Local Hole

Not to be confused with Local Void.

The KBC Void (or Local Hole) is an immense, comparatively empty region of space, named after astronomers Ryan Keenan, Amy Barger, and Lennox Cowie, who studied it in 2013.^[1] The existence of a local underdensity has been the subject of many pieces of literature and research articles.^[2][3][4]

The underdensity is proposed to be roughly spherical, approximately 2 billion light-years (600 megaparsecs, Mpc) in diameter. As with other voids, it is not completely empty; it contains the Milky Way, the Local Group, and the larger part of the Laniakea Supercluster. The Milky Way is within a few hundred million light-years of the void's center.^[5]

It is debated whether the existence of the KBC void is consistent with the ΛCDM model. While Haslbauer et al. say that voids as large as the KBC void are inconsistent with ΛCDM,^[6] Sahlén et al. argue that the existence of supervoids such as the KBC void is consistent with ΛCDM.^[7] Galaxies inside a void experience a gravitational pull from outside the void, which yields a larger local value for the Hubble constant, a cosmological measure of how fast the universe expands. Some authors have proposed the structure as the cause of the discrepancy between measurements of the Hubble constant using galactic supernovae and Cepheid variables (72–75 km/s/Mpc) and from the cosmic microwave background and baryon acoustic oscillation data (67–68 km/s/Mpc).^[8]

Other work has found no evidence for this in observations, finding the scale of the claimed underdensity to be incompatible with observations which extend beyond its radius.^[9] Important deficiencies were subsequently pointed out in this analysis, leaving open the possibility that the Hubble tension is indeed caused by outflow from the KBC void, albeit in the context of MOND gravity rather than general relativity.^[6] It was later discovered that this outflow model successfully predicted the bulk flow curve, an important measure of the velocity field in the local Universe.^[10]

See also

• Void (astronomy)
• Giant Void
• Local Void
• Observable universe
• List of largest voids
• Hubble bubble (astronomy)
• Northern Local Supervoid
• Southern Local Supervoid

References

1. Keenan, Ryan C.; Barger, Amy J.; Cowie, Lennox L. (2013). "Evidence for a ~300 Mpc Scale Under-density in the Local Galaxy Distribution". The Astrophysical Journal. 775 (1): 62. arXiv:1304.2884. Bibcode:2013ApJ...775...62K. doi:10.1088/0004-637X/775/1/62. S2CID 118433293.
2. Busswell, G. S.; Shanks, T.; W. J. Frith, P. J. O.; Metcalfe, N.; Fong, R. (2004-11-11). "The local hole in the galaxy distribution: new optical evidence". Monthly Notices of the Royal Astronomical Society. 354 (4): 991–1004. arXiv:astro-ph/0302330. Bibcode:2004MNRAS.354..991B. doi:10.1111/j.1365-2966.2004.08217.x. ISSN 0035-8711. S2CID 18260737.
3. Frith, W. J.; Busswell, G. S.; Fong, R.; Metcalfe, N.; Shanks, T. (November 2003). "The local hole in the galaxy distribution: evidence from 2MASS". Monthly Notices of the Royal Astronomical Society. 345 (3): 1049–1056. arXiv:astro-ph/0302331. Bibcode:2003MNRAS.345.1049F. doi:10.1046/j.1365-8711.2003.07027.x. S2CID 2115068.
4. Wong, Jonathan H W; Shanks, T; Metcalfe, N; Whitbourn, J R (2022-03-02). "The local hole: a galaxy underdensity covering 90 per cent of sky to ≈200 Mpc". Monthly Notices of the Royal Astronomical Society. 511 (4). Oxford University Press (OUP): 5742–5755. arXiv:2107.08505. doi:10.1093/mnras/stac396. ISSN 0035-8711.
5. Siegel, Ethan. "We're Way Below Average! Astronomers Say Milky Way Resides In A Great Cosmic Void". Forbes. Retrieved 2017-06-09.
6. Haslbauer, M.; Banik, I.; Kroupa, P. (2020-12-21). "The KBC void and Hubble tension contradict LCDM on a Gpc scale – Milgromian dynamics as a possible solution". Monthly Notices of the Royal Astronomical Society. 499 (2): 2845–2883. arXiv:2009.11292. Bibcode:2020MNRAS.499.2845H. doi:10.1093/mnras/staa2348. ISSN 0035-8711.
7. Sahlén, Martin; Zubeldía, Íñigo; Silk, Joseph (2016). "Cluster–Void Degeneracy Breaking: Dark Energy, Planck, and the Largest Cluster and Void". The Astrophysical Journal Letters. 820 (1): L7. arXiv:1511.04075. Bibcode:2016ApJ...820L...7S. doi:10.3847/2041-8205/820/1/L7. ISSN 2041-8205. S2CID 119286482.
8. Shanks, T; Hogarth, L M; Metcalfe, N (2019-03-21). "Gaia Cepheid parallaxes and 'Local Hole' relieve H 0 tension". Monthly Notices of the Royal Astronomical Society: Letters. 484 (1): L64–L68. arXiv:1810.02595. Bibcode:2019MNRAS.484L..64S. doi:10.1093/mnrasl/sly239. ISSN 1745-3925.
9. Kenworthy, W. D’Arcy; Scolnic, Dan; Riess, Adam (2019-04-24). "The Local Perspective on the Hubble Tension: Local Structure Does Not Impact Measurement of the Hubble Constant". The Astrophysical Journal. 875 (2): 145. arXiv:1901.08681. Bibcode:2019ApJ...875..145K. doi:10.3847/1538-4357/ab0ebf. ISSN 1538-4357. S2CID 119095484.
10. Mazurenko, S.; Banik, I.; Kroupa, P.; Haslbauer, M. (2024-01-21). "A simultaneous solution to the Hubble tension and observed bulk flow within 250/h Mpc". Monthly Notices of the Royal Astronomical Society. 527 (3): 4388–4396. arXiv:2311.17988. Bibcode:2024MNRAS.527.4388M. doi:10.1093/mnras/stad3357. ISSN 0035-8711.

Further reading

• Hoscheit, Benjamin L.; Barger, Amy J. (2018-02-09). "The KBC Void: Consistency with Supernovae Type Ia and the Kinematic SZ Effect in a ΛLTB Model". The Astrophysical Journal. 854 (1): 46. arXiv:1801.01890. Bibcode:2018ApJ...854...46H. doi:10.3847/1538-4357/aaa59b. S2CID 119220508.