I give an overview of the recent scientific results based on observations of PAH emission from circumstellar disks around young stars. The stellar radiation field plays a key role in the excitation and destruction of the PAH molecules in the disk. The detection rate of PAH emission in disks is optimal for stars of spectral type A. Around stars of similar temperature, the disk structure determines the PAH emission strength: disks with a flared geometry produce stronger PAH emission than flattened disks. The spectral properties of the emission features, indicative of the chemistry of the emitting hydrocarbons, is closely linked to the central star radiation field. The main PAH features shift to redder wavelengths with decreasing stellar effective temperature. This trend has been interpreted as an indication for a higher aliphatic/aromatic ratio of the hydrocarbon mixture around cool stars with respect to hot stars. An alternative explanation may be a more significant contribution to the infrared emission of very small grains around cooler stars.
{"title":"Observations of Hydrocarbon Emission in Disks Around Young Stars","authors":"B. Acke","doi":"10.1051/EAS/1146028","DOIUrl":"https://doi.org/10.1051/EAS/1146028","url":null,"abstract":"I give an overview of the recent scientific results based on observations of PAH emission from circumstellar disks around young stars. The stellar radiation field plays a key role in the excitation and destruction of the PAH molecules in the disk. The detection rate of PAH emission in disks is optimal for stars of spectral type A. Around stars of similar temperature, the disk structure determines the PAH emission strength: disks with a flared geometry produce stronger PAH emission than flattened disks. The spectral properties of the emission features, indicative of the chemistry of the emitting hydrocarbons, is closely linked to the central star radiation field. The main PAH features shift to redder wavelengths with decreasing stellar effective temperature. This trend has been interpreted as an indication for a higher aliphatic/aromatic ratio of the hydrocarbon mixture around cool stars with respect to hot stars. An alternative explanation may be a more significant contribution to the infrared emission of very small grains around cooler stars.","PeriodicalId":197011,"journal":{"name":"PAHs and the Universe","volume":"759 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2011-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126943258","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In the interstellar medium (ISM), PAHs are abundant and also carry most of the dust surface. They are thus privileged sites for surface reactions such as the formation of H2 . In regions penetrated by UV photons, PAHs loose electrons by the photoelectric effect and efficiently heat the gas. In more shielded regions, PAH recombine and may carry an important fraction of the cloud electronic charge which plays an important role in the gas dynamics and chemistry. We review here processes involving PAHs which control key aspects of the physics of the ISM. We also discuss the corresponding observational constraints. Most of these processes involve a detailed knowledge of the charge of PAHs and we therefore review current models in this area. We argue that more laboratory measurements of the rate of electronic capture on large PAH cations are needed.
{"title":"The Role of PAHs in the Physics of the Interstellar Medium","authors":"L. Verstraete","doi":"10.1051/EAS/1146043","DOIUrl":"https://doi.org/10.1051/EAS/1146043","url":null,"abstract":"In the interstellar medium (ISM), PAHs are abundant and also carry most of the dust surface. They are thus privileged sites for surface reactions such as the formation of H2 . In regions penetrated by UV photons, PAHs loose electrons by the photoelectric effect and efficiently heat the gas. In more shielded regions, PAH recombine and may carry an important fraction of the cloud electronic charge which plays an important role in the gas dynamics and chemistry. We review here processes involving PAHs which control key aspects of the physics of the ISM. We also discuss the corresponding observational constraints. Most of these processes involve a detailed knowledge of the charge of PAHs and we therefore review current models in this area. We argue that more laboratory measurements of the rate of electronic capture on large PAH cations are needed.","PeriodicalId":197011,"journal":{"name":"PAHs and the Universe","volume":"175 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2011-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114430978","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
T. Pino, Y. Carpentier, G. Féraud, H. Friha, D. Kokkin, T. Troy, N. Chalyavi, P. Bréchignac, T. Schmidt
Polycyclic aromatic hydrocarbons are a class of molecules of broad interest that has long been explored by various spectroscopic techniques. The electronic spectroscopy of these species is of particular interest since it provides a framework for the understanding of the electronic structure of large polyatomic molecules. Such studies also allow the systematic investigation of electronic relaxation mechanisms in large molecules. In this review, we focus on the gas-phase experimental work on such systems and present the latest progress. We also underline the challenges that remain to be tackled. A focus on the understanding of the electronic relaxation pathways at work in gas-phase PAHs will also be presented, as well as their possible manifestation in space.
