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 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.

Coarse-grained modeling of the nucleation of polycyclic aromatic hydrocarbons into soot precursors

2019 ◽  
Vol 21 (9) ◽  
pp. 5123-5132 ◽  
Author(s):  
J. Hernández-Rojas ◽  
F. Calvo
Keyword(s):  
Monte Carlo ◽  
Polycyclic Aromatic Hydrocarbons ◽  
Aromatic Hydrocarbons ◽  
Physical Growth ◽  
Coarse Grained ◽  
Soot Precursors ◽  
Polycyclic Aromatic ◽  
Hydrocarbon Molecules ◽  
A Minor ◽  
Monte Carlo Framework

The aggregation and physical growth of polycyclic aromatic hydrocarbon molecules was simulated using a coarse-grained potential and a stochastic Monte Carlo framework. In agreement with earlier studies, homomolecular nucleation of pyrene, coronene and circumcoronene is found to be limited at temperatures in the 500–1000 K range. Heteromolecular nucleation is found to occur with a minor spontaneous segregation toward pure and equi concentrations.

Research on Physical MPPT of Photovoltaic Array System Based on Image Processing

2013 ◽  
Vol 321-324 ◽  
pp. 1138-1144
Author(s):  
Chao Liu ◽  
Jing Hui
Keyword(s):  
Image Processing ◽  
Tracking Error ◽  
Elevation Angle ◽  
Image Sensor ◽  
Azimuth Angle ◽  
Field Of View ◽  
The Sun ◽  
Photovoltaic Array ◽  
Point Tracking ◽  
Power Point

Based on analyzing the development and the performance feature of existing solar tracker, we propose a solar Maximum Power Point Tracking (MPPT) strategy which combines photoelectric sensor and image processing. Firstly, photoelectric tracking mode positions the sun in the field of view of the image sensor. Then, the position of the sun image is captured by the image sensor. After that, we can find the coordinates of the sun spot in the field of view through image binarization processing. According to the number of steps of stepper motor rotation which is calculated by the deviation of coordinates, the controller drives the biaxial photosensitive (PV) array tracking device, making the sun spot always fall in the centre of the image. Tests show that the elevation angle and azimuth angle of the tracking range of the photovoltaic array are both 0～270°.The average tracking error of elevation angle is less than 0.7°, and the average tracking error of azimuth angle is less than 0.5°.

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 Theoretical Modelling of the Infrared Fluorescence by Interstellar Polycyclic Aromatic Hydrocarbons

1992 ◽  
Vol 150 ◽  
pp. 137-138
Author(s):  
W. A. Schutte ◽  
A. G. G. M. Tielens ◽  
L. J. Allamandola
Keyword(s):  
Polycyclic Aromatic Hydrocarbons ◽  
Size Distribution ◽  
Aromatic Hydrocarbons ◽  
Theoretical Modelling ◽  
Polycyclic Aromatic ◽  
Ir Emission

We modelled the IR emission of interstellar PAHs. Substantial differences between the IR properties of interstellar and laboratory PAHs are found, possibly resulting from ionization. The various IR features being dominated by distinctly different size PAHs, their observed relative intensities are sensitive indicators of the size distribution. A number of applications of our model related to future ISO and SIRTF IR data are pointed out.

scholarly journals Learning mid-IR emission spectra of PAH populations from observations

2019 ◽  
Vol 15 (S350) ◽  
pp. 406-407
Author(s):  
Sacha Foschino ◽  
Olivier Berné ◽  
Christine Joblin
Keyword(s):  
Emission Spectra ◽  
Large Data ◽  
Blind Signal Separation ◽  
Data Sets ◽  
Data Set ◽  
Blind Signal ◽  
James Webb Space Telescope ◽  
Astrophysical Objects ◽  
Polycyclic Aromatic ◽  
Ir Emission

AbstractObservations of the mid-infrared (mid-IR, 3-15 μm) spectra of photo-dissociation regions reveal ubiquitous, broad and intense emission bands, the aromatic infrared bands (AIBs), attributed to polycyclic aromatic hydrocarbons (PAHs). Studies of the AIBs showed spectral variations (e.g. in the band positions) between different astrophysical objects, or even within single object, thanks to hyperspectral images. The James Webb Space Telescope (JWST) will allow to get further spectral and spatial details compared to former space observatories. This will come with large data sets, which will require specific tools in order to perform efficient scientific analysis.We propose in this study a method based on blind signal separation to reduce the analysis of such large data set to that of a small number of elementary spectra, spectrally representative of the data set and physically interpretable as the spectra of populations of mid-IR emitters. The robustness and fastness of the method are improved compared to former algorithms. It is tested on a ISO-SWS data set, which approaches the best the characteristics of JWST data, from which four elementary spectra are extracted, attributed to cationic, neutral PAHs, evaporating very small grains and large and ionized PAHs.

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 CO line and radio continuum study of elephant trunks: the Pillars of Creation in M16

2020 ◽  
Vol 492 (4) ◽  
pp. 5966-5979 ◽  
Author(s):  
Yoshiaki Sofue
Keyword(s):  
Surface Brightness ◽  
Galactic Plane ◽  
Brightness Distribution ◽  
Radio Continuum ◽  
Very Large Array ◽  
Heating Source ◽  
Velocity Gradients ◽  
Magnetic Oscillation ◽  
H Ii Region ◽  
Line Survey

ABSTRACT Molecular line and radio continuum properties of the elephant trunks (ET, Pillars of Creation) in M16 are investigated by analysing 12CO(J = 1−0) , 13CO(J = 1−0) and C18O(J = 1−0) line survey data from the Nobeyama 45-m telescope and the Galactic plane radio survey at 20 and 90 cm with the Very Large Array. The head clump of Pillar West I is found to be the brightest radio source in M16, showing a thermal spectrum and the properties of a compact H ii region, with the nearest O5 star in NGC 6611 being the heating source. The radio pillars have a cometary structure concave to the molecular trunk head, and the surface brightness distribution obeys a simple illumination law from a remote excitation source. The molecular density in the pillar head is estimated to be several 104 H2 cm−3 and the molecular mass is $\sim 13\!-\!40 \, \mathrm{M}_\odot$. CO-line kinematics reveals random rotation of the clumps in the pillar tail at ∼1–2 km s−1, comparable with the velocity dispersion and estimated Alfvén velocity. It is suggested that the random directions of the velocity gradients would manifest as torsional magnetic oscillation of the clumps around the pillar axis.

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