Tully’s research focuses on the
astrophysics of galaxies, the
large-scale structure of the cosmos, and the distance scale of the universe.
Tully–Fisher Relation In 1977, with colleague J. Richard Fisher, Tully published what became known as the
Tully–Fisher relation, an empirical correlation between the rotational velocity of a spiral galaxy and its luminosity. This relation allows astronomers to estimate a galaxy’s distance by comparing its intrinsic brightness to its observed brightness, and it remains a fundamental tool in extragalactic astronomy.
Galaxy Mapping and Catalogs In 1988 Tully published
The Nearby Galaxies Catalog and the
Nearby Galaxies Atlas, which provided three-dimensional positions for thousands of galaxies in the local universe. These works were among the first comprehensive efforts to depict the distribution of galaxies in space. Subsequent distance catalogs published by Tully and collaborators now include measurements for 55,000 galaxies, the largest assembly of directly measured galaxy distances available. Tully curates his own catalogs and others extracted from the literature in the publicly accessible
Extragalactic Distance Database.
Cosmicflows and Large-Scale Structure Tully has played a leading role in the Cosmicflows program, which compiles galaxy distances and peculiar velocities (motions relative to cosmic expansion). Data from this program have been used to map the flows of galaxies and the distribution of matter, including dark matter, within a volume of hundreds of millions of light-years around Earth. Tully and collaborators identified and named the
Laniakea Supercluster, the vast supercluster of which the
Milky Way is a part, and contributed to the discovery of the
South Pole Wall, a large filament of galaxies in the nearby universe. == Scientific contributions ==