RSAA Colloquia / Seminars / Feast-of-Facts: Friday, 09 June 2017, 14:00-14:20; Duffield Lecture Theatre

Eloise Birchall

"End of Masters Talk: Tiny Grains Shining Bright in the Gaps of Herbig Ae Transitional Discs"

Planets form in protoplanetary discs. To image planets as they are forming, we observe discs known to have structure in their dust density distributions, as these features may be signs of planet formation. Here I talk about the work of my thesis which presents a study of two Herbig Ae transitional discs, Oph IRS 48 and HD 169142; which both have rings in the dust density of their discs. We use Keck observations in the L’ (3.8 mu m) to probe the regions inwards of ∼ 20 AU from the star in these discs. We introduce a new method for investigating these transitional discs, which involves a forward modelling approach: making a model of the disc, convolving it with a point-spread function of a calibrator star, and then comparing the convolved model with the observational data. In deconvolved images of our data we find that there is a ring of emission at ~ 13 AU in Oph IRS 48, and one at ~ 12 AU in HD 169142. With our method we do not confirm the presence of a planet in either disc, and find that the previously proposed planet in HD 169142 to be consistent with an asymmetry in the disc. We find that there are rings of small dust grains in regions where it was thought there was no dust or gas. The finding that the ’empty’ regions of these transitional discs are not devoid of material, but still contain dust and gas, implies that there is a hole in our understanding of the mechanisms associated with clearing of gaps in transitional discs.