E.F.G. van Heusden
- Do the Herschel cold clouds in the Galactic halo embody its dark matter?
- Physica Scripta
- Volume | Issue number
- 2012 | T151
- Pages (from-to)
- Document type
- Faculty of Science (FNWI)
- Institute for Theoretical Physics Amsterdam (ITFA)
Recent Herschel/SPIRE (Spectral and Photometric Imaging Receiver) maps of the Small and Large Magellanic Clouds (SMC, LMC) exhibit, in each, thousands of clouds. Observed at 250 μm, they must be cold, T ~ 15 K, hence the name 'Herschel cold clouds' (HCCs). From the observed rotational velocity profile of the Galaxy and the assumption of spherical symmetry, its mass density is modeled in a form close to that of an isothermal sphere. If the HCCs constitute a certain fraction of it, their angular size distribution has a specified shape. A fit to the data deduced from the SMC/LMC maps supports this and yields 1.7 pc for their average radius. There are so many HCCs that they will make up all the missing Halo mass density if there is spherical symmetry and their average mass is of the order of 10 000M⊙. This compares with the Jeans mass of about 40 000M⊙ and puts forward that the HCCs are, in fact, Jeans clusters, constituting all the Galactic dark matter and many of its missing baryons, a conclusion deduced before from a different field of the sky (Nieuwenhuizen et al 2011 J. Cosmol. 15 6017-29). A preliminary analysis of the intensities yields that the Jeans clusters themselves may consist of some billion MACHOs of a few dozen Earth masses. With a size of dozens of solar radii, they would mostly not lens, but cause occultation of stars in the LMC, SMC and toward the Galactic center, and may thus have been overlooked in microlensing.
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