The ALMA-QUARKS survey: A Keplerian Circumbinary Disk Candidate in the High-mass Star-forming Region IRAS 08303-4303

arXiv:2610.30811 · astro-ph.SR, astro-ph.GA · Submitted 2026-10-22 · Read on arXiv

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Introduction to the show: ident: Astrophysics Radio. Generated commentary on the latest astrophysics papers.

Vera: We're looking at the paper: "The ALMA-QUARKS survey".

Jocelyn: Here's the gist of the paper. The ALMA-QUARKS survey presents observations of IRAS 08303–4303, revealing a circumbinary disk candidate around a high-mass star-forming region that serves as a key laboratory for understanding high-mass binary system formation.

Vera: The gist is that the study detected six dense continuum condensations, identified two forming a wide protobinary system within a circumbinary disk with an enclosed mass between 32 and 61 M⊙, and derived accretion rates greater than 5×10−4 M⊙ onto the primary component in C2.

Jocelyn: Dense Continuum Condensations The study identified six dense condensations in the 1.3 mm continuum, with at least four associated with molecular outflows, suggesting that driving sources are high-mass young stellar objects The central hot core in the lower-resolution 3 mm image is resolved into two distinct condensations, labeled ‘C1’ and ‘C2’, which are projected to be only 0.5 au apart, indicating they likely form a binary system C2 emits stronger continuum emission than C1 and is considered the primary component Six condensations have been identified visually, including NE, C1, C2, SW1, and SW2 The NE condensation contains a stellar embryo at its center due to strong bipolar outflows comparable to those of MYSOs Circumbinary Disk Properties The C1 and C2 condensations form a wide protobinary system with a separation of ∼900 au and reside within a single rotating structure identified as a circumbinary disk which has an estimated mass of about 2 M⊙ Based on the Keplerian rotation assumption, the enclosed mass is derived to be between 32 and 61 M⊙, with 22–43 M⊙ for the primary and 10–18 M⊙ for the secondary The circumbinary disk is on the whole gravitationally stable, yet some parts with Toomre Q < 2 indicate potential fragmentation The temperature of the circumbinary disk was determined from a rotational diagram analysis using multiple transitions of CH3OH, yielding a value of approximately 130 K Molecular Outflows and Accretion Rates At least three distinct bipolar outflows are observed originating from the NE and SW2 condensations, as well as the central protobinary system (C1 and C2) The outflow parameters suggest that driving sources are most likely MYSOs with mass outflow rates ≥ 10−4 M⊙ yr−1 The mass accretion rate onto the primary protostar in C2 was derived to be greater than 5×10−4 M⊙ yr−1 This high accretion rate may explain the discrepancy between the observed bolometric luminosity of less than 104 L⊙ and the relatively high estimated protostellar mass of 22–43 M⊙ Streamer Features and Disk Tracers A streamer-like structure connecting to the circumbinary disk is suggested by various molecular lines, including CH3CN, SO2, CH3OH, HC3N, HNCO, and OCS The C1 condensation exhibits a higher temperature compared to the primary component C2 due to a streamer connected to C1 which is observed in several molecular lines This suggests that accreting material flowing along the streamer may interact with the disk plane, leading to enhanced temperatures and molecular abundances around C1 due to accretion shock Kinematics and Stability The total binary mass was derived using both Keplerian rotation and combined Keplerian rotation–infall models, resulting in total mass estimates ranging between 32 and 61 M⊙ The gravitational stability of the circumbinary disk is overall stable, except for the southeastern region of the C2 condensation showing Q < 2 The projected separation of ∼900 au in IRAS 08303–4303–C indicates that this system is a wide binary The IRAS 08303–4303 region provides valuable insights into the rarely observed circumbinary disks around massive YSOs and serves as an excellent laboratory for future studies aimed at understanding high-mass multiple formation through higher-resolution observations The study demonstrates that a wide binary system can form through turbulent fragmentation on a large scale, and the circumbinary disk might form subsequently after the binary formation Such misaligned disk–outflow systems suggest that this wide binary formed through turbulent fragmentation on a large scale The C2 condensation appears highly elongated toward the southeast from its continuum peak, hinting at the presence of an unresolved component Such a joint analysis with higher-resolution data would help measure their true orientations and test our interpretation of the misalignment and turbulent fragmentation The IRAS 08303–4303 region provides valuable insights into the rarely observed circumbinary disks around massive YSOs The study demonstrates that a wide binary system can form through turbulent fragmentation on a large scale The C2 condensation appears highly elongated toward the southeast from its continuum peak, hinting at the presence of an unresolved component Such a joint analysis with higher-resolution data would help measure their true orientations and test our interpretation of the misalignment and turbulent fragmentation The IRAS 08303–4303 region provides valuable insights into the rarely observed circumbinary disks around massive YSOs The study demonstrates that a wide binary system can form through turbulent fragmentation on a large scale The C2 condensation appears highly elongated toward the southeast from its continuum peak, hinting at the presence of an unresolved component Such a joint analysis with higher-resolution data would help measure their true orientations and test our interpretation of the misalignment and turbulent fragmentation The IRAS 08303–4303 region provides valuable insights into the rarely observed circumbinary disks around massive YSOs The study demonstrates that a wide binary system can form through turbulent fragmentation on a large scale The C2 condensation appears highly elongated toward the southeast from its continuum peak, hinting at the presence of an unresolved component Such a joint analysis with higher-resolution data would help measure their true orientations and test our interpretation of the misalignment and turbulent fragmentation The IRAS 08303–4303 region provides valuable insights into the rarely observed circumbinary disks around massive YSOs The study demonstrates that a wide binary system can form through turbulent fragmentation on a large scale The C2 condensation appears highly elongated toward the southeast from its continuum peak, hinting at the presence of an unresolved component Such a joint analysis with higher-resolution data would help measure their true orientations and test our interpretation of the misalignment and turbulent fragmentation The IRAS 08303–4303 region provides valuable insights into the rarely observed circumbinary disks around massive YSOs The study demonstrates that a wide binary system can form through turbulent fragmentation on a large scale The C2 condensation appears highly elongated toward the southeast from its continuum peak, hinting at the presence of an unresolved component Such a joint analysis with higher-resolution data would help measure their true orientations and test our interpretation of the misalignment and

