Pending Problems in QSOs
Martín López-Corredoira
DOI: 10.4236/ijaa.2011.12011   PDF    HTML     5,783 Downloads   11,982 Views   Citations


Quasars (Quasi Stellar Objects, abbreviated as QSOs) are still nowadays, close to half a century after their discovery, objects which are not completely understood. In this brief review a description of the pending problems, inconsistencies and caveats in the QSO's research is presented. The standard paradigm model based on the existence of very massive black holes that are responsible for the QSO's huge luminosities, re-sulting from to their cosmological redshifts, leaves many facts without explanation. There are several obser-vations which lack a clear explanation, for instance: the absence of bright QSOs at low redshifts, a mysteri-ous evolution not properly understood; the inconsistencies of the absorption lines, such as the different structure of the clouds along the QSO's line of sight and their tangential directions; the spatial correlation between QSOs and galaxies; and many others.

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M. López-Corredoira, "Pending Problems in QSOs," International Journal of Astronomy and Astrophysics, Vol. 1 No. 2, 2011, pp. 73-82. doi: 10.4236/ijaa.2011.12011.

Conflicts of Interest

The authors declare no conflicts of interest.


[1] W. H. de Vries, R. H. Becker and R. L. White, “Double-Lobed Radio Quasars from the Sloan Digital Sky Survey,” The Astronomical Journal, Vol. 131, No. 2, 2006, pp. 666-679.
[2] M. J. Rees, “Black Hole Models for Active Galactic Nuclei,” Annual Review of Astronomy and Astrophysics, Vol. 22, 1984, pp. 471-506.
[3] R. Antonucci, “Unified Models for Active Galactic Nuclei and Quasars,” Annual Review of Astronomy and Astrophysics, Vol. 31, 1993, pp. 473-521.
[4] A. K. Kembhavi and J. V. Narlikar, “Quasars and Active Galactic Nuclei,” Cambridge University Press, Cambridge, 1999.
[5] S. F. Yamada, Y. Shioya, Y. Taniguchi, et al., “Are Two z~6 Quasars Gravitationally Lensed?” Publications of the Astronomical Society of Japan, Vol. 55, No. 4, 2003, pp. 733-738.
[6] G. T. Richards, M. A. Strauss, B. Pindor, et al., “A Snapshot Survey for Gravitational Lenses among z>=4.0 Quasars. I. The z > 5.7 Sample,” The Astronomical Journal, Vol. 127, No. 3, 2004, pp. 1305-1312.
[7] S. G. Djorgovski, M. Volonteri, V. Springel, V. Bromm and G. Meylan, “The Origins and the Early Evolution of Quasars and Supermassive Black Holes,” In: H. Kleinert, R. T. Jantzen and R. Ruffini, Eds., Recent Developments in Theoretical and Experimental General Relativity, Gravitation and Relativistic Field Theories (11th Marcel Grossmann Meeting), World Scientific Publishing, Singapore, 2008, pp. 340-367.
[8] W. Kundt, “Critical Thoughts on Cosmology,” In: Cosmology and Gravitation: XIII Brazilian School on Cosmology and Gravitation (AIP Conference Proceedings), AIP, Melville, New York, Vol. 1132, 2009, pp. 288- 302.
[9] H. C. Arp, “Intergalactic Magnetic Field and the Distance of Quasars from Faraday Rotation,” Physics Letters A, Vol. 129, No. 3, 1988, pp. 135-139. doi:10.1016/0375-9601(88)90129-6
[10] M. R. S. Hawkins, “On Time Dilation in Quasar Light Curves,” Monthly Notices of the Royal Astronomical Society, Vol. 405, No. 3, 2010, pp. 1940-1946.
[11] A. Hewitt and G. Burbidge, “A New Optical Catalog of Quasi-Stellar Objects,” Astrophysical Journal Supplement Series, Vol. 63, 1987, pp. 1-246. doi:10.1086/191163
[12] M. Schramm, L. Wisotzki and K. Jahnke, “Host Galaxies of Bright High Redshift Quasars: Luminosities and Colours,” Astronomy & Astrophysics, Vol. 478, No. 2, 2008, pp. 311-319.
