Kavli Affiliate: Lile Wang
| First 5 Authors: Xiao Hu, Jaehan Bae, Zhaohuan Zhu, Lile Wang,
| Summary:
Magnetized winds and photoevaporative winds are critical in shaping
protoplanetary disk evolution. Using 2D axisymmetric (magneto-)hydrodynamic
simulations with Athena++ implementing fully coupled thermochemistry, we
investigate the signatures of the two winds in CO and [C~I] ALMA observations,
and examine the potential to distinguish the origins. Our simulations reveal
fundamental differences between the two winds: magnetized winds are colder and
denser, exhibiting super-Keplerian rotation with small poloidal velocities of
$lesssim 1~{rm km~s}^{-1}$ in the atmosphere ($z/Rgtrsim0.45$), while
photoevaporative winds are hotter and less dense, exhibiting sub-Keplerian
rotation with higher poloidal velocity of several ${rm km~s}^{-1}$. In
addition to previously identified factors like thermal pressure gradient and
disk’s self-gravity, we demonstrate that magnetic tension/pressure and
advection significantly influence rotational velocities of the gas in the wind,
which lead to emission patterns that are distinct from Keplerian rotation in
synthetic ALMA observations. Magnetized winds are visible in CO channel maps
when wind loss rates are $gtrsim10^{-8}~M_odot~{rm yr}^{-1}$. When wind loss
rates are lower, magnetized winds produce subtle perturbations in channel maps,
which resemble the so-called “velocity kinks” produced by protoplanets. While
photoevaporative winds dissociate CO through strong XUV radiation and thus are
weaker in CO, they can create observable ring-like substructures. [C~I]
emission is optically thin and could be most effective at detecting both winds
in disks with high gas mass and/or high [C~I] abundance. Due to the spatially
extended nature of the winds, using a large beam ($simeq0.4$" for disks in
nearby star-forming regions) will be helpful regardless of the tracer used.
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