Accretion disks are an essential component in the paradigm of the formation of low-mass stars. Recent observations further identify disks surrounding low-mass pre-main-sequence stars perturbed by flybys. Whether disks around more massive stars evolve in a similar manner has become an urgent question. We report the discovery of a Keplerian disk of a few solar masses surrounding a 32 M⊙ protostar in the Sagittarius C cloud around the Galactic Centre. The disk is gravitationally stable with two embedded spirals. A combined analysis of analytical solutions and numerical simulations demonstrates that the most likely scenario to form the spirals is through external perturbations induced by a close flyby, and one such perturber with the expected parameters is identified. The massive, early O-type star embedded in this disk forms in a similar manner as do low-mass stars, in the sense of not only disk-mediated accretion, but also flyby-impacted disk evolution.
This is a preview of subscription content, access via your institution
Subscribe to Nature+
Get immediate online access to Nature and 55 other Nature journal
Subscribe to Journal
Get full journal access for 1 year
only $9.92 per issue
All prices are NET prices.
VAT will be added later in the checkout.
Tax calculation will be finalised during checkout.
Get time limited or full article access on ReadCube.
All prices are NET prices.
This paper makes use of the following ALMA data: ADS/JAO.ALMA#2018.1.00641.S. The data are available at https://almascience.nao.ac.jp/aq by setting the observation code. The reduced data used for this study are available from the corresponding authors upon reasonable request.
The ALMA data were reduced using CASA versions 5.4.0 and 5.6.1, which are available at https://casa.nrao.edu/casa_obtaining.shtml. The code to make Fig. 3 is available at https://doi.org/10.5281/zenodo.6413326. The 3DBarolo code is available at https://github.com/editeodoro/Bbarolo. The Phantom code is available at https://github.com/danieljprice/phantom. The splash code is available at https://github.com/danieljprice/splash.
Longmore, S. N. et al. Variations in the Galactic star formation rate and density thresholds for star formation. Mon. Not. R. Astron. Soc. 429, 987–1000 (2013).
Barnes, A. T. et al. Star formation rates and efficiencies in the Galactic Centre. Mon. Not. R. Astron. Soc. 469, 2263–2285 (2017).
Kauffmann, J. et al. The Galactic Center Molecular Cloud Survey. I. A steep linewidth–size relation and suppression of star formation. Astron. Astrophys. 603, A89 (2017).
Lu, X. et al. A census of early-phase high-mass star formation in the Central Molecular Zone. Astrophys. J. Suppl. 244, 35 (2019).
Lu, X. et al. ALMA observations of massive clouds in the Central Molecular Zone: ubiquitous protostellar outflows. Astrophys. J. 909, 177 (2021).
Walker, D. L. et al. Star formation in ‘the Brick’: ALMA reveals an active protocluster in the Galactic centre cloud G0.253+0.016. Mon. Not. R. Astron. Soc. 503, 77–95 (2021).
Reid, M. J. et al. Trigonometric parallaxes of high-mass star-forming regions: our view of the Milky Way. Astrophys. J. 885, 131 (2019).
Beltrán, M. T. & de Wit, W. J. Accretion disks in luminous young stellar objects. Astron. Astrophys. Rev. 24, 6 (2016).
Zhao, B. et al. Formation and evolution of disks around young stellar objects. Space Sci. Rev. 216, 43 (2020).
Johnston, K. G. et al. A Keplerian-like disk around the forming O-type star AFGL 4176. Astrophys. J. Lett. 813, L19 (2015).
Sanna, A. et al. Discovery of a sub-Keplerian disk with jet around a 20 M⊙ young star. ALMA observations of G023.01-00.41. Astron. Astrophys. 623, A77 (2019).
Maud, L. T. et al. Substructures in the Keplerian disc around the O-type (proto-)star G17.64+0.16. Astron. Astrophys. 627, L6 (2019).
