Theoretical Systematics in Testing the Cosmological Principle with the Kinematic Quasar Dipole
The Cosmological Principle (CP) is part of the foundation that underpins the standard model of the Universe. In the era of precision cosmology, when stress tests of the standard model are uncovering various tensions and possible anomalies, it is critical to check the viability of this principle. A k...
| Main Authors: | , , , |
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| Format: | Article |
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IOP Publishing
2023-01-01
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| Series: | The Astrophysical Journal |
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| Online Access: | https://doi.org/10.3847/1538-4357/acdf46 |
| _version_ | 1797694531313860608 |
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| author | Caroline Guandalin Jade Piat Chris Clarkson Roy Maartens |
| author_facet | Caroline Guandalin Jade Piat Chris Clarkson Roy Maartens |
| author_sort | Caroline Guandalin |
| collection | DOAJ |
| description | The Cosmological Principle (CP) is part of the foundation that underpins the standard model of the Universe. In the era of precision cosmology, when stress tests of the standard model are uncovering various tensions and possible anomalies, it is critical to check the viability of this principle. A key test is the consistency between the kinematic dipoles of the cosmic microwave background and of the large-scale matter distribution. Results using radio continuum and quasar samples indicate a rough agreement in the directions of the two dipoles, but a larger than expected amplitude of the matter dipole. The resulting tension with the radiation dipole has been estimated at ∼5 σ for some cases, suggesting a potential new cosmological tension and a possible violation of the CP. However, the standard formalism for predicting the dipole in the two-dimensional projection of sources overlooks possible evolution effects in the luminosity function. In fact, radial information from the luminosity function is necessary for a correct projection of the three-dimensional source distribution. Using a variety of current models of the quasar luminosity function, we show that neglecting redshift evolution can significantly overestimate the relative velocity amplitude. While the models we investigate are consistent with each other and with current data, the dipole derived from these, which depends on derivatives of the luminosity function, can disagree by more than 3 σ . This theoretical systematic bias needs to be resolved before robust conclusions can be made about a new cosmic tension. |
| first_indexed | 2024-03-12T02:59:16Z |
| format | Article |
| id | doaj.art-9879349ea2414e8d90a8a9845c4c1163 |
| institution | Directory Open Access Journal |
| issn | 1538-4357 |
| language | English |
| last_indexed | 2024-03-12T02:59:16Z |
| publishDate | 2023-01-01 |
| publisher | IOP Publishing |
| record_format | Article |
| series | The Astrophysical Journal |
| spelling | doaj.art-9879349ea2414e8d90a8a9845c4c11632023-09-03T15:03:28ZengIOP PublishingThe Astrophysical Journal1538-43572023-01-01953214410.3847/1538-4357/acdf46Theoretical Systematics in Testing the Cosmological Principle with the Kinematic Quasar DipoleCaroline Guandalin0https://orcid.org/0000-0003-1490-9314Jade Piat1Chris Clarkson2https://orcid.org/0000-0001-7363-0722Roy Maartens3https://orcid.org/0000-0001-9050-5894School of Physical & Chemical Sciences, Queen Mary University of London , London E1 4NS, UK ; c.m.guandalin@qmul.ac.ukSchool of Physical & Chemical Sciences, Queen Mary University of London , London E1 4NS, UK ; c.m.guandalin@qmul.ac.uk; Aix-Marseille University , Marseille, FranceSchool of Physical & Chemical Sciences, Queen Mary University of London , London E1 4NS, UK ; c.m.guandalin@qmul.ac.uk; Department of Physics & Astronomy, University of Western Cape , Cape Town 7535, South Africa; Department of Mathematics and Applied Mathematics, University of Cape Town , Cape Town 7701, South AfricaDepartment of Physics & Astronomy, University of Western Cape , Cape Town 7535, South Africa; Institute of Cosmology & Gravitation, University of Portsmouth , Portsmouth PO1 3FX, UK; National Institute for Theoretical & Computational Sciences (NITheCS) , Cape Town 7535, South AfricaThe Cosmological Principle (CP) is part of the foundation that underpins the standard model of the Universe. In the era of precision cosmology, when stress tests of the standard model are uncovering various tensions and possible anomalies, it is critical to check the viability of this principle. A key test is the consistency between the kinematic dipoles of the cosmic microwave background and of the large-scale matter distribution. Results using radio continuum and quasar samples indicate a rough agreement in the directions of the two dipoles, but a larger than expected amplitude of the matter dipole. The resulting tension with the radiation dipole has been estimated at ∼5 σ for some cases, suggesting a potential new cosmological tension and a possible violation of the CP. However, the standard formalism for predicting the dipole in the two-dimensional projection of sources overlooks possible evolution effects in the luminosity function. In fact, radial information from the luminosity function is necessary for a correct projection of the three-dimensional source distribution. Using a variety of current models of the quasar luminosity function, we show that neglecting redshift evolution can significantly overestimate the relative velocity amplitude. While the models we investigate are consistent with each other and with current data, the dipole derived from these, which depends on derivatives of the luminosity function, can disagree by more than 3 σ . This theoretical systematic bias needs to be resolved before robust conclusions can be made about a new cosmic tension.https://doi.org/10.3847/1538-4357/acdf46CosmologyCosmological principleLarge-scale structure of the universeQuasarsLuminosity function |
| spellingShingle | Caroline Guandalin Jade Piat Chris Clarkson Roy Maartens Theoretical Systematics in Testing the Cosmological Principle with the Kinematic Quasar Dipole The Astrophysical Journal Cosmology Cosmological principle Large-scale structure of the universe Quasars Luminosity function |
| title | Theoretical Systematics in Testing the Cosmological Principle with the Kinematic Quasar Dipole |
| title_full | Theoretical Systematics in Testing the Cosmological Principle with the Kinematic Quasar Dipole |
| title_fullStr | Theoretical Systematics in Testing the Cosmological Principle with the Kinematic Quasar Dipole |
| title_full_unstemmed | Theoretical Systematics in Testing the Cosmological Principle with the Kinematic Quasar Dipole |
| title_short | Theoretical Systematics in Testing the Cosmological Principle with the Kinematic Quasar Dipole |
| title_sort | theoretical systematics in testing the cosmological principle with the kinematic quasar dipole |
| topic | Cosmology Cosmological principle Large-scale structure of the universe Quasars Luminosity function |
| url | https://doi.org/10.3847/1538-4357/acdf46 |
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