Extinction can dramatically reduce the observed intensity of your source, particularly in the ultraviolet. Figure 7.3
values applicable to our Galaxy, taken from Cardelli, Clayton, & Mathis (1989, ApJ, 345, 245
) assuming RV
= 3.1. This corresponds to the Milky Way Diffuse (Rv = 3.1)
selection of the ETC.
Extinction curves have a strong metallicity dependence, particularly at ultraviolet wavelengths. Sample extinction curves are presented in Gordon et al. [2003, ApJ, 594, 279
(LMC Average, LMC 30 Dor Shell, and SMC Bar)], Calzetti et al. [2000, ApJ, 533, 682
(starburst galaxies)], and references therein. At lower metallicities, the 2200 Å bump that is so prominent in the Galactic extinction curve disappears, and Aλ
(B – V
) increases at shorter UV wavelengths.