{"title":"Electronic Spectroscopy of PAHs","authors":"T. Pino, Y. Carpentier, G. Féraud, H. Friha, D. Kokkin, T. Troy, N. Chalyavi, P. Bréchignac, T. Schmidt","doi":"10.1051/EAS/1146037","DOIUrl":"https://doi.org/10.1051/EAS/1146037","url":null,"abstract":"Polycyclic aromatic hydrocarbons are a class of molecules of broad interest that has long been explored by various spectroscopic techniques. The electronic spectroscopy of these species is of particular interest since it provides a framework for the understanding of the electronic structure of large polyatomic molecules. Such studies also allow the systematic investigation of electronic relaxation mechanisms in large molecules. In this review, we focus on the gas-phase experimental work on such systems and present the latest progress. We also underline the challenges that remain to be tackled. A focus on the understanding of the electronic relaxation pathways at work in gas-phase PAHs will also be presented, as well as their possible manifestation in space.","PeriodicalId":197011,"journal":{"name":"PAHs and the Universe","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2011-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128787921","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Studies of dust analogs formed from hydrocarbon ( C H 4 , C 2 H 2 , C 2 H 4 , C 2 H 6 ) and PAH precursors have been performed using a new facility that we have developed to simulate interstellar and circumstellar processes. The species formed in a plasma are detected, characterized and monitored in situ with high-sensitivity techniques, which provide both spectroscopic and ion mass information. From these measurements we derive information on the nature, the size and the structure of dust particles, as well as a better understanding of the growth and destruction processes of extraterrestrial dust.
{"title":"Formation and Evolution of Circumstellar and Interstellar PAHs: A Laboratory Study","authors":"C. Contreras, C. L. Ricketts, Farid Salama","doi":"10.1051/EAS/1146021","DOIUrl":"https://doi.org/10.1051/EAS/1146021","url":null,"abstract":"Studies of dust analogs formed from hydrocarbon\u0000 ( C H 4 , C 2 H 2 , C 2 H 4 , C 2 H 6 ) and PAH precursors have\u0000 been performed using a new facility that we have developed to simulate interstellar and\u0000 circumstellar processes. The species formed in a plasma are detected, characterized and\u0000 monitored in situ with high-sensitivity techniques, which provide both\u0000 spectroscopic and ion mass information. From these measurements we derive information on\u0000 the nature, the size and the structure of dust particles, as well as a better\u0000 understanding of the growth and destruction processes of extraterrestrial dust.","PeriodicalId":197011,"journal":{"name":"PAHs and the Universe","volume":"76 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2011-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122019923","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In this contribution I review the PAH-DIB hypothesis. Firstly, I list several properties of PAHs and their behaviour and ex- pected signatures in space. Next, I give an overview of the current observational insights on the DIB carriers. I conclude with a brief de- scription of recent results on the search for the DIB carriers and the prospects we have for identification.
{"title":"The PAH-DIB Hypothesis","authors":"N. Cox","doi":"10.1051/EAS/1146036","DOIUrl":"https://doi.org/10.1051/EAS/1146036","url":null,"abstract":"In this contribution I review the PAH-DIB hypothesis. Firstly, I list several properties of PAHs and their behaviour and ex- pected signatures in space. Next, I give an overview of the current observational insights on the DIB carriers. I conclude with a brief de- scription of recent results on the search for the DIB carriers and the prospects we have for identification.","PeriodicalId":197011,"journal":{"name":"PAHs and the Universe","volume":"16 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2011-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123336425","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
T. Onaka, I. Sakon, R. Ohsawa, T. Shimonishi, Y. Okada, Masahiro Tanaka, H. Kaneda
Near-infrared (NIR; 2.5–5 μ m) low-resolution ( λ /Δ λ ~ 100) spectra were obtained for a number of Galactic and extragalactic objects with the Infrared Camera (IRC) in the AKARI warm mission. These data provide us with the first opportunity to make a systematic study of the 3.3–3.5 μ m PAH features in a galactic scale as well as within an object. Whereas the 3.3 μ m band is well resolved in most spectra, the 3.5 μ m band is not clearly separated from the 3.4 μ m band in the IRC spectrum. The intensity ratio of the summation of the 3.4 and 3.5 μ m bands to the 3.3 μ m band shows a tendency to increase towards the Galactic center, although a large variation in the ratio is also seen in a local scale. A search for deuterated PAH features in the 4 μ m region is carried out in IRC NIR spectra. Emission lines originating from the ionized gas together with the detector anomaly hamper an accurate search at certain wavelengths, but little convincing evidence has so far been obtained for the presence of significant features in 4.2–4.7 μ m. A conservative upper limit of a few percents is obtained for the integrated intensity ratio of the 4.4–4.7 μ m possible features to the 3.3–3.5 μ m PAH features in the spectra so far obtained.
