Ultraviolet Extinction Properties in the Milky Way

By L. Valencic, G. Clayton, K. Gordon. 2004

143 citations recorded by the source corpus.

We have assembled a homogeneous database of 417 ultraviolet (UV) extinction curves for reddened sight lines having International Ultraviolet Explorer spectra. We have combined these with optical and Two Micron All Sky Survey photometry, allowing estimates of the ratio of total-to-selective extinction, RV, for the entire sample. Fitzpatrick-Massa (FM) parameters have also been found for the entire sample. This is the largest study of parameterized UV extinction curves yet published, and it covers a wide range of environments, from dense molecular clouds to the diffuse interstellar medium, with extinctions AV ranging from 0.50 to 4.80. It is the first to extend far beyond the solar neighborhood and into the Galaxy at large, with 30 sight lines having distances greater than 5 kpc. Previously, the longest sight lines with FM parameters and RV extended ~1 kpc. We find that (1) the Cardelli, Clayton, & Mathis (CCM) extinction law applies for 93% of the sight lines, implying that dust processing in the Galaxy is efficient and systematic, (2) the central wavelength of the 2175 Å bump is constant, and (3) the 2175 Å bump width is dependent on environment. Only four sight lines show systematic deviations from CCM: HD 29647, 62542, 204827, and 210121. These sight lines all sample dense, molecule-rich clouds. The new extinction curves and values of RV allow us to revise the CCM law.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/b937ccb88e1b6dae50f64b81883fafa90c43c251

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Citations in the corpus

An Analysis of the Shapes of Interstellar Extinction Curves. V. The IR-through-UV Curve Morphology (2007, methodology): “Recently, for example, Valencic et al. (2004) found that 93% of a large sample of Galactic extinction curves obey a modified form of this relation.”
Average extinction curves and relative abundances for quasi-stellar object absorption-line systems at 1 ≤zabs < 2 (2006, background): “However, we note that virtually all of the known MW extinction curves are for relatively large values ofE(B − V ) (Valencic et al. 2004) and that for some very low extinction sightlines in theMW, the bump is weak or missing (Clayton, Gordon & Wolff 2000).”
Ultraviolet Survey of CO and H2 in Diffuse Molecular Clouds: The Reflection of Two Photochemistry Regimes in Abundance Relationships (2008, background): “…& Clayton 1991; Larson et al. 2000; Barbaro et al. 2001; Patriarchi et al. 2001; Whittet et al. 2001; Ducati et al. 2003; Patriarchi et al. 2003; Valencic et al. 2004; Fitzpatrick & Massa 2005; Larson & Whittet 2005; Sofia et al. 2005), the shape of the UV extinction curve (Massa et al. 1983;…”