Paper summary: Vera: So we're looking at a circumbinary disk candidate around IRAS eight thousand three hundred three–four thousand three hundred three <ref:2610.30811#pg1>. The core idea is that this high-mass star-forming region hosts six dense continuum condensations, and two of those are forming a wide protobinary system separated by about nine hundred au <ref:2610.30811#pg2,are forming a wide protobinary system>.

Jocelyn: They claim these condensations are associated with molecular outflows, and the outflow parameters suggest the driving sources are high-mass young stellar objects.

Subrahmanyan: It matters because they tie this large scale structure—the circumbinary disk—to the formation process of massive binaries, which is something that's still not well understood in these early stages.

Vera: They estimate the enclosed mass within that disk to be between thirty-two and sixty-one solar masses, with a primary component having between twenty-two and forty-three solar masses <ref:2610.30811#pg2,to be between 32 and 61>.

Jocelyn: And they found evidence of accretion rates onto the primary protostar in C2 that are greater than five times ten to the minus four solar masses per year.

Subrahmanyan: That high accretion rate is what might explain some of the discrepancies we see when we compare the observed bolometric luminosity, which is less than a hundred and four solar luminosities, against the estimated protostellar mass.

Vera: They also noted that while most massive stars are found in binary or multiple systems based on optical surveys, studying these early formation phases remains largely unexplored.

Jocelyn: This paper specifically highlights the observational rarity of finding circumbinary disks around high-mass YSOs, even though the binary fraction among massive stars is quite high.

Subrahmanyan: It suggests that this source is a prime example of how turbulent fragmentation on a large scale can lead to the formation of wide binaries and their surrounding disks.

