VOcabulary for the IVOA Unified Content Descriptors (Version 2007-08-31) Arithmetic quantities Difference between two quantities described by the same UCD Numerical factor Gradient Rate (per time unit) Ratio between two quantities described by the same UCD Zero point Electromagnetic spectrum Infrared part of the spectrum Infrared between 1.0 and 1.5 micron Infrared between 1.5 and 2 micron Infrared between 2 and 3 micron Infrared between 3 and 4 micron Infrared between 4 and 8 micron Infrared between 8 and 15 micron Infrared between 15 and 30 micron Infrared between 30 and 60 micron Infrared between 60 and 100 micron Near-Infrared, 1-5 microns Medium-Infrared, 5-30 microns Far-Infrared, 30-100 microns Ultraviolet part of the spectrum Ultraviolet between 10 and 50 nm Ultraviolet between 50 and 100 nm Ultraviolet between 100 and 200 nm Ultraviolet between 200 and 300 nm Far-Ultraviolet X-ray part of the spectrum Soft X-ray (0.12 - 2 keV) Medium X-ray (2 - 12 keV) Hard X-ray (12 - 120 keV) Channel / instrumental spectral bin coordinate (bin number) Energy value in the em frame Frequency value in the em frame Gamma rays part of the spectrum Soft gamma ray (120 - 500 keV) Hard gamma ray (>500 keV) Designation of major atomic lines 21cm hydrogen line H-Lyalpha line H-alpha line H-beta line H-gamma line H-delta line Bracket gamma line [OIII] line whose rest wl is 500.7 nm CO radio line, e.g. 12CO(1-0) rest wl 115GHz Millimetric/submillimetric part of the spectrum Millimetric between 30 and 50 GHz Millimetric between 50 and 100 GHz Millimetric between 100 and 200 GHz Millimetric between 200 and 400 GHz Millimetric between 400 and 750 GHz Millimetric between 750 and 1500 GHz Millimetric between 1500 and 3000 GHz Optical part of the spectrum Optical band between 300 and 400 nm Optical band between 400 and 500 nm Optical band between 500 and 600 nm Optical band between 600 and 750 nm Optical band between 750 and 1000 nm Radio part of the spectrum Radio between 20 and 100 MHz Radio between 100 and 200 MHz Radio between 200 and 400 MHz Radio between 400 and 750 MHz Radio between 750 and 1500 MHz Radio between 1500 and 3000 MHz Radio between 3 and 6 GHz Radio between 6 and 12 GHz Radio between 12 and 30 GHz Wavenumber value in the em frame Wavelength value in the em frame Central wavelength Effective wavelength Instrument sv:device.instrument Instrumental background Bandpass (e.g.: band name) of instrument Bandwidth of the instrument Baseline for interferometry Beam sv:optics.beam Calibration parameter Detector sv:device.detector Instrument noise sv:device.detector.noise Point Spread Function sv:optics.pointSpreadFunction Quantum efficiency sv:device.detector.quantumEfficiency Dispersion of a spectrograph Filter sv:device.filter Field of view sv:optics.field-of-view Observatory, satellite, mission Seeing Offset angle respect to main direction of observation Spectral order in a spectrograph sv:optics.order Various instrumental parameters Pixel (default size: angular) Photographic plate Plate emulsion sv:device.detector.film Instrument precision Instrument saturation threshold Instrument scale (for CCD, plate, image) Instrument sensitivity, detection threshold Instrument configuration or setup Sky level Sky temperature Telescope sv:device.telescope Telescope focal length sv:device.telescope;sv:optics.focalLength Metadata Abstract (of paper, proposal,etc.) Bibliographic reference Author name Bibcode Figure in a paper Journal name Page number Volume number Code or flag Classification code limit uncertainty error flag Membership code MIME type Multiplicity or binarity flag Quality, precision, reliability flag or code Status code (e.g.: status of a proposal/observation) Unknown or impossible to understand quantity Identity of man/organization responsible for the data Dataset Curation/contact e-mail File FITS standard Identifier, name or designation Identifier of associated counterpart Name of Co-Investigator Cross identification Identification of parent source Part of identifier, suffix or sub-component Name of Principal Investigator Main value of something Quantity was produced by a model Note or remark (longer than a code or flag) Number (of things; e.g. nb of object in an image) Record number Reference, or origin IVORN, Int. VO Resource Name (ivo://) URI, universal resource identifier