Institute of Integrative and Interdisciplinary Research

Astrophysics and Star Formation

This program investigates the fundamental physical mechanisms of star formation, with particular emphasis on the role of binary and multiple systems as essential regulators of angular momentum, mass accretion, and dynamical stability. Drawing on observational constraints from Gaia, JWST, ALMA, and CARMENES, as well as theoretical and numerical modeling, the research addresses unresolved questions concerning the necessity of binarity, persistence-selection effects, hidden formation histories, and the limits of observational inference in protostellar environments.

The following research questions outline the current frontier problems pursued within this framework. The accompanying reference collection integrates foundational literature with ongoing contributions developed at the Institute.

Research Questions: Astrophysics and Star Formation

  • What physical conditions are strictly required for the transition from diffuse, turbulently supported molecular gas to irreversible gravitational collapse?
  • Are early binary or multiple configurations dynamically favored over isolated protostellar collapse under realistic magnetized and turbulent conditions?
  • Can binary formation be understood not as an optional outcome, but as a necessary mechanism for angular momentum regulation and mass growth?
  • Which environmental triggers most effectively initiate star formation in different regimes, including low-metallicity and high-redshift environments?
  • What physical processes determine whether a collapsing core fragments into binaries or remains single?
  • How do magnetic fields, turbulence, and radiation feedback jointly constrain the stability of young protostellar systems?
  • Why do many observed stellar systems appear dynamically “simple” despite likely having undergone complex early interactions?
  • To what extent are past binary interactions observationally erasable, leading to hidden formation histories?
  • Can the apparent dominance of binaries be quantitatively explained as a persistence-selected outcome of open, embedded dynamics?
  • What are the strict kinematic and geometric limits on accretion in binary versus isolated protostars?
  • How does episodic accretion and mass recycling operate differently in binary systems compared to single-star formation?
  • Which observable chemical or kinematic signatures could reliably reveal prior coupling or merger events?
  • Can numerical simulations reproduce the proposed necessity of binaries under a wide range of initial conditions?
  • How sensitive are stellar formation pathways to small early asymmetries or advantages in mass and angular momentum?
  • What role do protostellar mergers play in the production of apparently single massive stars?
  • Is it possible to construct a minimal set of physical constraints that any viable theory of star formation must satisfy?
  • How can AI-driven parameter exploration help map the high-dimensional space of initiation and stability conditions?
  • Which aspects of current observational surveys (Gaia, JWST, ALMA) can most directly test the persistence-selection hypothesis?
  • Are ternary or higher-order systems required in some regimes to achieve dynamical closure where binaries alone are insufficient?
  • What predictive framework can integrate initiation, stability, and observational asymmetry into a coherent, falsifiable model of stellar formation?