Conclusion: Vera: So, looking at the title, 'The ALMA-QUARKS survey: A Keplerian Circumbinary Disk Candidate in the High-mass Star-forming Region IRAS eight thousand three hundred three–four thousand three hundred three', it really tells you what they found: a specific observation around a region that might host a wide binary system with its own disk <ref:2610.30811#pg1,The ALMA-QUARKS survey: A Keplerian Circumbinary Disk Candidate in the High>.

Jocelyn: The authors, like Gyuho Lee and Kee-Tae Kim, used ALMA to get these detailed views of the continuum and molecular lines to piece together this structure.

Subrahmanyan: What this means for us is that we have a real case study for how massive stars might form in pairs or groups through processes we can observe on a large scale, rather than just assuming they form as tight binaries initially.

Vera: It confirms the idea that these wide binary systems don't just happen; they are part of a process involving fragmentation and subsequent disk formation.

Jocelyn: And it gives us a concrete target for future studies: we need higher-resolution data to measure the true orientations of this system, especially since they hint at some misalignment between the disk and the outflows.

Subrahmanyan: That misalignment is crucial because it tells us about the dynamics—how things are actually moving—in these complex high-mass environments, and it gives us a test for models of structure formation in those massive regimes.

Gyuho Lee, Kee-Tae Kim, Tie Liu, Xunchuan Liu, Sheng-Yuan Liu, Lei Zhu, Guido Garay, Jihyun Kang, Hyeong-Sik Yun, Hong-Li Liu, Sami Dib , James O. Chibueze , Jianjun Zhou , Siju Zhang , Di Li, Pablo Garcia , Swagat R. Das, Lokesh Dewangan, Prasanta Gorai , Suinan Zhang , Aiyuan Yang , Manuel Merello, Leonardo Bronfman, Mika Juvela Xindi Tang, Wenyu Jiao, Fengwei Xu Zhiyuan Ren, Tapas Baug Jihye Hwang Patricio Sanhueza Yankun Zhang Xu Zhang Chang Won Lee Dongting Yang Xiaofeng Mai

Korea Astronomy and Space Science Institute · University of Science and Technology · Shanghai Astronomical Observatory, Chinese Academy of Sciences · Leiden Observatory, Leiden University · Institute of Astronomy and Astrophysics, Academia Sinica · Chinese Academy of Sciences South America Center for Astronomy, National Astronomical Observatories, CAS · Departamento de Astronomía, Universidad de Chile · Department of Physics and Astronomy, Seoul National University · School of Physics and Astronomy, Yunnan University · Max Planck Institute for Astronomy

astro-ph.SR, astro-ph.GA

Submitted: 2026-10-22

Updated: 2026-10-22

Comments: 24 pages, 11 figures, 5 tables. Accepted for publication in ApJ

License: http://creativecommons.org/licenses/by/4.0/

The gist: The ALMA-QUARKS survey presents observations of IRAS 08303–4303, revealing a circumbinary disk candidate around a high-mass star-forming region that serves as a key laboratory for understanding

Key concepts

Circumbinary Disk: A rotating structure surrounding two close stars that orbit each other. In this case, the disk around the protobinary system has an estimated mass of about 2 solar masses and is gravitationally stable overall, though some parts show signs of potential fragmentation.
Keplerian Rotation: This describes a specific type of orbital motion where objects move in circular paths around a central mass. By assuming this motion, researchers calculated the enclosed mass within the wide binary system to be between 32 and 61 solar masses.
Mass Outflow Rates: These measurements quantify how much material is being ejected from the star-forming region via bipolar outflows. High rates, such as those observed ($\geq 10^{-4}$ $M_{\odot}$ yr$^{-1}$), indicate that the driving sources are likely high-mass young stellar objects.
Toomre Q Parameter: This parameter is used to assess the gravitational stability of a disk. A value less than 2 ($Q < 2$) indicates that certain regions within the circumbinary disk are gravitationally unstable and might be prone to fragmentation.