Motogi, K. et al. The first bird’s-eye view of a gravitationally unstable accretion disk in high-mass star formation. Astrophys. J. Lett. 877, L25 (2019).
Zapata, L. A. et al. An asymmetric Keplerian disk surrounding the O-type protostar IRAS 16547-4247. Astrophys. J. 872, 176 (2019).
Johnston, K. G. et al. Spiral arms and instability within the AFGL 4176 mm1 disc. Astron. Astrophys. 634, L11 (2020).
Sanna, A. et al. Physical conditions in the warped accretion disk of a massive star. 349 GHz ALMA observations of G023.01-00.41. Astron. Astrophys. 655, A72 (2021).
Shu, F. H., Adams, F. C. & Lizano, S. Star formation in molecular clouds: observation and theory. Annu. Rev. Astron. Astrophys. 25, 23–81 (1987).
Cesaroni, R. et al. Chasing discs around O-type (proto)stars: evidence from ALMA observations. Astron. Astrophys. 602, A59 (2017).
Toomre, A. On the gravitational stability of a disk of stars. Astrophys. J. 139, 1217–1238 (1964).
Durisen, R. H. et al. in Protostars and Planets V (eds Reipurth, B. et al.) 607 (Univ. Arizona Press, 2007).
Clarke, C. J. & Pringle, J. E. Accretion disc response to a stellar fly-by. Mon. Not. R. Astron. Soc. 261, 190–202 (1993).
Pfalzner, S. Spiral arms in accretion disk encounters. Astrophys. J. 592, 986–1001 (2003).
Bate, M. R., Bonnell, I. A. & Bromm, V. The formation of a star cluster: predicting the properties of stars and brown dwarfs. Mon. Not. R. Astron. Soc. 339, 577–599 (2003).
Xiang-Gruess, M. Generation of highly inclined protoplanetary discs through single stellar flybys. Mon. Not. R. Astron. Soc. 455, 3086–3100 (2016).
Vincke, K. & Pfalzner, S. Cluster dynamics largely shapes protoplanetary disk sizes. Astrophys. J. 828, 48 (2016).
Winter, A. J. et al. Protoplanetary disc truncation mechanisms in stellar clusters: comparing external photoevaporation and tidal encounters. Mon. Not. R. Astron. Soc. 478, 2700–2722 (2018).
Cuello, N. et al. Flybys in protoplanetary discs: I. Gas and dust dynamics. Mon. Not. R. Astron. Soc. 483, 4114–4139 (2019).
Cabrit, S., Pety, J., Pesenti, N. & Dougados, C. Tidal stripping and disk kinematics in the RW Aurigae system. Astron. Astrophys. 452, 897–906 (2006).
Dai, F., Facchini, S., Clarke, C. J. & Haworth, T. J. A tidal encounter caught in the act: modelling a star–disc fly-by in the young RW Aurigae system. Mon. Not. R. Astron. Soc. 449, 1996–2009 (2015).
Kurtovic, N. T. et al. The Disk Substructures at High Angular Resolution Project (DSHARP). IV. Characterizing substructures and interactions in disks around multiple star systems. Astrophys. J. Lett. 869, L44 (2018).
Rodriguez, J. E. et al. Multiple stellar flybys sculpting the circumstellar architecture in RW Aurigae. Astrophys. J. 859, 150 (2018).
Akiyama, E. et al. A tail structure associated with a protoplanetary disk around SU Aurigae. Astron. J. 157, 165 (2019).
Pérez, S. et al. Resolving the FU Orionis system with ALMA: interacting twin disks? Astrophys. J. 889, 59 (2020).
Ménard, F. et al. Ongoing flyby in the young multiple system UX Tauri. Astron. Astrophys. 639, L1 (2020).
Zapata, L. A. et al. Tidal interaction between the UX Tauri A/C disk system revealed by ALMA. Astrophys. J. 896, 132 (2020).
