The diffuse interstellar bands: A major problem in astronomical spectroscopy

Sarre, P. J.

doi:10.1016/j.jms.2006.03.009

Cited by 247 publications

(208 citation statements)

References 79 publications

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“…This is furthermore supported by an investigation from Xiang et al (2011), who were unable to find any correlation between the 2175 Å feature and nine of the strongest DIBs. Finally, if we assume that the optical emission bands in the Red Rectangle Nebula are caused by some of the DIB carriers (see Sarre 2006), there is yet another argument against a connection between the interstellar PAH population and the DIBs because no correlation was found between these optical bands and the aromatic infrared emission at 3.3 μm (Sarre 2006).…”

Section: Discussionmentioning

confidence: 99%

“…The upper wavelength limit below which DIBs have been observed was recently shifted to 1800 nm (Geballe et al 2011). The origin of the DIBs remains enigmatic, but numerous atomic, molecular, and solid state carriers have been proposed (for a review, see Sarre 2006). Among these proposals, neutral and ionized polycyclic aromatic hydrocarbons (PAHs) are considered to belong to the most promising candidates (Cox 2011).…”

Section: Introductionmentioning

confidence: 99%

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The smoothness of the interstellar extinction curve in the UV

Steglich

Carpentier

Jäger

et al. 2012

A&A

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Context. As revealed by high-resolution spectral investigations in the wavelength range between 300 and 400 nm, the interstellar extinction curve does not display any of the sharp electronic absorption bands that are characteristic for large polyatomic molecules, such as polycyclic aromatic hydrocarbons (PAHs), which belong to the most abundant interstellar molecules. Aims. We aim to verify whether the absorption curves of mixtures of medium-sized PAHs produced in the laboratory can explain the astronomical observations. Methods. The PAH mixtures were synthesized by infrared laser pyrolysis and subsequent chemical extraction and size separation. The matrix isolation technique was used to study the absorption spectra of isolated molecules at low temperature. Results. Our experimental results demonstrate that the UV-visible absorption curves of PAH mixtures can be very smooth, displaying no sharp bands, if the molecular diversity is sufficiently high. Conclusions. In view of the absence of sharp electronic features on the interstellar extinction curve for 300 < λ < 400 nm, we conclude from our experimental findings that the interstellar PAH population must be very diverse. The low fractional abundances of individual species prevent their detection on the basis of spectral fingerprints in the UV.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

The smoothness of the interstellar extinction curve in the UV

Steglich

Carpentier

Jäger

et al. 2012

A&A

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“…Intensity and polarisation spectra are only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/531/A25 intensity is related to the extinction by dust grains their (spectral) properties and behaviour are more consistent with large gas-phase molecules (see also the review by Sarre 2006). In particular the substructure in several DIB profiles indicates that the carrier(s) are large gas phase molecules (Sarre et al 1995;Ehrenfreund & Foing 1996;Cami et al 2004).…”

Section: Introductionmentioning

confidence: 99%

Linear and circular spectropolarimetry of diffuse interstellar bands

Cox

Ehrenfreund

Foing

et al. 2011

A&A

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Context. The identification of the carriers of diffuse interstellar bands (DIBs) remains one of the long-standing mysteries in astronomy. The detection of a polarisation signal in a DIB profile can be used to distinguish between a dust or gas-phase carrier. The polarisation profile can give additional information on the grain or molecular properties of the absorber. Aims. To measure the polarisation efficiency of the carriers of the diffuse interstellar bands. Methods. In order to detect and measure the linear and circular polarisation of the DIBs we observed reddened lines of sight showing continuum polarisation. For this study we selected two stars HD 197770 and HD 194279. We used high-resolution (R ∼ 64 000) spectropolarimetry in the wavelength range from 3700 to 10 480 Å with the ESPaDOnS échelle spectrograph mounted at the CFHT. Results. High S/N and high resolution Stokes V (circular), Q and U (linear) spectra were obtained. We constrained upper limits by a factor of 10 for previously observed DIBs. Furthermore, we analysed ∼30 additional DIBs for which no spectropolarimetry data has been obtained before. This included the 9577 Å DIB and the 8621 Å DIB. The former is attributed to the C + 60 fullerene, which could become aligned in a magnetic field. The latter shows a tight correlation with the amount of dust in the line-of-sight and therefore most likely may show a polarisation signal related the aligned grains. Conclusions. The lack of polarisation in 45 DIB profiles suggests that none of the absorption lines is induced by a grain-type carrier. The strict upper limits, less than ∼0.01%, derived for the observed lines-of-sight imply that if DIBs are due to gas-phase molecules these carriers have polarisation efficiencies which are at least 6 times, and up to 300 times, smaller than those predicted for grainrelated carriers.

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“…These are the so-called Diffuse Interstellar Bands (DIBs) (see Herbig 1995;Sarre 2006, for a review). They were already noticed around the early 20's by Heger (see McCall & Griffin 2013, for a revision of the history of the DIBs discovery) and their interstellar origin was established in the 30's (Merrill 1934(Merrill , 1936.…”

Section: Introductionmentioning

confidence: 99%

Measuring diffuse interstellar bands with cool stars

Monreal-Ibero

Lallement

2017

A&A

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Context. Diffuse Stellar Bands (DIBs) are ubiquitous in stellar spectra. Traditionally, they have been studied through their extraction from hot (early-type) stars, because of their smooth continuum. In an era where there are several going-on or planned massive Galactic surveys using multi-object spectrographs, cool (late-type) stars constitute an appealing set of targets. However, from the technical point of view, the extraction of DIBs in their spectra is more challenging due to the complexity of the continuum. Aims. In this contribution we will provide the community with an improved set of stellar lines in the spectral regions associated to the strong DIBs at λ6196.0, λ6269.8, λ6283.8, and λ6379.3. These lines will allow for the creation of better stellar synthetic spectra, reproducing the background emission and a more accurate extraction of the magnitudes associated with a given DIB (e.g. equivalent width, radial velocity). Methods. The Sun and Arcturus were used as representative examples of dwarf and giant stars, respectively. A high quality spectrum for each of them was modeled using TURBOSPECTRUM and the VALD stellar line list. The oscillator strength log(g f ) and/or wavelength of specific lines were modified to create synthetic spectra where the residuals in both the Sun and Arcturus were minimized. Results. The TURBOSPECTRUM synthetic spectra based on the improved line lists reproduce the observed spectra for the Sun and Arcturus in the mentioned spectral ranges with greater accuracy. Residuals between the synthetic and observed spectra are always ∼ < 10%, much better than with previously existing options. The new line list has been tested with some characteristic spectra, from a variety of stars, including both giant and dwarf stars, and under different degrees of extinction. As it happened with the Sun and Arcturus residuals in the fits used to extract the DIB information are smaller when using synthetic spectra made with the updated line lists. Tables with the updated parameters are provided to the community.

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The diffuse interstellar bands: A major problem in astronomical spectroscopy

Cited by 247 publications

References 79 publications

The smoothness of the interstellar extinction curve in the UV

The smoothness of the interstellar extinction curve in the UV

Linear and circular spectropolarimetry of diffuse interstellar bands

Measuring diffuse interstellar bands with cool stars

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