A ∼75 per cent occurrence rate of debris discs around F stars in the β Pic moving group

Only 20 percent of old field stars have detectable debris discs, leaving open the question of what disc, if any, is present around the remaining 80 percent. 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 beta 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 63au radius disc of HD 164249. Comparing the BPMG results to disc samples from similar to 45-Myr and similar to 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/age(2). We attribute this depletion to embedded planets, which would be around 170 M-earth 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.

Automated summary

This paper examines the population of F stars in the 23 Myr-old beta Pictoris moving group (BPMG) and finds that 9/12 targets in the group possess debris discs. Comparing the results with other moving groups and field stars, it is revealed that young moving groups have a comparable or higher incidence rate of debris discs and tend to have smaller discs compared to field stars. The study also suggests that the depletion of debris discs in young populations may be attributed to embedded planets and different birth environments.