{"title":"AKARI Near-Infrared Spectroscopy of 3 Micron PAH and 4 Micron PAD Features","authors":"T. Onaka, I. Sakon, R. Ohsawa, T. Shimonishi, Y. Okada, Masahiro Tanaka, H. Kaneda","doi":"10.1051/EAS/1146006","DOIUrl":"https://doi.org/10.1051/EAS/1146006","url":null,"abstract":"Near-infrared (NIR; 2.5–5 μ m) low-resolution ( λ /Δ λ ~ 100) spectra were obtained for a number of Galactic and extragalactic objects with the Infrared Camera (IRC) in the AKARI warm mission. These data provide us with the first opportunity to make a systematic study of the 3.3–3.5 μ m PAH features in a galactic scale as well as within an object. Whereas the 3.3 μ m band is well resolved in most spectra, the 3.5 μ m band is not clearly separated from the 3.4 μ m band in the IRC spectrum. The intensity ratio of the summation of the 3.4 and 3.5 μ m bands to the 3.3 μ m band shows a tendency to increase towards the Galactic center, although a large variation in the ratio is also seen in a local scale. A search for deuterated PAH features in the 4 μ m region is carried out in IRC NIR spectra. Emission lines originating from the ionized gas together with the detector anomaly hamper an accurate search at certain wavelengths, but little convincing evidence has so far been obtained for the presence of significant features in 4.2–4.7 μ m. A conservative upper limit of a few percents is obtained for the integrated intensity ratio of the 4.4–4.7 μ m possible features to the 3.3–3.5 μ m PAH features in the spectra so far obtained.","PeriodicalId":197011,"journal":{"name":"PAHs and the Universe","volume":"30 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2011-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115653296","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Near infrared observations of reflection nebulae have set the historical ground for the discovery of interstellar PAHs, but since, space observations have focused on their mid-IR features, and data shortward of 5 μ m have remained scarce. The Spitzer/IRAC images in the 3.6 and 4.5 μ m channels do show that the near-IR emission from small dust particles is ubiquitous across the Galaxy, but provide no spectroscopic information. To investigate the nature of this near-IR dust emission, we have obtained AKARI spectroscopic observations, over the 2.5−5 μ m spectral range, for a set of archetype PDRs mapped with the Spitzer spectrometer at mid-IR wavelengths. These AKARI data supplement earlier observations with the SWS ISO spectrometer, in providing the gain in sensitivity needed to observe low excitation sources, and the spatial information required to spatially correlate near-IR spectroscopic signatures with physical conditions and observed changes in mid-IR spectra. This paper presents the first results of the data analysis, in relation to two open questions on interstellar PAHs. (1) Is there an evolutionary link from aliphatic carbon dust to PAHs? (2) What is the origin of the near-IR dust continuum? The AKARI spectra display features longward of the main 3.29 μ m PAH feature, and continuum emission. The intensity ratio between the features ascribed to aliphatic CH bonds and the 3.29 μ m aromatic band, varies spatially in a way that may be interpreted as evidence for aromatization of the smallest dust particles by photo-processing. The continuum displays a striking step-increase across the 3.29 μ m feature. We also present a spectrum of a photodissociation region with a feature at 4.65 μ m, which has been speculated to be related to the CD stretch in aliphatic hydrocarbon side-groups on PAHs.
