scholarly journals Unidentified Infrared Emission Features

2012 ◽  
Vol 10 (H16) ◽  
pp. 699-700 ◽  
Author(s):  
Christine Joblin
Keyword(s):  
Polycyclic Aromatic Hydrocarbon ◽  
Infrared Emission ◽  
Interstellar Matter ◽  
Physical Conditions ◽  
Evolutionary Scenario ◽  
Polycyclic Aromatic ◽  
Aromatic Species ◽  
Hydrocarbon Molecules ◽  
Uv Photons ◽  
Ir Bands

AbstractWhen referring to unidentified infrared emission features, one has in mind the series of aromatic IR bands (AIBs) between 3.3 and 15 μm that are observed in emission in many environments where UV photons irradiate interstellar matter. These bands are now used by astronomers to classify objects and characterize local physical conditions. However, a deep analysis cannot proceed without understanding the properties of the band carriers. Large polycyclic aromatic hydrocarbon molecules are attractive candidates but interstellar species are still poorly characterized. Various studies emphasize the need for tackling the link between molecular aromatic species, aliphatic material and very small carbonaceous grains. Other unidentified emission features such as the 6.9, 21 and 30 μm bands could be involved in the evolutionary scenario.

scholarly journals The PAH Hypothesis after 25 Years

2011 ◽  
Vol 7 (S280) ◽  
pp. 149-161 ◽  
Author(s):  
Els Peeters
Keyword(s):  
Polycyclic Aromatic Hydrocarbon ◽  
Aromatic Hydrocarbon ◽  
Infrared Spectra ◽  
The Past ◽  
Polycyclic Aromatic ◽  
Hydrocarbon Molecules ◽  
Uv Photons

AbstractThe infrared spectra of many galactic and extragalactic objects are dominated by emission features at 3.3, 6.2, 7.7, 8.6 and 11.2 μm. The carriers of these features remained a mystery for almost a decade, hence the bands were dubbed the unidentified infrared (UIR) bands. Since the mid-80's, the UIR bands are generally attributed to the IR fluorescence of Polycyclic Aromatic Hydrocarbon molecules (PAHs) upon absorption of UV photons – the PAH hypothesis. Here we review the progress made over the past 25 years in understanding the UIR bands and their carriers.

scholarly journals Measurements of the 3.3 μm Diffuse Galactic Emission Feature with AROME

1990 ◽  
Vol 139 ◽  
pp. 212-213
Author(s):  
M. Giard ◽  
F. Pajot ◽  
J. M. Lamarre ◽  
G. Serra
Keyword(s):  
Surface Brightness ◽  
Galactic Plane ◽  
Elevation Angle ◽  
Emission Feature ◽  
Field Of View ◽  
Interstellar Matter ◽  
Galactic Emission ◽  
Polycyclic Aromatic ◽  
Hydrocarbon Molecules ◽  
Ir Emission

AROME∗ is a balloon-borne experiment which was built to carry out measurements of IR emission features in the diffuse galactic flux. The field of view is 0.5° and surface brightness gradients are detected through azimuthal scanning at a constant elevation angle. The detection of a feature is done by comparison of the fluxes measured in narrow and wide photometric bands centered on the feature's wavelength. Two flights have been performed (August 1987, October 1988), which detected a 3.3 μm feature in the direction of the galactic plane −6° < b < 6°, 60° > l > −50°. Since this feature is characteristic of aromatic C-H bonds, we assigned it to the emission of transiently heated polycyclic aromatic hydrocarbon molecules (PAHs). With this assumption, AROME measurements show that PAHs are an ubiquitous component of the interstellar matter which contain about 10% of the available cosmic carbon.

scholarly journals IONIZATION OF POLYCYCLIC AROMATIC HYDROCARBON MOLECULES AROUND THE HERBIG Ae/Be ENVIRONMENT

2011 ◽  
pp. 143-154
Author(s):  
ITSUKI SAKON ◽  
TAKASHI ONAKA ◽  
YOSHIKO K. OKAMOTO ◽  
HIROKAZU KATAZA ◽  
HIDEHIRO KANEDA ◽  
...  
Keyword(s):  
Polycyclic Aromatic Hydrocarbon ◽  
Aromatic Hydrocarbon ◽  
Polycyclic Aromatic ◽  
Hydrocarbon Molecules

scholarly journals Chemistry of Molecular Clouds

1989 ◽  
Vol 120 ◽  
pp. 2-12
Author(s):  
A. Dalgarno
Keyword(s):  
Polycyclic Aromatic Hydrocarbon ◽  
Ultraviolet Radiation ◽  
Aromatic Hydrocarbon ◽  
Molecular Clouds ◽  
Cosmic Ray ◽  
Radiation Fields ◽  
Polycyclic Aromatic ◽  
Hydrocarbon Molecules ◽  
Ultraviolet Photons

AbstractA discussion is presented of the chemistry of quiescent molecular clouds, and the effects of the presence of polycyclic aromatic hydrocarbon molecules and of cosmic-ray induced ultraviolet photons are examined. A comparison is made with the chemistry occurring in molecular clouds that are subjected to shocks and the differences between dissociative and non-dissociative shocks are described. The changes in composition caused by intense cosmic ray fluxes or intense ultraviolet radiation fields are explored.

scholarly journals The survival of PAHs and (hydro)carbon nanoparticles in H II regions

2015 ◽  
Vol 11 (A29A) ◽  
Author(s):  
Elisabetta R. Micelotta ◽  
Marco Bocchio ◽  
Aurélie Rémy-Ruyer ◽  
Melanie Köhler ◽  
Nathalie Ysard ◽  
...  
Keyword(s):  
Polycyclic Aromatic Hydrocarbon ◽  
Vibrational Relaxation ◽  
Carbon Nanoparticles ◽  
Infrared Emission ◽  
H Ii Regions ◽  
Destruction Mechanism ◽  
Hydro Carbon ◽  
First Results ◽  
Polycyclic Aromatic ◽  
Physical Response

AbstractObservations show that emission from the Unidentified Infrared (UIR) bands is strongly suppressed in H II regions. UIR bands are generally attributed to vibrational relaxation of FUV - excited Polycyclic Aromatic Hydrocarbon (PAH) molecules or hydrocarbon nanoparticles containing aromatic domains. If the strongly reduced UIR emission in H II regions is due to the suppression of the carriers, an efficient destruction mechanism is required to explain observations. The aim of this work is to clarify whether UV processing of PAHs and nanoparticles is indeed responsible for the observed lack of infrared emission. We present here our first results on the physical response to photo-processing of the proposed UIR-bands carriers.

Sign in / Sign up

Export Citation Format

Share Document