Investigating the Limits of Chemical Complexity in Sagittarius B2(N): A Rigorous Attempt to Confirm 1,3-Dihydroxyacetone

Abstract

A search for confirming transitions of 1,3-dihydroxyacetone, (CH 2 OH) 2 CO (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 ! 5 #10 13 cm Ϫ2 , suggesting that this species, a three-carbon keto sugar, is less abundant than the two-carbon aldehyde sugar, glycolaldehyde (CH 2 OHCHO), 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.

Improved line frequencies for the nucleic acid base uracil for a radioastronomical search

“…However, since at 3 additional line positions no significant features could be detected above the noise level, these coincidences appear to be accidental 3 . This finding is another example of the problem of line confusion in line-rich sources as Sgr B2(N) at mm-wavelengths, which has been recently discussed in the context of the detection of other large organic species (Snyder et al 2005;Apponi et al 2006). Spectral line confusion is less pronounced in the cm-wavelength region, and the capability of detecting complex molecules in Sgr B2(N) at cm-wavelengths has been recently demonstrated by GBT observations of acetamide, propenal and propanal (Hollis et al 2004b(Hollis et al , 2006.…”

“…In such a cold environment rotational transitions of uracil peak in the 3 mm band and its gas phase emission spectrum might be observable, provided that an efficient formation and ejection process exists, possibly one caused by shocks. Based on these assumptions, we searched for uracil emission lines in two recent line surveys of the Sgr B2(N) region by Apponi (2006) and Belloche (2006) performed with the Kitt Peak 12 m and IRAM 30 m radio telescopes, respectively, and obtained an upper limit for the uracil column density of N = 6.0 × 10 13 cm −2 , which is only slightly less than the pyrimidine upper limit of 1.7 × 10 14 cm −2 in this source (Kuan et al 2003b). Out of the 18 lines which fall within the range of the surveys, 13 coincide with emission lines and 2 with absorption features.…”

A new weapon for the interstellar complex organic molecule hunt: the minimum energy principle

“…Detection of dihydroxyacetone (HOCH 2 COCH 2 OH), DHA, has been claimed by Widicus Weaver & Blake (2005) but soon after was challenged by Apponi et al (2006).…”

LABORATORY DETECTION OF HOCN AND TENTATIVE IDENTIFICATION IN Sgr B2

“…Nevertheless, unambiguous identification of a new molecule in a crowded source like Sgr B2 requires considerable caution. In at least two recent cases, mistakes have been made in the identification there of complex organic molecules (Snyder et al 2005;Apponi et al 2006). Owing to the difficulty encountered in identifying a new molecule in a rich wideline source, unusually tight rules of evidence are required to claim a certain detection: specifically, (1) close agreement of astronomical frequencies with laboratory data; (2) detection of more than a few unblended lines with good signal to noise; and (3) observation of the molecule in another source.…”