ALMA Observations of HD141569's Circumstellar Disk

Abstract

We present ALMA band 7 (345 GHz) continuum and ${}^{12}$CO(J = 3-2) observations of the circumstellar disk surrounding HD141569. At an age of about 5 Myr, the disk has a complex morphology that may be best interpreted as a nascent debris system with gas. Our $870\hat{\mathrm{I}}¼\mathrm{m}$ ALMA continuum observations resolve a dust disk out to approximately $56\mathrm{au}$ from the star (assuming a distance of 116 pc) with $0."38$ resolution and $0.07\mathrm{mJy}\mathrm{bea}{\mathrm{m}}^{-1}$ sensitivity. We measure a continuum flux density for this inner material of $3.8\pm 0.4\mathrm{mJy}$ (including calibration uncertainties). The ${}^{12}$CO(3-2) gas is resolved kinematically and spatially from about 30 to 210 au. The integrated ${}^{12}$CO(3-2) line flux density is $15.7\pm 1.6\mathrm{Jy}\mathrm{km}{\mathrm{s}}^{-1}$. We estimate the mass of the millimeter debris and ${}^{12}$CO(3-2) gas to be $\gtrsim 0.04{\mathrm{M}}_{\oplus }$ and $\sim 2\times 10^{-3}{\mathrm{M}}_{\oplus }$, respectively. If the millimeter grains are part of a collisional cascade, then we infer that the inner disk ($<50$ au) has $\sim 160{\mathrm{M}}_{\oplus }$ contained within objects less than 50 km in radius, depending on the planetesimal size distribution and density assumptions. MCMC modeling of the system reveals a disk morphology with an inclination of $53.4^{\circ }$ centered around a $\mathrm{M}=2.39{\mathrm{M}}_{\odot }$ host star ($\mathrm{Msin}(\mathrm{i})=1.92{\mathrm{M}}_{\odot }$). We discuss whether the gas in HD141569's disk may be second generation. If it is, the system can be used to study the clearing stages of planet formation.

35 pages, 7 figures, submitted to ApJ