Gas-to-dust ratio in massive star-forming galaxies at z~1.4

TL;DR

This study measures the gas-to-dust ratios in massive star-forming galaxies at z~1.4, revealing ratios significantly higher than local galaxies, using CO observations and dust modeling.

Contribution

First measurement of gas-to-dust ratios in z~1.4 galaxies using CO and dust emission data, highlighting their differences from local counterparts.

Findings

Gas-to-dust ratios range from 220 to 1450.

Ratios are several times higher than in local star-forming galaxies.

No clear dependence on far-infrared luminosity density.

Abstract

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.