Publications

  • Abbott, R., et al. (LIGO-Virgo-KAGRA Collaboration). (2023). Population of merging compact binaries inferred using gravitational waves through GWTC-3. Physical Review X, 13(1), 011048. https://doi.org/10.1103/PhysRevX.13.011048
  • Alves, F. O., Caselli, P., Girart, J. M., Segura-Cox, D., Franco, G. A. P., Schmiedeke, A., & Zhao, B. (2019). Gas flow and accretion via spiral streamers and circumstellar disks in a young binary protostar. Science, 366(6461), 90–93. https://doi.org/10.1126/science.aaw3491
  • Arenou, F., Babusiaux, C., & Gaia Collaboration. (2023). Gaia Data Release 3: Stellar multiplicity, a teaser for the hidden treasure. Astronomy & Astrophysics, 674, A34. https://doi.org/10.1051/0004-6361/202243782
  • Arzoumanian, D., André, P., Könyves, V., Palmeirim, P., Roy, A., Schneider, N., … & Ward-Thompson, D. (2019). Characterizing the properties of nearby molecular filaments observed with Herschel. Astronomy & Astrophysics, 621, A42. https://doi.org/10.1051/0004-6361/201832725
  • Batygin, K., Brown, M. E., & Betts, H. (2024). The generation of the distant Kuiper Belt by Planet Nine from an initially broad perihelion distribution. The Astrophysical Journal Letters, 966(2), L2. https://doi.org/10.3847/2041-8213/ad3cd2
  • Bora, K., Sengupta, C., & Chakraborty, A. (2024). On the detectability and parameterisation of binary stars with broadband photometry. Monthly Notices of the Royal Astronomical Society, 528(3), 4272–4290. https://doi.org/10.1093/mnras/stae274
  • Broekgaarden, F. S., Berger, E., Neijssel, C. J., Vigna-Gómez, A., Chattopadhyay, D., Stevenson, S., … & Zapartas, E. (2022). Impact of massive binary star and cosmic evolution on gravitational wave observations II: Double compact object rates and properties. Monthly Notices of the Royal Astronomical Society, 516(4), 5737–5761. https://doi.org/10.1093/mnras/stac1677
  • Caballero, J. A., González-Álvarez, E., Brady, M., Trifonov, T., Ellis, T. G., Cifuentes, C., … & Zechmeister, M. (2022). The CARMENES search for exoplanets around M dwarfs: Two terrestrial planets orbiting G 264-012 and one terrestrial planet orbiting Gl 393. Astronomy & Astrophysics, 665, A120. https://doi.org/10.1051/0004-6361/202243548
  • Chevance, M., Kruijssen, J. M. D., Hygate, A. P. S., Schruba, A., Longmore, S. N., Groves, B., … & Schinnerer, E. (2020). The lifecycle of molecular clouds in nearby star-forming disc galaxies. Monthly Notices of the Royal Astronomical Society, 493(2), 2872–2909. https://doi.org/10.1093/mnras/stz3525
  • Cifuentes, C., Caballero, J. A., González-Payo, J., Amado, P. J., Béjar, V. J. S., Burgasser, A. J., … & Zapatero Osorio, M. R. (2025). CARMENES input catalogue of M dwarfs: IX. Multiplicity from close spectroscopic binaries to ultra-wide systems. Astronomy & Astrophysics, 693, A228. https://doi.org/10.1051/0004-6361/202452527
  • Fukui, Y., Habe, A., Inoue, T., Enokiya, R., Tachihara, K., Torii, K., … & Yamamoto, H. (2021). Cloud–cloud collisions and triggered star formation. Publications of the Astronomical Society of Japan, 73(Supplement_1), S1–S34. https://doi.org/10.1093/pasj/psaa103
  • Gaia Collaboration, Panuzzo, P., Mazeh, T., Arenou, F., Holl, B., Frémat, Y., … & Zwitter, T. (2024). Discovery of a dormant 33 solar-mass black hole in a wide binary. Astronomy & Astrophysics, 686, L2. https://doi.org/10.1051/0004-6361/202449763
  • Hacar, A., Clark, S., Heitsch, F., Kainulainen, J., Panopoulou, G., Seifried, D., & Smith, R. (2023). Initial conditions for star formation: A physical description of the filamentary ISM. In Protostars and Planets VII. Astronomical Society of the Pacific. https://doi.org/10.48550/arXiv.2203.09562
  • Hennebelle, P., & Inutsuka, S. (2019). The role of magnetic field in molecular cloud formation and evolution. Frontiers in Astronomy and Space Sciences, 6, 5. https://doi.org/10.3389/fspas.2019.00005
  • Howell, S. B., Matson, R. A., & Marzari, F. (2022). Editorial: The effect of stellar multiplicity on exoplanetary systems. Frontiers in Astronomy and Space Sciences, 8, 830980. https://doi.org/10.3389/fspas.2021.830980
  • Kriger, B. (2025). Binary-first star formation as a persistence-selected outcome of open, embedded protostellar dynamics. Zenodo. https://doi.org/10.5281/zenodo.18155356
  • Kriger, B. (2026). Can a star be proven single? Observational limits and theoretical implications. Zenodo. https://doi.org/10.5281/zenodo.18203209
  • Kriger, B. (2026). Survival of the bound: A quantitative theory of persistence-driven binary dominance in dense star-forming regions. Zenodo. https://doi.org/10.5281/zenodo.18155400
  • Kriger, B. (2026). Swept-volume geometry and overlap corrections in protostellar binary accretion: A kinematic upper bound and its limitations. Zenodo. https://doi.org/10.5281/zenodo.18155283
  • Kriger, B. (2026). The paradox of protostellar core formation: A critical assessment of whether current theoretical mechanisms are sufficient. Zenodo. https://doi.org/10.5281/zenodo.18164699
  • Kriger, B. (2026). Why binary systems are optimal for star formation. Zenodo. https://doi.org/10.5281/zenodo.18144257
  • Kuruwita, R., & Haugbølle, T. (2023). The role of the envelope in the evolution of protostellar discs. Astronomy & Astrophysics, 674, A112. https://doi.org/10.1051/0004-6361/202245702
  • Portegies Zwart, S. (2024). The formation of the Oort Cloud and the origin of Sedna-like objects. Astronomy & Astrophysics, 682, A141. https://doi.org/10.1051/0004-6361/202348530
  • Ribas, I., Reiners, A., Zechmeister, M., Caballero, J. A., Bauer, F. F., Béjar, V. J. S., … & Zimmerman, K. (2023). The CARMENES search for exoplanets around M dwarfs: A long-period planet around GJ 1151 and a planet candidate around GJ 1148. Astronomy & Astrophysics, 670, A139. https://doi.org/10.1051/0004-6361/202244879
  • Sicilia, D., Mapelli, M., Santoliquido, F., Bouffanais, Y., Iorio, G., Costa, G., & Artale, M. C. (2024). The mass budget of stellar-mass black holes in the Milky Way. Monthly Notices of the Royal Astronomical Society, 527(4), 11842–11855. https://doi.org/10.1093/mnras/stad3998
  • Stanway, E. R., & Eldridge, J. J. (2019). Re-evaluating old stellar populations. Monthly Notices of the Royal Astronomical Society, 479(1), 75–93. https://doi.org/10.1093/mnras/sty1353
  • Tobin, J. J., Offner, S. S. R., Kratter, K. M., Megeath, S. T., Sheehan, P. D., Looney, L. W., … & van ‘t Hoff, M. L. R. (2022). The VLA/ALMA Nascent Disk and Multiplicity (VANDAM) survey of Orion protostars. VI. Insights from radiative transfer modeling. The Astrophysical Journal, 925(1), 39. https://doi.org/10.3847/1538-4357/ac36d2
  • Vorobyov, E. I., Akimkin, V., Stoyanovskaya, O., Pavlyuchenkov, Y., & Liu, H. B. (2018). Early evolution of viscous and self-gravitating circumstellar disks with a dust component. Astronomy & Astrophysics, 614, A98. https://doi.org/10.1051/0004-6361/201731690
  • Yen, H.-W., Takakuwa, S., Gu, P.-G., Hirano, N., Lee, Y.-N., Muto, T., … & Aso, Y. (2019). HL Tau disk in HCO+ (3–2) and (1–0) with ALMA: Gas density, temperature, gap, and one-arm spiral. The Astrophysical Journal, 880(2), 69. https://doi.org/10.3847/1538-4357/ab29f8