scholarly journals Abundances of Refractory Elements in the Orion Nebula

1992 ◽  
Vol 150 ◽  
pp. 281-283
Author(s):  
R. H. Rubin ◽  
E. F. Erickson ◽  
M. R. Haas ◽  
S.W.J. Colgan ◽  
J. P. Simpson ◽  
...  
Keyword(s):  
Gas Phase ◽  
High Dispersion ◽  
Temperature Structure ◽  
Dust Grains ◽  
Orion Nebula ◽  
Refractory Elements ◽  
Solar Si

We assess the gas-phase abundances of Si, C, and Fe from our recent measurements of Si++, C++, and Fe++ in the Orion Nebula by expanding on our earlier “blister” models. The Fe++ 22.9 μm line measured with the KAO yields Fe/H ~ 3 × 10−6 - considerably larger than in the diffuse ISM, where relative to solar, Fe/H is down by ~ 100. However, in Orion, Fe/H is still lower than solar by a factor ~ 10. The C and Si abundances are derived from new IUE high dispersion spectra of the C++ 1907, 1909 Å and Si++ 1883, 1892 Å lines. Gas-phase Si/C = 0.016 in the Orion ionized volume and is particularly insensitive to uncertainties in extinction and temperature structure. The solar value is 0.098. Gas-phase C/H = 3 × 10−4 and Si/H = 4.8 × 10−6. Compared to solar, Si is depleted by 0.135 in the ionized region, while C is essentially undepleted. This suggests that most Si and Fe resides in dust grains even in the ionized volume.

The 6.4 keV Fe Line and the SiO Emission in the GC

2001 ◽  
Vol 205 ◽  
pp. 36-37
Author(s):  
J. Martín-Pintado ◽  
P. de Vicente ◽  
N. Rodríguez-Fernández ◽  
A. Fuente ◽  
P. Planesas
Keyword(s):  
Spatial Distribution ◽  
Gas Phase ◽  
Molecular Clouds ◽  
Galactic Center ◽  
X Rays ◽  
Refractory Elements

We present a map of the Galactic center in the J=l-0 line of SiO covering the region mapped with the ASCA satellite in the 6.4 keV Fe line. We find a correlation between the spatial distribution of the Fe 6.4 keV line and the SiO emission. The SiO abundance increases by more than a factor of 20 in the regions with strong Fe 6.4 keV line. This indicates that the Fe 6.4 keV line mainly arises from molecular clouds with large gas phase abundance of refractory elements. We discuss the implications of the correlation on the origin of the hard X-rays, and the heating and the chemistry of the molecular clouds in the GC.

scholarly journals Possible depletion of metals into dust grains in the core of the Centaurus cluster of galaxies

2019 ◽  
Vol 623 ◽  
pp. A17 ◽  
Author(s):  
K. Lakhchaura ◽  
F. Mernier ◽  
N. Werner
Keyword(s):  
Dust Emission ◽  
Temperature Structure ◽  
Central Metal ◽  
Dust Grains ◽  
Cluster Of Galaxies ◽  
Systematic Uncertainties ◽  
Central Regions ◽  
Metal Abundance ◽  
Reactive Metals ◽  
The Continuum

We present azimuthally averaged metal abundance profiles from a full, comprehensive, and conservative re-analysis of the deep (∼800 ks total net exposure) Chandra/ACIS-S observation of the Centaurus cluster core (NGC 4696). After carefully checking various sources of systematic uncertainties, including the choice of the spectral deprojection method, assumptions about the temperature structure of the gas, and uncertainties in the continuum modeling, we confirm the existence of a central drop in the abundances of the “reactive” elements Fe, Si, S, Mg, and Ca, within r≲10 kpc. The same drops are also found when analyzing the XMM-Newton/EPIC data (∼150 ks). Adopting our most conservative approach, we find that, unlike the central drops seen for Fe, Si, S, Mg and Ca, the abundance of the “nonreactive” element Ar is fully consistent with showing no central drop. This is further confirmed by the significant (> 3σ) central radial increase of the Ar/Fe ratio. Our results corroborate the previously proposed “dust depletion scenario”, in which central metal abundance drops are explained by the deposition of a significant fraction of centrally cooled reactive metals into dust grains present in the central regions of the Centaurus cluster. This is also supported by the previous findings that the extent of the metal abundance drops in NGC 4696 broadly coincides with the infrared dust emission.

