2009/10/23 by Madhura Killedar, Geraint F. Lewis · 17 citations
Physics and Astronomy · #Acceleration #Astronomy #Astrophysics #Classical mechanics #Cosmology and Gravitation Theories #Galaxies: Formation, Evolution, Phenomena #Galaxy #Gravitational lens #Line-of-sight #Noise (video) #Physics #Proper motion #Radio Astronomy Observations and Technology #Redshift #Stars #astro-ph.CO
paper · pdf · doi:10.1111/j.1365-2966.2009.15913.x
published in Monthly Notices of the Royal Astronomical Society 402(1), 650-656 (Oxford University Press) · 8 pages, 1 figure. Accepted by MNRAS
arxiv created 2009/10/23 · openalex publication_date 2009/12/04 · arxiv updated 2015/05/14 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
The evolution of the expansion rate of the Universe results in a drift in the redshift of distant sources over time. A measurement of this drift would provide us with a direct probe of expansion history. The Lyman α (Lyα) forest has been recognized as the best candidate for this experiment, but the signal would be weak and it will take next generation large telescopes coupled with ultrastable high-resolution spectrographs to reach the cm s−1 resolution required. One source of noise that has not yet been assessed is the transverse motion of Lyα absorbers, which varies the gravitational potential in the line of sight and subsequently shifts the positions of background absorption lines. We examine the relationship between the pure cosmic signal and the observed redshift drift in the presence of moving Lyα clouds, particularly the collapsed structures associated with Lyman limit systems and damped Lyα systems. Surprisingly, the peculiar velocities and peculiar accelerations both enter the expression, although the acceleration term stands alone as an absolute error, whilst the velocity term appears as a fractional noise component. An estimate of the magnitude of the noise reassures us that the motion of the Lyα absorbers will not pose a threat to the detection of the signal.