Gas-to-dust ratio in massive star-forming galaxies at z~1.4
  We present results of 12CO(J=2-1) observations toward four massive
star-forming galaxies at z~1.4 with the Nobeyama 45~m radio telescope. The
galaxies are detected with Spitzer/MIPS in 24 um, Herschel/SPIRE in 250 um, and
350 um and they mostly reside in the main sequence. Their gas-phase
metallicities derived with N2 method by using the Ha and [NII]6584 emission
lines are near the solar value. CO lines are detected toward three galaxies.
The molecular gas masses obtained are (9.6-35) x 10^{10} Msun by adopting the
Galactic CO-to-H2 conversion factor and the CO(2-1)/CO(1-0) flux ratio of 3.
The dust masses derived with the modified blackbody model (assuming the dust
temperature of 35 K and the emissivity index of 1.5) are (2.4-5.4) x 10^{8}
Msun. The resulting gas-to-dust ratios (not accounting for HI mass) at z~1.4
are 220-1450, which are several times larger than those in local star-forming
galaxies. A dependence of the gas-to-dust ratio on the far-infrared luminosity
density is not clearly seen.
