Tracing large-scale structures in circumstellar disks with ALMA
Context. Planets are supposed to form in circumstellar disks. The additional gravitational potential of a planet perturbs the disk and leads to characteristic structures, i.e. spiral waves and gaps, in the disk's density profile.
Aims: We perform a large-scale parameter study of the observability of these planet-induced structures in circumstellar disks in the (sub)mm wavelength range for the Atacama Large (Sub)Millimeter Array (ALMA).
Methods: On the basis of hydrodynamical and magneto-hydrodynamical simulations of star-disk-planet models, we calculated the disk temperature structure and (sub)mm images of these systems. These were used to derive simulated ALMA images. Because appropriate objects are frequent in the Taurus-Auriga region, we focused on a distance of 140 pc and a declination of ≈ 20°. The explored range of star-disk-planet configurations consists of six hydrodynamical simulations (including magnetic fields and different planet masses), nine disk sizes with outer radii ranging from 9 AU to 225 AU, 15 total disk masses in the range between 2.67 × 10-7 M⊙ and 4.10 × 10-2 M⊙, six different central stars, and two different grain size distributions, resulting in 10 000 disk models.
Results: On almost all scales and in particular down to a scale of a few AU, ALMA is able to trace disk structures induced by planet-disk interaction or by the influence of magnetic fields on the wavelength range between 0.4 and 2.0 mm. In most cases, the optimum angular resolution is limited by the sensitivity of ALMA. However, within the range of typical masses of protoplanetary disks (0.1-0.001 M⊙) the disk mass has a minor impact on the observability. It is possible to resolve disks down to 2.67 × 10-6 M⊙ and trace gaps induced by a planet with Mp/M⋆ = 0.001 in disks with 2.67 × 10-4 M⊙ with a signal-to-noise ratio greater than three. The central star has a major impact on the observability of gaps, as well as the considered maximum grainsize of the dust in the disk. In general, it is more likely to trace planet-induced gaps in our magnetohydrodynamical disk models, because gaps are wider in the presence of magnetic fields. We also find that zonal flows resulting from magneto-rotational instability (MRI) create gap-like structures in the disk's re-emission radiation, which are observable with ALMA.
Conclusions: Through the unprecedented resolution and sensitivity of ALMA in the (sub)mm wavelength range, the expected detailed observations of planet-disk interaction and global disk structures will deepen our understanding of the planet formation and disk evolution process.
Astronomy and Astrophysics
- Pub Date:
- January 2013
- planets and satellites: formation;
- submillimeter: planetary systems;
- planet-disk interactions;
- magnetohydrodynamics (MHD);
- protoplanetary disks;
- Astrophysics - Solar and Stellar Astrophysics;
- Astrophysics - Earth and Planetary Astrophysics
- 17 pages, 21 figures