First results of the SONS survey: submillimetre detections of debris discs

Abstract

New detections of debris discs at submillimetre wavelengths present highly valuable complementary information to prior observations of these sources at shorter wavelengths. Characterization of discs through spectral energy distribution modelling including the submillimetre fluxes is essential for our basic understanding of disc mass and temperature, and presents a starting point for further studies using millimetre interferometric observations. In the framework of the ongoing SCUBA-2 Observations of Nearby Stars, the instrument SCUBA-2 on the James Clerk Maxwell Telescope was used to provide measurements of 450 and 850 µm fluxes towards a large sample of nearby main-sequence stars with debris discs detected previously at shorter wavelengths. We present the first results from the ongoing survey, concerning 850 µm detections and 450 µm upper limits towards 10 stars, the majority of which are detected at submillimetre wavelengths for the first time. One, or possibly two, of these new detections is likely a background source. We fit the spectral energy distributions of the star+disc systems with a blackbody emission approach and derive characteristic disc temperatures. We use these temperatures to convert the observed fluxes to disc masses. We obtain a range of disc masses from 0.001 to 0.1 M ⊕ , values similar to the prior dust mass measurements towards debris discs. There is no evidence for evolution in dust mass with age on the main sequence, and indeed the upper envelope remains relatively flat at ≈0.5 M ⊕ at all ages. The inferred disc masses are lower than those from disc detections around pre-main-sequence stars, which may indicate a depletion of solid mass. This may also be due to a change in disc opacity, though limited sensitivity means that it is not yet known what fraction of pre-main-sequence stars have discs with dust masses similar to debris disc levels. New, high-sensitivity detections are a path towards investigating the trends in dust mass evolution.

Dynamical evolution of an eccentric planet and a less massive debris disc

“…However, there remains some uncertainty as to whether the offset emission in such systems arises from circumstellar material or from background galaxies (e.g. Panić et al 2013). Galaxies have a similar temperature to that expected for cold dust at ∼ 100 au from a star, and are ubiquitous enough to be commonly found in close proximity to nearby stars.…”

Five steps in the evolution from protoplanetary to debris disk

“…We compiled a sample of Atype stars from these works, and for which ages have been determined. Older stars were taken from Su et al (2006) and the DEBRIS and SONS surveys (Matthews et al 2010;Panić et al 2013). We also included sources with B9 spectral type designation, given that these are often characterised as A0 or B9/A0 stars.…”

Insights into Planet Formation from Debris Disks

“…However, while the disappearance of the protoplanetary gas disk does make the formation of gas giant planets like Jupiter rather problematic, this does not necessarily prevent the continued growth of solid rocky or icy planets. From an observational perspective we can only say that the mass present in less than cm-sized dust cannot be significant after the protoplanetary disk has dispersed (Panić et al 2013). The majority of the solid mass in the system could instead be locked up in planets (or planetary embryos) that continue to grow.…”