Cosmological inference from within the peculiar local universe
The existence of ‘peculiar’ velocities due to the formation of cosmic structure marks a point of discord between the real universe and the usually assumed Friedmann–Lemaítre–Robertson–Walker metric, which accomodates only the smooth Hubble expansion on large scales. In the standard ΛCDM model framew...
| Main Authors: | , , |
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| Format: | Journal article |
| Language: | English |
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MDPI
2024
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| _version_ | 1811140492527665152 |
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| author | Mohayaee, R Rameez, M Sarkar, S |
| author_facet | Mohayaee, R Rameez, M Sarkar, S |
| author_sort | Mohayaee, R |
| collection | OXFORD |
| description | The existence of ‘peculiar’ velocities due to the formation of cosmic structure marks a point of discord between the real universe and the usually assumed Friedmann–Lemaítre–Robertson–Walker metric, which accomodates only the smooth Hubble expansion on large scales. In the standard ΛCDM model framework, Type Ia supernovae data are routinely “corrected” for the peculiar velocities of both the observer and the supernova host galaxies relative to the cosmic rest frame, in order to infer evidence for acceleration of the expansion rate from their Hubble diagram. However, observations indicate a strong, coherent local bulk flow that continues outward without decaying out to a redshift 𝑧≳0.1, contrary to the ΛCDM expectation. By querying the halo catalogue of the Dark Sky Hubble-volume N-body simulation, we find that an observer placed in an unusual environment like our local universe should see correlations between supernovae in the JLA catalogue that are 2–8 times stronger than seen by a typical or Copernican observer. This accounts for our finding that peculiar velocity corrections have a large impact on the value of the cosmological constant inferred from supernova data. We also demonstrate that local universe-like observers will infer a downward biased value of the clustering parameter 𝑆8 from comparing the density and velocity fields. More realistic modelling of the peculiar local universe is thus essential for correctly interpreting cosmological data. |
| first_indexed | 2024-09-25T04:22:51Z |
| format | Journal article |
| id | oxford-uuid:e576ae65-49ce-4971-a01b-45e8b3bedeef |
| institution | University of Oxford |
| language | English |
| last_indexed | 2024-09-25T04:22:51Z |
| publishDate | 2024 |
| publisher | MDPI |
| record_format | dspace |
| spelling | oxford-uuid:e576ae65-49ce-4971-a01b-45e8b3bedeef2024-08-16T15:57:22ZCosmological inference from within the peculiar local universeJournal articlehttp://purl.org/coar/resource_type/c_dcae04bcuuid:e576ae65-49ce-4971-a01b-45e8b3bedeefEnglishSymplectic ElementsMDPI2024Mohayaee, RRameez, MSarkar, SThe existence of ‘peculiar’ velocities due to the formation of cosmic structure marks a point of discord between the real universe and the usually assumed Friedmann–Lemaítre–Robertson–Walker metric, which accomodates only the smooth Hubble expansion on large scales. In the standard ΛCDM model framework, Type Ia supernovae data are routinely “corrected” for the peculiar velocities of both the observer and the supernova host galaxies relative to the cosmic rest frame, in order to infer evidence for acceleration of the expansion rate from their Hubble diagram. However, observations indicate a strong, coherent local bulk flow that continues outward without decaying out to a redshift 𝑧≳0.1, contrary to the ΛCDM expectation. By querying the halo catalogue of the Dark Sky Hubble-volume N-body simulation, we find that an observer placed in an unusual environment like our local universe should see correlations between supernovae in the JLA catalogue that are 2–8 times stronger than seen by a typical or Copernican observer. This accounts for our finding that peculiar velocity corrections have a large impact on the value of the cosmological constant inferred from supernova data. We also demonstrate that local universe-like observers will infer a downward biased value of the clustering parameter 𝑆8 from comparing the density and velocity fields. More realistic modelling of the peculiar local universe is thus essential for correctly interpreting cosmological data. |
| spellingShingle | Mohayaee, R Rameez, M Sarkar, S Cosmological inference from within the peculiar local universe |
| title | Cosmological inference from within the peculiar local universe |
| title_full | Cosmological inference from within the peculiar local universe |
| title_fullStr | Cosmological inference from within the peculiar local universe |
| title_full_unstemmed | Cosmological inference from within the peculiar local universe |
| title_short | Cosmological inference from within the peculiar local universe |
| title_sort | cosmological inference from within the peculiar local universe |
| work_keys_str_mv | AT mohayaeer cosmologicalinferencefromwithinthepeculiarlocaluniverse AT rameezm cosmologicalinferencefromwithinthepeculiarlocaluniverse AT sarkars cosmologicalinferencefromwithinthepeculiarlocaluniverse |