NGC 3198

NGC 3198
Name	NGC 3198
Type	SB(rs)c
Epoch	J2000
Constellation	Ursa Major
Redshift	0.00226
Dist ly	47 million light years
Appmag v	10.7
Size v	8.5′ × 3.2′
Names	UGC 5576; PGC 30497

NGC 3198 is a barred spiral galaxy in Ursa Major notable for its well-measured rotation curve and role in the development of evidence for dark matter and galactic dynamics. It has been a target for studies of spiral galaxy morphology, neutral hydrogen mapping, and Cepheid variable distance calibration, linking investigations across observational programs such as Hubble Space Telescope, Very Large Array, and optical surveys like the Sloan Digital Sky Survey. The galaxy's fairly regular disk galaxy structure and extended HI region have made it a benchmark in comparisons with theoretical models from Lambda-CDM cosmology and alternative theories such as MOND.

Description and morphology

The galaxy is classified SB(rs)c in the Hubble sequence, featuring a pronounced bar and loosely wound spiral arm pattern, similar in morphology to prototypes studied by observers at institutions including Palomar Observatory and Mount Wilson Observatory. Its stellar disk shows a prominent young population in the spiral arm regions, with star-forming complexes comparable to those cataloged by the Hubble Space Telescope Key Project on the Extragalactic Distance Scale and surveys by the Spitzer Space Telescope and the Galaxy Evolution Explorer. Structural analyses reference methodologies from the de Vaucouleurs system and photometric decompositions used by teams at European Southern Observatory and Max Planck Institute for Astronomy.

Distance and location

Located in the northern sky near other members of the Ursa Major Cluster and the M81 Group vicinity, the galaxy's distance has been refined via Cepheid variable measurements from Hubble Space Telescope programs and independent indicators used by research groups at Carnegie Institution for Science and Johns Hopkins University. Distance estimates place it at roughly 13–15 megaparsecs, aligning with calibrations from the Cosmic Distance Ladder efforts that involve comparisons with Type Ia supernova standards and Tully–Fisher relation studies performed by teams at University of California, Berkeley and University of Cambridge.

Observational history

Discovered in the 19th century by observers working with telescopes at facilities like William Herschel’s instruments and later cataloged in the New General Catalogue compiled by John Dreyer, the galaxy entered modern study through radio astronomy programs led by researchers at the National Radio Astronomy Observatory and optical spectroscopy conducted at Kitt Peak National Observatory and Cerro Tololo Inter-American Observatory. Major observational campaigns include HI synthesis mapping by the Very Large Array and photometry from the Hubble Space Telescope, building on historical atlases produced by the Royal Astronomical Society and data reduction techniques from groups at Space Telescope Science Institute.

Rotation curve and dark matter studies

The extended flat rotation curve revealed by HI observations was pivotal for the rise of contemporary dark matter research, paralleled by theoretical work at institutions such as Princeton University, Harvard–Smithsonian Center for Astrophysics, and the Institute for Advanced Study. Analysis of rotational velocities using methods from Vera Rubin's legacy and mass-modeling approaches from Navarro–Frenk–White profiles provided constraints for cold dark matter halos consistent with simulations by teams at Los Alamos National Laboratory and Kavli Institute for Cosmological Physics. Alternative gravity frameworks such as Modified Newtonian Dynamics have also been tested against the rotation curve by researchers affiliated with University of Cambridge and University of Bologna.

Star formation and interstellar medium

Star formation rates and interstellar medium properties have been characterized through multiwavelength campaigns involving the Spitzer Space Telescope, the Herschel Space Observatory, and ground-based facilities like Subaru Telescope and Keck Observatory. Observations identified HII regions and emission-line complexes analogous to those cataloged by the Palomar Observatory Sky Survey and studies at Max Planck Institute for Astrophysics, informing comparisons to Kennicutt–Schmidt law scalings used by teams at University of Minnesota and University of Arizona. The galaxy's HI envelope and molecular gas traced by CO surveys tie into surveys by the IRAM and Atacama Large Millimeter/submillimeter Array consortia.

Companion galaxies and environment

Situated within a loose group environment, the galaxy has nearby companions cataloged in surveys from the Third Reference Catalogue of Bright Galaxies and studies by the European Southern Observatory. Its local environment and tidal interactions have been compared with dynamics observed in the Local Group and environments studied by the Two Micron All Sky Survey and the ALFALFA survey at the Arecibo Observatory, with environment analyses conducted by researchers at Max Planck Institute for Extraterrestrial Physics and University of Tokyo.

Notable observations and imaging studies

Notable imaging includes high-resolution Hubble Space Telescope exposures from the Key Project on the Extragalactic Distance Scale and radio HI maps from the Very Large Array and the Westerbork Synthesis Radio Telescope. Infrared imaging from the Spitzer Space Telescope and far-infrared data from Herschel Space Observatory complemented ultraviolet surveys from the Galaxy Evolution Explorer, enabling cross-wavelength syntheses akin to those published by teams at the Jet Propulsion Laboratory and the European Space Agency. The combined data sets have been used in publications appearing in journals such as The Astrophysical Journal, Monthly Notices of the Royal Astronomical Society, and Astronomy & Astrophysics.

Category:Barred spiral galaxies Category:Ursa Major