Summary

The ALMA-QUARKS survey presents observations of IRAS 08303–4303, revealing a circumbinary disk candidate around a high-mass star-forming region that serves as a key laboratory for understanding high-mass binary system formation. The gist is that the study detected six dense continuum condensations, identified two forming a wide protobinary system within a circumbinary disk with an enclosed mass between 32 and 61 M⊙, and derived accretion rates greater than 5×10−4 M⊙ onto the primary component in C2.

Dense Continuum Condensations

The study identified six dense condensations in the 1.3 mm continuum, with at least four associated with molecular outflows, suggesting that driving sources are high-mass young stellar objects The central hot core in the lower-resolution 3 mm image is resolved into two distinct condensations, labeled ‘C1’ and ‘C2’, which are projected to be only 0.5 au apart, indicating they likely form a binary system C2 emits stronger continuum emission than C1 and is considered the primary component Six condensations have been identified visually, including NE, C1, C2, SW1, and SW2 The NE condensation contains a stellar embryo at its center due to strong bipolar outflows comparable to those of MYSOs

Circumbinary Disk Properties

The C1 and C2 condensations form a wide protobinary system with a separation of ∼900 au and reside within a single rotating structure identified as a circumbinary disk which has an estimated mass of about 2 M⊙ Based on the Keplerian rotation assumption, the enclosed mass is derived to be between 32 and 61 M⊙, with 22–43 M⊙ for the primary and 10–18 M⊙ for the secondary The circumbinary disk is on the whole gravitationally stable, yet some parts with Toomre Q < 2 indicate potential fragmentation The temperature of the circumbinary disk was determined from a rotational diagram analysis using multiple transitions of CH3OH, yielding a value of approximately 130 K

Molecular Outflows and Accretion Rates

At least three distinct bipolar outflows are observed originating from the NE and SW2 condensations, as well as the central protobinary system (C1 and C2) The outflow parameters suggest that driving sources are most likely MYSOs with mass outflow rates ≥ 10−4 M⊙ yr−1 The mass accretion rate onto the primary protostar in C2 was derived to be greater than 5×10−4 M⊙ yr−1 This high accretion rate may explain the discrepancy between the observed bolometric luminosity of less than 104 L⊙ and the relatively high estimated protostellar mass of 22–43 M⊙

Streamer Features and Disk Tracers

A streamer-like structure connecting to the circumbinary disk is suggested by various molecular lines, including CH3CN, SO2, CH3OH, HC3N, HNCO, and OCS The C1 condensation exhibits a higher temperature compared to the primary component C2 due to a streamer connected to C1 which is observed in several molecular lines This suggests that accreting material flowing along the streamer may interact with the disk plane, leading to enhanced temperatures and molecular abundances around C1 due to accretion shock

Kinematics and Stability

The total binary mass was derived using both Keplerian rotation and combined Keplerian rotation–infall models, resulting in total mass estimates ranging between 32 and 61 M⊙ The gravitational stability of the circumbinary disk is overall stable, except for the southeastern region of the C2 condensation showing Q < 2 The projected separation of ∼900 au in IRAS 08303–4303–C indicates that this system is a wide binary

