The effect of our local motion on the Sandage-Loeb test of the cosmic expansion

Abstract

Redshifts of an astronomical body measured at multiple epochs (e.g., separated by 10 years) are different due to the cosmic expansion. This so-called Sandage-Loeb test offers a direct measurement of the expansion rate of the Universe. However, acceleration in the motion of Solar System with respect to the cosmic microwave background also changes redshifts measured at multiple epochs. If not accounted for, it yields a biased cosmological inference. To address this, we calculate the acceleration of Solar System with respect to the Local Group of galaxies to quantify the change in the measured redshift due to local motion. Our study is motivated by the recent determination of the mass of Large Magellanic Cloud (LMC), which indicates a significant fraction of the Milky Way mass. We find that the acceleration towards the Galactic Center dominates, which gives a redshift change of 7 cm/s in 10 years, while the accelerations due to LMC and M31 cannot be ignored depending on lines of sight. We create all-sky maps of the expected change in redshift and the corresponding uncertainty, which can be used to correct for this effect.

6 pages, 3 figures. Accepted for publication in PASJ

References in corpus (6)

• Cosmic dynamics in the era of Extremely Large Telescopes
• The Half Million Quasars (HMQ) Catalogue
• VLBI measurement of the secular aberration drift
• Exploring the Dark Energy Redshift Desert with the Sandage-Loeb Test
• The time evolution of cosmological redshift as a test of dark energy
• Peculiar acceleration

Cited by in corpus (1)

• Intensity correlation speckles as a technique for removing Doppler broadening