Please note that eDoc will be permanently shut down in the first quarter of 2021!      Home News About Us Contact Contributors Disclaimer Privacy Policy Help FAQ

Quick Search
My eDoc
Session History
Support Wiki
Direct access to
document ID:

          Institute: MPI für Astronomie     Collection: Publikationen_mpia     Display Documents

ID: 559094.0, MPI für Astronomie / Publikationen_mpia
LABOCA observations of giant molecular clouds in the southwest region of the Small Magellanic Cloud
Authors:Bot, C.; Rubio, M.; Boulanger, F.; Albrecht, M.; Leroy, A.; Bolatto, A. D.; Bertoldi, F.; Gordon, K.; Engelbracht, C.; Block, M.; Misselt, K.
Date of Publication (YYYY-MM-DD):2010
Title of Journal:Astronomy and Astrophysics
Journal Abbrev.:Astronomy and Astrophysics
Start Page:id.A52
Review Status:not specified
Audience:Experts Only
Abstract / Description:Context. The amount of molecular gas is a key to understanding the future star formation in a galaxy. Because H2 is difficult to observe directly in dense and cold clouds, tracers such as the CO molecule are used. However, at low metallicities especially, CO only traces the shielded interiors of the clouds. In this context, millimeter dust emission can be used as a tracer to unveil the total dense gas masses. However, the comparison of masses deduced from the continuum SIMBA 1.2 mm emission and virial masses (understood to trace the entire potential of the clouds) in a sample of giant molecular clouds in the Small Magellanic Cloud (SMC) by previous studies found a discrepancy between these two quantities that requires explanation. <BR /> Aims: We attempt to more accurately assess possible uncertainties in the dust emission observed in the sample of giant molecular clouds from the SMC. We focus on the mass comparison in the densest parts of the giant molecular clouds where CO is detected to confirm the mass discrepancy previously observed. <BR /> Methods: New observations of the southwest region of the SMC were obtained with the LABOCA camera on the APEX telescope. All the giant molecular clouds previously observed in CO are detected and their emission at 870 μm is compared to ancillary data. The different contributions to the sub-millimeter emission are estimated, as well as dust properties (temperatures, emissivities), to determine molecular cloud masses precisely. <BR /> Results: The (sub-)millimeter emission observed in the giant molecular clouds in the southwest region of the SMC is dominated by dust emission, and masses are deduced for the part of each cloud where CO is detected and compared to the virial masses. The mass discrepancy between both methods is confirmed at 870 μm using the LABOCA observations: the virial masses are on average 4 times lower than the masses of dense gas inferred from dust emission, in contrast to what is observed for equivalent clouds in our Galaxy. <BR /> Conclusions: At present, the origin of this mass discrepancy in the SMC remains unknown. The direct interpretation of this effect is that the CO linewidth used to compute virial masses do not measure the full velocity distribution of the gas. Geometrical effects and uncertainties in the dust properties are also discussed.
Free Keywords:ISM: clouds; submillimeter; ISM: molecules; Magellanic Clouds
External Publication Status:published
Document Type:Article
Communicated by:N. N.
Affiliations:MPI für Astronomie
Identifiers:URL: [ID No:1]
The scope and number of records on eDoc is subject to the collection policies defined by each institute - see "info" button in the collection browse view.