A&A 381, 168-177 (2002)
DOI: 10.1051/0004-6361:20011506
Cometary molecular clouds around RNO 6
On-going star formation near the double cluster
h and
Persei
R. Bachiller, A. Fuente and M. S. N. Kumar IGN Observatorio Astronómico Nacional, Apartado 1143, 28800 Alcalá de Henares, Spain
(Received 29 August 2001 / Accepted 18 October 2001 )
Abstract
We present molecular line observations of the star-forming
cloud around RNO 6 along with a newly discovered nearby molecular
cloud that we name RNO 6 NW. Both clouds display striking
similarities in their cometary structures and overall kinematics. By
using
13CO line observations, we estimate that these clouds
have similar sizes (~4.5 pc) and masses (~200
).
Both molecular clouds RNO 6 and RNO 6 NW are active
in star formation. From new high resolution near-IR narrowband
images, we confirm that RNO 6 hosts an embedded IR cluster that
includes a Herbig Be star. A conspicuous H
2 filament is found to
delineate the dense cometary head of the globule. RNO 6 NW hosts
at least two IR sources and a bipolar molecular outflow of ~0.9 pc
of length and ~0.5
of mass.
We show that the
cometary structure of both clouds has been created by the UV
radiation from numerous OB stars lying ~1.5° to the north.
Such OB stars are associated with the double cluster
h and
Persei, and are probably members of the Per OB1 association. Thus
star formation inside these clouds has been very likely triggered by
the Radiation Driven Implosion (RDI) mechanism. From comparison to
RDI theoretical models, we find that the similar kinematics and
morphology of both clouds is well explained if they are at a
re-expansion phase. Triggered sequential star formation also
explains the observed spatial distribution of the members of the
near-IR cluster inside the RNO 6 cloud, and the morphology of the
H
2 filament. We conclude that the RNO 6 and RNO 6 NW clouds are
high-mass counterparts to the cometary globules of smaller masses
which have been studied up to now. Thus our observations demonstrate
that the RDI mechanism can produce, not only low mass stars in small
globules, but also intermediate mass stars and clusters in massive
clouds.
Key words: stars: formation -- interstellar medium: individual objects: RNO 6 -- interstellar medium: jets and outflows -- interstellar medium: molecules
Offprint request: R. Bachiller bachiller@oan.es
SIMBAD Objects
© ESO 2002