ALMA Survey of Lupus Class III Stars: Early Planetesimal Belt Formation and Rapid Disk Dispersal
| Autor: | Lovell, J. B., Wyatt, M. C., Ansdell, M., Kama, M., Kennedy, G. M., Manara, C. F., Marino, S., Matrà, L., Rosotti, G., Tazzari, M., Testi, L., Williams, J. P. |
|---|---|
| Rok vydání: | 2020 |
| Předmět: | |
| Druh dokumentu: | Working Paper |
| DOI: | 10.1093/mnras/staa3335 |
| Popis: | Class III stars are those in star forming regions without large non-photospheric infrared emission, suggesting recent dispersal of their protoplanetary disks. We observed 30 class III stars in the 1-3 Myr Lupus region with ALMA at ${\sim}856\mu$m, resulting in 4 detections that we attribute to circumstellar dust. Inferred dust masses are $0.036{-}0.093M_\oplus$, ${\sim}1$ order of magnitude lower than any previous measurements; one disk is resolved with radius ${\sim}80$ au. Two class II sources in the field of view were also detected, and 11 other sources, consistent with sub-mm galaxy number counts. Stacking non-detections yields a marginal detection with mean dust mass ${\sim}0.0048M_\oplus$. We searched for gas emission from the CO J=3-2 line, and present its detection to NO Lup inferring a gas mass ($4.9 {\pm} 1.1$) ${\times}10^{-5} M_\oplus$ and gas-to-dust ratio $1.0{\pm}0.4$. Combining our survey with class II sources shows a gap in the disk mass distribution from $0.09{-}2M_\oplus$ for ${>}0.7M_\odot$ Lupus stars, evidence of rapid dispersal of mm-sized dust from protoplanetary disks. The class III disk mass distribution is consistent with a population model of planetesimal belts that go on to replenish the debris disks seen around main sequence stars. This suggests that planetesimal belt formation does not require long-lived protoplanetary disks, i.e., planetesimals form within ${\sim}$2 Myr. While all 4 class III disks are consistent with collisional replenishment, for two the gas and/or mid-IR emission could indicate primordial circumstellar material in the final stages of protoplanetary disk dispersal. Two class III stars without sub-mm detections exhibit hot emission that could arise from ongoing planet formation processes inside ${\sim}1$ au. Comment: 30 pages, 20 figures. This is a pre-copyedited, author-produced PDF of an article accepted for publication in MNRAS following peer review |
| Databáze: | arXiv |
| Externí odkaz: |
|