Gaps and Rings in an ALMA Survey of Disks in the Taurus Star-forming Region (1810.06044v1)

Abstract: Rings are the most frequently revealed substructure in ALMA dust observations of protoplanetary disks, but their origin is still hotly debated. In this paper, we identify dust substructures in 12 disks and measure their properties to investigate how they form. This subsample of disks is selected from a high-resolution ($\sim0.12''$) ALMA 1.33 mm survey of 32 disks in the Taurus star-forming region, which was designed to cover a wide range of sub-mm brightness and to be unbiased to previously known substructures. While axisymmetric rings and gaps are common within our sample, spiral patterns and high contrast azimuthal asymmetries are not detected. Fits of disk models to the visibilities lead to estimates of the location and shape of gaps and rings, the flux in each disk component, and the size of the disk. The dust substructures occur across a wide range of stellar mass and disk brightness. Disks with multiple rings tend to be more massive and more extended. The correlation between gap locations and widths, the intensity contrast between rings and gaps, and the separations of rings and gaps could all be explained if most gaps are opened by low-mass planets (super-Earths and Neptunes) in the condition of low disk turbulence ($\alpha=10^{-4}$). The gap locations are not well correlated with the expected locations of CO and N$_2$ ice lines, so condensation fronts are unlikely to be a universal mechanism to create gaps and rings, though they may play a role in some cases.

• The paper demonstrates that ALMA observations reveal prevalent gap and ring substructures in Taurus disks, likely shaped by low-mass planet interactions in low-turbulence environments.
• The study employs high-resolution 1.33 mm imaging to characterize 19 gap-ring pairs among 32 disks, detailing variations in size, location, and contrast.
• The research challenges the role of ice lines in ring formation, implicating alternative mechanisms such as magnetic effects and zonal flows in disk evolution.

Gaps and Rings in an ALMA Survey of Disks in the Taurus Star-forming Region

The paper "Gaps and Rings in an ALMA Survey of Disks in the Taurus Star-forming Region" provides a comprehensive analysis of the structures observed in protoplanetary disks within the Taurus star-forming region. Leveraging high-resolution observations from the Atacama Large Millimeter/submillimeter Array (ALMA) at 1.33 mm, this research aims to decipher the origins of the frequently observed ring-like structures in these disks.

Key Findings

• Prevalence and Characteristics of Substructures: The survey reveals that rings and gaps are commonplace in these protoplanetary disks. Among 32 examined disks, 12 display prominent substructures. The 19 gap-ring pairs identified exhibit diverse characteristics in terms of size, location, and intensity contrast.
• Substructure Formation: The paper postulates that many of these rings and gaps result from low-mass planets (super-Earths or Neptunes) interacting with low turbulence disks (turbulence parameter, $\alpha=10^{-4}$). The correlation between stellar mass, gap location, and ring properties was explored, revealing that the features can be interpreted with mechanisms related to planetary formation, particularly under low turbulence conditions.
• Ice Lines and Other Mechanisms: The correlation between substructure location and volatile condensation fronts, such as ice lines of CO and N$_2$, was investigated. Despite expectations, gaps do not align consistently with these CO and N$_2$ ice lines, suggesting that ice line-induced substructures are not universally applicable.

Implications

The results of this survey have significant implications for the understanding of disk evolution and planet formation. The identified correlation between gap structures and planetary formation presents a compelling case for the role of young, hidden planets in shaping disk morphology.

1. Practical Implications for Planet Formation:
   • The identification of super-Earths and Neptunes as potential gap-opening bodies encourages further searches for these planets in young disks.
   • Given the prevalence of rings, these regions might significantly impact dust retention and growth, potentially enhancing the midplane conditions necessary for planetesimal formation.
2. Implications for Disk Evolution and Theory:
   • This paper challenges the universality of ice lines as a mechanism for ring formation, pushing for deeper analyses of alternative causes, such as magnetic effects and zonal flows.
   • The variation in ring contrast and size underlines the complexity in disk dynamics, hinting at diverse environmental effects influencing disk gas and dust interactions.

Future Directions

For future research, acquiring multi-wavelength observations that cover different grain sizes could differentiate between dust trapping mechanisms. Additionally, more detailed models including hydrodynamic and temperature profiles could better resolve the debate between planetary vs. non-planetary causes for these substructures. Ultimately, the iterative feedback between observational surveys and theoretical models will enhance our capability to interpret these complex disk environments in the context of planetary system formation.