[13] P. Magain, G. Letawe, F. Courbin, P. Jablonka, K. Jahnke, L. Wisotzki and G. Meylan, “Discovery of a Bright Quasar without a Massive Host Galaxy,” Nature, Vol. 473, 2005, pp. 381-384. doi:10.1038/nature04013
[14] F. Walter, D. A. Riechers, C. L. Carilli, F. Bertoldi, A. Weiss and P. Cox, “High-Resolution CO Imaging of High-Redshift QSO Host Galaxies,” In: A. J. Baker, J. Glenn, A. I. Harris, J. G. Mangum and M. S. Yun, Eds., From Z-Machines to ALMA: (Sub) Millimeter Spectroscopy of Galaxies (ASP Conference Series), ASP, San Francisco, Vol. 375, 2007, p. 182.
[15] S. J. Curran, M. T. Whiting and J. K. Webb, “Where Is the Cold Neutral Gas in the Hosts of High Redshift AGN?” Memorie della Società Astronomica Italiana, Vol. 79, 2008, p. 1113.
[16] D. Jain and A. Dev, “Age of High Redshift Objects—A Litmus Test for the Dark Energy Models,” Physical Letters B, Vol. 633, No. 4-5, 2006, pp. 436-440. doi:10.1016/j.physletb.2005.12.007
[17] X. Fan, V. K. Narayanan, R. H. Lupton, et al., “A Survey of z > 5.8 Quasars in the Sloan Digital Sky Survey. I. Discovery of Three New Quasars and the Spatial Density of Luminous Quasars at z~6,” The Astronomical Journal, Vol. 122, No. 6, 2001, pp. 2833-2849.
[18] R. H. Becker, X. Fan, R. L. White, et al., “Evidence for Reionization at z~6: Detection of a Gunn-Peterson Trough in a z=6.28 Quasar,” The Astronomical Journal, Vol. 122, No. 6, 2001, pp. 2850-2857.
[19] A. Constantin, J. C. Shields, F. Hamann, C. B. Foltz and F. H. Chaffee, “Emission-Line Properties of z > 4 Quasars,” Astrophysical Journal, Vol. 565, No. 1, 2002, pp. 50-62. doi:10.1086/324395
[20] L. E. Simon, F. W. Hamann and M. Pettini, “Physical Properties of Absorbers in High Redshift Quasars,” In: R. Guzmán, C. Packham, J. M. Rodríguez-Espinosa and S. Torres-Peimbert, Eds., First Light Science with the GTC, Instituto de Astronomaia, Universidad Nacional Autao- noma de Maexico, Miami, Vol. 29, 2007, p. 177.
[21] F. Iwamuro, K. Motohara, T. Maihara, M. Kimura, Y. Yoshii and M. Doi, “Fe II/Mg II Emission-Line Ratios of QSOs within 0 < z < 5.3,” Astrophysical Journal, Vol. 565, No. 1, 2002, pp. 63-77.doi:10.1086/324540
[22] M. Dietrich, F. Hamann, I. Appenzeller and M. Vestergaard, “Fe II/Mg II Emission-Line Ratio in High-Redshift Quasars,” Astrophysical Journal, Vol. 596, No. 2, 2003, pp. 817-829. doi:10.1086/378045
[23] W. Freudling, M. R. Corbin and K. T. Korista, “Iron Emission in z~6 QSOs,” Astrophysical Journal, Vol. 587, No. 2, 2003, pp. L67-L70. doi:10.1086/375338
[24] R. Maiolino, Y. Juarez, R. Mujica, N. Nagar and E. Oliva, “Early Star Formation Traced by the Highest Redshift Quasars,” Astrophysical Journal, Vol. 596, No. 2, 2003, pp. L155-L158. doi:10.1086/379600
[25] A. J. Barth, P. Martini, C. H. Nelson and L. C. Ho, “Iron Emission in the z = 6.4 Quasar SDSS J114816.64+ 525150.3,” Astrophysical Journal, Vol. 594, No. 2, 2003, pp. L95-L98. doi:10.1086/378735
[26] L. Dunne, S. Eales, R. Ivison, H. Morgan and M. Edmunds, “Type II Supernovae as a Significant Source of Interstellar Dust,” Nature, Vol. 424, 2003, pp. 285-287. doi:10.1038/nature01792
[27] P. F. Hopkins, G. T. Richards and L. Hernquist, “An Observational Determination of the Bolometric Quasar Luminosity Function,” Astrophysical Journal, Vol. 654, No. 2, 2007, pp. 731-753. doi:10.1086/509629
[28] M. B. Bell, “Further Evidence That the Redshifts of AGN Galaxies May Contain Intrinsic Components,” Astrophysical Journal, Vol. 667, No. 2, 2007, pp. L129-L132. doi:10.1086/522337
[29] S. Shen, S. D. M. White, H. J. Mo, W. Voges, G. Kauffmann, C. Tremonti and S. F. Anderson, “The Soft X-Ray Properties of Quasars in the Sloan Digital Sky Survey,” Monthly Notices of the Royal Astronomical Society, Vol. 369, No. 4, 2006, pp. 1639-1653. doi:10.1111/j.1365-2966.2006.10463.x
[30] A. H. Bridle and R. A. Perley, “Extragalactic Radio Jets,” Annual Review of Astronomy and Astrophysics, Vol. 22, 1984, pp. 319-358.