Electron spin fine structure constants of the ã3B1 state of SO2

1976 ◽  
Vol 54 (21) ◽  
pp. 2118-2127 ◽  
Author(s):  
K.-E. J. Hallin ◽  
Y. Hamada ◽  
A. J. Merer
Keyword(s):  
Angular Momentum ◽  
Fine Structure ◽  
Solid State ◽  
Gas Phase ◽  
Interaction Parameter ◽  
Electron Spin ◽  
Spin Interaction ◽  
High Dispersion ◽  
Rotational Analysis ◽  
Structure Constants

Rotational analyses have been carried out for the (0,0) bands of the [Formula: see text] absorption systems of S16O2 and S18O2, from high dispersion plates taken with the gases at dry ice temperature. The rotational analysis of the (0,0) band of S16O2 given by Brand, Jones, and di Lauro is confirmed in general, but their values for the anisotropic electron spin fine structure constants are found to be in error. Our new values remove the discrepancy in the sign of the spin–spin interaction parameter β = E between the gas phase work and the solid state value given by Tinti. This discrepancy had been rationalized by Brand, Jones, and di Lauro in terms of a different choice of phases for the angular momentum operators, but this argument is shown to be incorrect. The spectrum of S18O2 confirms our new values for the spin constants in detail.

scholarly journals The ejecta of η Carinae

2006 ◽  
Vol 2 (14) ◽  
pp. 204-204
Author(s):  
Theodore R. Gull
Keyword(s):  
Metal Oxides ◽  
Lower Limit ◽  
High Dispersion ◽  
Dust Grains ◽  
Spectroscopic Observations ◽  
Relative Abundances ◽  
Η Car

AbstractHigh-dispersion spectroscopic observations of the neutral Homunculus and the ionized Little Homunculus, ejecta of η Car, are being analyzed to determine the relative abundances of metals. Thousands of lines of neutral and singly-ionized metals and molecules seen in the Homunculus suggest that this oxygen-, carbon-poor, nitrogen-, helium-rich gas contains very different dust grains likely devoid of metal oxides. The gas to dust ratio is likely much larger than the canonical 100:1 implying that the 12 M⊙ estimate of the ejecta is a lower limit.

scholarly journals Aperture Synthesis Maps of NH2D and CH3OD Lines Toward Orion-KL: The Origin of NH3 and CH3OH

1994 ◽  
Vol 140 ◽  
pp. 241-242 ◽  
Author(s):  
S. Saito ◽  
H. Mikami ◽  
S. Yamamoto ◽  
Y. Murata ◽  
R. Kawabe
Keyword(s):  
Gas Phase ◽  
Aperture Synthesis ◽  
Dust Grains ◽  
Peak Intensity

AbstractThe 111−-101+ transition of NH2D and the 21−20 E transition of CH3OD were mapped toward Orion-KL with the Nobeyama Millimeter Array. The synthesized beamwidth is 4″ to 5″. NH2D and CH3OD are mainly distributed over the peak-intensity regions of NH3 and CH3OH in Orion A, respectively. These results suggest that “most” of the gas-phase ammonia and methanol in the region of Orion-KL originate from dust grains.

scholarly journals Titanium Dioxide-Based Nanocomposites for Enhanced Gas-Phase Photodehydrogenation

Materials ◽  
2019 ◽  
Vol 12 (19) ◽  
pp. 3093 ◽  
Author(s):  
Danny Zanardo ◽  
Elena Ghedini ◽  
Federica Menegazzo ◽  
Elti Cattaruzza ◽  
Maela Manzoli ◽  
...  
Keyword(s):  
Titanium Dioxide ◽  
Gas Phase ◽  
High Surface ◽  
High Surface Area ◽  
Ethanol Conversion ◽  
High Dispersion ◽  
Chemical Production ◽  
Co Catalyst ◽  
Co Catalysts ◽  
Insertion Method

Light-driven processes can be regarded as a promising technology for chemical production within the bio-refinery concept, due to the very mild operative conditions and high selectivity of some reactions. In this work, we report copper oxide (CuO)-titanium dioxide (TiO2) nanocomposites to be efficient and selective photocatalysts for ethanol photodehydrogenation under gas phase conditions, affording 12-fold activity improvement compared to bare TiO2. In particular, the insertion method of the CuO co-catalyst in different TiO2 materials and its effects on the photocatalytic activity were studied. The most active CuO co-catalyst was observed to be highly dispersed on titania surface, and highly reducible. Moreover, such high dispersion was observed to passivate some surface sites where ethanol is strongly adsorbed, thus improving the activity. This kind of material can be obtained by the proper selection of loading technique for both co-catalysts, allowing a higher coverage of photocatalyst surface (complex-precipitation in the present work), and the choice of titania material itself. Loading copper on a high surface area titania was observed to afford a limited ethanol conversion, due to its intrinsically higher reactivity affording to a strong interaction with the co-catalyst.

