Carbon-chain and Organic Molecules around Very Low Luminosity Protostellar Objects of L1521F-IRS and IRAM 04191+1522
Molecular-line spectra toward L1521F (left) and IRAM 04191+1522 (right). Spectra from molecules such as C3H2, CH3CCH, and C4H, so-called "carbon-chain" molecules, are more intense in L1521F than in IRAM 04191+1522.
There are more than one hundred molecular species detected in molecular clouds. It is well known that chemistry in star-forming regions is non-equilibrium and time-dependent. Molecular abundances in star-forming regions could be used as a clock of physical evolution of star-formation process. Observations of two archetypal protostellar sources of L1521F and IRAM 04191+1522 were performed with the Nobeyama 45-meter telescope in several molecular lines. These include "carbon-chain" molecular lines, which are tracers of molecular clouds at the early (< 105 year) chemical evolutionary stage. We found that the carbon-chain molecules are several times more abundant toward L1521F than IRAM 04191+1522. This result suggests that L1521F is in the earlier evolutionary stage than IRAM 04191+1522, and that through observations of the chemical status we can trace the evolutionary sequence of protostars. (Shigehisa Takakuwa et al. 2011 ApJ 728 101)