An ALMA Survey of Protoplanetary Disks in the σ Orionis Cluster

By M. Ansdell, Jonathan P. Williams, C. Manara, A. Miotello, S. Facchini, N. Marel, L. Testi, E. V. van Dishoeck. 2017

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The σ Orionis cluster is important for studying protoplanetary disk evolution, as its intermediate age (∼3–5 Myr) is comparable to the median disk lifetime. We use ALMA to conduct a high-sensitivity survey of dust and gas in 92 protoplanetary disks around σ Orionis members with M* ≳ 0.1 M⊙. Our observations cover the 1.33 mm continuum and several CO J = 2–1 lines: out of 92 sources, we detect 37 in the millimeter continuum and 6 in 12CO, 3 in 13CO, and none in C18O. Using the continuum emission to estimate dust mass, we find only 11 disks with Mdust ≳ 10 M⊕, indicating that after only a few Myr of evolution most disks lack sufficient dust to form giant planet cores. Stacking the individually undetected continuum sources limits their average dust mass to 5× lower than that of the faintest detected disk, supporting theoretical models that indicate rapid dissipation once disk clearing begins. Comparing the protoplanetary disk population in σ Orionis to those of other star-forming regions supports the steady decline in average dust mass and the steepening of the Mdust–M* relation with age; studying these evolutionary trends can inform the relative importance of different disk processes during key eras of planet formation. External photoevaporation from the central O9 star is influencing disk evolution throughout the region: dust masses clearly decline with decreasing separation from the photoionizing source, and the handful of CO detections exist at projected separations of >1.5 pc. Collectively, our findings indicate that giant planet formation is inherently rare and/or well underway by a few Myr of age.

Subfields: Astronomy and Astrophysics, Spectroscopy

View Paper: https://www.semanticscholar.org/paper/740ac2a483ac3cfac4c5f99f1f05d14c7f9d9cf2

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Citations in the corpus

ALMA Survey of Lupus Protoplanetary Disks. II. Gas Disk Radii (2018, background): “…I (Pascucci et al. 2016) regions, with those of the intermediate-aged (∼3–5 Myr) σ Orionis cluster (Ansdell et al. 2017) and the evolved (∼5–10 Myr) Upper Sco association (Barenfeld et al. 2016), reveal a clear decline in disk dust mass (Mdust) with age (see Figure 8 in Ansdell et al. 2017).”
On the diversity and statistical properties of protostellar discs (2018, background): “Over the past decade, improvements in (sub-)millimetre resolution have allowed statistical studies of disc masses and radii to be carried out in many nearby star-forming regions, including Ophiuchus and Taurus (Andrews et al. 2009, 2010, 2013; Tripathi et al. 2017), Lupus (Ansdell et al. 2016; Tazza”
Why do protoplanetary disks appear not massive enough to form the known exoplanet population? (2018, background): “…to near-infrared spectroscopic surveys, are showing that the mass of the dust content of protoplanetary disks increases with stellar mass following a steeper than linear relation and decreases with time (e.g., Ansdell et al. 2016; Pascucci et al. 2016; Barenfeld et al. 2016; Ansdell et al. 2017).”
Formation of planetary systems by pebble accretion and migration (2018, background): “ALMA surveys of million-year-old star-forming regions argue for dust masses between crudely ∼1 and ∼100 ME, as inferred from (sub-) millimetre emission around Class II sources (Ansdell et al. 2017; Dullemond et al. 2018).”