Testing the Cosmological Principle: On the Time Dilation of Distant Sources

Abstract

We present a novel test of the cosmological principle: the idea that, on sufficiently large scales, the universe should appear homogeneous and isotropic to observers comoving with the Hubble flow. This is a fundamental assumption in modern cosmology, underpinning the use of the Friedmann-Lemaître-Robertson-Walker metric as part of the concordance $\Lambda$CDM paradigm. However, the observed dipole imprinted on the Cosmic Microwave Background (CMB) is interpreted as our departure from the Hubble flow, and such a proper motion will induce a directionally-dependent time dilation over the sky. We illustrate the feasibility of detection of this 'time dilation dipole' and sketch the practical steps involved in its extraction from a catalogue of sources with intrinsic time-scales. In essence, whilst the scale of this dilation is small, being of order of 0.1%, it will in principle be detectable in large scale surveys of variable cosmological sources, such as quasars and supernovae. The degree of alignment of the time dilation dipole with the kinematic dipole derived from the CMB will provide a new assessment of the cosmological principle, and address the tension in dipole measures from other observations.

arXiv comment9 pages, 4 figures, accepted for publication in MNRAS

References in corpus (37)

• SciPy 1.0--Fundamental Algorithms for Scientific Computing in Python
• Array Programming with NumPy
• The Wide-field Infrared Survey Explorer (WISE): Mission Description and Initial On-orbit Performance
• HEALPix -- a Framework for High Resolution Discretization, and Fast Analysis of Data Distributed on the Sphere
• LSST: from Science Drivers to Reference Design and Anticipated Data Products
• dynesty: A Dynamic Nested Sampling Package for Estimating Bayesian Posteriors and Evidences
• Planck 2018 results. I. Overview and the cosmological legacy of Planck
• Are the Variations in Quasar Optical Flux Driven by Thermal Fluctuations?
• Modeling the Time Variability of SDSS Stripe 82 Quasars as a Damped Random Walk
• Is Quasar Optical Variability a Damped Random Walk?
• The CatWISE2020 Catalog
• The Rapid ASKAP Continuum Survey I: Design and First Results
• A Test of the Cosmological Principle with Quasars
• Flexible and Scalable Methods for Quantifying Stochastic Variability in the Era of Massive Time-Domain Astronomical Data Sets
• Is the Observable Universe Consistent with the Cosmological Principle?
• Detection of the velocity dipole in the radio galaxies of the NRAO VLA Sky Survey
• A Challenge to the Standard Cosmological Model
• Are the Variability Properties of the Kepler AGN Light Curves Consistent with a Damped Random Walk?
• New test of the FLRW metric using the distance sum rule
• High redshift radio galaxies and divergence from the CMB dipole
• Probing the Cosmological Principle in the counts of radio galaxies at different frequencies
• Cosmological implications of the anisotropy of ten galaxy cluster scaling relations
• Is the Universe homogeneous?
• Limitations on the recovery of the true AGN variability parameters using Damped Random Walk modeling
• The Cosmic Radio Dipole: Estimators and Frequency Dependence
• Time Dilation in Type Ia Supernova Spectra at High Redshift
• Optical Variability of Quasars with 20-Year Photometric Light Curves
• Extracting Information from AGN Variability
• Testing the cosmic curvature at high redshifts: the combination of LSST strong lensing systems and quasars as new standard candles
• Inference of the cosmic rest-frame from supernovae Ia
• Cosmological Time Dilation in Durations of Swift Long Gamma-Ray Bursts
• A large disparity in cosmic reference frames determined from the sky distributions of radio sources and the microwave background radiation
• The Impact of Observing Strategy on Cosmological Constraints with LSST
• Peculiar motion of Solar system from the Hubble diagram of supernovae Ia and its implications for cosmology
• Model-independent Estimations for the Cosmic Curvature from the Latest Strong Gravitational Lensing Systems
• New evidence for a cosmological distribution of stellar mass primordial black holes
• LSST Cadence Strategy Evaluations for AGN Time-series Data in Wide-Fast-Deep Field

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• An Independent Measure of the Kinematic Dipole from SDSS
• Homology reveals significant anisotropy in the cosmic microwave background