Issue |
A&A
Volume 508, Number 1, December II 2009
|
|
---|---|---|
Page(s) | 259 - 274 | |
Section | Interstellar and circumstellar matter | |
DOI | https://doi.org/10.1051/0004-6361/200811099 | |
Published online | 15 October 2009 |
Dense and warm molecular gas in the envelopes and outflows of southern low-mass protostars
1
Leiden Observatory, Leiden University, PO Box 9513, 2300 RA Leiden, The Netherlands
2
Center for Astrophysics, 60 Garden Street, MS 78, Cambridge, MA 02138, USA e-mail: tvankempen@cfa.harvard.edu
3
Max Planck Institut für Extraterrestrische Physik (MPE), Giessenbachstr. 1, 85748 Garching, Germany
4
Max Planck Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
Received:
7
October
2008
Accepted:
6
October
2009
Context. Observations of dense molecular gas lie at the basis of our
understanding of the density and temperature structure of
protostellar envelopes and molecular outflows. The
Atacama Pathfinder EXperiment (APEX) opens up the study of
southern (Dec )
protostars.
Aims. We aim to characterize the properties of the protostellar envelope, molecular outflow and surrounding cloud, through observations of high excitation molecular lines within a sample of 16 southern sources presumed to be embedded YSOs, including the most luminous Class I objects in Corona Australis and Chamaeleon.
Methods. Observations of submillimeter lines of
CO, HCO+ and their isotopologues,
both single spectra and small maps (up to ), were
taken with the FLASH and APEX-2a instruments mounted on APEX to
trace the gas around the sources. The HARP-B instrument on the JCMT was used to map IRAS 15398-3359 in these lines. HCO+ mapping probes the presence
of dense centrally condensed gas, a characteristic of
protostellar envelopes. The rare isotopologues C18O and
H13CO+ are also included to determine the optical depth,
column density, and source velocity. The combination of multiple CO
transitions, such as 3–2, 4–3 and 7–6, allows to constrain
outflow properties, in particular the temperature. Archival
submillimeter continuum data are used to determine envelope masses.
Results. Eleven of the sixteen sources have associated warm and/or dense (≥ 106 cm-3) quiescent gas characteristic of protostellar envelopes, or an associated outflow. Using the strength and degree of concentration of the HCO+ 4–3 and CO 4–3 lines as a diagnostic, five sources classified as Class I based on their spectral energy distributions are found not to be embedded YSOs. The C18O 3–2 lines show that for none of the sources, foreground cloud layers are present. Strong molecular outflows are found around six sources, with outflow forces an order of magnitude higher than for previously studied Class I sources of similar luminosity.
Conclusions. This study provides a starting point for future ALMA and Herschel surveys by identifying truly embedded southern YSOs and determining their larger scale envelope and outflow characteristics.
Key words: astrochemistry / stars: formation / submillimeter / ISM: jets and outflows / ISM: molecules
© ESO, 2009
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.