Oral Presentation
DCN in protoplanetary disks
Presenter: Gianni Cataldi (National Astronomical Observatory of Japan / The University of Tokyo)
Debris disks were traditionally seen as essentially gas-free. However, ALMA continues to detect more and more debris disks in CO emission. In some systems the CO mass is very small, while in others it is comparable to protoplanetary disks. The gas might be accreted by forming terrestrial planets and strongly modify their atmospheres.
It is still debated where this gas is coming from: is it leftover from the protoplanetary phase, or produced from evaporating cometary bodies? In the latter case, we have the opportunity to study the composition of exo-comets and compare to Solar System comets.
One way to get new insight into the origin and evolution of debris disks gas is by observations of neutral carbon. C gas is produced from CO photodissociation. The C/CO ratio can inform us about the physical and chemical processes operating in gaseous debris disks. For example, C can shield CO from photodissociation and therefore considerably reduce the CO destruction rate, which might explain the large CO mass observed in some systems.
Here I will present our results from ALMA observations of neutral C in the CO-rich HD 32297 debris disk. We found a surprisingly small C gas mass, less than what is expected from CO photodissociation. This implies that C needs to be removed somehow from the system, potentially by sticking to dust grains. I will also present preliminary results from an ALMA mini-survey to search for emission of neutral carbon towards a small sample of debris disks.
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