Using galaxy pairs as cosmological tracers

Alicia Bueno Belloso, Guido W. Pettinari, Nikolai Meures, Will J. Percival

Research output: Contribution to journalArticlepeer-review


The Alcock-Paczynski effect uses the fact that, when analyzed with the correct geometry, we should observe structure that is statistically isotropic in the Universe. For structure undergoing cosmological expansion with the background, this constrains the product of the Hubble parameter and the angular diameter distance. However, the expansion of the Universe is inhomogeneous and local curvature depends on density. We argue that this distorts the Alcock-Paczynski effect on small scales. After analyzing the dynamics of galaxy pairs in the Millennium Simulation, we find an interplay between peculiar velocities, galaxy properties and local density that affects how pairs trace cosmological expansion. We find that only low-mass, isolated galaxy pairs trace the average expansion with a minimum “correction” for peculiar velocities. Other pairs require larger, more cosmology- and redshift-dependent peculiar velocity corrections and, in the small separation limit of being bound in a collapsed system, do not carry cosmological information.
Original languageEnglish
Article number023530
Pages (from-to)023530
JournalPhysical Review D
Issue number2
Publication statusPublished - 20 Jul 2012


Dive into the research topics of 'Using galaxy pairs as cosmological tracers'. Together they form a unique fingerprint.

Cite this