Extended debris discs around nearby, Sun-like stars as a probe of disc-planet interactions Astronomical Society of Australia ASM 5th July 2016 Dr. Jonty Marshall

The Solar system’s debris belts Asteroid belt ~ 2–3 au Edgeworth-Kuiper belt ~ 30–50 au [NASA JPL Minor Planet Centre]

Components of planetary systems [Wyatt 2008; Marshall et al. 2014 Wittenmyer & Marshall 2015] Components of planetary systems Debris discs Exo-Neptunes Exo-Jupiters

Linking stars, planets and debris Planet-bearing stars: 28/99 = 28±5% with disks No known planets: 43/203 = 21±3% with disks Debris disk luminosity is correlated with the presence of known planets at >99% significance. [Bryden et al. 2013]

Spectral energy distribution

Radial extent of the disc from the SED [Morales et al. 2011]

Collisional state of planetesimals from the SED HD76582 5.0 [Macgregor et al. 2016, Marshall et al. 2016]

Architectures of planetary systems id = 0° i★ = 90° id = 90° [Greaves et al. 2014]

Dynamical influence of an unseen planet perturbs the motion of dust in a disc A planet on an eccentric orbit will exert a gravitational influence on remnant debris, sculpting the planetesimal belt and trapping the dust grains, creating visible asymmetries in the disc’s brightness distribution The presence of a planet in regions of mass–semi-major axis parameter space that would otherwise be difficult to detect can thus be revealed (t) Herschel PACS images of ζ2 Ret at 100 μm (l) and 160 μm (r). (b) Synthetic disc image at 100 μm (l) convolved with PACS PSF (r) [Wyatt 2003; Mustill & Wyatt 2009; Faramaz et al. 2014; Pearce et al. 2014]

An asymmetric debris disc around ηCru Poster #42 by Shane Hengst! An asymmetric debris disc around ηCru [Hengst et al. in prep.]

Disc extent as a function of dust temperature, stellar luminosity [Booth et al. 2013; Pawellek et al. 2014, Pawellek & Krivov 2015]

Disc extent as a function of dust temperature, stellar luminosity [Pawellek & Krivov 2015]

Constraining the composition of unresolved discs [Montesinos et al. 2016, Marshall et al. in prep.]

Inferring the presence of planets from the disc extent [Moor et al. 2015]

Extent vs. age for Herschel-resolved debris discs

Questions? Debris discs around Sun-like stars are a visible remnant of planet formation processes. They are most commonly identified through the presence of excess emission at infrared wavelengths. By comparison of their emission properties with those of a well characterized sample of spatially resolved discs, the extent, composition, and collisional state of unresolved discs can be deduced. Resolved imaging reveals asymmetries in the disc emission. The collisional state of parent planetesimals can be deduced from the size distribution of dust grains. At young ages, large discs are inferred to be the result of planetary migration stirring parent planetesimals.