Speaker
Description
In the past decade many population studies have been performed with the Atacama Large Millimeter/submillimeter Array (ALMA) to understand the bulk properties of planet-forming disks around young stars. These population studies mostly consist of late spectral type (i.e., G, K & M) stars, with relatively few intermediate mass Herbig stars (spectral types B, A, F). With GAIA updated distances, now is a good time to use ALMA archival data to do a Herbig disk population study, an important step towards understanding the planet formation puzzle, as Herbig disks are the progenitors of directly imaged exoplanetary systems such as HR 8799 and Beta Pictoris, and massive exoplanets are optimally forming around these intermediate mass stars. For a significant fraction of all known Herbig disks up to Orion, ALMA Band 6 or 7 archival data is available to determine the dust and gas masses and sizes. In this talk I will show how Herbig disk masses compare to disks around lower mass T Tauri stars. We find that Herbig disks are massive and both the dust mass and radial extent are larger when compared to the disks around lower mass stars. Additionally, using the thermochemical code DALI, we find that the gas masses based on CO isotopologue observations are consistent with an ISM gas-to-dust ratio of 100, which is in contrast to T Tauri disks for which CO is missing above the amount that is expected to freeze out in these colder disks, lowering the inferred gas-to-dust ratio. Herbig disks are an as of yet overlooked part of planet formation, obtaining complete samples are vital to our understanding of high mass planet formation.
