Large quasar group

A large quasar group (LQG) is a collection of quasars (a form of supermassive black hole active galactic nuclei) that form what are thought to constitute the largest astronomical structures in the observable universe. LQGs are thought to be precursors to the sheets, walls and filaments of galaxies found in the relatively nearby universe.^[1]

Prominent LQGs

On January 11, 2013, the discovery of the Huge-LQG was announced by the University of Central Lancashire, as the largest known structure in the universe by that time. It is composed of 74 quasars and has a minimum diameter of 1.4 billion light-years, but over 4 billion light-years at its widest point.^[2] According to researcher and author, Roger Clowes, the existence of structures with the size of LQGs was believed theoretically impossible. Cosmological structures had been believed to have a size limit of approximately 1.2 billion light-years.^[3][4]

List of LQGs

An artist's impression of a single quasar powered by a black hole with a mass two billion times that of the Sun

Redshift, denoted as "z," is a fundamental concept in astrophysics used to measure the spectral line shift in light emitted by celestial objects like quasars due to their motion away from Earth. In the table below, higher redshift values directly correspond to greater cosmic distances.

Large Quasar Groups

LQG	Date	Mean Distance	Dimension	# of quasars	Notes
Webster LQG (LQG 1)	1982	z=0.37	100 Mpc	5	First LQG discovered. At the time of its discovery, it was the largest structure known.[1][4][5]
Crampton–Cowley–Hartwick LQG (LQG 2, CCH LQG, Komberg-Kravtsov-Lukash LQG 10)	1987	z=1.11	60 Mpc	28	Second LQG discovered [1][4][6]
Clowes–Campusano LQG (U1.28, CCLQG, LQG 3)	1991	z=1.28	longest dimension: 630 Mpc	34	Third LQG discovered [4][7]
U1.90	1995	z=1.9	120 Mpc/h	10	Discovered by Graham, Clowes, Campusano.[1][6][8]
7Sf Group (U0.19)	1995	z=0.19	60 Mpc/h	7	Discovered by Graham, Clowes, Campusano; this is a grouping of 7 Seyfert galaxies.[1][6][8]
Komberg–Kravtsov–Lukash LQG 1	1996	z=0.6	R=96 Mpc/h	12	Discovered by Komberg, Kravtsov, Lukash.[1][6]
Komberg–Kravtsov–Lukash LQG 2	1996	z=0.6	R=111 Mpc/h	12	Discovered by Komberg, Kravtsov, Lukash.[1][6]
Komberg–Kravtsov–Lukash LQG 3	1996	z=1.3	R=123 Mpc/h	14	Discovered by Komberg, Kravtsov, Lukash.[1][6]
Komberg–Kravtsov–Lukash LQG 4	1996	z=1.9	R=104 Mpc/h	14	Discovered by Komberg, Kravtsov, Lukash.[1][6]
Komberg–Kravtsov–Lukash LQG 5	1996	z=1.7	R=146 Mpc/h	13	Discovered by Komberg, Kravtsov, Lukash.[1][6]
Komberg–Kravtsov–Lukash LQG 6	1996	z=1.5	R=94 Mpc/h	10	Discovered by Komberg, Kravtsov, Lukash.[1][6]
Komberg–Kravtsov–Lukash LQG 7	1996	z=1.9	R=92 Mpc/h	10	Discovered by Komberg, Kravtsov, Lukash.[1][6]
Komberg–Kravtsov–Lukash LQG 8	1996	z=2.1	R=104 Mpc/h	12	Discovered by Komberg, Kravtsov, Lukash.[1][6]
Komberg–Kravtsov–Lukash LQG 9	1996	z=1.9	R=66 Mpc/h	18	Discovered by Komberg, Kravtsov, Lukash.[1][6]
Komberg–Kravtsov–Lukash LQG 11	1996	z=0.7	R=157 Mpc/h	11	Discovered by Komberg, Kravtsov, Lukash.[1][6]
Komberg–Kravtsov–Lukash LQG 12	1996	z=1.2	R=155 Mpc/h	14	Discovered by Komberg, Kravtsov, Lukash.[1][6]
Newman LQG (U1.54)	1998	z=1.54	150 Mpc/h	21	Discovered by P.R. Newman[9] et al. This structure is parallel to the CCLQG, with its discovery, suggesting that the cellular structure of sheets and voids already existed in this era, as found in later void bubbles and walls of galaxies.,[1][7]
Tesch–Engels LQG	2000	z=0.27	140 Mpc/h	7	The first X-ray selected LQG.[1]
U1.11	2011	z=1.11	longest dimension: 780 Mpc	38	[4][7]
Huge-LQG (U1.27)	2013	z=1.27	characteristic size: 500 Mpc longest dimension: 1240 Mpc	73	The largest structure known in the observable universe[4][10] until it was eclipsed by the Hercules–Corona Borealis Great Wall found one year later.[11][12][13]

