The mass and size of Herbig disks as seen by ALMA

Abstract

Many population studies have been performed with the Atacama Large Millimeter/submillimeter Array (ALMA) to understand the bulk properties of protoplanetary disks around young stars. The studied populations mostly consisted of G, K & M stars, with relatively few more massive Herbig stars. With GAIA updated distances, now is a good time to use ALMA archival data for a Herbig disk population study and take an important step forward in our understanding of planet formation. This work determines the masses and sizes of all Herbig dust disks observed with ALMA to date out to 450 pc. These masses and sizes are put into context of the Lupus and Upper Sco T Tauri disk populations. ALMA Band 6 and Band 7 archival data of 36 Herbig stars are used, making this work 64% complete excluding Orion. Using stellar parameters and distances the dust masses and sizes of the disks are determined and survival analysis is used to make cumulative distributions of the dust masses and radii. Herbig disks have a higher dust mass than the T Tauri disk populations of Lupus and Upper Sco by factors of $\sim3$ and $\sim7$ respectively. In addition, Herbig disks are often larger than the typical T Tauri disk. Although the masses and sizes of Herbig disks extend over a similar range as those of T Tauri disks, the distributions of masses and sizes of Herbig disks are significantly skewed toward higher values. Lastly, group I disks are more massive than group II disks. Based on these findings we speculate that these differences between Herbig and T Tauri disks find their origin in an initial disk mass that scales with the stellar mass, and that subsequent disk evolution enlarges the observable differences, especially if (sub)mm continuum optical depth plays a role. Moreover, the larger disk masses and sizes of Herbig stars could be linked to the increasing prevalence of giant planets with host star mass.