A&A Supplement series, Vol. 121, February 1997, 255-274
Received February 14; accepted May 20, 1996
G. Anglada
- I. Sepúlveda
- J.F. Gómez
Send offprint request: G. Anglada
Departament d'Astronomia i Meteorologia, Universitat de
Barcelona, Av. Diagonal 647, E-08028 Barcelona, Spain
Instituto de Astronomía, UNAM, Apdo. Postal 70-264, 04510 México DF,
Mexico
Laboratorio de Astrofísica Espacial y Física Fundamental, INTA,
Apdo. Correos 50727, E-28080 Madrid, Spain
Instituto de Astrofísica de Andalucía,
CSIC, Apdo. Correos 3004, C/ Sancho Panza s/n, E-18080 Granada, Spain
We observed the (J,K) = (1,1) and (J,K) = (2,2)
inversion transitions of the 
molecule towards several
regions with molecular or optical outflows: RNO 43, HH 83,
HH 84, HH 86/87/88, L1641-N, L100, L483, L673, IRAS
20188+3928, L1228, L1048, HHL 73, L1251 (IRAS 22343+7501
and IRAS 22376+7455) and L1262, using the 37 m radio
telescope of the Haystack Observatory. Additionally, we searched for the 
\
maser line towards nine regions, detecting a weak 
maser near IRAS
20188+3928. We detected and mapped 
emission in 14 of the 15 regions
observed, and we estimated physical parameters for the high density gas.
We systematically found that the position of the best candidate for the
outflow excitation in each region is very close to an 
emission peak.
From a statistical study of the data presented in this paper, together
with previously published data, we conclude that the 
line emission is
more intense towards molecular outflow sources than towards sources with
only optical outflows. Therefore, molecular outflows appear to be
associated with larger amounts of high density gas. This result suggests
a possible evolutive scheme in which young objects associated with
molecular outflows lose progressively their neighboring high-density gas,
weakening both the 
emission and the molecular outflow in the process,
and making optical jets more easily detectable as the total amount of gas
decreases.
keywords: ISM: jets and outflows -- ISM: molecules -- masers -- stars: formation