Marco Lombardi (University of Milan) Talk – University of Copenhagen

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Marco Lombardi (University of Milan) Talk

Speaker: Marco Lombardi (University of Milan)

Title: On the structure of molecular clouds

Time and Place: Wednesday June 3 at 12:00, DARK lounge

Abstract:  Stars and planets form within molecular clouds, but progress on the study of these objects has been slow. Molecular clouds are among the coldest known objects in the Universe and their main mass component, molecular hydrogen, cannot be detected directly. Most of all we know today about their physical properties has been derived through radio spectroscopy of H2 surrogate molecules, but results obtained using these techniques, especially the estimate of column densities, are not always straightforward to interpret and are plagued by several poorly constrained effects.

Ultimately, our inability to accurately map the distribution of gas inside clouds has been a major impediment to understanding the star formation process.  In the last few years, this situation has changed significantly.  We can now use both dust extinction and emission to map robustly and at high resolution molecular clouds, and the high-resolution images provided by the Herschel satellite have shown the complex structure of molecular clouds and the pervasive presence of filaments. Additionally, we can use several multiwavelength observations ranging from the optical to the submillimeter to discover protostars and investigate the star-formation efficiency of different clouds.

Nearby molecular clouds represent our best chance to study the structure of molecular clouds and the early stages of star formation. In this talk I will present a coordinated study of the Gould Belt based on data from the 2MASS archive and the Spitzer, Herschel, and Planck missions. I will discuss the structure of these objects as revealed from large-scale extinction and emission maps, and present the scaling laws that have been found using these observations: the third Larson's law regarding the constancy of the surface density of clouds, the (local) Schmidt law for star formation, and the column-density probability distribution.