Brackett alpha and gamma Observations of Starburst and Seyfert Galaxies

Br (Brackett) α and γ line fluxes of starburst and Seyfert galaxies are presented. The Bra line has been detected in seven of 12 galaxies. These data are combined with published Brackett line fluxes of M82 and NGC 253 to examine the relation between the extinction, A_v_, derived from the Brα/Brγ ratio and the optical depth, τ(10), of the silicate absorption at 10 microns. Generally speaking, a line of slope A_v_/τ(10) = 14 fits the data well, which is the same relation as found in the Milky Way. In the type 2 Seyferts NGC 1068 and NGC 5506, the observed Brα/Brγ ratios may not be simply explained by case B recombination with heavy extinction. The extinction values derived from Brα/Brγ are compared with those determined from optical and X-ray observations, and the implications are discussed.