A Tale of Two Mysteries in Interstellar Astrophysics: The 2175 Å Extinction Bump and Diffuse Interstellar Bands

Xiang, Fu-Yuan; Li, Aigen; Zhong, Jianxin

doi:10.1088/0004-637x/733/2/91

Cited by 45 publications

(50 citation statements)

References 101 publications

(141 reference statements)

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“…The present results and their interpretation are also in line with another recent study implying that the DIBs, unlike the interstellar UV bump, very probably do not originate from PAHs (Steglich et al 2011). 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: Discussionsupporting

confidence: 93%

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: Discussionsupporting

confidence: 93%

The smoothness of the interstellar extinction curve in the UV

Steglich

Carpentier

Jäger

et al. 2012

A&A

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“…Quantitative studies of DIBs in the LMC and SMC sightlines would allow us to gain insight into the effects of UV radiation and dust extinction on DIBs (e.g., see Cox & Spaans 2006). Xiang et al (2011) explored the relation between the EWs of nine DIBs and the 2175Å extinction bump of 84 sightlines, using πc 3 /2γ as a measure of the bump strength. No correlation was found.…”

Section: Discussionmentioning

confidence: 99%

“…Making use of these advances, we aim at an extensive revisit of the possible "missing link" between the UV extinction and DIBs. In an earlier paper, we have examined the relation between the 2175Å bump and DIBs (see Xiang, Li, & Zhong 2011) and found no correlation. In this paper we shall focus on the relation between the FUV extinction and DIBs.…”

Section: Introductionmentioning

confidence: 97%

“…An extensive exploration and understanding of the possible links between the DIBs and the interstellar extinction curve, particularly the 2175Å extinction bump and the far-UV (FUV) rise at λ −1 > 5.9 µm −1 , can provide useful information on the origin and composition of the elusive carriers as well as on the physical conditions prevailing in the regions where they are found (Wu 1972, Herbig 1975, Nandy & Thompson 1975, Dorschner et al 1977, Schmidt 1978, Danks 1980, Wu et al 1981, Nandy et al 1982, Witt et al 1983, Seab & Snow 1984, Krelowski et al 1987, Benvenuti & Porceddu 1989, Désert et al 1995, Magier et al 2001, 2005, Xiang, Li, & Zhong 2011, Clayton 2014.…”

Section: Introductionmentioning

confidence: 99%

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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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“…We also refer to Xiang et al (2011) for an extensive review of the detections of the UV bump in Galactic and extragalactic interstellar media.…”

Section: Introductionmentioning

confidence: 99%

GOODS-Herschel: evidence of a UV extinction bump in galaxies atz > 1

Buat

Giovannoli

Heinis

et al. 2011

A&A

103

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Context. Dust attenuation curves in external galaxies are useful for studying their dust properties as well as interpreting their intrinsic spectral energy distributions. These functions are not very well known in the UV range whether at low or high redshift. In particular, the presence or absence of a UV bump at 2175 Å remains an open issue that has consequences on the interpretation of broad band colours of galaxies involving the UV range. Aims. We want to study the dust attenuation curve in the UV range at z > 1 where the UV is redshifted into the visible and with Herschel data to constrain dust emission and a global dust attenuation. In particular, we search for a UV bump and related implications for dust attenuation determinations. Methods. We use deep photometric data of the Chandra Deep Field South obtained with intermediate and broad band filters by the MUSYC project to sample the UV rest frame of galaxies with 1 < z < 2. Herschel/PACS and Spitzer/MIPS data are used to measure the dust emission. We select 30 galaxies with high S/N in all bands. Their SEDs from the UV to the far-IR are fitted using the CIGALE code and the characteristics of the dust attenuation curves obtained as Bayesian outputs of the SED fitting process. Results. The mean dust attenuation curve we derive exhibits a significant UV bump at 2175 Å whose amplitude corresponds to 35% (76%) that of the Milky Way (Large Magellanic Cloud: LMC2 supershell) extinction curve. An analytical expression of the average attenuation curve (A(λ)/A V ) is given and found to be slightly steeper than the Calzetti et al. one, although at a 1σ level. Our galaxy sample is used to study the derivation of the slopes of the UV continuum from broad band colours, including the rest frame GALEX FUV − NUV colour. Systematic errors induced by the presence of the bump are quantified. We compare dust attenuation factors measured with CIGALE to the slope of the UV continuum and find that there is a large scatter around the relation valid for local starbursts (∼0.7 mag). The uncertainties on the determination of the UV slope lead to an extra systematic error in a range of 0.3 to 0.7 mag on dust attenuation when a filter overlaps the UV bump.

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A Tale of Two Mysteries in Interstellar Astrophysics: The 2175 Å Extinction Bump and Diffuse Interstellar Bands

Cited by 45 publications

References 101 publications

The smoothness of the interstellar extinction curve in the UV

The smoothness of the interstellar extinction curve in the UV

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

GOODS-Herschel: evidence of a UV extinction bump in galaxies atz > 1

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