Astronomy and Astrophysics, volume 622A, 32-32 (2019/2-1)
C2H N = 1 - 0 and N2H+ J = 1 - 0 observations of Planck Galactic cold clumps.
LIU X.-C., WU Y., ZHANG C., LIU T., YUAN J., QIN S.-L., JU B.-G. and LI L.-X.
Abstract (from CDS):
A survey of C2H N=1-0 and N2H+ J=1-0 toward Planck Galactic cold clumps (PGCCs) was performed using the Purple Mountain Observatory's 13.7m telescope. C2H and N2H+ were chosen to study the chemical evolutionary states of PGCCs. Among 121 observed molecular cores associated with PGCCs, 71 and 58 are detected with C2H N=1-0 and N2H+ J=1-0, respectively. The detected lines of most sources can be fitted with a single component with compatible VLSR and line widths, which confirms that these PGCC cores are very cold (with gas temperatures 9-21K) and quiescent while still dominanted by turbulence. The ratio between the column densities of C2H and N2H+ (N(C2H)/N(N2H+)) is found to be a good tracer for the evolutionary states of PGCC cores. Gas-grain chemical model can reproduce the decreasing trend of N(C2H)/N(N2H+) as a function of time. The cores with the lowest abundances of N2H+ (X[N2H+]<10–10) are the youngest, and have nearly constant abundances of C2H. In evolved cores with X[N2H+]∼10–9, abundances of C2H drop quickly as the exhaustion of carbon atoms. Although these PGCC cores are in different evolutionary states, they are all quite young (<5x105yr) with N(C2H)>N(N2H+). Mapping observations are carried out toward 20 PGCC cores. The PGCC cores in Cepheus have lower N(C2H)/N(N2H+) and larger line widths compared with those in Taurus. This implies that PGCC cores in Taurus are less chemically evolved than those in Cepheus.
© ESO 2019
ISM: molecules - ISM: abundances - ISM: kinematics and dynamics - stars: formation - ISM: clouds
Tables A.1-A.3: [LWZ2019] GLLL.l+BBAN N=71.
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