scholarly journals Spitzer Space Telescope spectra of post-AGB stars in the Large Magellanic Cloud – polycyclic aromatic hydrocarbons at low metallicities

2014 ◽  
Vol 439 (2) ◽  
pp. 1472-1493 ◽  
Author(s):  
Mikako Matsuura ◽  
Jeronimo Bernard-Salas ◽  
T. Lloyd Evans ◽  
Kevin M. Volk ◽  
Bruce J. Hrivnak ◽  
...  
Keyword(s):  
Polycyclic Aromatic Hydrocarbons ◽  
Aromatic Hydrocarbons ◽  
Large Magellanic Cloud ◽  
Magellanic Cloud ◽  
Agb Stars ◽  
Spitzer Space Telescope ◽  
Space Telescope ◽  
Polycyclic Aromatic

scholarly journals Spitzer spectroscopy of unusual hydrocarbons in cool radiative environments

2008 ◽  
Vol 4 (S251) ◽  
pp. 191-194 ◽  
Author(s):  
G. C. Sloan
Keyword(s):  
Polycyclic Aromatic Hydrocarbons ◽  
Aromatic Hydrocarbons ◽  
Laboratory Data ◽  
Aliphatic Hydrocarbons ◽  
Spitzer Space Telescope ◽  
Space Telescope ◽  
Radiation Fields ◽  
Polycyclic Aromatic ◽  
Class C ◽  
Larger Sample

AbstractThe Spitzer Space Telescope has discovered several objects with unusual spectra, where the emission features from polycyclic aromatic hydrocarbons (PAHs) are shifted to longer wavelengths than normally observed. Previously, only two of these class C PAH spectra had been identified. The new and larger sample reveals that PAHs emit at longer wavelengths when processed by cooler radiation fields. Limited laboratory data show that samples with mixtures of aromatic and aliphatic hydrocarbons produce emission features at longer wavelengths than purely aromatic samples. The aliphatic bonds are more fragile and would only survive in cooler radiation fields. In harsher radiation fields, the aliphatics attached to the aromatic hydrocarbons are destroyed.

scholarly journals The chemistry of carbon dust formation

1999 ◽  
Vol 191 ◽  
pp. 251-260 ◽  
Author(s):  
Isabelle Cherchneff ◽  
Piero Cau
Keyword(s):  
Silicon Carbide ◽  
Polycyclic Aromatic Hydrocarbons ◽  
Aromatic Hydrocarbons ◽  
Laboratory Experiments ◽  
Carbonaceous Material ◽  
Dust Formation ◽  
Agb Stars ◽  
Metal Carbides ◽  
Chemical Models ◽  
Polycyclic Aromatic

We shall review the various types of chemistry involved in the formation of carbonaceous material present in carbon-rich AGB stars, mainly amorphous carbon, silicon carbide and other metal carbides discovered in pre-solar Stardust extracted from meteorites. The chemistry is discussed in the context of laboratory experiments and their application to circumstellar AGB winds. Emphasis is put on polycyclic aromatic hydrocarbons (PAHs), titanium carbide clusters and silicon carbide grains. Attempt to explain the condensation sequences derived from the study of pre-solar grains of meteoretical origin is made on the basis of physio-chemical models which describe the periodically shocked gas close to the photosphere of AGB stars.

scholarly journals The properties of Polycyclic Aromatic Hydrocarbons in galaxies: constraints on PAH sizes, charge and radiation fields

2021 ◽  
Author(s):  
D Rigopoulou ◽  
M Barale ◽  
D C Clary ◽  
X Shan ◽  
A Alonso-Herrero ◽  
...  
Keyword(s):  
Polycyclic Aromatic Hydrocarbons ◽  
Radiation Field ◽  
Aromatic Hydrocarbons ◽  
Density Functional ◽  
Infrared Emission ◽  
Band Ratio ◽  
Space Telescope ◽  
Band Ratios ◽  
Polycyclic Aromatic ◽  
The Impact

Abstract Based on theoretical spectra computed using Density Functional Theory we study the properties of Polycyclic Aromatic Hydrocarbons (PAH). In particular using bin-average spectra of PAH molecules with varying number of carbons we investigate how the intensity of the mid-infrared emission bands, 3.3, 6.2, 7.7 and 11.3 μm, respond to changes in the number of carbons, charge of the molecule, and the hardness of the radiation field that impinges the molecule. We confirm that the 6.2/7.7 band ratio is a good predictor for the size of the PAH molecule (based on the number of carbons present). We also investigate the efficacy of the 11.3/3.3 ratio to trace the size of PAH molecules and note the dependence of this ratio on the hardness of the radiation field. While the ratio can potentially also be used to trace PAH molecular size, a better understanding of the impact of the underlying radiation field on the 3.3 μm feature and the effect of the extinction on the ratio should be evaluated. The newly developed diagnostics are compared to band ratios measured in a variety of galaxies observed with the Infrared Spectrograph on board the Spitzer Space Telescope. We demonstrate that the band ratios can be used to probe the conditions of the interstellar medium in galaxies and differentiate between environments encountered in normal star forming galaxies and Active Galactic Nuclei. Our work highlights the immense potential that PAH observations with the James Webb Space Telescope will have on our understanding of the PAH emission itself and of the physical conditions in galaxies near and far.

scholarly journals Studying Asymptotic Giant Branch Stars in the JWST Era

Universe ◽  
2020 ◽  
Vol 6 (12) ◽  
pp. 223
Author(s):  
Paolo Ventura ◽  
Ester Marini ◽  
Silvia Tosi ◽  
Flavia Dell’Agli
Keyword(s):  
Large Magellanic Cloud ◽  
Magellanic Cloud ◽  
Asymptotic Giant Branch ◽  
Dust Formation ◽  
Asymptotic Giant Branch Stars ◽  
Agb Stars ◽  
Space Telescope ◽  
James Webb Space Telescope ◽  
Giant Branch Stars

We explore the potential offered by the incoming launch of the James Webb Space Telescope, to study the stars evolving through the asymptotic giant branch (AGB) phase. To this aim we compare data of AGB stars in the Large Magellanic Cloud, taken with the IRS spectrograph, with the results from modelling of AGB evolution and dust formation in the wind. We find that the best diagrams to study M- and C-stars are, respectively, ([F770W]−[F2500W], [F770W]) and ([F770W]−[F1800W], [F1800W]). ([F770W]−[F2500W], [F770W]) turns out to be the best way of studying the AGB population in its entirely.

scholarly journals THESPITZERSURVEY OF THE SMALL MAGELLANIC CLOUD (S3MC): INSIGHTS INTO THE LIFE CYCLE OF POLYCYCLIC AROMATIC HYDROCARBONS

2010 ◽  
Vol 715 (2) ◽  
pp. 701-723 ◽  
Author(s):  
Karin M. Sandstrom ◽  
Alberto D. Bolatto ◽  
B. T. Draine ◽  
Caroline Bot ◽  
Snežana Stanimirović
Keyword(s):  
Polycyclic Aromatic Hydrocarbons ◽  
Life Cycle ◽  
Aromatic Hydrocarbons ◽  
Magellanic Cloud ◽  
Small Magellanic Cloud ◽  
Polycyclic Aromatic
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