[31] M. B. Bell, “Evidence that Quasars and Related Active Galaxies are Good Radio Standard Candles and that They are Likely to Be a Lot Closer than Their Redshifts Imply,” 2006., astro-ph/0602242.
[32] C. Vignali, W. N. Brandt, D. P. Schneider and S. Kaspi, “X-Ray Lighthouses of the High-Redshift Universe. II. Further Snapshot Observations of the Most Luminous z > ~4 Quasars with Chandra,” Astrophysical Journal, Vol. 129, No. 6, 2005, pp. 2519-2530.
[33] L. E. Segal and J. F. Nicoll, “Cosmological Implications of a Large Complete Quasar Sample,” Proceedings of the National Academy of Sciences of the United States of America, Vol. 95, No. 9, 1998, pp. 4804-4807. doi:10.1073/pnas.95.9.4804
[34] M. López-Corredoira and C. M. Gutiérrez, “On the non- evolution of black hole masses and Eddington ratios for QSOs,” Monthly Notices of the Royal Astronomical Society, Submitted, 2011.
[35] A. Stockton, “Compact Companions to QSOs,” Astrophysical Journal, Vol. 257, No. 1, 1982, pp. 33-39. doi:10.1086/159959
[36] G. Canalizo and A. Stockton, “Quasi-Stellar Objects, Ultraluminous Infrared Galaxies, and Mergers,” Astrophysical Journal, Vol. 555, No. 2, 2001, pp. 719-743. doi:10.1086/321520
[37] H. Horst and W. J. Duschl, “A Simple Model for Quasar Density Evolution,” In: Relativistic Astrophysics Legacy and Cosmology, Springer-Verlag, Berlin, 2008, p. 224.
[38] K. Jahnke, L. Wisotzki, F. Courbin and G. Letawe, “Spatial Decomposition of on-Nucleus Spectra of Quasar Host Galaxies,” Monthly Notices of the Royal Astronomical Society, Vol. 378, No. 1, 2007, pp. 23-40. doi:10.1111/j.1365-2966.2007.11623.x
[39] N. Bennert, G. Canalizo, B. Jungwiert, A. Stockton, F. Schweizer, C. Y. Peng and M. Lacy, “Evidence for Mer- ger Remnants in Early-Type Host Galaxies of Low- Redshift QSOs,” Astrophysical Journal, Vol. 677, No. 2, 2008, pp. 846-857. doi:10.1086/529068
[40] N. Bennert, G. Canalizo, B. Jungwiert, A. Stockton, F. Schweizer, C. Y. Peng and M. Lacy, “Fueling QSOs: the Relevance of Mergers,” Memorie della Società Astronomica Italiana, Vol. 79, 2008, pp. 1247-1250.
[41] G. V. Coldwell and D. G. Lambas, “Properties of Galaxies in Sloan Digital Sky Survey Quasar Environments at z < 0.2,” Monthly Notices of the Royal Astronomical Society, Vol. 371, No. 2, 2006, pp. 786-792. doi:10.1111/j.1365-2966.2006.10712.x
[42] M. Wold, M. Lacy, P. B. Lilje and S. Serjeant, “QSO Environments at Intermediate Redshifts,” In: I. Márquez, J. Masegosa, A. del Olmo, L. Lara, E. García and J. Molina, Eds., QSO Host and Their Environments, Kluwer Academic/Plenum Publishers, New York, 2001, p. 33.