Dong, R. et al. A likely flyby of binary protostar Z CMa caught in action. Nat. Astron. 6, 331–338 (2022).
Chambers, E. T., Yusef-Zadeh, F. & Roberts, D. Methanol maser emission from Galactic Center sources with excess 4.5 μm emission. Astrophys. J. 733, 42 (2011).
Kendrew, S. et al. Early-stage massive star formation near the Galactic Center: Sgr C. Astrophys. J. Lett. 775, L50 (2013).
Lu, X. et al. Star formation rates of massive molecular clouds in the Central Molecular Zone. Astrophys. J. 872, 171 (2019).
Borchert, E. M. A., Price, D. J., Pinte, C. & Cuello, N. On the rise times in FU Orionis events. Mon. Not. R. Astron. Soc. 510, L37–L41 (2022).
Tobin, J. J. et al. A triple protostar system formed via fragmentation of a gravitationally unstable disk. Nature 538, 483–486 (2016).
Kruijssen, J. M. D., Dale, J. E. & Longmore, S. N. The dynamical evolution of molecular clouds near the Galactic Centre—I. Orbital structure and evolutionary timeline. Mon. Not. R. Astron. Soc. 447, 1059–1079 (2015).
Molinari, S. et al. A 100 pc elliptical and twisted ring of cold and dense molecular clouds revealed by Herschel around the Galactic Center. Astrophys. J. Lett. 735, L33 (2011).
Möller, T., Endres, C. & Schilke, P. eXtended CASA Line Analysis Software Suite (XCLASS). Astron. Astrophys. 598, A7 (2017).
Panagia, N. Some physical parameters of early-type stars. Astron. J. 78, 929–934 (1973).
Scoville, N. Z. & Kwan, J. Infrared sources in molecular clouds. Astrophys. J. 206, 718–727 (1976).
Garay, G. & Lizano, S. Massive stars: their environment and formation. Publ. Astron. Soc. Pac. 111, 1049–1087 (1999).
Di Teodoro, E. M. & Fraternali, F. 3DBAROLO: a new 3D algorithm to derive rotation curves of galaxies. Mon. Not. R. Astron. Soc. 451, 3021–3033 (2015).
Ossenkopf, V. & Henning, T. Dust opacities for protostellar cores. Astron. Astrophys. 291, 943–959 (1994).
D’Onghia, E., Vogelsberger, M., Faucher-Giguere, C.-A. & Hernquist, L. Quasi-resonant theory of tidal interactions. Astrophys. J. 725, 353–368 (2010).
Price, D. J. et al. Phantom: a smoothed particle hydrodynamics and magnetohydrodynamics code for astrophysics. Publ. Astron. Soc. Aust. 35, e031 (2018).
Breslau, A., Steinhausen, M., Vincke, K. & Pfalzner, S. Sizes of protoplanetary discs after star–disc encounters. Astron. Astrophys. 565, A130 (2014).
Bhandare, A., Breslau, A. & Pfalzner, S. Effects of inclined star–disk encounter on protoplanetary disk size. Astron. Astrophys. 594, A53 (2016).
Price, D. J. splash: an interactive visualisation tool for smoothed particle hydrodynamics simulations. Publ. Astron. Soc. Aust. 24, 159–173 (2007).
Cuello, N. et al. Flybys in protoplanetary discs—II. Observational signatures. Mon. Not. R. Astron. Soc. 491, 504–514 (2020).
Davies, M. B. in The Astrophysics of Planetary Systems: Formation, Structure, and Dynamical Evolution Vol. 276 (eds Sozzetti, A. et al.) 304–307 (Cambridge Univ. Press, 2011).
Pfalzner, S. Early evolution of the birth cluster of the Solar System. Astron. Astrophys. 549, A82 (2013).
Otter, J. et al. Small protoplanetary disks in the Orion Nebula Cluster and OMC1 with ALMA. Astrophys. J. 923, 221 (2021).
