Testing velocity kinks as a planet-detection method: Do velocity kinks in surface gas emission trace planetary spiral wakes in the midplane continuum?

TL;DR

This study investigates whether velocity kinks caused by embedded planets in gas emission maps also produce detectable spiral structures in dust continuum observations, testing the reliability of velocity kinks as planet indicators.

Contribution

The paper provides an observational test for the correlation between velocity kinks and dust spirals, revealing inconsistencies and challenges in using velocity kinks alone to locate planets in disks.

Findings

No clear dust spiral counterparts for 6 of 10 velocity kink candidates.

Detected dust spirals do not align with predicted planet locations.

Vertical effects may influence the detectability and interpretation of spirals.

Abstract

Spiral density waves generated by an embedded planet are understood to cause ``kinks'' in observed velocity channel maps of CO surface emission, by perturbing the gas motion within the spiral arms. If velocity kinks are a reliable probe of embedded planets, we should expect to see the planet-driven spiral arms in other observational tracers. We test this prediction by searching the dust continuum for the midplane counterparts of the spirals responsible for all of the velocity kink planet candidates reported to date, whose orbits lie inside the dust continuum disk. We find no clear detection of any spiral structure in current continuum observations for 6 of the 10 velocity kink planet candidates in our sample (DoAr 25, GW Lup, Sz 129, HD 163296 #2, P94, and HD 143006), despite the high planet masses inferred from the kink amplitude. The remaining 4 cases include 3 clear detections of two-armed dust spirals (Elias 27, IM Lup and WaOph 6) wherein neither spiral arm aligns with a wake originating from reported planet location, suggesting that under the planetary-origin hypothesis, an accurate method for inferring the location of the planet in the midplane may need to encompass vertical effects. The 10th case, HD 97048, is inconclusive with current knowledge of the disk geometry.