[43] P. B. Westoby, C. G. Mundell and I. K. Baldry, “Are Galaxies with Active Galactic Nuclei a Transition Population?” Monthly Notices of the Royal Astronomical Society, Vol. 382, No. 4, 2007, pp. 1541-1551. doi:10.1111/j.1365-2966.2007.12553.x
[44] A. Constantin, F. Hoyle and M. S. Vogeley, “Active Galactic Nuclei in Void Regions,” Astrophysical Journal, Vol. 673, No. 2, 2008, pp. 715-729. doi:10.1086/524310
[45] N. E. Strand, R. J. Brunner and A. D. Myers, “AGN Environments in the Sloan Digital Sky Survey. I. Dependence on Type, Redshift, and Luminosity,” Astrophysical Journal, Vol. 688, No. 1, 2008, pp. 180-189. doi:10.1086/592099
[46] M. Cisternas, K. J. Inskip, K. Jahnke, et al., “The Bulk of the Black Hole Growth Since z ~ 1 Occurs in a Secular Universe: No Major Merger-AGN Connection,” Astrophysical Journal, Vol. 726, No. 1, 2011, pp. 57-70. doi:10.1088/0004-637X/726/2/57
[47] L. C. Ho, “AGNs and Starbursts: What Is the Real Connection?” 2005,, astro-ph/0511157.
[48] M. H. Cohen, “Relativistic Motion in Quasars,” In: S. L. Shapiro and S. A. Teukolsky, Eds., Highlights of Modern Astrophysics, Wiley Interscience, New York, 1986, p. 299.
[49] M. L. Lister, M. H. Cohen, D. C. Homan, et al., “MOJAVE: Monitoring of Jets in Active Galactic Nuclei with VLBA Experiments. VI. Kinematics Analysis of a Complete Sample of Blazar Jets,” The Astronomical Journal, Vol. 138, No. 6, 2009, pp. 1874-1892.
[50] M. J. Rees, “Studies in Radio Source Structure-I. A Relativistically Expanding Model for Variable Quasi-Stellar Radio Sources,” Monthly Notices of the Royal Astronomical Society, Vol. 135, 1967, pp. 345-360.
[51] S. M. Chitre and J. V. Narlikar, “On the Apparent Superluminal Separation of Radio Source Components,” Monthly Notices of the Royal Astronomical Society, Vol. 187, 1979, pp. 655-659.doi:10.1007/BF02714473
[52] J. V. Narlikar and S. M. Chitre, “Faster-Than-Light Motion in Quasars,” Journal of Astrophysics and Astronomy, Vol. 5, 1984, pp. 495-506.
[53] Y. Liu and S. N. Zhang, “The Lorentz Factor Distribution and Luminosity Function of Relativistic Jets in AGNs,” Astrophysical Journal, Vol. 667, No. 2, 2007, pp. 724- 730. doi:10.1086/520040
[54] G. R. Burbidge and S. L. O’Dell, “The Distribution of Redshifts of Quasi-Stellar Objects and Related Emission- Line Objects,” Astrophysical Journal, Vol. 178, 1972, pp. 583-606. doi:10.1086/151820
[55] M. B. Bell and D. McDiarmid, “Six Peaks Visible in the Redshift Distribution of 46,400 SDSS Quasars Agree with the Preferred Redshifts Predicted by the Decreasing Intrinsic Redshift Model,” Astrophysical Journal, Vol. 648, No. 1, 2006, pp. 140-147. doi:10.1086/503792
[56] J. G. Hartnett, “Unknown Selection Effect Simulates Redshift Periodicity in Quasar Number Counts from Sloan Digital Sky Survey,” Astrophysics and Space Science, Vol. 324, No. 1, 2009, pp. 13-16.
[57] K. G. Karlsson, “On the Existence of Significant Peaks in the Quasar Redshift Distribution,” Astronomy & Astrophysics, Vol. 58, No. 1-2, 1977, pp. 237-240.
[58] W. M. Napier, “Statistics of Redshift Periodicities,” In: J.-C. Pecker and J. V. Narlikar, Eds., Current Issues in Cosmology, Cambridge University Press, Cambridge, 2006, pp. 207-216.
[59] E. Hawkins, S. Maddox and M. Merrifield, “No Periodicities in 2dF Redshift Survey Data,” Monthly Notices of the Royal Astronomical Society, Vol. 336, No. 1, 2002, pp. L13-L16. doi:10.1046/j.1365-8711.2002.05940.x
[60] S. M. Tang and S. N. Zhang, “Critical Examinations of QSO Redshift Periodicities and Associations with Galaxies in Sloan Digital Sky Survey Data,” Astrophysical Journal, Vol. 633, No. 1, 2005, pp. 41-51. doi:10.1086/432754
[61] S. M. Tang and S. N. Zhang, “Evidence against Non- Cosmological Redshifts of QSOs in SDSS Data,” In: D. Basu, Ed., Redshifts in Spectral Lines of Quasi Stellar Objects, Research Signpost, Kerala, 2010, pp. 125-136.