See also

• List of largest cosmic structures
• Large-scale structure of the cosmos

References

1. R.G.Clowes; "Large Quasar Groups - A Short Review"; 'The New Era of Wide Field Astronomy', ASP Conference Series, Vol. 232.; 2001; Astronomical Society of the Pacific; ISBN 1-58381-065-X ; Bibcode:2001ASPC..232..108C
2. Wall, Mike (2013-01-11). "Largest structure in universe discovered". Fox News.
3. Wall, Mike (2013-01-11). "Largest Structure In Universe, Large Quasar Group, Challenges Cosmological Principle". The Huffington Post.
4. Clowes, R. G.; Harris, K. A.; Raghunathan, S.; Campusano, L. E.; Sochting, I. K.; Graham, M. J. (January 11, 2013). "A structure in the early Universe at z ~ 1.3 that exceeds the homogeneity scale of the R-W concordance cosmology". Monthly Notices of the Royal Astronomical Society. 429 (4): 2910–2916. arXiv:1211.6256. Bibcode:2013MNRAS.429.2910C. doi:10.1093/mnras/sts497.
5. Webster, Adrian (May 1982). "The clustering of quasars from an objective-prism survey". Monthly Notices of the Royal Astronomical Society. 199 (3): 683–705. Bibcode:1982MNRAS.199..683W. doi:10.1093/mnras/199.3.683.
6. Komberg, Boris V.; Kravtsov, Andrey V.; Lukash, Vladimir N. (October 1996). "The search and investigation of the Large Groups of Quasars". Monthly Notices of the Royal Astronomical Society. 282 (3): 713–722. arXiv:astro-ph/9602090. doi:10.1093/mnras/282.3.713.
7. Clowes, Roger; Luis E. Campusano, Matthew J. Graham and Ilona K. S¨ochting (2001-09-01). "Two close Large Quasar Groups of size ~ 350 Mpc at z ~ 1.2". Monthly Notices of the Royal Astronomical Society. 419 (1): 556–565. arXiv:1108.6221. Bibcode:2012MNRAS.419..556C. doi:10.1111/j.1365-2966.2011.19719.x. S2CID 31553670.
8. Graham, M. J.; Clowes, R. G.; Campusano, L. E. (1995). "Finding Quasar Superstructures". Monthly Notices of the Royal Astronomical Society. 275 (3): 790. Bibcode:1995MNRAS.275..790G. doi:10.1093/mnras/275.3.790.
9. Newman, Peter R (1999). Large groups of quasars in an ultraviolet-excess survey (Thesis). University of Central Lancashire. Bibcode:1999PhDT..........N. doi:10.17030/uclan.thesis.00020658.
10. ScienceDaily, "Biggest Structure in Universe: Large Quasar Group Is 4 Billion Light Years Across", Royal Astronomical Society, 11 January 2013 (accessed 13 January 2013)
11. Horváth, István; Hakkila, Jon; Bagoly, Zsolt (2014). "Possible structure in the GRB sky distribution at redshift two". Astronomy & Astrophysics. 561: L12. arXiv:1401.0533. Bibcode:2014A&A...561L..12H. doi:10.1051/0004-6361/201323020. S2CID 24224684.
12. Horvath, I.; Hakkila, J.; Bagoly, Z. (2013). "The largest structure of the Universe, defined by Gamma-Ray Bursts". arXiv:1311.1104 [astro-ph.CO].
13. Klotz, Irene (2013-11-19). "Universe's Largest Structure is a Cosmic Conundrum". Discovery. Retrieved 2013-11-22.

Further reading

• R. G. Clowes; "Large Quasar Groups - A Short Review"; 'The New Era of Wide Field Astronomy', ASP Conference Series, Vol. 232.; 2001; Astronomical Society of the Pacific; ISBN 1-58381-065-X ; Bibcode:2001ASPC..232..108C