Homogeneous Analysis of the Dust Morphology of Transition Disks Observed with ALMA: Investigating Dust Trapping and the Origin of the Cavities

Abstract

We analyze the dust morphology of 29 transition disks (TDs) observed with Atacama Large (sub-)Millimeter Array (ALMA) at (sub-)millimeter emission. We perform the analysis in the visibility plane to characterize the total flux, cavity size, and shape of the ring-like structure. First, we found that the M dust -M å relation is much flatter for TDs than the observed trends from samples of class II sources in different star-forming regions. This relation demonstrates that cavities open in high (dust) mass disks, independent of the stellar mass. The flatness of this relation contradicts the idea that TDs are a more evolved set of disks. Two potential reasons (not mutually exclusive) may explain this flat relation: the emission is optically thick or/and millimeter-sized particles are trapped in a pressure bump. Second, we discuss our results of the cavity size and ring width in the context of different physical processes for cavity formation. Photoevaporation is an unlikely leading mechanism for the origin of the cavity of any of the targets in the sample. Embedded giant planets or dead zones remain as potential explanations. Although both models predict correlations between the cavity size and the ring shape for different stellar and disk properties, we demonstrate that with the current resolution of the observations, it is difficult to obtain these correlations. Future observations with higher angular resolution observations of TDs with ALMA will help discern between different potential origins of cavities in TDs.

Hints on the origins of particle traps in protoplanetary disks given by the Mdust – M⋆ relation

“…To compare the two samples, we calculate the Kolmogorov-Smirnov (KS) two-sided test, and we find a maximum deviation between the cumulative distributions of only 0.15 with a high probability (∼80%) that the two samples are similar. Overall, the M dust − M correlation of the whole sample is dominated by TDs, and it is shallower than seen from all disks in nearby star-forming as found in Pinilla et al (2018), to which some of these disks actually belong to.…”

“…We gathered a total of 73 disks (43 TDs and 30 disks with substructures, see Table in the appendix). The sample of TDs double the number of targets presented previously in Pinilla et al (2018). We placed the TDs and disks with substructures in the M dust − M relation and fit these points with the following relation: log 10 (M dust /M ⊕ ) = β log 10 (M /M ) + α.…”

“…However, in these models, the disks are short in solids compared with observations taken after 1 Myr of evolution. When considering disks with large inner cavities resolved at millimeterwavelengths (the so-called transition disks; TDs), Pinilla et al (2018) find that this relation is much flatter, suggesting that the flatness is due to an effective reduction of radial drift in pressure bumps.…”

Dust-depleted Inner Disks in a Large Sample of Transition Disks through Long-baseline ALMA Observations

“…In reality the cavity radius edge is usually more complex than a sharp edge (see e.g. Pinilla et al 2018) but as we only aim for an approximate profile of Σ d (r) compared to the inner disk, this approach is sufficient. Our derived values for R cav are generally within 20% of the literature values of R cav derived using more detailed fitting methods.…”

“…Scattered light observations show shadowing of the outer disk in sev-eral objects (e.g. DoAr 44, Casassus et al (2018), RXJ1604.3 -2130, Pinilla et al (2018)) which are well described by a misaligned or warped inner disk. Observations of the gas motion as traced by CO also display velocity patterns consistent with a misaligned inner gas disk (e.g.…”