[62] W. Napier and G. R. Burbidge, “The Detection of Periodicity in QSO Data Sets,” Monthly Notices of the Royal Astronomical Society, Vol. 342, No. 2, 2003, pp. 601-604. doi:10.1046/j.1365-8711.2003.06567.x
[63] Y. Chu, X. Zhu, G. Burbidge and A. Hewitt, “Statistical Evidence for Possible Association between QSOs and Bright Galaxies,” Astronomy & Astrophysics, Vol. 138, No. 2, 1984, pp. 408-414.
[64] X. F. Zhu and Y. Q. Chu, “The Association between Quasars and the Galaxies of the Virgo Cluster,” Astronomy & Astrophysics, Vol. 297, 1995, pp. 300-304.
[65] G. R. Burbidge, J. V. Narlikar and A. Hewitt, “The Statistical Significance of Close Pairs of QSOs,” Nature, Vol. 317, 1985, pp. 413-415. doi:10.1038/317413a0
[66] G. R. Burbidge, “Noncosmological Redshifts,” Publications of the Astronomical Society of the Pacific, Vol. 113, 2001, pp. 899-902. doi:10.1086/322152
[67] N. Benítez, J. L. Sanz and E. Martínez-González, “Quasar-Galaxy Associations Revisited,” Monthly Notices of the Royal Astronomical Society, Vol. 320, No. 2, 2001, pp. 241-248. doi:10.1046/j.1365-8711.2001.03936.x
[68] E. Gazta?aga, “Correlation between Galaxies and Quasi- Stellar Objects in the Sloan Digital Sky Survey: A Signal from Gravitational Lensing Magnification?” Astrophysical Journal, Vol. 589, No. 1, 2003, pp. 82-99. doi:10.1086/374616
[69] J. G. Nollenberg and L. R. Williams, “Galaxy-Quasar Co- rrelations between APM Galaxies and Hamburg-ESO QSOs,” Astrophysical Journal, Vol. 634, No. 2, 2005, pp. 793-805. doi:10.1086/497103
[70] Y. L. Bukhmastova, “Quasars Lensed by Globular Clusters of Spiral and Elliptical Galaxies,” Astronomy Letters, Vol. 33, No. 6, 2007, pp. 355-367. Translated from: Pi’sma v Astronomicheckii Zhurnal, Vol. 33, No. 6, 2007, pp. 403-416.
[71] H. C. Arp, “QSOs, Redshifts and Controversies,” Interstellar Media, Berkeley, 1987.
[72] H. C. Arp, Catalogue of Discordant Redshift Associations, Apeiron, Montreal, 2003.
[73] M. B. Bell, “Further Evidence for Large Intrinsic Redshifts,” Astrophysical Journal, Vol. 566, No. 2, 2002, pp. 705-711. doi:10.1086/338272
[74] M. B. Bell, “On Quasar Distances and Lifetimes in a Local Model,” Astrophysical Journal, Vol. 567, No. 2, 2002, pp. 801-810.doi:10.1086/338754
[75] M. López-Corredoira and C. M. Gutiérrez, “Research on Candidates for Non-Cosmological Redshifts,” In: E. J. Lerner and J. B. Almeida, Eds., First Crisis in Cosmology Conference (AIP Conference Proceedings 822), AIP, Melville, New York, 2006, pp. 75-92.
[76] M. López-Corredoira, “Apparent Discordant Redshift Qso-Galaxy Associations,” In: H. A. Harutyunian, A. M. Mickaelian and Y. Terzian, Eds., Evolution of Cosmic Objects through Their Physical Activity, (Viktor Ambartsumian’s 100th anniversary), Gitutyun Publishing House of NAS RA, Yerevan, 2010, pp. 196-205.
[77] J. W. Sulentic, “Accretion Disks in Quasars?” In: J.-C. Pecker and J. V. Narlikar, Eds., Current Issues in Cosmology, Cambridge University Press, Cambridge, pp. 37-45.
[78] I. Goldman and J. N. Bahcall, “Asymmetric Emission- Line Regions with Out-Flowing Mass in QSOs and the z/ab/ at Least Equal to z/em/ Systems,” Astronomy & Astrophysics, Vol. 115, No. 2, 1982, pp. 242-248.
