Millimeter dust continuum emission revealing the true mass of giant molecular clouds in the Small Magellanic Cloud

Details Millimeter dust continuum emission revealing the true mass of giant molecular clouds in the Small Magellanic Cloud Millimeter dust continuum emission revealing the true mass of giant molecular clouds in the Small Magellanic Cloud

Aug 2007

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2007a%26a...471..103b&link_type=abstract

Astronomy and Astrophysics, Volume 471, Issue 1, August III 2007, pp.103-112

Astronomy and Astrophysics

Astrophysics

28

Ism: Clouds, Submillimeter, Ism: Molecules, Magellanic Clouds, Ism: Magnetic Fields

Scientific paper

Context: CO observations have been the best way so far to trace molecular gas in external galaxies, but in low metallicity environments the gas mass deduced could be largely underestimated due to enhanced photodissociation of the CO molecule. Large envelopes of H2 could therefore be missed by CO observations. Aims: At present, the kinematic information of CO data cubes are used to estimate virial masses and trace the total mass of the molecular clouds. Millimeter dust emission can also be used as a dense gas tracer and could unveil H2 envelopes lacking CO. These different tracers must be compared in different environments. Methods: This study compares virial masses to masses deduced from millimeter emission, in two GMC samples: the local molecular clouds in our Galaxy (10^4-105 M&sun;), and their equivalents in the Small Magellanic Cloud (SMC), one of the nearest low metallicity dwarf galaxies. Results: In our Galaxy, mass estimates deduced from millimeter (FIRAS) emission are consistent with masses deduced from gamma ray analysis and therefore trace the total mass of the clouds. Virial masses are systematically larger (twice on average) than mass estimates from millimeter dust emission. This difference decreases toward high masses and has been reported in previous studies. This is not the case for SMC giant molecular clouds: molecular cloud masses deduced from SIMBA millimeter observations are systematically higher (twice on average for conservative values of the dust to gas ratio and dust emissivity) than the virial masses from SEST CO observations. The observed excess cannot be accounted for by any plausible change of dust properties. Taking a general form for the virial theorem, we show that a magnetic field strength of ~15 μG in SMC clouds could provide additional support for the clouds and explain the difference observed. Conclusions: We conclude that masses of SMC molecular clouds have so far been underestimated. Magnetic pressure may contribute significantly to their support.
The SIMBA data for the SMC is available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/471/103

Affiliated with

Also associated with

No associations

Rating

Millimeter dust continuum emission revealing the true mass of giant molecular clouds in the Small Magellanic Cloud does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.

If you have personal experience with Millimeter dust continuum emission revealing the true mass of giant molecular clouds in the Small Magellanic Cloud, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Millimeter dust continuum emission revealing the true mass of giant molecular clouds in the Small Magellanic Cloud will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-957523