Astronomy and Astrophysics – Astrophysics – Cosmology and Extragalactic Astrophysics
Scientific paper
2010-08-17
Astronomy and Astrophysics
Astrophysics
Cosmology and Extragalactic Astrophysics
7 pages, 6 figures; accepted in A&A
Scientific paper
Dust emission at submm to cm wavelengths is often simply the Rayleigh-Jeans tail of dust particles at thermal equilibrium and is used as a cold mass tracer in various environments including nearby galaxies. However, well-sampled spectral energy distributions of the nearby, star-forming Magellanic Clouds have a pronounced (sub-)millimeter excess (Israel et al., 2010). This study attempts to confirm the existence of such a millimeter excess above expected dust, free-free and synchrotron emission and to explore different possibilities for its origin. We model NIR to radio spectral energy distributions of the Magellanic Clouds with dust, free-free and synchrotron emission. A millimeter excess emission is confirmed above these components and its spectral shape and intensity are analysed in light of different scenarios: very cold dust, Cosmic Microwave Background (CMB) fluctuations, a change of the dust spectral index and spinning dust emission. We show that very cold dust or CMB fluctuations are very unlikely explanations for the observed excess in these two galaxies. The excess in the LMC can be satisfactorily explained either by a change of the spectral index due to intrinsic properties of amorphous grains, or by spinning dust emission. In the SMC however, due to the importance of the excess, the dust grain model including TLS/DCD effects cannot reproduce the observed emission in a simple way. A possible solution was achieved with spinning dust emission, but many assumptions on the physical state of the interstellar medium had to be made. Further studies, using higher resolution data from Planck and Herschel, are needed to probe the origin of this observed submm-cm excess more definitely. Our study shows that the different possible origins will be best distinguished where the excess is the highest, as is the case in the SMC.
Bernard Jean-Philippe
Bot Caroline
Israel Frank P.
Lagache Guilaine
Paradis Deborah
No associations
LandOfFree
Submillimeter to centimeter excess emission from the Magellanic Clouds. II. On the nature of the excess 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 Submillimeter to centimeter excess emission from the Magellanic Clouds. II. On the nature of the excess, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Submillimeter to centimeter excess emission from the Magellanic Clouds. II. On the nature of the excess will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-397847