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Infrared Emission (infrared + emission)
Selected AbstractsA semi-empirical model of the infrared emission from galaxiesMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 3 2008D. C. Ford ABSTRACT We present a semi-empirical model for the infrared emission of dust around star-forming sites in galaxies. Our approach combines a simple model of radiative transfer in dust clouds with a state-of-the-art model of the microscopic optical properties of dust grains pioneered by Draine & Li. In combination with the starburst99 stellar spectral synthesis package, this framework is able to produce synthetic spectra for galaxies which extend from the Lyman limit through to the far-infrared. We use it to probe how model galaxy spectra depend on the physical characteristics of their dust grain populations, and on the energy sources which heat that dust. We compare the predictions of our model with the 8- and 24-,m luminosities of sources in the Spitzer First Look Survey, and conclude by using the models to analyse the relative merits of various colour diagnostics in distinguishing systems out to a redshift of 2 with ongoing star formation from those with only old stellar populations. [source] Non-thermal X-rays, a high-abundance ridge and fossil bubbles in the core of the Perseus cluster of galaxiesMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 1 2005J. S. Sanders ABSTRACT Using a deep Chandra observation of the Perseus cluster of galaxies, we find a high-abundance shell 250 arcsec (93 kpc) from the central nucleus. This ridge lies at the edge of the Perseus radio mini-halo. In addition we identify two H, filaments pointing towards this shell. We hypothesize that this ridge is the edge of a fossil radio bubble, formed by entrained enriched material lifted from the core of the cluster. There is a temperature jump outside the shell, but the pressure is continuous indicating a cold front. A non-thermal component is mapped over the core of the cluster with a morphology similar to the mini-halo. Its total luminosity is 4.8 × 1043 erg s,1, extending in radius to ,75 kpc. Assuming the non-thermal emission to be the result of inverse Compton scattering of the cosmic microwave background and infrared emission from NGC 1275, we map the magnetic field over the core of the cluster. [source] Infrared [Fe ii] emission in the circumstellar nebulae of luminous blue variablesMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 2 2002Nathan Smith Abstract After a serendipitous discovery of bright [Fe ii],16435 emission in nebulae around , Carinae and P Cygni, infrared spectra of other luminous blue variables (LBV) and LBV candidates were obtained. Bright infrared [Fe ii] emission appears to be a common property among LBVs with prominent nebulae; this is an interesting discovery because strong [Fe ii],16435 is typically seen in shock-excited objects like supernova remnants and outflows from newly formed massive stars, as well as in active galactic nuclei (AGN), where the excitation mechanism is uncertain. This paper presents spectra in the H-band (1.5 to 1.75 ,m) for the central stars and nebulae of , Car, AG Car, P Cyg, Wra 751, HR Car, HD 168625, HD 160529, R 127 and S Doradus. Seven of nine targets show bright [Fe ii],16435 in their nebulae, while it is absent in all central stars except the LBV candidate Wra 751. The two objects (S Dor and HD 160529) without prominent [Fe ii],16435 are not yet known to have nebulae detected in optical images, and both lack bright thermal infrared emission from dust. The possible excitation mechanisms for this line and the implications of its discovery in LBV nebulae are discussed; there are good reasons to expect shock excitation in some objects, but other mechanisms cannot be ruled out. [source] A model for the infrared emission of FSC 10214+4724MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY: LETTERS (ELECTRONIC), Issue 1 2006Andreas Efstathiou ABSTRACT A model for the infrared emission of the high-redshift ultraluminous infrared galaxy FSC 10214+4724 is presented. The model assumes three components of emission: a dusty torus viewed edge-on, clouds that are associated with the narrow-line region and a highly obscured starburst. It is demonstrated that the presence of clouds in the narrow-line region, with a covering factor of 17 per cent, can explain why the mid-infrared spectrum of FSC 10214+4724 shows a silicate feature in emission despite the fact that its torus is viewed edge-on. It is also shown that the same model, but with the torus viewed face-on, predicts a spectrum with silicate emission features that is characteristic of the spectra of quasars recently observed with Spitzer. [source] Spectroscopic studies of the infrared emission from Tm doped AlxGa1,xN thin filmsPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 7 2005E. Nyein Abstract The infrared (IR) emission properties of in-situ Tm doped AlxGa1,xN thin films (0 , x , 1) prepared by solid-source molecular-beam epitaxy were investigated. All samples exhibited 1.48 µm photoluminescence (PL) from the 3H4,3F4 transition of Tm3+. The absolute intensity of the 1.48 µm PL varied strongly with Al content and reached a maximum for Al0.81Ga0.19N:Tm. The integrated 1.48 (m PL from Al0.81Ga0.19N:Tm was weakly temperature dependent and decreased by less than a factor of two between 15 K and 300 K. The PL lifetime of the 3H4 state decreased only slightly from ,102 (s to ,86 (s for the same temperature range. The results suggest that non-radiative decay processes in the 3H4 level are small in Al0.81Ga0.19N:Tm, which is supported by the well-known energy-gap law for multiphonon relaxations. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] NONCONTACT TEMPERATURE MONITORING OF A PELLETING PROCESS USING INFRARED THERMOGRAPHYJOURNAL OF FOOD PROCESS ENGINEERING, Issue 1 2007C. SALAS-BRINGAS ABSTRACT Contact methods are commonly used to determine temperature during food and feed manufacturing processes. This may, however, result in incorrect temperature measurements, because many food and feed materials easily agglomerate around the thermowell tip of the sensors, decreasing their time response; also, it is difficult to measure temperature from moving objects using contact methods. This article assesses the use of thermography to measure temperature throughout the manufacture of poultry feed. The experiment showed that precaution should be used when the temperature difference, between the meal at the outlet of the conditioner and pellets at the outlet of the pellet press, is associated with the temperature rise across the die. Precaution should also be used when the temperature of the pellets at the outlet of the pellet press is used as the peak temperature during the process. Temperature measurements through infrared emissions require improved instrument design to operate in a dusty, damp, steamy and oily environment. [source] Rare earth ions in porous silicon: optical propertiesPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 5 2007H. Elhouichet Abstract Porous silicon (PS) is doped with rare earth (RE) ions (Er, Eu, Tb) by electrochemical anodisation. The penetration of RE into the PS layer is confirmed by Rutherford Backscattering Spectroscopy (RBS) and by Energy Dispersive X-ray (EDX) measurements. Efficient visible and infrared emissions were observed at room temperature. The activation temperatures of Eu, Tb and Er in PS are determined from the effect of thermal annealing on the photoluminescence (PL) intensity. From the evolution of the PL intensity versus temperature, it was found that a RE related level defect can be involved on the excitation and emission processes. Pump intensity dependent PL studies revealed that for the electrochemical incorporation, most of the RE ions are localized inside the Si nanocrystallites and not in stochiometric SiO2. The optical cross section is close to that of erbium in Si nanocrystallites. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] | ||||||||||||||||||||||