What is recorded here?
Tully and Fisher developed and calibrated an extragalactic distance method connecting corrected global neutral-hydrogen profile width with intrinsic photographic luminosity or galaxy diameter, and applied it to nearby calibrators and two galaxy clusters. A distant galaxy looks dimmer both when it is intrinsically faint and when it is far away. The global width of its neutral-hydrogen radio line supplies another observable: after projection correction, it reflects the internal motion of the galaxy without itself requiring the distance. Tully and Fisher used nearby galaxies with independently constrained distances to calibrate a width-luminosity relation, then compared cluster samples at approximately common distances. Apparent brightness and the estimated intrinsic brightness provide a distance modulus. The original work also explored a diameter-width relation. Its new contribution is the calibrated distance application and supporting observations; it explicitly acknowledges earlier observations of width-luminosity correlations. Calibration, inclination, extinction, sample selection and cluster membership matter. The paper states that its small samples do not establish the intrinsic scatter, and its note added during publication preserves a disagreement with Sandage and Tammann that could reflect systematic corrections. The historical photographic slope corresponds algebraically to a luminosity exponent near2.5 under its specific width definition, rather than the later baryonic fourth-power formulation. Its preliminary distance and Hubble-constant values are historical outputs, not current accepted measurements.
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Scientific scope
The empirical relation connects specified galaxy luminosity and rotational line-width measures with calibration, inclination and sample assumptions. Scatter and selection effects limit individual distance estimates. It is not an exact universal law for every galaxy or an independently replayed modern distance calibration. Later refinements retain separate credit.
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People and systems
R. Brent Tully; J. Richard Fisher
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English catalogue narrative
Tully and Fisher: using galaxy line widths to estimate distances
Tully and Fisher developed and calibrated an extragalactic distance method connecting corrected global neutral-hydrogen profile width with intrinsic photographic luminosity or galaxy diameter, and applied it to nearby calibrators and two galaxy clusters.
A distant galaxy looks dimmer both when it is intrinsically faint and when it is far away. The global width of its neutral-hydrogen radio line supplies another observable: after projection correction, it reflects the internal motion of the galaxy without itself requiring the distance. Tully and Fisher used nearby galaxies with independently constrained distances to calibrate a width-luminosity relation, then compared cluster samples at approximately common distances. Apparent brightness and the estimated intrinsic brightness provide a distance modulus. The original work also explored a diameter-width relation. Its new contribution is the calibrated distance application and supporting observations; it explicitly acknowledges earlier observations of width-luminosity correlations. Calibration, inclination, extinction, sample selection and cluster membership matter. The paper states that its small samples do not establish the intrinsic scatter, and its note added during publication preserves a disagreement with Sandage and Tammann that could reflect systematic corrections. The historical photographic slope corresponds algebraically to a luminosity exponent near2.5 under its specific width definition, rather than the later baryonic fourth-power formulation. Its preliminary distance and Hubble-constant values are historical outputs, not current accepted measurements.
Scientific scope
The empirical relation connects specified galaxy luminosity and rotational line-width measures with calibration, inclination and sample assumptions. Scatter and selection effects limit individual distance estimates. It is not an exact universal law for every galaxy or an independently replayed modern distance calibration. Later refinements retain separate credit.
People and systems
R. Brent Tully; J. Richard Fisher