Juergen Steinecker (IPAG)
Jeudi 8 Mars - 11 h 00
Salle Manuel Forestini - IPAG
What causes the onset of star formation in dense molecular cloud cores ? Which of the physical agents control the complex interplay of gravitation, gas dynamics, magnetic fields, cooling, and chemistry ? We do not know yet - there is no general paradigm that puts together the information from the different wavelength regimes and the outcome of the simulations.
Last year, a new source of information was revealed by the detection of the coreshine. Unexpectedly, the densest part of cores shows up in emission in the 3.6 and 4.5 micron IRAC Spitzer bands. Originally detected in L183, further investigations showed that the effect is wide-spread and visible in about half of all cores investigated sofar. It was shown that the effect is the first direct evidence for the existence of grown dust grains in dense cores : only scattering by grains with sizes of about 1 micron can explain the observed fluxes and their spatial variation.
As a major application, the strong correlation of coreshine and extinction suggests that coreshine can trace the density of cores. Moreover, studying grain growth through the new coreshine window has implication for grain surface chemistry, the study of the history of local environments up to long-term changes in entire regions, and the impact on the seed population of planet growth in circumstellar disks. Comparing grain size data with opt./NIR extinction data and FIR/mm maps emission data, however, requires multi-wavelengths modeling, that is to deal with radiative transfer as the grand challenge of computational star formation.
In this talk, I will introduce the topic and describe the coreshine effect and it implications like a grain growth clock for the core age or the routinely applied tracing of gas density using NIRCAM/JWST. An coreshine application of special interest is to reveal the seed population for dust in circumstellar disks which later serves as building blocks to form earth-like planets. In the ANR-funded CHEX project SEED - Starting planEt formation by Early Dust growth, this effect will be investigated at IPAG. The goals of the project will be described along with the offer of expertise in 3D radiative transfer and automated parameter optimization as intended by the chaires d’excellence program.
Figure Caption : Coreshine seen in a variety of pre- and proto-stellar objects ranging from cores to disks. The emission is visible in the 3.6 micron Spitzer IRAC image in the densest parts (left) which are seen in absorption at 8 micron (right) against the bright background.
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