Galactic Cluster NGC 3603

1984 ◽  
Vol 108 ◽  
pp. 257-258
Author(s):  
Michael Rosa ◽  
Jorge Melnick ◽  
Preben Grosbol
Keyword(s):  
Core Region ◽  
H Ii Regions ◽  
Central Object ◽  
The Core ◽  
Dominant Component ◽  
Galactic Cluster ◽  
H Ii Region

The massive H II region NGC 3603 is the closest galactic counterpart to the giant LMC nebula 30 Dor. Walborn (1973) first compared the ionizing OB/WR clusters of the two H II regions and suggested that R 136, the unresolved luminous WR + 0 type central object of 30 Dor, might be a multiple system like the core region of NGC 3603. Suggestions that the dominant component of R 136, i.e. R 136A, might be either a single or a very few supermassive and superluminous stars (Schmidt-Kaler and Feitzinger 1982, Savage et al. 1983) have recently been disputed by Moffat and Seggewiss (1983) and Melnick (1983), who have presented spectroscopic and photometric evidence to support the hypothesis of an unresolved cluster of stars. We have extended Walborn's original comparison of the apparent morphology of the two clusters by digital treatment of the images to simulate how the galactic cluster would look like if it were located in the LMC

scholarly journals Three generations of stars: a possible case of triggered star formation

2020 ◽  
Vol 496 (1) ◽  
pp. 870-874
Author(s):  
M B Areal ◽  
A Buccino ◽  
S Paron ◽  
C Fariña ◽  
M E Ortega
Keyword(s):  
Star Formation ◽  
Young Stellar Objects ◽  
H Ii Regions ◽  
Stellar Objects ◽  
Three Generations ◽  
The North ◽  
Western Border ◽  
H Ii Region ◽  
New Generation ◽  
North Western

ABSTRACT Evidence for triggered star formation linking three generations of stars is difficult to assemble, as it requires convincingly associating evolved massive stars with H ii regions that, in turn, would need to present signs of active star formation. We present observational evidence for triggered star formation relating three generations of stars in the neighbourhood of the star LS II +26 8. We carried out new spectroscopic observations of LS II +26 8, revealing that it is a B0 III-type star. We note that LS II +26 8 is located exactly at the geometric centre of a semi-shell-like H ii region complex. The most conspicuous component of this complex is the H ii region Sh2-90, which is probably triggering a new generation of stars. The distances to LS II +26 8 and to Sh2-90 are in agreement (between 2.6 and 3 kpc). Analysis of the interstellar medium on a larger spatial scale shows that the H ii region complex lies on the north-western border of an extended H2 shell. The radius of this molecular shell is about 13 pc, which is in agreement with what an O9 V star (the probable initial spectral type of LS II +26 8 as inferred from evolutive tracks) can generate through its winds in the molecular environment. In conclusion, the spatial and temporal correspondences derived in our analysis enable us to propose a probable triggered star formation scenario initiated by the evolved massive star LS II +26 8 during its main-sequence stage, followed by stars exciting the H ii region complex formed in the molecular shell, and culminating in the birth of young stellar objects around Sh2-90.

scholarly journals Evidence for feedback and stellar-dynamically regulated bursty star cluster formation: the case of the Orion Nebula Cluster

2018 ◽  
Vol 612 ◽  
pp. A74 ◽  
Author(s):  
Pavel Kroupa ◽  
Tereza Jeřábková ◽  
František Dinnbier ◽  
Giacomo Beccari ◽  
Zhiqiang Yan
Keyword(s):  
Molecular Cloud ◽  
Massive Stars ◽  
Cluster Formation ◽  
Life Time ◽  
Molecular Gas ◽  
Orion Nebula ◽  
Main Sequence Stars ◽  
Sequence Of Events ◽  
Proposed Model ◽  
Magnitude Diagram

A scenario for the formation of multiple co-eval populations separated in age by about 1 Myr in very young clusters (VYCs, ages less than 10 Myr) and with masses in the range 600–20 000 M⊙ is outlined. It rests upon a converging inflow of molecular gas building up a first population of pre-main sequence stars. The associated just-formed O stars ionise the inflow and suppress star formation in the embedded cluster. However, they typically eject each other out of the embedded cluster within 106 yr, that is before the molecular cloud filament can be ionised entirely. The inflow of molecular gas can then resume forming a second population. This sequence of events can be repeated maximally over the life-time of the molecular cloud (about 10 Myr), but is not likely to be possible in VYCs with mass <300 M⊙, because such populations are not likely to contain an O star. Stellar populations heavier than about 2000 M⊙ are likely to have too many O stars for all of these to eject each other from the embedded cluster before they disperse their natal cloud. VYCs with masses in the range 600–2000 M⊙ are likely to have such multi-age populations, while VYCs with masses in the range 2000–20 000 M⊙ can also be composed solely of co-eval, mono-age populations. More massive VYCs are not likely to host sub-populations with age differences of about 1 Myr. This model is applied to the Orion Nebula Cluster (ONC), in which three well-separated pre-main sequences in the colour–magnitude diagram of the cluster have recently been discovered. The mass-inflow history is constrained using this model and the number of OB stars ejected from each population are estimated for verification using Gaia data. As a further consequence of the proposed model, the three runaway O star systems, AE Aur, μ Col and ι Ori, are considered as significant observational evidence for stellar-dynamical ejections of massive stars from the oldest population in the ONC. Evidence for stellar-dynamical ejections of massive stars in the currently forming population is also discussed.

scholarly journals Abundance Analysis of the J4 Equatorial Knot of the Born-again Planetary Nebula A30

2022 ◽  
Vol 6 (1) ◽  
pp. 4
Author(s):  
Jordan Simpson ◽  
David Jones ◽  
Roger Wesson ◽  
Jorge García-Rojas
Keyword(s):  
Binary System ◽  
Planetary Nebula ◽  
Planetary Nebulae ◽  
Upper Limit ◽  
Chemical Segregation ◽  
Born Again ◽  
Physical And Chemical

Abstract A30 belongs to a class of planetary nebulae identified as “born-again”, containing dense, hydrogen-poor ejecta with extreme abundance discrepancy factors (ADFs), likely associated with a central binary system. We present intermediate-dispersion spectroscopy of one such feature—the J4 equatorial knot. We confirm the apparent physical and chemical segregation of the polar and equatorial knots observed in previous studies, and place an upper limit on the ADF for O2+ of 35, significantly lower than that of the polar knots. These findings further reinforce the theory that the equatorial and polar knots originate from different events.

scholarly journals The H II region-molecular cloud complex W3 - Observations of CO, CS, and HCN

1980 ◽  
Vol 237 ◽  
pp. 711 ◽  
Author(s):  
H. R. Dickel ◽  
J. R. Dickel ◽  
W. J. Wilson ◽  
M. W. Werner
Keyword(s):  
Molecular Cloud ◽  
H Ii Region ◽  
Cloud Complex
Sign in / Sign up

Export Citation Format

Share Document