NRAO/Socorro Colloquium Series: 20 September 1996

Martha Haynes

Cornell University


The Peculiar Velocity Field in the Local Universe


Tully-Fisher (TF) distances for a homogeneous sample of 1600 Sbc-Sc galaxies are used to analyze the peculiar velocity field within the volume to cz ~ 7500 km/s. To derive TF distances, a template TF relation is derived using a sample of 782 spiral galaxies in 24 groups and clusters within z < .04. Locally, the velocity field derived from the TF measurements resembles closely that predicted from self-consistent reconstructions based on all-sky redshift surveys. Large peculiar velocities are seen in the neighborhoods of the prominent nearby superclusters, Hydra-Centaurus and Pisces-Perseus. While we detect a bulk motion of ~300 km/s within a top-hat window of 6000 km/s in radius, the flow within the surveyed volume is not coherent. It results from the known asymmetry of the local mass distribution, in particular, the location of the Local Group in a region characterized by a large gradient in the mass density. Furthermore, no signature of the large bulk flow reported by Lauer and Postman is evident. While nearby clusters are seen to move with us, the average of distant clusters is at rest, implying that the convergence depth is on the order of 6000 km/s. We conclude that locally at least, light traces mass.






Friday, 20 September 1996
11:00am

Array Operations Center Auditorium

Local Host: Liese Van Zee


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mrupen@nrao.edu