{"title":"Near-Infrared Spectroscopy of Interstellar Dust","authors":"F. Boulanger, T. Onaka, P. Pilleri, C. Joblin","doi":"10.1051/EAS/1146041","DOIUrl":"https://doi.org/10.1051/EAS/1146041","url":null,"abstract":"Near infrared observations of reflection nebulae have set the historical ground for the discovery of interstellar PAHs, but since, space observations have focused on their mid-IR features, and data shortward of 5 μ m have remained scarce. The Spitzer/IRAC images in the 3.6 and 4.5 μ m channels do show that the near-IR emission from small dust particles is ubiquitous across the Galaxy, but provide no spectroscopic information. To investigate the nature of this near-IR dust emission, we have obtained AKARI spectroscopic observations, over the 2.5−5 μ m spectral range, for a set of archetype PDRs mapped with the Spitzer spectrometer at mid-IR wavelengths. These AKARI data supplement earlier observations with the SWS ISO spectrometer, in providing the gain in sensitivity needed to observe low excitation sources, and the spatial information required to spatially correlate near-IR spectroscopic signatures with physical conditions and observed changes in mid-IR spectra. This paper presents the first results of the data analysis, in relation to two open questions on interstellar PAHs. (1) Is there an evolutionary link from aliphatic carbon dust to PAHs? (2) What is the origin of the near-IR dust continuum? The AKARI spectra display features longward of the main 3.29 μ m PAH feature, and continuum emission. The intensity ratio between the features ascribed to aliphatic CH bonds and the 3.29 μ m aromatic band, varies spatially in a way that may be interpreted as evidence for aromatization of the smallest dust particles by photo-processing. The continuum displays a striking step-increase across the 3.29 μ m feature. We also present a spectrum of a photodissociation region with a feature at 4.65 μ m, which has been speculated to be related to the CD stretch in aliphatic hydrocarbon side-groups on PAHs.","PeriodicalId":197011,"journal":{"name":"PAHs and the Universe","volume":"19 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2011-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133256861","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Lunar minerals and impact glasses, convert the polyatomic beam of solar wind (SW) ions into a flux of small molecules ( e.g. , H 2 , N 2 , H 2 O, CO, CO 2 , CH 4 , C 2 H 4 , C 2 H 6 , HCN, metal carbides and deuterides, etc.). They thus behave as “Solid State Molecular Reactors”. Moreover, ~100–200 μ m size micrometeoroids ( μ Ms) have also been exposed to the SW in the zodiacal cloud, before being captured by the Earth and recovered as Antarctic micrometeorites. They are mostly composed of a PAH-rich hydrous-carbonaceous material, which amplifies their power as molecular reactors. In particular, during the first ~200 Myr of the post-lunar period, about 75% of the μ Ms have been melted and/or volatilized upon atmospheric entry. The release of their volatile species triggered a cosmic volcanism around the mesopause that ruled the formation of the early Earth’s atmosphere and climate. Furthermore, a fraction of the μ Ms that survive unmelted upon atmospheric entry did settle on the proto-oceans floors. Upon further burial in sediments their constituent PAH-rich kerogen was cracked into abiotic oil, which generated giant oil slicks that fed prebiotic chemistry. Many stars, of all ages and types, are embedded into a secondary debris-disk loaded with ion implanted μ Ms. Some of them are expelled to the interstellar medium (ISM) where they behave first as “dormant-invisible” molecular reactors, until they became reactivated by various processes to synthesize interstellar molecules. This short paper only focus on some highlights of this research dealing with the synthesis of important interstellar molecules, including the most abundant ones (H 2 and CO) and H 2 O, HCN and PAHs, all involved in prebiotic chemistry.
{"title":"Solid State Molecular Reactors in Space","authors":"M. Maurette","doi":"10.1051/EAS/1146033","DOIUrl":"https://doi.org/10.1051/EAS/1146033","url":null,"abstract":"Lunar minerals and impact glasses, convert the polyatomic beam of solar wind (SW) ions\u0000 into a flux of small molecules ( e.g. , H 2 , N 2 ,\u0000 H 2 O, CO, CO 2 , CH 4 , C 2 H 4 ,\u0000 C 2 H 6 , HCN, metal carbides and deuterides, etc.). They thus behave\u0000 as “Solid State Molecular Reactors”. Moreover, ~100–200 μ m\u0000 size micrometeoroids ( μ Ms) have also been exposed to the SW in the\u0000 zodiacal cloud, before being captured by the Earth and recovered as Antarctic\u0000 micrometeorites. They are mostly composed of a PAH-rich hydrous-carbonaceous material,\u0000 which amplifies their power as molecular reactors. In particular, during the first\u0000 ~200 Myr of the post-lunar period, about 75% of the μ Ms have\u0000 been melted and/or volatilized upon atmospheric entry. The release of their volatile\u0000 species triggered a cosmic volcanism around the mesopause that ruled the formation of the\u0000 early Earth’s atmosphere and climate. Furthermore, a fraction of the μ Ms\u0000 that survive unmelted upon atmospheric entry did settle on the proto-oceans floors. Upon\u0000 further burial in sediments their constituent PAH-rich kerogen was cracked into abiotic\u0000 oil, which generated giant oil slicks