Complex organic molecules (COMs) have been observed toward several low-mass young stellar objects (LYSOs). Small and heterogeneous samples have so far precluded conclusions on typical COM abundances, as well as the origin(s) of abundance variations between sources. We present observations toward 16 deeply embedded (Class 0/I) low-mass protostars using the IRAM 30 m telescope. We detect CH2CO, CH3CHO, CH3OCH3, CH3OCHO, CH3CN, HNCO, and HC3N toward 67%, 37%, 13%, 13%, 44%, 81%, and 75% of sources, respectively. Median column densities derived using survival analysis range between 6.0 × 1010 cm-2 (CH3CN) and 2.4 × 1012 cm-2 (CH3OCH3), and median abundances range between 0.48% (CH3CN) and 16% (HNCO) with respect to CH3OH. Column densities for each molecule vary by about one order of magnitude across the sample. Abundances with respect to CH3OH are more narrowly distributed, especially for oxygen-bearing species. We compare observed median abundances with a chemical model for low-mass protostars and find fair agreement, although some modeling work remains to bring abundances higher with respect to CH3OH. Median abundances with respect to CH3OH in LYSOs are also found to be generally comparable to observed abundances in hot cores, hot corinos, and massive YSOs. Compared with comets, our sample is comparable for all molecules except HC3N and CH2CO, which likely become depleted at later evolutionary stages.Based on observations carried out under project nos. 003-14 and 006-13 with the IRAM 30 m Telescope. IRAM is supported by INSU/CNRS (France), MPG (Germany), and IGN (Spain).
The Astrophysical Journal
- Pub Date:
- June 2017
- ISM: molecules;
- stars: protostars;
- Astrophysics - Solar and Stellar Astrophysics;
- Astrophysics - Astrophysics of Galaxies