分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： DR Tau has been noted for its unusually high variability in comparison with other T Tauri stars. Although it is one of the most extensively studied pre-main sequence stars, observations with millimeter interferometry have so far been relatively limited. We present NOEMA images of $^{12}$CO, $^{13}$CO, C$^{18}$O, SO, DCO$^+$, and H$_2$CO toward DR Tau at a resolution of $\sim0.5''$ ($\sim100$ au). In addition to the protoplanetary disk, CO emission reveals an envelope, a faint asymmetric outflow, and a spiral arm with a clump. The $\sim1200$ au extent of the CO arm far exceeds that of the spiral arms previously detected in scattered light, which underlines the necessity of sensitive molecular imaging for contextualizing the disk environment. The kinematics and compact emission distribution of C$^{18}$O, SO, DCO$^+$, and H$_2$CO indicate that they originate primarily from within the Keplerian circumstellar disk. The SO emission, though, also exhibits an asymmetry that may be due to interaction with infalling material or unresolved substructure. The complex environment of DR Tau is reminiscent of those of outbursting FUor sources and some EXor sources, suggesting that DR Tau's extreme stellar activity could likewise be linked to disk instabilities promoted by large-scale infall.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： Carbon is an essential element for life but its behavior during Earth's accretion is not well understood. Carbonaceous grains in meteoritic and cometary materials suggest that irreversible sublimation, and not condensation, governs carbon acquisition by terrestrial worlds. Through astronomical observations and modeling we show that the sublimation front of carbon carriers in the solar nebula, or the soot line, moved inward quickly so that carbon-rich ingredients would be available for accretion at 1 au after the first million years. On the other hand, geological constraints firmly establish a severe carbon deficit in Earth, requiring the destruction of inherited carbonaceous organics in the majority of its building blocks. The carbon-poor nature of the Earth thus implies carbon loss in its precursor material through sublimation within the first million years.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Jenny K. Calahan
Edwin A. Bergin
Arthur D. Bosman
Evan Rich
Sean M. Andrews
Jennifer B. Bergner
L. Ilsedore Cleeves
Viviana V. Guzman
Jane Huang
John D. Ilee
Charles J. Law
Romane Le Gal
Karin I. Oberg
Richard Teague
Catherine Walsh
David J. Wilner
Ke Zhang
摘要： The chemical reservoir within protoplanetary disks has a direct impact on planetary compositions and the potential for life. A long-lived carbon-and nitrogen-rich chemistry at cold temperatures ( 1) to form carbon-bearing radicals and ions. This further results in gas phase formation of organic molecules, which then would be accreted by any actively forming planets present in the evolved disk.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Jane Huang
Christian Ginski
Myriam Benisty
Bin Ren
Alexander J. Bohn
Élodie Choquet
Karin I. Öberg
Álvaro Ribas
Jaehan Bae
Edwin A. Bergin
Til Birnstiel
Yann Boehler
Stefano Facchini
Daniel Harsono
Michiel Hogerheijde
Feng Long
Carlo F. Manara
François Ménard
Paola Pinilla
Christophe Pinte
摘要： While protoplanetary disks are often treated as isolated systems in planet formation models, observations increasingly suggest that vigorous interactions between Class II disks and their environments are not rare. DO Tau is a T Tauri star that has previously been hypothesized to have undergone a close encounter with the HV Tau system. As part of the DESTINYS ESO Large Programme, we present new VLT/SPHERE polarimetric observations of DO Tau and combine them with archival HST scattered light images and ALMA observations of CO isotopologues and CS to map a network of complex structures. The SPHERE and ALMA observations show that the circumstellar disk is connected to arms extending out to several hundred au. HST and ALMA also reveal stream-like structures northeast of DO Tau, some of which are at least several thousand au long. These streams appear not to be gravitationally bound to DO Tau, and comparisons with previous Herschel far-IR observations suggest that the streams are part of a bridge-like structure connecting DO Tau and HV Tau. We also detect a fainter redshifted counterpart to a previously known blueshifted CO outflow. While some of DO Tau's complex structures could be attributed to a recent disk-disk encounter, they might be explained alternatively by interactions with remnant material from the star formation process. These panchromatic observations of DO Tau highlight the need to contextualize the evolution of Class II disks by examining processes occurring over a wide range of size scales.
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