diskdominated

Diskdominated is an adjective used in astronomy to describe systems in which the disk component—whether a stellar disk in galaxies or an accretion disk around a compact object—provides the primary contribution to mass, light, or energy output, compared with other components such as a central bulge, halo, or corona. The term is most commonly used in two contexts: galactic structure and accretion physics.

In galactic morphology, disk-dominated galaxies have a relatively small bulge, characterized by low bulge-to-total light ratios (B/T), typically late-type spirals and irregulars. Their surface brightness profiles are dominated by a disk that follows an exponential law with a scale length. They show rotation-dominated kinematics (high v/σ). They tend to host ongoing star formation in their disks and often lack a central, prominent spheroid.

In accretion physics, disk-dominated states refer to systems where the accretion disk around a compact object—black holes in active galactic nuclei or X-ray binaries—dominates the emission across optical/UV or X-ray bands, usually associated with higher accretion rates. In such contexts, the disk's radiation or thermal continuum outshines coronal or jet components.

Measurement and implications: Disk dominance is quantified via bulge-disk decomposition of luminosity, bulge-to-total ratio, contribution to the spectral energy distribution, or spectral decomposition. Disk domination informs theories of galaxy formation, secular evolution, and accretion physics, and helps classify objects along the Hubble sequence or accretion states.