Direct Estimate of the Post-Newtonian Parameter and Cosmic Curvature from Galaxy-scale Strong Gravitational Lensing

Abstract

Einstein's theory of general relativity (GR) has been precisely tested on solar system scales, but extragalactic tests are still poorly performed. In this work, we use a newly compiled sample of galaxy-scale strong gravitational lenses to test the validity of GR on kiloparsec scales. In order to solve the circularity problem caused by the preassumption of a specific cosmological model based on GR, we employ the distance sum rule in the Friedmann-Lema\^ıtre-Robertson-Walker metric to directly estimate the parameterized post-Newtonian (PPN) parameter ${\gamma }_{\mathrm{PPN}}$ and the cosmic curvature ${\Omega }_k$ by combining observations of strong lensing and Type Ia supernovae. This is the first simultaneous measurement of ${\gamma }_{\mathrm{PPN}}$ and ${\Omega }_k$ without any assumptions about the contents of the universe or the theory of gravity. Our results show that ${\gamma }_{\mathrm{PPN}}=1.11_{-0.09}^{+0.11}$ and ${\Omega }_k=0.48_{-0.71}^{+1.09}$, indicating a strong degeneracy between the two quantities. The measured ${\gamma }_{\mathrm{PPN}}$, which is consistent with the prediction of 1 from GR, provides a precise extragalactic test of GR with a fractional accuracy better than 9.0\%. If a prior of the spatial flatness (i.e., ${\Omega }_k=0$) is adopted, the PPN parameter constraint can be further improved to ${\gamma }_{\mathrm{PPN}}=1.07_{-0.07}^{+0.07}$, representing a precision of 6.5\%. On the other hand, in the framework of GR (i.e., ${\gamma }_{\mathrm{PPN}}=1$), our results are still marginally compatible with zero curvature (${\Omega }_k=-0.12_{-0.36}^{+0.48}$), supporting no significant deviation from a flat universe.

Updated to match the published version in ApJ Letters

References in corpus (13)

• The Confrontation between General Relativity and Experiment
• Correcting Type Ia Supernova Distances for Selection Biases and Contamination in Photometrically Identified Samples
• Non-parametric spatial curvature inference using late-universe cosmological probes
• The Baryon Fractions and Mass-to-Light Ratios of Early-Type Galaxies
• The XMM Cluster Survey: Testing chameleon gravity using the profiles of clusters
• Constraint on the Post-Newtonian Parameter gamma on Galactic Size Scales
• Measurements of the Hubble constant and cosmic curvature with quasars: ultra-compact radio structure and strong gravitational lensing
• Constraining cosmological parameters in FLRW metric with lensed GW+EM signals
• Revisiting Studies of the Statistical Property of a Strong Gravitational Lens System and Model-independent Constraint on the Curvature of the Universe
• Cosmology-independent Estimate of the Hubble Constant and Spatial Curvature Using Time-delay Lenses and Quasars
• Model-independent Estimations for the Cosmic Curvature from the Latest Strong Gravitational Lensing Systems
• Constraints on cosmic curvature with lensing time delays and gravitational waves
• Model-independent constraints on cosmic curvature: implication from the future gravitational wave observation DECIGO

Cited by in corpus (13)

• Exploring the Hubble Tension and Spatial Curvature from the Ages of Old Astrophysical Objects
• Null test for cosmic curvature using Gaussian process
• Prospects of strongly lensed fast radio bursts: Simultaneous measurement of post-Newtonian parameter and Hubble constant
• Cosmological Parameter Estimation Using Current and Future Observations of Strong Gravitational Lensing
• TEGLIE: Transformer encoders as strong gravitational lens finders in KiDS
• A test of the evolution of gas depletion factor in galaxy clusters using strong gravitational lensing systems
• Probing a scale dependent gravitational slip with galaxy strong lensing systems
• High precision measurement of cosmic curvature: from gravitational waves and cosmic chronometer
• Cosmological application of the lens-redshift probability distribution with improved galaxy-scale gravitational lensing sample
• Pixel-level modelling of group-scale strong lens CASSOWARY 19
• Exploring Scalarized Einstein-Gauss-Bonnet Theories Through the Lens of Parametrized Post-Newtonian Formalism
• Discrimination of metric theories
• Testing General Relativity on Galactic Scales via DESI-BAO and Strong Lensing: Circumventing Assumptions on the Hubble Constant, Sound Horizon, and Dark Energy