Gas-phase CO in protoplanetary disks: A challenge for turbulent mixing
نویسنده
چکیده
This is the first paper in a series where we study the influence of turbulent diffusion and advective transport on the chemical evolution of protoplanetary disks, using a 2D flared disk model and a 2D mixing gas-grain chemical code with surface reactions. A first interesting result concerns the abundance of gasphase CO in the outer regions of protoplanetary disks. In this Letter we argue that the gas-phase CO concentration in the disk regions, where the temperature is lower than ∼ 25K, can be significantly enhanced due to the combined effect of vertical and radial mixing. This finding has a potential implication for the current observational data on the DM Tau disk chemistry. Subject headings: accretion, accretion disks — astrochemistry — circumstellar matter — molecular processes — planetary systems: protoplanetary disks — turbulence
منابع مشابه
On the Ionisation Fraction in Protoplanetary Disks II: The Effect of Turbulent Mixing on Gas–phase Chemistry
We calculate the ionisation fraction in protostellar disk models using two different gas–phase chemical networks, and examine the effect of turbulent mixing by modelling the diffusion of chemical species vertically through the disk. The aim is to determine in which regions of the disk gas can couple to a magnetic field and sustain MHD turbulence. The disk models are conventional α–disks, and th...
متن کاملA deep search for H2D+ in protoplanetary disks⋆
Context. The structure in density and temperature of protoplanetary disks surrounding low-mass stars is not well known yet. The protoplanetary disks’ midplane are expected to be very cold and thus depleted in molecules in gas phase, especially CO. Recent observations of molecules at very low apparent temperatures (∼6 K) challenge this current picture of the protoplanetary disk structures. Aims....
متن کاملTurbulent-diffusion Mediated CO Depletion in Weakly Turbulent Protoplanetary Disks
Volatiles, especially CO, are important gas tracers of protoplanetary disks (PPDs). Freeze-out and sublimation processes determine their division between gas and solid phases, which affects both which disk regions can be traced by which volatiles, and the formation and composition of planets. Recently, multiple lines of evidence have suggested that CO is substantially depleted from the gas in t...
متن کاملCold CO Gas in Protoplanetary Disks
In a disk around DM Tau, previous observation of CO (J = 2− 1 and 1− 0 transitions) derived the CO gas temperature of ∼ 13−20K, which is lower than the sublimation temperature of CO (20 K). We argue that the existence of such cold CO can be explained by a vertical mixing of disk material. As the gas is transported from a warm layer to a cold layer, CO is depleted onto dust grains with a timesca...
متن کاملParticle Pile-ups and Planetesimal Formation
Solid particles in protoplanetary disks that are sufficiently super-solar in metallicity overcome turbulence generated by vertical shear to gravitationally condense into planetesimals. Super-solar metallicities result if solid particles pile up as they migrate starward due to aerodynamic drag. Previous analyses of aerodynamic drift rates that account for mean flow differences between gas and pa...
متن کامل