Detectability of Glycine in Solar-type System Precursors
  Glycine (NH2CH2COOH) is the simplest amino acid relevant for life. Its
detection in the interstellar medium is key to understand the formation
mechanisms of pre-biotic molecules and their subsequent delivery onto planetary
systems. Glycine has extensively been searched for toward hot molecular cores,
although these studies did not yield any firm detection. In contrast to hot
cores, low-mass star forming regions, and in particular their earliest stages
represented by cold pre-stellar cores, may be better suited for the detection
of glycine as well as more relevant for the study of pre-biotic chemistry in
young Solar System analogs. We present 1D spherically symmetric radiative
transfer calculations of the glycine emission expected to arise from the
low-mass pre-stellar core L1544. Water vapour has recently been reported toward
this core, indicating that a small fraction of the grain mantles in L1544
(~0.5%) has been injected into the gas phase. Assuming that glycine is
photo-desorbed together with water in L1544, and considering a solid abundance
of glycine on ices of ~1E-4 with respect to water, our calculations reveal that
several glycine lines between 67 GHz and 80 GHz have peak intensities larger
than 10 mK. These results show for the first time that glycine could reach
detectable levels in cold objects such as L1544. This opens up the possibility
to detect glycine, and other pre-biotic species, at the coldest and earliest
stages in the formation of Solar-type systems with near-future instrumentation
such as the Band 2 receivers of ALMA.
