The First 40 Million Years of Circumstellar Disk Evolution: The Signature of Terrestrial Planet Formation

Abstract

We characterize the first 40 Myr of evolution of circumstellar disks through a unified study of the infrared properties of members of young clusters and associations with ages from 2 Myr up to ∼40 Myr: NGC 1333, NGC 1960, NGC 2232, NGC 2244, NGC 2362, NGC 2547, IC 348, IC 2395, Chamaeleon I, Orion OB1a and OB1b, Taurus, the β Pictoris Moving Group, ρ Ophiuchi, and the associations of Argus, Carina, Columba, Scorpius-Centaurus, and Tucana-Horologium. Our work features: (1) a filtering technique to flag noisy backgrounds; (2) a method based on the probability distribution of deflections, P(D), to obtain statistically valid photometry for faint sources; and (3) use of the evolutionary trend of transitional disks to constrain the overall behavior of bright disks. We find that the fraction of disks three or more times brighter than the stellar photospheres at 24 μm decays relatively slowly initially and then much more rapidly by ∼10 Myr. However, there is a continuing component until ∼35 Myr, probably due primarily to massive clouds of debris generated in giant impacts during the oligarchic/chaotic growth phases of terrestrial planets. If the contribution from primordial disks is excluded, the evolution of the incidence of these oligarchic/chaotic debris disks can be described empirically by a log-normal function with the peak at 12-20 Myr, including ∼13% of the original population, and with a postpeak mean duration of 10-20 Myr.

Looking Deep into the Rosette Nebula’s Heart: The (Sub)stellar Content of the Massive Young Cluster NGC 2244

“…As a side note, in the bottom left panel of Fig. 4, there is a group of relatively bright sources not recognized as members by Meng et al (2017), located to the right and above the red lines (roughly J < 13 and G − J > 1). Only about 10% of these sources pass all our membership cuts.…”

“…The resulting list contains 3498 objects. We then cross-matched the Gaia DR2 result with the catalog of 718 clusters members from Meng et al (2017), constructed based on X-ray detection, infrared excess, proper motion, optical color selection, and a cut-off in the clustrocentric distance. The total number of matched sources with a valid fivepoint astrometric solution is 528.…”

“…There is a distinct overabundance of sources close to the position µ α , µ δ ≈ (−1.5, 0.2) mas yr −1 , corresponding to the location of the cluster members. An enlarged version of this plot is shown in the upper right panel, with the blue open circles marking the matched members from Meng et al (2017). The mean proper motion of the matched members are µ α = −1.62 ± 0.65 mas yr −1 and µ δ = 0.15 ± 0.70 mas yr −1 .…”

“…4. 242 of the 345 selected sources belong also to the members list of Meng et al (2017). We note that our criteria may cause us to miss some members (mainly due to the relatively narrow allowed proper motion space, especially considering individual proper motion uncertainties), but the idea here is to minimize the number of interlopers that could bias our distance analysis, rather than to do a sophisticated membership analysis at this point.…”

“…We matched the sources selected in this section with the member list of Meng et al (2017), who select as member candidates all sources detected in both X-rays and Spitzer/IRAC, or those that show excess at wavelengths 8−24 µm. The depth of their survey seems to be fairly complete down to the 2MASS completeness limit at J = 15.8 mag, and we restrict the comparison down to that value.…”