Secular Extragalactic Parallax: Measurement Methods and Predictions for Gaia
Abstract
Secular extragalactic parallax caused by the solar system's velocity relative to the cosmic microwave background rest frame may be observable as a dipole proper motion field for nearby galaxies. Nearby galaxies also exhibit proper motions caused by their transverse peculiar velocities that prevent detection of secular parallax for any single galaxy, although a statistical detection may be made instead. Such a detection could constrain the local Hubble parameter. We present methods to measure secular parallax using correlated extragalactic proper motions and find a first limit on the secular parallax amplitude using proper motions of nearby galaxies from Gaia Data Release 2. Using the local peculiar velocity field derived from Cosmicflows-3, we simulate galaxy proper motions and predict that a significant detection of secular parallax will be possible by Gaia's end of mission. We further investigate the implications of our simulations for the study of transverse peculiar velocities, which we find to be consistent with large scale structure theory. The peculiar velocity field additionally results in low-multipole correlated proper motions that may be confounded with other cosmological proper motion measurements, such as limits on the gravitational wave background and the isotropy of the Hubble expansion. The authors acknowledge support from the NSF Graduate Research Fellowship Program, the NSF grant AST-1411605, and the NASA grant 14-ATP14-0086.
- Publication:
-
American Astronomical Society Meeting Abstracts #235
- Pub Date:
- January 2020
- Bibcode:
- 2020AAS...23527908P