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Abstract

Water maser emission is a powerful tracer of the presence of embedded sources in dense clouds since it requires elevated
temperatures (>100 K) and densities (>107 cm−3) that can be found in circumstellar disks and/or jets/outflows associated with Young
Stellar Objects. Bright rimmed clouds compressed by ionization fronts from nearby massive stars are considered good examples of
externally triggered star formation, possibly resulting in the formation of massive stars.
Aims. We aim to determine the water maser emission frequency and characteristics of 45 bright rimmed clouds in the southern
hemisphere identified by Sugitani & Ogura (1994, ApJS, 92, 163).
Methods. We have used the Tidbinbilla 70-m radiotelescope to perform a high sensitivity survey at 22.2 GHz of the maser emission
from the 616−523 rotational transition of H2O molecules.
Results. We found 7 water maser sources out of 44 (16% detection rate), 5 being new detections. With the exception of the maser
associated with BRC 68, all the other maser are characterized by low integrated fluxes and luminosities.
Conclusions. Most maser sources fall below the correlation between the H2O and far-infrared luminosity found in other studies
towards a variety of star forming regions. These results are similar to those found in the companion survey of BRCs in the northern
hemisphere by Valdettaro et al. (2005, A&A, 443, 535). The low detection frequency and the properties of water maser emission from
BRCs indicate that low-mass star formation is the most natural outcome of the external compression induced by the ionization front
from nearby massive stars.

Item Type:	Article
Authors/Creators:	Valdettaro, R and Chapman, JM and Lovell, JEJ and Palla, F
Keywords:	ISM: clouds -- masers -- stars: formation -- radio lines: ISM
Journal or Publication Title:	Astronomy & Astrophysics
Publisher:	EDP Sciences S A
ISSN:	0004-6361
DOI / ID Number:	https://doi.org/10.1051/0004-6361:20066778
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