Co (j = 4 ! 3) and 650 M Continuum Observations of the Z=0.93 Hyperluminous Infrared Galaxy Fsc 15307+3252

We report the results of our CO J = 4 ! 3 line and rest frame 650 m continuum observations of the z=0.93 hyperluminous infrared galaxy FSC 15307+3252 using the Owens Valley Millimeter Array. No line or continuum emission was detected, but the derived limits provide a useful constraint on the temperature, emissivity, and mass of the cold dust associated with FSC 15307+3252 and its molecular gas content. The 3 upper limit on the velocity integrated CO (4{3) line ux is 1.6 Jy km s ?1 (for V = 300 km s ?1). This corresponds to a surprisingly small total molecular gas mass limit of 5 10 9 h ?2 M for this galaxy with infrared luminosity L F I R > 10 13 L. Combined with existing photometry data, our 3 upper limit of 5.1 mJy for the 239 GHz (650 m rest wavelength) continuum ux yields a total dust mass of 0.4-1.5 times 10 8 M. The CO luminosity (thus molecular gas content) and the resulting gas-to-dust ratio are lower than the values typical for the more gas-rich infrared galaxies, but they are within the observed ranges. On the other hand, FSC 15307+3252 has a dust content and infrared luminosity 40 and 200 times larger than the infrared bright elliptical-like galaxies NGC 1275 and Cygnus A. The FIR luminosity to dust mass ratios, L F I R =M dust , for all three galaxies hosting a powerful AGN (FSC 10214+4724, FSC 15307+3252, Cygnus A) are larger than reasonably expected for a galaxy dominated by a starburst and four times larger than Arp 220. Therefore the bulk of the observe FIR luminosity in these galaxies is likely powered by their luminous active nucleus.