that fed prebiotic chemistry. Many stars, of all\u0000 ages and types, are embedded into a secondary debris-disk loaded with ion implanted\u0000 μ Ms. Some of them are expelled to the interstellar medium (ISM) where\u0000 they behave first as “dormant-invisible” molecular reactors, until they became reactivated\u0000 by various processes to synthesize interstellar molecules. This short paper only focus on\u0000 some highlights of this research dealing with the synthesis of important interstellar\u0000 molecules, including the most abundant ones (H 2 and CO) and H 2 O, HCN\u0000 and PAHs, all involved in prebiotic chemistry.","PeriodicalId":197011,"journal":{"name":"PAHs and the Universe","volume":"20 6","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2011-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132758472","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The relevance of organometallic complexes in the chemistry of the interstellar medium (ISM) was first suggested in the early 90s. This initial proposal has recently been re-considered in the light of new astronomical data, benefiting from pioneering experimental techniques and theoretical methods. In this article, a review of recent theoretical and experimental results obtained for PAHs coordinated to Fe atoms is presented, focusing on: -(i)- the IR spectra of [FePAH]+ and [Fe(PAH)2]+ complexes, found to be in line with the AIBs, with additional specific features in the far-IR range and -(ii)- the photo-evaporation of [FexPAHy]+ clusters as possible candidates for very small grains releasing PAHs in photodissociation regions. These results call for new astronomical data at high spatial resolution. Studies on larger clusters will require further experimental and theoretical developments.
{"title":"[FePAH]+ Complexes and [FexPAHy]+ Clusters in the Interstellar Medium: Stability and Spectroscopy","authors":"A. Simon, M. Rapacioli, F. Spiegelman, C. Joblin","doi":"10.1051/EAS/1146045","DOIUrl":"https://doi.org/10.1051/EAS/1146045","url":null,"abstract":"The relevance of organometallic complexes in the chemistry of the interstellar medium (ISM) was first suggested in the early 90s. This initial proposal has recently been re-considered in the light of new astronomical data, benefiting from pioneering experimental techniques and theoretical methods. In this article, a review of recent theoretical and experimental results obtained for PAHs coordinated to Fe atoms is presented, focusing on: -(i)- the IR spectra of [FePAH]+ and [Fe(PAH)2]+ complexes, found to be in line with the AIBs, with additional specific features in the far-IR range and -(ii)- the photo-evaporation of [FexPAHy]+ clusters as possible candidates for very small grains releasing PAHs in photodissociation regions. These results call for new astronomical data at high spatial resolution. Studies on larger clusters will require further experimental and theoretical developments.","PeriodicalId":197011,"journal":{"name":"PAHs and the Universe","volume":"17 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2011-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125266661","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The infrared (IR) spectra of many galactic and extragalactic objects are dominated by emission features at 3.3, 6.2, 7.7, 8.6 and 11.2 μ m, generally attributed to the IR fluorescence of Polycyclic Aromatic Hydrocarbon molecules (PAHs). These PAH bands have been found in a wide variety of environments throughout theUniverse and contain up to 10% of the total power output of star-forming galaxies. Ground-based telescopes, the Infrared Space Observatory (ISO) and the Spitzer Space Telescope revealed a plethora of weaker PAH bands and provided extensive evidence for significant variability in the PAH spectrum from source to source and spatially within sources. Here we review the spectral characteristics of astronomical PAHs, their dependence on the local physical conditions and the implications for the physical and chemical characteristics of the carriers.
{"title":"Astronomical Observations of the PAH Emission Bands","authors":"E. Peeters","doi":"10.1051/EAS/1146002","DOIUrl":"https://doi.org/10.1051/EAS/1146002","url":null,"abstract":"The infrared (IR) spectra of many galactic and extragalactic objects are dominated by emission features at 3.3, 6.2, 7.7, 8.6 and 11.2 μ m, generally attributed to the IR fluorescence of Polycyclic Aromatic Hydrocarbon molecules (PAHs). These PAH bands have been found in a wide variety of environments throughout theUniverse and contain up to 10% of the total power output of star-forming galaxies. Ground-based telescopes, the Infrared Space Observatory (ISO) and the Spitzer Space Telescope revealed a plethora of weaker PAH bands and provided extensive evidence for significant variability in the PAH spectrum from source to source and spatially within sources. Here we review the spectral characteristics of astronomical PAHs, their dependence on the local physical conditions and the implications for the physical and chemical characteristics of the carriers.","PeriodicalId":197011,"journal":{"name":"PAHs and the Universe","volume":"65 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2011-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121514170","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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