Polycyclic Aromatic Hydrocarbons and the Diffuse Interstellar Bands: A Survey

Salama, Farid; Галазутдинов, Г. А.; Krełowski, J.; Biennier, Ludovic; Beletsky, Y.; Song, I.

doi:10.1088/0004-637x/728/2/154

Cited by 158 publications

(157 citation statements)

References 43 publications

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“…They range from 0.8 × 10 12 cm −2 for anthracene to 1 × 10 14 cm −2 for phenanthrene. Similar upper limit values for PAHs were derived by Salama et al (2011).…”

Section: Gas-phase Studiessupporting

confidence: 84%

Laboratory Studies on the Role of PAHs as DIB Carriers

et al. 2013

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Abstract. The electronic spectroscopy of various polycyclic aromatic hydrocarbon (PAH) molecules has been studied in the laboratory at low temperatures using both molecular beam and matrix isolation spectroscopy techniques. While molecular beam spectra can be readily compared to astronomical observations, the band positions measured in Ne and Ar matrices are extrapolated to obtain rather good estimates for the same transitions in the gas phase. Absolute absorption cross sections are determined for gas-phase and matrix spectra by comparing them with calibrated solution spectra. All laboratory results are analyzed and discussed in view of the role that PAHs can play as carriers of the diffuse interstellar bands (DIBs). Our studies suggest that regular neutral PAHs are not responsible for any of the known strong DIBs.

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“…They range from 0.8 × 10 12 cm −2 for anthracene to 1 × 10 14 cm −2 for phenanthrene. Similar upper limit values for PAHs were derived by Salama et al (2011).…”

Section: Gas-phase Studiessupporting

confidence: 84%

Laboratory Studies on the Role of PAHs as DIB Carriers

et al. 2013

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“…The DIBs are a set of several hundred absorption features spanning the wavelength range of the near ultraviolet (UV) at λ 4000Å (e.g., see York et al 2006, Gredel et al 2011, Salama et al 2011, Bhatt & Cami 2015 to the near infrared (IR) at λ 1.8 µm (e.g., see Joblin et al 1990, Geballe et al 2011, Cox et al 2014, Zasowski et al 2015, Hamano et al 2015, with most of the bands falling in the visible wavelength range. The DIBs were originally discovered in 1919 by Herger (1922) and their interstellar nature was established based on their stationary nature as observed toward spectroscopic binaries.…”

Section: Introductionmentioning

confidence: 99%

Diffuse Interstellar Bands and the Ultraviolet Extinction Curves: The Missing Link Revisited

Xiang

Zhong

2017

ApJ

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A large number of interstellar absorption features at ∼ 4000Å-1.8 µm, known as the "diffuse interstellar bands" (DIBs), remains unidentified. Most recent works relate them to large polycyclic aromatic hydrocarbon (PAH) molecules or ultrasmall carbonaceous grains which are also thought to be responsible for the 2175Å extinction bump and/or the far ultraviolet (UV) extinction rise at λ −1 > 5.9 µm −1 . Therefore, one might expect some relation between the UV extinction and DIBs. Such a relationship, if established, could put important constraints on the carrier of DIBs. Over the past four decades, whether DIBs are related to the shape of the UV extinction curves has been extensively investigated. However, the results are often inconsistent, partly due to the inconsistencies in characterizing the UV extinction. Here we re-examine the connection between the UV extinction curve and DIBs. We compile the extinction curves and the equivalent widths of 40 DIBs along 97 slightlines. We decompose the extinction curve into three Drude-like functions composed of the visible/near-infrared component, the 2175Å bump, and the far-UV extinction at λ −1 > 5.9 µm −1 . We argue that the wavelength-integrated far-UV extinction derived from this decomposition technique best measures the strength of the far-UV extinction. No correlation is found between the far-UV extinction and most (∼ 90%) of the DIBs. We have also shown that the color excess E(1300 − 1700), the extinction difference at 1300Å and 1700Å often used to measure the strength of the far-UV extinction, does not correlate with DIBs. Finally, we confirm the earlier findings of no correlation between the 2175Å bump and DIBs or between the 2175Å bump and the far-UV extinction.

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“…Many possible carriers have been proposed, ranging from grain impurities and exotic molecules to H 2 . In the past two decades the field has converged towards larger carbonaceous molecules, like the fullerenes and polycyclic aromatic hydrocarbons (PAHs), which have electronic transitions in the optical (see for example Salama et al 1999;Ruiterkamp et al 2005;Kokkin & Schmidt 2006;Zhou et al 2006;and Salama et al 2011). New diffuse bands have been detected in one line-of-sight which appear to match with naphthalene and anthracene cations (Iglesias-Groth et al 2008 and the weak 5450 Å DIB is found to match with an absorption band arising from a hydrocarbon plasma created in the laboratory (Linnartz et al 2010).…”

Section: Introductionmentioning

confidence: 99%

Diffuse interstellar bands in Upper Scorpius: probing variations in the DIB spectrum due to changing environmental conditions

Vos

Cox

Kaper

et al. 2011

A&A

101

177

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Aims. We study the effects of local environmental conditions affecting the diffuse interstellar band (DIB) carriers within the Upper Scorpius subgroup of the Sco OB2 association. The aim is to reveal how the still unidentified DIB carriers respond to different physical conditions prevailing in interstellar clouds, in order to shed light on the origin of the DIB carriers. Methods. We obtained optical spectra with FEROS on the ESO 1.52 m telescope at La Silla, Chile, and measured the equivalent widths of five DIBs (at 5780, 5797, 6196, 6379, and 6613 Å) as well as those of absorption lines of di-atomic molecules (CH, CH + , CN) and atoms (K i, Ca i) towards 89 targets in the direction of Upper Scorpius. We construct a simple radiative transfer and chemical network model of the diffuse interstellar medium (ISM) sheet in front of Upp Sco to infer the effective radiation field. Results. By measuring the DIB and molecular spectrum of diffuse clouds towards 89 sightlines in the Upper Scorpius region, we have obtained a valuable statistical dataset that provides information on the physical conditions that influence the band strengths of the DIBs. Both the interstellar radiation field strength, I UV , and the molecular hydrogen fraction, f H 2 , have been derived for 55 sightlines probing the Upp Sco ISM. We discuss the relations between DIB strengths, CH and CH + line strengths, E (B−V) , I UV , and f H 2 . The ratio between the 5780 and 5797 Å DIBs reveals a (spatial) dependence on the local environment in terms of cloud density and exposure to the interstellar radiation field, reflecting the molecular nature of these DIB carriers.

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Polycyclic Aromatic Hydrocarbons and the Diffuse Interstellar Bands: A Survey

Cited by 158 publications

References 43 publications

Laboratory Studies on the Role of PAHs as DIB Carriers

Laboratory Studies on the Role of PAHs as DIB Carriers

Diffuse Interstellar Bands and the Ultraviolet Extinction Curves: The Missing Link Revisited

Diffuse interstellar bands in Upper Scorpius: probing variations in the DIB spectrum due to changing environmental conditions

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