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

Vos, D.A.I.; Cox, Nicholas; Kaper, L.; Spaans, Marco; Ehrenfreund, P.

doi:10.1051/0004-6361/200809746

Cited by 97 publications

(202 citation statements)

References 95 publications

(193 reference statements)

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“…This is very likely also caused by environment effects, since those bands are strongly influenced by the radiation field. The same remarks apply to the correlation coefficients measured by Vos et al (2011) for the upper Scorpius region that, except for DIB 5797, are lower than found here. Josafatsson & Snow (1987) computed Pearson coefficients for three DIBS in common, 5780, 5849, and 5797 Å, using early-type target stars in reflection nebulae.…”

Section: Correlation With the Color Excesssupporting

confidence: 71%

“…Many of them are significantly or weakly correlated with interstellar integrated quantities, namely the HI, H 2 column or the color excess, as shown by numerous studies (e.g. Friedman et al 2011;Vos et al 2011). In particular, the correlation of the DIB strength with the extinction or the color excess has been investigated for a large number of bands, and it has been shown that the degree of correlation is highly variable among the DIBs (see e.g.…”

Section: Introductionmentioning

confidence: 97%

See 1 more Smart Citation

Automated measurements of diffuse interstellar bands in early-type star spectra

Puspitarini¹,

Lallement²,

Chen³

2013

A&A

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Aims. Stellar spectroscopic surveys may bring useful statistical information on the links between diffuse interstellar bands (DIBs) and the interstellar environment. DIB databases can also be used as a complementary tool for locating interstellar (IS) clouds. Our goal is to develop fully automated methods of DIB measurements to be applied to extensive data from stellar surveys. Methods. We present a method that is appropriate for early-type nearby stars, along with its application to high-resolution spectra of ∼130 targets recorded with the ESO FEROS spectrograph and comparisons with other determinations. Using a DIB average profile deduced from the most reddened stars, we performed an automated fitting of a combination of a smooth stellar continuum, the DIB profile, and, when necessary, a synthetic telluric transmission. Results. Measurements are presented for 16 DIBs in the optical domain that could be extracted automatically: 4726.8, 4762.6, 4963.9, 5780.4, 5797.1, 5849.8, 6089.8, 6196.0, 6203.0−6204.5, 6269.8, 6283.8, 6379.3, 6445.3, 6613.6, 6660.7, and 6699.3 Å. Two approaches to determining equivalent width (fitted equivalent width and continuum-integrated equivalent width) were tested and the two determinations were found to agree within the uncertainties, except for the 6203−6204 multiple band, and are compatible with previous non automated measurements. Errors arising from statistical noise and continuum placement were estimated conservatively by means of the "sliding window" method. We derived the mean relationship between the DIB equivalent width and the color excess. Parameters of the linear correlation relationships are positively compared with published values, and most correlation coefficients were found to be higher than those based on an earlier type, UV bright target stars, which confirms previous results on the influence of the radiation field. We provide the first correlation parameters for the 5849.8, 6089.8, 6269.8, 6445.3, 6660.7, and 6699.3 Å bands in the Galaxy. The coefficients are within the same range as for other optical bands. Conclusions. Automated DIB equivalent width extractions can be performed for nearby early-type stars without significant losses in accuracy. This opens the perspective of building extended DIB catalogs based on high-resolution spectroscopic surveys. We discuss the limitations of this method in the case of distant stars and potential improvements.

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Section: Correlation With the Color Excesssupporting

confidence: 71%

Section: Introductionmentioning

confidence: 97%

Automated measurements of diffuse interstellar bands in early-type star spectra

Puspitarini¹,

Lallement²,

Chen³

2013

A&A

View full text Add to dashboard Cite

show abstract

“…Given the value of the ratio between these two DIBs as a tracer of the characteristics of the environment (i.e. radiation field) (Cami et al 1997;Vos et al 2011;Cordiner et al 2013), there is a strong motivation for a similar work to the one presented here for this spectral range. Likewise, the DIB at λ6614 is relatively strong and, as such, the creation of synthetic spectra in this spectral range should be contemplated, though a preliminary exploration of this range, not discussed here, points towards a need for a more delicate approach, where for some stellar lines, additional parameters other than log(g f ) should be tuned and/or effects like departures form LTE, explored.…”

Section: Discussionmentioning

confidence: 83%

“…However, DIBs seem sensitive to the radiation field of these stars (Vos et al 2011;Dahlstrom et al 2013;Cordiner et al 2013), and therefore hot stars are not the optimal targets to prove the typical conditions of the general ISM of our Galaxy. In fact, Raimond et al (2012) showed how using cooler target stars correlations between DIBs (and reddening) improve, confirming that the radiation field of UV bright stars has a significant influence on the DIB strength.…”

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 DIB at λ5797.1 was not included in the fit since we did not see any evidence for it in our spectra. It is known that the ratio of the equivalent width of these two DIBs can vary up to a factor ∼5, depending on the characteristics of the ISM in the sight line of consideration (Vos et al 2011), but only in very specific situations both DIBs are comparable. Typically, the DIB λ5797.1 is ∼3-5 times fainter.…”

Section: Feature Fittingmentioning

confidence: 99%

Towards DIB mapping in galaxies beyond 100 Mpc

Monreal-Ibero

Weilbacher

Wendt

et al. 2015

A&A

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Context. Diffuse interstellar bands (DIBs) are non-stellar weak absorption features of unknown origin found in the spectra of stars viewed through one or several clouds of the interstellar medium (ISM). Research of DIBs outside the Milky Way is currently very limited. In particular, spatially resolved investigations of DIBs outside of the Local Group are, to our knowledge, inexistent. Aims. In this contribution, we explore the capability of the high-sensitivity integral field spectrograph, MUSE, as a tool for mapping diffuse interstellar bands at distances larger than 100 Mpc. Methods. We used MUSE commissioning data for AM 1353-272 B, the member with the highest extinction of the Dentist's Chair, an interacting system of two spiral galaxies. High signal-to-noise spectra were created by co-adding the signal of many spatial elements distributed in a geometry of concentric elliptical half-rings. Results. We derived decreasing radial profiles for the equivalent width of the λ5780.5 DIB both in the receding and approaching side of the companion galaxy up to distances of ∼4.6 kpc from the centre of the galaxy. The interstellar extinction as derived from the Hα/Hβ line ratio displays a similar trend, with decreasing values towards the external parts. This translates into an intrinsic correlation between the strength of the DIB and the extinction within AM 1353-272 B, consistent with the currently existing global trend between these quantities when using measurements for Galactic and extragalactic sightlines. Conclusions. It seems feasible to map the DIB strength in the Local Universe, which has up to now only been performed for the Milky Way. This offers a new approach to studying the relationship between DIBs and other characteristics and species of the ISM in addition to using galaxies in the Local Group or sightlines towards very bright targets outside the Local Group.

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

Cited by 97 publications

References 95 publications

Automated measurements of diffuse interstellar bands in early-type star spectra

Automated measurements of diffuse interstellar bands in early-type star spectra

Measuring diffuse interstellar bands with cool stars

Towards DIB mapping in galaxies beyond 100 Mpc

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