Extinction in star-forming disk galaxies from inclination-dependent composite spectra

Ching Wa Yip, Alex S. Szalay, Rosemary F.G. Wyse, Lszló Dobos, Tams Budavri, Istvan Csabai

Research output: Article

24 Citations (Scopus)


Extinction in galaxies affects their observed properties. In scenarios describing the distribution of dust and stars in individual disk galaxies, the amplitude of the extinction can be modulated by the inclination of the galaxies. In this work, we investigate the inclination dependency in composite spectra of star-forming disk galaxies from the Sloan Digital Sky Survey Data Release 5. In a volume-limited sample within a redshift range 0.065-0.075 and a r-band Petrosian absolute magnitude range -19.5 to -22 mag which exhibits a flat distribution of inclination, the inclined relative to face-on extinction in the stellar continuum is found empirically to increase with inclination in the g, r, and i bands. Within the central 0.5 intrinsic half-light radius of the galaxies, the g-band relative extinction in the stellar continuum for the highly inclined objects (axis ratio b/a = 0.1) is 1.2 mag, agreeing with previous studies. The extinction curve of the disk galaxies is given in the rest-frame wavelengths 3700-8000, identified with major optical emission and absorption lines in diagnostics. The Balmer decrement, Hα/Hβ, remains constant with inclination, suggesting a different kind of dust configuration and/or reddening mechanism in the H II region from that in the stellar continuum. One factor is shown to be the presence of spatially non-uniform interstellar extinction, presumably caused by clumped dust in the vicinity of the H II region.

Original languageEnglish
Pages (from-to)780-790
Number of pages11
JournalAstrophysical Journal
Issue number2
Publication statusPublished - jan. 1 2010

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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