Low-temperature condensation of carbonaceous dust grains from PAHs

2019 ◽  
Vol 15 (S350) ◽  
pp. 465-467
Author(s):  
Lisseth Gavilan Marin ◽  
Salma Bejaoui ◽  
Gregory Gate ◽  
Michael Haggmark ◽  
Nathan Svadlenak ◽  
...  
Keyword(s):  
Low Temperature ◽  
Gas Phase ◽  
Solid Particles ◽  
Dust Grains ◽  
Supersonic Expansion ◽  
Laser Desorption Mass Spectrometry ◽  
Parent Molecule ◽  
Aromatic Molecules ◽  
Gas Phase Molecules ◽  
Two Phases

AbstractInterstellar carbon has been detected in both gas-phase molecules and solid particles. The goal of this study is to identify the link between these two phases of cosmic carbon. Here we report preliminary results on the low temperature formation of carbonaceous dust grains from gas-phase aromatic hydrocarbon precursors. This is done using the supersonic expansion of an argon jet seeded with aromatic molecules and exposed to an electrical discharge. We report experimental evidence of efficient carbon dust condensation from aromatic molecules including benzene and naphthalene. The molecular content of the solid grains is probed with laser desorption mass spectrometry. The mass spectra reveal a rich molecular composition including fragments of the parent molecule but also growth into larger molecular species.

scholarly journals Effects of Dust Formation on Chemical Abundances

1983 ◽  
Vol 103 ◽  
pp. 259-264 ◽  
Author(s):  
G. A. Shields
Keyword(s):  
Gas Phase ◽  
Planetary Nebula ◽  
Planetary Nebulae ◽  
Infrared Emission ◽  
Chemical Abundances ◽  
Line Intensities ◽  
Refractory Elements ◽  
Grain Formation ◽  
Residual Gas ◽  
Inner Parts

Gas-phase abundances of C, Mg, Si, Ca, and Fe have been measured for a number of planetary nebulae on the basis of optical, ultraviolet, and infrared emission-line intensities. The abundances of Si, Ca, and Fe show characteristic depletions of one to two orders-of-magnitude as a result of grain formation. Magnesium shows a similar depletion in the outer parts of several planetary nebulae, but it is undepleted in their inner parts. Carbon is not detectably depleted by grain formation. Efficient condensation of refractory elements can easily occur during the early stages of formation of a planetary nebula; but the observed, residual gas-phase abundances are not understood. Observations of molecules in the envelopes of late-type stars may provide useful clues.

scholarly journals Variations in the abundance of small particles

1991 ◽  
Vol 147 ◽  
pp. 151-160
Author(s):  
F. Boulanger
Keyword(s):  
Gas Phase ◽  
Large Amplitude ◽  
Molecular Clouds ◽  
Velocity Structure ◽  
Size Range ◽  
Interstellar Matter ◽  
Dust Grains ◽  
Small Particles ◽  
Order Of Magnitude ◽  
Ir Emission

IRAS images of nearby molecular clouds show that the mid-IR emission from small particles in the size range 102 to 105 atoms is distributed very differently from the 100 μm emission from large dust grains. Variations in color ratios by as much as one order of magnitude are seen on all angular scales. We summarize observational properties of the color variations and argue that neither their large amplitude nor their morphology can be explained by changes of the excitation by the UV radiation field only. The color variations reflect considerable inhomogeneities in the abundance of small particles. We suggest that the abundance variations are related to the cycling of interstellar matter between the gas phase and dust grains. This interpretation entails that clouds with distinct IR colors differ in their density and velocity structure and that cycling of matter between gas phase and dust grains is more ubiquitous and rapid that generally thought.

scholarly journals Laboratory constraints on ice formation, restructuring and desorption

2015 ◽  
Vol 11 (A29A) ◽  
pp. 309-312
Author(s):  
Karin I. Öberg
Keyword(s):  
Gas Phase ◽  
Chemical Reactions ◽  
Organic Molecules ◽  
Protoplanetary Disks ◽  
Ice Formation ◽  
Circumstellar Dust ◽  
Dust Grains ◽  
Complex Molecules ◽  
Detailed Understanding ◽  
Complex Organic

AbstractIces form on the surfaces of interstellar and circumstellar dust grains though freeze-out of molecules and atoms from the gas-phase followed by chemical reactions. The composition, chemistry, structure and desorption properties of these ices regulate two important aspects of planet formation: the locations of major condensation fronts in protoplanetary disks (i.e. snow lines) and the formation efficiencies of complex organic molecules in astrophysical environments. The latter regulates the availability of prebiotic material on nascent planets. With ALMA it is possible to directly observe both (CO) snowlines and complex organics in protoplanetary disks. The interpretation of these observations requires a detailed understanding of the fundamental ice processes that regulate the build-up, evolution and desorption of icy grain mantles. This proceeding reviews how experiments on thermal CO and N2 ice desorption, UV photodesorption of CO ice, and CO diffusion in H2O ice have been used to guide and interpret astrochemical observations of snowlines and complex molecules.

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