Thinkshop 2020

Snowlines, in particular the water snowline, are important for the formation of planets in protoplanetary disks. However, locating the water snowline directly is challenging. Firstly, due to the proximity of the water snowline to the host star. But ALMA can now resolve this region for the first time. Secondly, due to the absorption of water in the Earth's atmosphere. A chemical tracer, HCO+, provides a solution to the latter problem. HCO+ is destroyed by gas-phase water, therefore no HCO+ is expected to be present when water desorps from the grains. It has already been shown by van 't Hoff et al. (2018) that the optically thin isotopologue, H13CO+, acts as a tracer of the water snowline in the envelope around a Class 0 object. We investigate whether this also works in Class 2 objects where planets form. The HCO+ abundance is modeled using our small chemical network and using the density and temperature structure from a DALI model. The expected emission is modeled for different transitions of H13CO+. I will discuss how well H13CO+ traces the water snowline in disks. We can already confirm that the HCO+ abundance drops when water desorps from the grains and I will discuss what observations are needed to locate the water snowline with ALMA.