SIMBAD references

A search for confirming transitions of 1,3-dihydroxyacetone, (CH₂OH)₂CO (hereafter DHA), has been made toward Sgr B2(N) using the Arizona Radio Observatory Submillimeter Telescope (SMT) and 12 m telescope at millimeter wavelengths. In addition, data for this species have been obtained at the Green Bank Telescope. In all, 63 new transitions of DHA were sought; no plausible emission was detected at 97% of these frequencies. Typical peak-to-peak limits of 10-30 mK were achieved, indicating that DHA is not present in Sgr B2(N) at the level reported by Widicus Weaver & Blake in 2005, by at least a factor of 300. The upper limit to the DHA column density is N_tot<5x10¹³/cm2, suggesting that this species, a three-carbon keto sugar, is less abundant than the two-carbon aldehyde sugar, glycolaldehyde (CH₂OHCHO), by a factor of at least 4. If sugars of higher complexity are formed in interstellar clouds, their synthesis may proceed one carbon atom at a time, possibly through aldehyde intermediates.