The Cosmic Web — Voids, Sheets, and Coordination

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   Note 2. eRASS1 catalog: A. Merloni et al., “The SRG/eROSITA All-Sky Survey: The first X-ray catalog,” A&A 682 (2024): A34. The Abell 3667–3651 filament: J. Dietl et al., “Discovery of a >13 Mpc long X-ray filament,” A&A 691 (2024): A286.

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   Note 10. Pisani, A., Sutter, P.M., Hamaus, N., et al., “Counting voids to probe dark energy,” Physical Review D 92 (2015): 083531; Verza, G., Pisani, A., Carbone, C., Hamaus, N., and Guzzo, L., “The Void Size Function in Dynamical Dark Energy Cosmologies,” JCAP 2019:12 (2019): 040; Bos, E.G.P., van de Weygaert, R., Dolag, K., and Pettorino, V., “The darkness that shaped the void,” MNRAS 426:1 (2012): 440–461.

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    Note 11. Sutter, P.M., Lavaux, G., Wandelt, B.D., and Weinberg, D.H., “A first application of the Alcock-Paczynski test to stacked cosmic voids,” The Astrophysical Journal 761 (2012): 187.

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    Note 12. Void galaxy properties: Void Galaxy Survey (C. M. Moorman et al., MNRAS 458, 2016: 394–406); CAVITY project (J. Domínguez-Gómez et al., A&A 680, 2023: A111); CO-CAVITY molecular gas survey (J. Romero-Gómez et al., A&A 692, 2024). The TNG300 simulation reproduces the evolutionary delay (A. M. Rodríguez-Medrano, V. Springel, F. A. Stasyszyn, and D. J. Paz, “The evolutionary path of void galaxies in TNG300 simulation,” MNRAS 528, 2024: 2822–2833).

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    Note 13. Zucker, Catherine, Goodman, Alyssa A., Alves, João, et al., “Star formation near the Sun is driven by expansion of the Local Bubble,” Nature 601 (2022): 334-337.

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    Note 13b. Koll, Dominik, et al., “Local Interstellar Cloud Structure Imprinted in Antarctic Ice by Supernova ⁶⁰Fe,” Physical Review Letters (2026). DOI: 10.1103/nxjq-jwgp.

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    Note 13c. Kreckel, K., Egorov, O. V., Drory, N., et al., “SDSS-V LVM: Verifying what, and where, the ‘Galactic Center’ Lobe is,” Astronomy & Astrophysics 710, A205 (2026). DOI: 10.1051/0004-6361/202659505. arXiv:2604.16601. Comparing ionized-gas reddening against 3D dust maps places the shell at roughly 2 kiloparsecs (the Galactic center lies at about 8); [N II] kinematics show a uniform velocity within 5 km/s of rest, with no expansion signature or Galactic-center rotation gradient. The authors identify Barnard’s Loop as a possible analog and themselves propose the “Greatly Confused Loop” rereading.

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    Note 14. DESI Collaboration (A.G. Adame et al.), “DESI 2024 VI: Cosmological Constraints from BAO,” JCAP 2025:02. arXiv:2404.03002.

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    Note 16. Indranil Banik, Harry Desmond, Vasileios Kalaitzidis, and Sergij Mazurenko, “The local void model for the Hubble and BAO tensions,” arXiv:2602.03928 (2026).

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    Note 17. Hierarchical void scaling: N. Hamaus, A. Pisani, P. M. Sutter, et al., Physical Review Letters 117 (2016): 091302; Shim, J. and Park, C., MNRAS 527 (2024).

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    Note 19. S. Granett, M. C. Neyrinck, and I. Szapudi, “An imprint of superstructures on the microwave background,” The Astrophysical Journal Letters 683 (2008): L99–L102. For recent approaches: A. Kovács et al., arXiv:2510.16799 (2025).

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    Note 26. Ewoud Wempe, Amina Helmi, et al., “The mass distribution in and around the Local Group,” Nature Astronomy, 27 January 2026. The reconstruction used BORG (Bayesian Origin Reconstruction from Galaxies) with 169 resimulations run in the Gadget-4 code. The sheet stretches about 30 million light-years, and its central plane is about twice the cosmic average density. Local Group halo mass: 3.3 ± 0.6 × 10¹² M☉.

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    Note 27. Dan P. Marrone et al., “Galaxy growth in a massive halo in the first billion years of cosmic history,” Nature, 6 December 2017. DOI: 10.1038/nature24629.

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    Note 28. Andreas Koch and Eva K. Grebel, “The Anisotropic Distribution of M31 Satellite Galaxies,” The Astronomical Journal 131(3), 1405–1415 (2006).

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    Note 29. Rodrigo A. Ibata et al., “A vast, thin plane of co-rotating dwarf galaxies orbiting the Andromeda galaxy,” Nature 493, 62–65 (2013).

32. 29b

    Note 29b. A third such plane orbits Centaurus A: Oliver Müller, Marcel S. Pawlowski, Federico Lelli et al., “The coherent motion of Cen A dwarf satellite galaxies remains a challenge for ΛCDM cosmology,” Astronomy & Astrophysics 645, L5 (2021). The tidal-debris alternative is the standing rival account for all three systems; it explains the co-rotation naturally, but tidal dwarfs should carry little dark matter while the internal motions of these satellites look dark-matter dominated, and reconciling the two takes this account outside standard cosmology as well. Tuomas Sawala et al., “The Milky Way’s plane of satellites is consistent with ΛCDM,” Nature Astronomy 7, 481–491 (2023) argue the Milky Way plane is a transient alignment. The debate is unresolved.

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    Note 30. Andrew C. Fabian, “Observational Evidence of Active Galactic Nuclei Feedback,” Annual Review of Astronomy and Astrophysics 50, 455–489 (2012).

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    Note 31. Brian R. McNamara and Paul E.J. Nulsen, “Mechanical Feedback from Active Galactic Nuclei in Galaxies, Groups, and Clusters,” New Journal of Physics 14, 055023 (2012).

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    Note 42. G. V. Pignataro, S. P. O’Sullivan, A. Bonafede, et al., “Detection of Magnetic Fields in Superclusters of Galaxies,” Astronomy and Astrophysics 696 (2025): A203. DOI: 10.1051/0004-6361/202553709.

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    Note 45. Markus J. Aschwanden, “Order out of Randomness: Self-Organization Processes in Astrophysics,” Space Science Reviews 214, 55 (2018).

Chapter 13b: The Cosmic Web: Voids, Sheets, and Coordination The Deeper Law