14-18 October 2019
T-Hotel Cagliari
Europe/Rome timezone

Probing Snow Surfaces/Lines in Protoplanetary Disks

15 Oct 2019, 12:25
T-Hotel Cagliari

T-Hotel Cagliari

Via Dei Giudicati, 66 | 09131 Cagliari | Sardinia, Italy


Dr Chunhua Qi


Contributed talk

"Protoplanetary disk radial and vertical thermal temperature gradients result in 2D snow surfaces, or condensation fronts. These are analogous to 1D snowlines, which are located where snow surfaces intersect with the disk midplane. CO and N2 are two of the most abundant disk molecules, and their snow surface locations could provide disk temperature structure diagnostics, while their snowline locations regulate the C/N/O ratios of outer Solar System planets and planetesimals. N2H+ is expected to only be abundant between the CO and N2 snow surfaces because it is destroyed by CO and formed from N2, and could therefore be used to probe the snow surfaces of both molecules in disks. Here we present Atacama Large Millimeter/submillimeter Array (ALMA) observations of N2H+ 3-2 at 0.2"-0.4" resolution in a sample of protoplanetary disks. We find two distinctive emission morphologies: N2H+ is either present in a bright narrow ring surrounded by the extended tenuous emission or in a single broad ring. These emission patterns can be explained by two different kinds of vertical temperature structures. Bright narrow N2H+ rings are expected in disks with vertical isothermal disk midplanes, where vertical snow surfaces at the midplane CO and N2 snow line locations produce a N2H+ emission peak defined by the CO and N2 snowline locations. Broad N2H+ rings are expected in disks that lack vertical isothermal midplanes and therefore present little exce  ss N2H+ emission between the two snowline radii. For the first group, we use the inner and outer edges of the bright N2H+ ring to constrain a first set of CO and N2 snowline pairs in the disks. "

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