A Revised Estimate of the COJ = 1–0 Emission from the Host Galaxy of GRB 030329 Using the Nobeyama Millimeter Array

A sensitive observation of the CO (J=1-0) molecular line emission in the hostgalaxy of GRB 030329 (z =0.1685) has been performed using the NobeyamaMillimeter Array in order to detect molecular gas and hidden star formation. Nosign of CO emission was detected, which invalidates our previous report on thepresence of molecular gas. The 3sigma upperlimit on the CO line luminosity(L'_CO) of the host galaxy is 6.9 x 10^8 K km s^-1 pc^2. The lowerlimit of thehost galaxy's metallicity is estimated to be 12+log(O/H) ~ 7.9, which yields aCO line luminosity to H_2 conversion factor of alpha_CO = 40 Msun (K km s^-1pc^2)^-1. Assuming this alpha_CO factor, the 3sigma upperlimit on the moleculargas mass of the host galaxy is 2.8 x 10^10 Msun. Based on the Schmidt law, the3sigma upperlimit of the total star formation rate (SFR) of the host galaxy isestimated to be 38 Msun yr^-1. These results independently confirm theinferences of previous observations in the optical, submillimeter, and X-rayband, which regard this host galaxy as a compact dwarf galaxy, and not amassive, aggressively star forming galaxy.Comment: 8 pages, 3 figures, accepted for publication in Ap