2016/08/24 by Takaya Nozawa
Physics and Astronomy · #Astrophysics #Astrophysics and Star Formation Studies #Cosmic dust #Extinction (optical mineralogy) #Galaxy #Gamma-ray bursts and supernovae #Interstellar medium #Log-normal distribution #Milky Way #Molar absorptivity #Optics #Physics #Power law #Stars #Statistics #Stellar, planetary, and galactic studies #Wavelength #astro-ph.GA
paper · pdf · doi:10.1016/j.pss.2016.08.006
16 pages, 7 figures, 7 tables, accepted for publication in Planetary and Space Science (special issue for Cosmic Dust VIII)
arxiv created 2016/08/24 · openalex publication_date 2016/08/24 · openalex created_date 2016/09/16 · arxiv updated 2016/12/07 · openalex updated_date 2026/08/05
It is well known that the extinction properties along lines of sight to Type Ia supernovae are described by steep extinction curves with unusually low total-to-selective extinction ratios of Rv = 1.0-2.0. In order to reveal the properties of interstellar dust that causes such peculiar extinction laws, we perform the fitting calculations to the measured extinction curves by applying a two-component dust model composed of graphite and silicate. As for the size distribution of grains, we consider two function forms of the power-law and lognormal distributions. We find that the steep extinction curves derived from the one-parameter formula by Cardelli et al. (1989) with Rv = 2.0, 1.5, and 1.0 can be reasonably explained even by the simple power-law dust model that has a fixed power index of -3.5 with the maximum cut-off radii of amax = 0.13 um, 0.094 um, and 0.057 um, respectively. These maximum cut-off radii are smaller than amax ~ 0.24 um considered to be valid in the Milky Way, clearly demonstrating that the interstellar dust responsible for steep extinction curves is highly biased to smaller sizes. We show that the lognomal size distribution can also lead to good fits to the extinction curves with Rv = 1.0-3.1 by taking the appropriate combinations of the relevant parameters. We discuss that the extinction data at ultraviolet wavelengths are essential for constraining the composition and size distribution of interstellar dust.