4-8 October 2015
Hans Harnack Haus
Europe/Berlin timezone
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Contribution Contributed Talk

Hans Harnack Haus -
FROM CLOUDS TO DENSE CORES 2

Star formation through the chemical lens: distortions induced and how to avoid them

Speakers

  • Prof. Konstantinos TASSIS

Primary authors

Co-authors

Content

Observations of star-forming sites rely heavily on the use of molecular tracers. However, the abundance of these tracers is not constant: it is a result of a complex network of chemical reactions, and it depends on the age, density, and dynamical history of the star-forming site. This chemical lens can introduce distortions in our observational understanding of star formation.

In this talk, I will use a suite of chemodynamical models to discuss two such major distorting effects. The first involves measurements of the ratio between mass and magnetic flux in molecular clouds, which determines the relative importance of magnetic and gravitational forces in the evolution of clouds and their cores. When comparing regions with different densities, the effect of depletion of the tracer used (for example OH) can be so severe as to even reverse the direction of the underlying trends: for example, the mass-to-flux ratio may appear to decrease as we move to higher density regions, contrary to theoretical expectations.

The second effect involves the use of neutral/ion pairs to study the processs of ambipolar diffusion (neutral/ion drift ) in molecular clouds. The ion and neutral species used in such studies need to be co-spatial at every scale and density if they are to trace the same region, something which, as I will show, is not necessarily the case with the species typically used. I will propose instead new ion-neutral pairs that are good candidates for such observations, because they have similar evolution and are approximately co-spatial

Finally, I will discuss some newly proposed observables with maximal potential for discrimination between different models of cloud evolution and star formation. These results are especially timely as current and future facilities, such as ALMA and SKA, will be able to measure these quantities and contribute to the resolution of long-standing questions in star formation.