[79] A. Robinson, “On the Diversity of the Broad Emission- Line Profiles in Active Galactic Nuclei,” Monthly Notices of the Royal Astronomical Society, Vol. 272, No. 3, 1995, pp. 647-664.
[80] A. Lawrence, “Classification of Active Galaxies and the Prospect of a Unified Phenomenology,” Publications of the Astronomical Society of the Pacific, Vol. 99, 1987, pp. 309-334. doi:10.1086/131989
[81] D. Dultzin, J. J. González, Y. Krongold, et al., “Activity Induced by Gravitational Interaction in Galaxy Pairs. Mixed (E+S) Morphology Pairs,” Memorie della Società Astronomica Italiana, Vol. 79, pp. 1326-1329.
[82] J. W. Colbert and M. A. Malkan, “NICMOS Snapshot Survey of Damped Lyα Quasars,” Astrophysical Journal, Vol. 566, No. 1, 2002, pp. 51-67. doi:10.1086/324779
[83] J. X. Prochaska and A. M. Wolfe, “The UCSD HIRES/ Keck I Damped Lyα Abundance Database. II. The Implications,” Astrophysical Journal, Vol. 566, No. 1, 2002, pp. 68-92. doi:10.1086/338080
[84] D. M. Russell, S. L. Ellison and C. R. Benn, “An Excess of Damped Lyman α Galaxies Near Quasi-Stellar Objects,” Monthly Notices of the Royal Astronomical Society, Vol. 347, No. 1, 2006, pp. 412-422. doi:10.1111/j.1365-2966.2005.09964.x
[85] M. Zaldarriaga, L. Hui and M. Tegmark, “Constraints from the Lyα Forest Power Spectrum,” Astrophysical Journal, Vol. 557, No. 2, 2001, pp. 519-526. doi:10.1086/321652
[86] A. Dobrzycki, J. Bechtold, J. Scott and M. Morita, “A Uniform Analysis of the Lyα Forest at z = 0-5. IV. The Clustering and Evolution of Clouds at z <= 1.7,” Astrophysical Journal, Vol. 571, No. 2, 2002, pp. 654-664. doi:10.1086/339983
[87] J. F. Hennawi and J. X. Prochaska, ”Quasars Probing Quasars. II. The Anisotropic Clustering of Optically Thick Absorbers around Quasars,” Astrophysical Journal, Vol. 655, No. 2, 2007, pp. 735-748. doi:10.1086/509770
[88] G. E. Prochter, J. X. Prochaska, H.-W. Chen, et al., “On the Incidence of Strong Mg II Absorbers along Gamma- Ray Burst Sight Lines,” Astrophysical Journal, Vol. 648, No. 2, 2006, pp. L93-L96. doi:10.1086/508061
[89] N. Tejos, S. López, J. X. Prochaska, J. S. Bloom, H.-W. Chen, M. Dessauges-Zavadsky and M. J. Maureira, “Casting Light on the “Anomalous” Statistics of Mg II Absorbers Toward Gamma-Ray Burst Afterglows: The Incidence of Weak Systems,” Astrophysical Journal, Vol. 706, No. 2, 2009, pp. 1309-1315. doi:10.1088/0004-637X/706/2/1309
[90] N. Tejos, S. López, J. X. Prochaska, H.-W. Chen and M. Dessauges-Zavadsky, “On the Incidence of C IV Absorbers Along the Sight Lines to Gamma-Ray Bursts,” Astrophysical Journal, Vol. 671, No. 1, 2007, pp. 622- 627. doi:10.1086/523088
[91] V. Sudilovsky, S. Savaglio, P. Vreeswijk, C. Ledoux, A. Smette and J. Greiner, “Intervening Metal Systems in GRB and QSO Sight Lines: The Mg II and C IV Question,” Astrophysical Journal, Vol. 669, No. 2, 2007, pp. 741-748. doi:10.1086/521525
[92] S. Frank, M. C. Bentz, K. Z. Stanek, M. Dietrich, C. S. Kochanek, S. Mathur and B. M. Peterson, “Disparate MG II Absorption Statistics towards Quasars and Gamma-Ray Bursts: A Possible Explanation,” Astrophysics and Space Science, Vol 312, No. 3-4, 2007, pp. 325-330.
[93] C. Porciani, M. Viel and S. J. Lilly, “Strong Mg II Systems in Quasar and Gamma-Ray Burst Spectra,” Astrophysical Journal, Vol. 669, No. 1, 2007, pp. 218-224. doi:10.1086/512358

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