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| Barred spiral galaxies | |
|---|---|
| Name | Barred spiral galaxy |
| Type | SB |
| Epoch | J2000 |
Barred spiral galaxies are a major morphological class of disk galaxies distinguished by a linear stellar structure, or bar, crossing the central region and connecting to spiral arms. They occupy a prominent place in the Hubble sequence and in studies of galaxy morphology, dynamics, and evolution. Observational programs using facilities such as the Hubble Space Telescope, Sloan Digital Sky Survey, and Very Large Telescope have characterized their prevalence, internal kinematics, and role in secular processes across cosmic time.
Barred systems appear across local surveys including the Local Group, the Virgo Cluster, and the Coma Cluster, and feature in targeted programs like the Galaxy Zoo citizen science project, the Two Micron All Sky Survey, and the Spitzer Space Telescope infrared campaigns. Historical classification schemes such as those of Edwin Hubble, Gérard de Vaucouleurs, and Allan Sandage incorporated bars into the modified Hubble sequence and the de Vaucouleurs system. Studies by teams at institutions including the National Aeronautics and Space Administration, the European Southern Observatory, and the Max Planck Society examine bar frequency versus parameters like stellar mass, environment, and redshift.
Morphological subdivisions follow notations from de Vaucouleurs (e.g., SB0, SBa, SBb, SBc) and variants used by observers at the Carnegie Institution for Science and the Royal Observatory Edinburgh. Bars vary in length, strength, and box/peanut bulge signatures studied by groups at the Instituto de Astrofísica de Canarias and the Kavli Institute for Astronomy and Astrophysics. High-resolution imaging from the Hubble Space Telescope Advanced Camera for Surveys and the James Webb Space Telescope near-infrared instruments reveals inner rings, nuclear bars, and ansae structures analyzed by researchers affiliated with the Harvard–Smithsonian Center for Astrophysics, the California Institute of Technology, and the University of Cambridge.
Theoretical frameworks draw on fluid dynamics, collisionless N-body simulations, and perturbation theory developed by scientists at the Princeton University, the Institute for Advanced Study, and the Max Planck Institute for Astrophysics. Bars can form via internal disk instabilities described in work by Ostriker, Peebles-type instability analyses, or be induced by tidal interactions with companions such as those cataloged in the Messier Catalogue, the New General Catalogue, and the Sloan Digital Sky Survey companion studies. Angular momentum transfer between disk, bar, and dark matter halo components modeled in simulations by groups at Columbia University, University of California, Berkeley, and University of Oxford predicts bar slowdown, buckling, and secular thickening phenomena explored in papers from the Royal Astronomical Society and the Astrophysical Journal.
Bars drive gas inflows to central kiloparsec regions, enhancing nuclear star formation observed with instruments like the Atacama Large Millimeter/submillimeter Array, the Chandra X-ray Observatory, and the Very Large Array. Spectroscopic programs at the Keck Observatory, the European Extremely Large Telescope planning teams, and the Anglo-Australian Telescope map star formation rates, metallicity gradients, and age distributions, linking bar-driven inflows to central bulge growth and possible fueling of active nuclei studied by collaborations associated with the European Southern Observatory and the Space Telescope Science Institute. Stellar population synthesis applied by groups at the Max Planck Institute for Astronomy and the University of Tokyo distinguishes old bar-dominated populations from younger spiral-arm populations.
Bars influence secular evolution, redistributing mass and angular momentum and contributing to pseudobulge formation discussed in works from the Carnegie Institution for Science and the Royal Society. Environmental effects from group and cluster membership cataloged by researchers at the Harvard & Smithsonian and the University of Michigan modulate bar frequency, with interactions recorded in surveys such as the Two Degree Field Galaxy Redshift Survey and the Galaxy And Mass Assembly project. The connection between bars and supermassive black hole growth is investigated by teams at the European Southern Observatory and the Space Telescope Science Institute through correlations between bar presence and activity in samples from the Sloan Digital Sky Survey and the ROSAT archives.
Imaging from the Hubble Space Telescope, the James Webb Space Telescope, and ground-based facilities like the Subaru Telescope and the Gemini Observatory provides morphological classification, while integral field units on instruments such as MUSE and SAMI deliver two-dimensional kinematics. Large photometric and spectroscopic datasets from the Sloan Digital Sky Survey, the Two Micron All Sky Survey, GALEX, and the Wide-field Infrared Survey Explorer enable statistical analyses led by teams at the University of California, Santa Cruz, Pennsylvania State University, and the University of Edinburgh. Citizen science projects like Galaxy Zoo and archival efforts at the European Space Agency expand training sets for machine learning approaches developed at institutions such as Google DeepMind and MIT.
Well-known barred systems include nearby galaxies cataloged as M31 (whose bar has been debated), M83, M95, NGC 1300, and NGC 1365, studied with facilities including the Hubble Space Telescope and the Spitzer Space Telescope. Statistical studies report that a substantial fraction—often quoted between ~30% and ~70% depending on wavelength and sample selection—of disk galaxies host bars, with results published in journals overseen by the American Astronomical Society and the Royal Astronomical Society. Ongoing surveys by teams at the European Southern Observatory, National Optical-Infrared Astronomy Research Laboratory, and the Max Planck Institute for Astronomy continue to refine bar demographics across mass, morphology, and cosmic epoch.
Category:Galaxies