Abstract
ABSTRACT Only 20 per cent of old field stars have detectable debris discs, leaving open the question of what disc, if any, is present around the remaining 80 per cent. Young moving groups allow to probe this population, since discs are expected to have been brighter early on. This paper considers the population of F stars in the 23 Myr-old β Pictoris moving group (BPMG) where we find that 9/12 targets possess discs. We also analyse archival ALMA data to derive radii for four of the discs, presenting the first image of the 63 au radius disc of HD 164249. Comparing the BPMG results to disc samples from ∼45-Myr and ∼150-Myr-old moving groups, and to discs found around field stars, we find that the disc incidence rate in young moving groups is comparable to that of the BPMG and significantly higher than that of field stars. The BPMG discs tend to be smaller than those around field stars. However, this difference is not statistically significant due to the small number of targets. Yet, by analysing the fractional luminosity versus disc radius parameter space, we find that the fractional luminosities in the populations considered drop by two orders of magnitude within the first 100 Myr. This is much faster than expected by collisional evolution, implying a decay equivalent to 1/age2. We attribute this depletion to embedded planets, which would be around 170 Mearth to cause a depletion on the appropriate time-scale. However, we cannot rule out that different birth environments of nearby young clusters result in brighter debris discs than the progenitors of field stars that likely formed in a more dense environment.
Highlights
After its protoplanetary disc has dispersed, a star is left with - if anything - a system of planets and debris belts
The disc around HD 164249 was observed with Atacama Large Millimeter/submillimeter Array (ALMA) at 1.35 mm and is spatially resolved for the first time increasing the number of resolved debris discs reported in the literature to 153 according to the database for resolved discs2
We note that our data-set does contain the data used in Kral et al (2020), but a combination of those with data from the “Resolved ALMA and SMA Observations of Nearby Stars” (REASONS) programme (Sepulveda et al 2019) which have a higher spatial resolution, as well as older observations from 2012
Summary
After its protoplanetary disc has dispersed, a star is left with - if anything - a system of planets and debris belts The dust in those debris belts is inferred to originate in the break-up of planetesimals at least kilometres in size (e.g., Wyatt 2008; Krivov 2010; Hughes et al 2018), and is seen in far-infrared (FIR) surveys towards ∼20% of nearby several Gyr-old stars (e.g., Eiroa et al 2013; Sibthorpe et al 2018), where a slightly higher detection rate is noted for earlier type stars (e.g., Su et al 2006; Sibthorpe et al 2018). FIR surveys of nearby stars show that debris disc luminosities decrease with age in a manner explained by population models in which all stars are born with a debris belt that is depleted by collisions amongst the planetesimals (Wyatt et al 2007; Gáspár et al 2013).
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
