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| Tully–Fisher | |
|---|---|
| Name | Tully–Fisher relation |
| Discoverers | Raymond A. Tully; J. Richard Fisher |
| Year | 1977 |
| Field | Astrophysics; Extragalactic astronomy |
| Relevance | Distance indicator; Galaxy dynamics; Dark matter |
Tully–Fisher
The Tully–Fisher relation is an empirical correlation between the intrinsic luminosity of a spiral galaxy and its rotation velocity, widely used as a distance indicator and probe of mass distribution in galaxies. Discovered through observations of southern sky galaxies, the relation connects measurements from optical and radio facilities to cosmological distance scales and the study of Dark matter halos. It plays a central role in projects spanning Hubble Space Telescope programs, Sloan Digital Sky Survey, and local flow mapping efforts anchored to the Cosmic Microwave Background reference frame.
The relation was first presented by Raymond A. Tully and J. Richard Fisher during studies at the Palomar Observatory and in collaboration with teams using the Arecibo Observatory and the Parkes Observatory. Early applications tied to extragalactic distance ladders alongside the Cepheid variable work of the Hubble Space Telescope Key Project and the Leavitt Law, while subsequent refinements involved analyses by groups at the Max Planck Institute for Astrophysics, Carnegie Institution for Science, and the Royal Observatory Edinburgh. The Tully–Fisher relation became integral to mapping peculiar velocities in surveys such as the 2MASS Redshift Survey and the 6dF Galaxy Survey, influencing debates at conferences like the IAU General Assembly and workshops led by the International Astronomical Union.
The canonical form expresses absolute magnitude M or luminosity L as a power-law function of rotational velocity v_rot: L ∝ v_rot^α, commonly rewritten as M = a + b log(v_rot). Calibration constants a and b were determined using distance anchors like Cepheid variable distances in the Local Group and geometric maser measurements in the Megamaser Cosmology Project. The rotation metric often uses the 21-cm neutral hydrogen line width from facilities such as the Very Large Array or the Green Bank Telescope, or optical emission-line rotation curves obtained at Keck Observatory and Very Large Telescope. Statistical fitting techniques leverage methods developed in the context of Markov chain Monte Carlo and Frequentist regression frameworks implemented within teams at the Institute for Advanced Study and the Space Telescope Science Institute.
Tully–Fisher is applied to measure distances to spiral galaxies across the Local Supercluster, to construct velocity fields for comparisons to Lambda-CDM predictions, and to estimate baryonic and dynamical masses in surveys such as DEEP2 and COSMOS. It supports constraint-setting on the Hubble constant using local flow models complementary to probes like Type Ia supernovae and Cosmic Microwave Background anisotropy measurements from Planck (spacecraft). Teams at the European Southern Observatory and the National Radio Astronomy Observatory have used the relation to examine environmental effects in clusters like the Virgo Cluster and the Coma Cluster, and to test galaxy formation prescriptions in simulations run by groups at Princeton University and University of California, Santa Cruz.
Variants include the optical-band Tully–Fisher, infrared calibrations using 2MASS K-band photometry favored by the Infrared Astronomical Satellite community, and the baryonic Tully–Fisher relation (BTFR) which replaces luminosity with total baryonic mass (stars plus gas), calibrated by HI surveys such as the Arecibo Legacy Fast ALFA Survey and CO observations from IRAM. Empirical calibrations have been produced by consortiums including the Carnegie Hubble Program and the Cosmicflows project, often cross-checking against distances from Tip of the Red Giant Branch measurements and geometric parallaxes from Gaia.
Physically, the relation emerges from a coupling between luminous mass and the dark matter halo potential traced by rotation curves measured in studies led by researchers at the Max Planck Institute for Astronomy and the Harvard & Smithsonian. Theoretical explanations draw on Cold Dark Matter halo scaling laws, baryonic feedback prescriptions developed in simulations from the Illustris and EAGLE projects, and analytical models inspired by work at the Institute for Computational Cosmology. Alternative interpretations invoke modified gravity proposals tested against Tully–Fisher scaling in analyses connected to the MOND literature and discussions at the Royal Society meetings.
Practical measurements combine 21-cm HI line widths from radio observatories including the Westerbork Synthesis Radio Telescope, optical rotation curves from integral-field units on instruments at the Gemini Observatory and Subaru Telescope, and photometry from space missions such as Spitzer Space Telescope and ground-based programs at Cerro Tololo Inter-American Observatory. Data pipelines employ reduction software developed in collaboration with teams from Space Telescope Science Institute and statistical toolkits originating at institutions like Lawrence Berkeley National Laboratory. Corrections for inclination, internal extinction, and beam smearing reference morphological catalogs such as those from the Third Reference Catalogue of Bright Galaxies and classification efforts tied to the Galaxy Zoo project.
Systematics arise from selection biases highlighted by studies at University of Cambridge, zeropoint calibration tied to local distance anchors like NGC 4258 maser measurements, bandpass-dependent stellar population effects mapped by groups at Johns Hopkins University, and environmental processes observed in clusters analyzed by researchers at University of Tokyo. Scatter is introduced by noncircular motions, warp and bar dynamics characterized in surveys using the Atacama Large Millimeter/submillimeter Array, and uncertainties in stellar mass-to-light ratios assessed by teams at Rutgers University and Columbia University. Ongoing efforts by collaborations including COSMOS and SAGA aim to reduce these uncertainties by combining multiwavelength datasets and improved theoretical priors from cosmological simulations.
Category:Extragalactic astronomy