Ginsburg, A. & Kruijssen, J. M. D. A high cluster formation efficiency in the Sagittarius B2 complex. Astrophys. J. Lett. 864, L17 (2018).
Andrews, S. M., Rosenfeld, K. A., Kraus, A. L. & Wilner, D. J. The mass dependence between protoplanetary disks and their stellar hosts. Astrophys. J. 771, 129 (2013).
Garufi, A. et al. Evolution of protoplanetary disks from their taxonomy in scattered light: spirals, rings, cavities, and shadows. Astron. Astrophys. 620, A94 (2018).
We thank H. B. Liu, Y. Cheng and P. Sanhueza for helpful discussions. X.L. acknowledges support from the Initial Funding of Scientific Research for High-Level Talents at Shanghai Astronomical Observatory, and the Japan Society for the Promotion of Science KAKENHI grant 20K14528. G.-X.L. thanks M. Krause for discussions on the flyby scenario. G.-X.L. acknowledges support from NSFC grants W820301904 and 12033005. This work made use of the High Performance Computing Resource in the Core Facility for Advanced Research Computing at Shanghai Astronomical Observatory, and the Multi-wavelength Data Analysis System operated by the Astronomy Data Center, National Astronomical Observatory of Japan. It made use of the following ALMA data: ADS/JAO.ALMA#2018.1.00641.S. ALMA is a partnership of ESO (representing its member states), NSF (USA) and NINS (Japan), together with NRC (Canada), MOST and ASIAA (Taiwan) and KASI (Republic of Korea), in cooperation with the Republic of Chile. The Joint ALMA Observatory is operated by ESO, AUI/NRAO and NAOJ.
The authors declare no competing interests.
Peer review information
Nature Astronomy thanks Susanne Pfalzner, Nicolas Cuello and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.
Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Left: the velocity field of the disk and the two condensations, derived from the CH3OCHO line. The blue and red contours show the blue and red-shifted SiO emission from previous ALMA observations5. The blue-shifted SiO emission is integrated between − 80 and − 51 kms−1, and the red-shifted SiO emission between − 48 and − 25 km s−1. The bipolar outflow associated with the disk, which has been identified in Ref. 5 using multiple molecular lines including SiO, is marked by the blue and red arrows. The best-fit kinematic major axis of the disk is denoted by the green dashed line, same as in Fig. 1b. A candidate bipolar outflow associated with condensation A is marked by the dashed blue and red arrows. Right: the radio continuum emission in this region observed by the Very Large Array (VLA). Green contours are the 23 GHz continuum emission37, while red contours are the 5.6 GHz continuum emission4. The contour levels are between 20% and 80% and increment by 20% of the peak intensity. The synthesized beams at the two frequencies are shown in the top left and top right corners, respectively. At both frequencies, the radio continuum emission is unresolved or marginally resolved. The background image and gray contours show the ALMA 1.3 mm continuum emission, same as in Fig. 1.
The two maps are derived from two groups of molecular lines: CH3CN on the left, and 13CH3CN on the right, with the same scale range for comparison. The green contours show the continuum emission, with the same contour levels as in Fig. 1a.
Left: the case when using the sound speed only. Right: the case when using the epicyclic frequency following Equ. (5).
When the periastron distance is small (bottom panels), the perturber penetrates the disk and leaves a strong dynamical impact, thus truncating the disk. When large (top panels), the dynamical effect becomes insignificant. When the angular velocity at the periastron is low (left panels), the perturber is able to resonate only with outer radii of the disk that rotate more slowly. When high (right panels), the perturber resonates with the inner disk, disturbing smaller radii than observed. The only viable solution remains to the one identified in Fig. 3.
About this article
Cite this article
Lu, X., Li, GX., Zhang, Q. et al. A massive Keplerian protostellar disk with flyby-induced spirals in the Central Molecular Zone. Nat Astron 6, 837–843 (2022). https://doi.org/10.1038/s41550-022-01681-4