2004/08/23 by Lynne A. Valencic, Geoffrey C. Clayton, Karl D. Gordon · 187 citations
Physics and Astronomy · #Astronomy and Astrophysical Research #Astrophysics and Star Formation Studies #Extinction (optical mineralogy) #Galaxies: Formation, Evolution, Phenomena #Galaxy #Interstellar cloud #Interstellar medium #Milky Way #Photometry (optics) #Ultraviolet #Wavelength #astro-ph
paper · pdf · doi:10.1086/424922
published in The Astrophysical Journal 616(2), 912-924 (IOP Publishing) · 32 pages, 12 figures
arxiv created 2004/08/23 · openalex publication_date 2004/12/01 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
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, R V , 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 A V 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 R V 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 R V allow us to revise the CCM law.