Detection of Diffuse Interstellar Bands in the Magellanic Clouds

Ehrenfreund, P.; Cami, J.; Jiménez-Vicente, J.; Foing, B. H.; Kaper, L.; Meer, A. van der; Cox, N. L. J.; D’Hendecourt, L.; Maier, John P.; Salama, Farid; Sarre, P. J.; Snow, Theodore P.; Sonnentrucker, Paule

doi:10.1086/343731

Cited by 76 publications

(94 citation statements)

References 17 publications

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“…Cardelli et al 1989;O'Donnell 1994;Fitzpatrick 1999;Fitzpatrick & Massa 2007). Voshchinnikov & Das (2008) derive P(λ)/A(λ) ∝ λ , with = 1.41 for HD 197770 (from 1000 Å to 1 μm), which matches with the power-law index of 1.4 computed for P(λ)/A(λ) using Eq.…”

Section: Polarisation and Total Intensity Line Profilessupporting

confidence: 76%

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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Section: Polarisation and Total Intensity Line Profilessupporting

confidence: 76%

Linear and circular spectropolarimetry of diffuse interstellar bands

Cox

Ehrenfreund

Foing

et al. 2011

A&A

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“…Studies of DIBs in the Magellanic Clouds (Ehrenfreund et al 2002;Cox et al , 2007Welty et al 2006), M 31 (Cordiner et al 2008a,b) and beyond (e.g. Heckman & Lehnert 2000;York et al 2006;Sollerman et al 2005;Cox & Patat 2008) illustrate that DIB carrier abundances (per amount of dust and gas) can be similar to Galactic values.…”

Section: Introductionmentioning

confidence: 98%

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

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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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“…Most measured DIBs have a Galactic origin. Still, they have also been detected in the Magellanic clouds, M31 and M33 (Ehrenfreund et al 2002;Welty et al 2006;Cordiner et al 2008aCordiner et al , 2008bCordiner et al , 2011van Loon et al 2013) and in a few line of sights toward e.g., starburst galaxies or in SNe Ia spectra (Sollerman et al 2005;Cox & Patat 2008;Heckman & Lehnert 2000;Phillips et al 2013). Recently a DIB gradient was established for the first time in a 160 Mpc distant galaxy (Monreal-Ibero et al 2015).…”

Section: Introductionmentioning

confidence: 95%

A CATALOG OF 1.5273 μm DIFFUSE INTERSTELLAR BANDS BASED ON APOGEE HOT TELLURIC CALIBRATORS

Elyajouri

Monreal-Ibero

Remy

et al. 2016

ApJS

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High resolution stellar spectroscopic surveys provide massive amounts of diffuse interstellar bands (DIBs) measurements. Data can be used to study the distribution of the DIB carriers and those environmental conditions that favor their formation. In parallel, recent studies have also proved that DIBs extracted from stellar spectra constitute new tools for building the 3D structure of the Galactic interstellar medium (ISM). The amount of details on the structure depends directly on the quantity of available lines of sight. Therefore there is a need to construct databases of high-quality DIB measurements as large as possible. We aim at providing the community with a catalog of high-quality measurements of the 1.5273 μm DIB toward a large fraction of the Apache Point Observatory Galactic Evolution Experiment (APOGEE) hot stars observed to correct for the telluric absorption and not used for ISM studies so far. This catalog would complement the extensive database recently extracted from the APOGEE observations and used for 3D ISM mapping. We devised a method to fit the stellar continuum of the hot calibration stars and extracted the DIB from the normalized spectrum. Severe selection criteria based on the absorption characteristics are applied to the results. In particular limiting constraints on the DIB widths and Doppler shifts are deduced from the H I 21 cm measurements, following a new technique of decomposition of the emission spectra. From ∼16,000 available hot telluric spectra we have extracted ∼6700 DIB measurements and their associated uncertainties. The statistical properties of the extracted absorptions are examined and our selection criteria are shown to provide a robust dataset. The resulting catalog contains the DIB total equivalent widths, central wavelengths and widths. We briefly illustrate its potential use for the stellar and interstellar communities.

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Detection of Diffuse Interstellar Bands in the Magellanic Clouds

Cited by 76 publications

References 17 publications

Linear and circular spectropolarimetry of diffuse interstellar bands

Linear and circular spectropolarimetry of diffuse interstellar bands

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

A CATALOG OF 1.5273 μm DIFFUSE INTERSTELLAR BANDS BASED ON APOGEE HOT TELLURIC CALIBRATORS

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