  Rest-frame 0.48-1.1 micron emission line strengths and molecular gas mass
(H_2) upper limits for 3 luminous infrared sources - the hyperluminous infrared
galaxies IR F09105+4108 (z=0.44), IR F15307+3252 (z=0.93), and the
optically-selected QSO PG 1634+706 (z=1.3) - are presented. Diagnostic
emission-line ratios indicate a Seyfert 2-like spectrum for both infrared
galaxies, consistent with previously published work. The upper limits of
molecular gas mass for all 3 sources are M(H_2) < 1-3x10^10 h^-2 M_sun (q=0.5,
H=100h km/s/Mpc), less than that of the most gas-rich infrared galaxies in the
local Universe. All 3 sources have L_ir/L'_CO = 1300-2000, and thus are the
extragalactic sources with the most extreme L_ir/L'_CO values measured to date.
Given the relatively warm far-infrared colors for all 3 objects, much of their
infrared luminosity may emanate from a relatively modest amount of warm dust
(e.g. M_d = 10^5-7 M_sun, T_d = 200-100 K) near the AGN...