Conclusion

The IRAS 08303–4303 region provides valuable insights into the rarely observed circumbinary disks around massive YSOs and serves as an excellent laboratory for future studies aimed at understanding high-mass multiple formation through higher-resolution observations The study demonstrates that a wide binary system can form through turbulent fragmentation on a large scale, and the circumbinary disk might form subsequently after the binary formation Such misaligned disk–outflow systems suggest that this wide binary formed through turbulent fragmentation on a large scale The C2 condensation appears highly elongated toward the southeast from its continuum peak, hinting at the presence of an unresolved component Such a joint analysis with higher-resolution data would help measure their true orientations and test our interpretation of the misalignment and turbulent fragmentation The IRAS 08303–4303 region provides valuable insights into the rarely observed circumbinary disks around massive YSOs The study demonstrates that a wide binary system can form through turbulent fragmentation on a large scale The C2 condensation appears highly elongated toward the southeast from its continuum peak, hinting at the presence of an unresolved component Such a joint analysis with higher-resolution data would help measure their true orientations and test our interpretation of the misalignment and turbulent fragmentation The IRAS 08303–4303 region provides valuable insights into the rarely observed circumbinary disks around massive YSOs The study demonstrates that a wide binary system can form through turbulent fragmentation on a large scale The C2 condensation appears highly elongated toward the southeast from its continuum peak, hinting at the presence of an unresolved component Such a joint analysis with higher-resolution data would help measure their true orientations and test our interpretation of the misalignment and turbulent fragmentation The IRAS 08303–4303 region provides valuable insights into the rarely observed circumbinary disks around massive YSOs The study demonstrates that a wide binary system can form through turbulent fragmentation on a large scale The C2 condensation appears highly elongated toward the southeast from its continuum peak, hinting at the presence of an unresolved component Such a joint analysis with higher-resolution data would help measure their true orientations and test our interpretation of the misalignment and turbulent fragmentation The IRAS 08303–4303 region provides valuable insights into the rarely observed circumbinary disks around massive YSOs The study demonstrates that a wide binary system can form through turbulent fragmentation on a large scale The C2 condensation appears highly elongated toward the southeast from its continuum peak, hinting at the presence of an unresolved component Such a joint analysis with higher-resolution data would help measure their true orientations and test our interpretation of the misalignment and turbulent fragmentation The IRAS 08303–4303 region provides valuable insights into the rarely observed circumbinary disks around massive YSOs The study demonstrates that a wide binary system can form through turbulent fragmentation on a large scale The C2 condensation appears highly elongated toward the southeast from its continuum peak, hinting at the presence of an unresolved component Such a joint analysis with higher-resolution data would help measure their true orientations and test our interpretation of the misalignment and

Improvements for AI systems

Improved AI system can perform high-resolution kinematic modeling of circumbinary disks by implementing a Keplerian velocity distribution model fitter like Keplerfit to derive enclosed mass ranges between 32 and 61 Msun, as done in Section 4.
Improved AI system can predict the gravitational stability of circumbinary disks using the Toomre Q parameter calculation derived from Equation 4, specifically identifying regions where Q is less than 2, such as the "southeast region of the C2 condensation showing Q < 2".
Improved AI system can quantify mass accretion rates onto primary protostars by utilizing outflow parameters and adopting a fixed jet velocity consistent with typical high-mass protostellar jets, deriving an accretion rate greater than 5 x 10-4 Msun yr-1.
Improved AI system can characterize the thermal structure of molecular regions by performing rotational temperature map analysis using multiple CH3OH transitions, determining that the region surrounding C1 has a higher temperature compared to C2.
Improved AI system can identify potential streamers connected to dense condensations by analyzing integrated line intensity maps for molecules like CH3OH and CH3CN, detecting an arc-like structure extending southeast from C1.

Abstract

We present the ALMA Band 6 continuum and molecular line observations of IRAS 08303-4303, a high-mass star-forming region, with an angular resolution of about 0.3'' (about 700 au at the distance of 2.35 kpc). Six dense condensations are identified in the 1.3 mm continuum, and at least four of them are associated with molecular outflows. The estimated outflow parameters, particularly mass outflow rates at least 10-4 M yr-1, suggest that the driving sources are high-mass young stellar objects. Two of the condensations are forming a wide protobinary system with a separation of about 900 au. They reside within a single rotating structure, identified as a circumbinary disk which has a mass of about 2 M. This structure is traced by multiple molecular lines and exhibits a Keplerian rotation pattern. Based on the Keplerian rotation assumption, the enclosed mass is derived to be between 32 and 61 M: 22-43 M for the primary and 10-18 M for the secondary. The circumbinary disk is on the whole gravitationally stable, yet some parts with Toomre Q < 2 indicate potential fragmentation. Various molecular lines reveal a streamer-like structure connecting to the circumbinary disk, suggesting transfer of material from the envelope to the protobinary system through it. Despite the observational rarity of such circumbinary disks around high-mass YSOs, the high binary fraction among massive stars underscores their significance. This source, therefore, serves as a key laboratory for understanding the formation of high-mass binary systems.