URL, web address Software used in generating data Table or catalogue Title or explanation UCD Unit Version Observation Airmass sv:sky.airmass Atmosphere, atmospheric phenomena affecting an observation Atmospheric extinction Atmospheric refraction angle Calibration observation Related to flat-field calibration observation (dome, sky, ..) Exposure Region covered by the observation Image Observer, discoverer Various observation or reduction parameter Observation proposal Proposal cycle Sequence of observations, exposures or events Photometry Antenna temperature Photometric calibration Color index or magnitude difference color excess Dereddened color Flux expressed in counts fluence Photon flux Bolometric flux Flux density (per wl/freq/energy interval) Flux density surface brightness Flux surface brightness Limb-darkening coefficients Photometric magnitude Bolometric correction Bolometric magnitude Distance modulus Dereddened magnitude Surface brightness in magnitude units Physical quantities sv:physics Star formation rate Extinction or absorption along the line of sight sv:physics.absorption Absorption coefficient (e.g. in a spectral line) Galactic extinction Optical depth Abundance sv:physics.abundance Fe/H abundance Hydrogen abundance Helium abundance Metallicity abundance Acceleration sv:physics.acceleration Albedo or reflectance sv:physics.albedo Angular area Angular momentum Angular size width diameter dimension extension major minor axis extraction radius angular size extent or extension of semi-major axis angular size extent or extension of semi-minor axis Area (in linear units) sv:math.area Atomic and molecular physics (shared properties) Branching ratio Related to collisions Collisional strength Configuration Atomic / molecular cross-section Element Atomic molecular excitation parameter sv:physics.excitation Quantity refers to atomic/molecular final/ground state, level, ecc. Quantity refers to atomic/molecular initial state, level, ecc. Ion, ionization stage Related to ionization Lande factor Atomic level Lifetime of a level Line shifting coefficient Atomic number Z Oscillator strength Parity Quantum number Type of radiation characterizing atomic lines (electric dipole/quadrupole, magnetic dipole) Type of nuclear spin symmetry Statistical weight Statistical weight for nuclear spin states Atomic term Transition between states Transition probability, Einstein A coefficient Weighted oscillator strength Atomic weight Column density Quantities related to composition of objects Mass to light ratio Mass yield Related to cosmology sv:cosmology Generic damping quantities Density (of mass, electron, ...) Complex dielectric function Dispersion measure Electric field Electron sv:physics.particle.fermion.lepton.electron Electron degeneracy parameter Emission measure Emissivity Energy Energy-density Entropy Equation of state Excitation parameter U Gaunt factor/correction Gravity sv:physics.gravity Ionization parameter Collisional ionization Radiative ionization Luminosity Luminosity function Absolute magnitude Bolometric absolute magnitude Magnetic field sv:physics.magneticField Mass Mass loss sv:process.mass-loss Molecular data Molecular dipole Molecular electric dipole moment Molecular magnetic dipole moment Molecular dissociation Formation heat for molecules Molecular quadrupole Molecular electric quadrupole moment Molecular rotation Molecular vibration Related to neutrino sv:physics.particle.fermion.lepton.neutrino Polarization degree (or percentage) sv:physics.polarization Circular polarization sv:physics.polarization.circular Linear polarization sv:physics.polarization.linear Rotation measure polarization Stokes polarization Pressure Recombination coefficient Refraction index Linear size, length (not angular) Axis ratio (a/b) or (b/a) Diameter Radius Linear semi major axis Linear semi minor axis Temperature Effective temperature Electron temperature Transmission (of filter, instrument, ...) Space velocity Angular velocity Velocity dispersion Escape velocity Expansion velocity Microturbulence velocity Orbital velocity Pulsational velocity Rotational velocity Transverse / tangential velocity Related to virial quantities (mass, radius, ..) Position and coordinates Angular distance, elongation Angular resolution Position in alt-azimutal frame Alt-azimutal altitude sv:sky.altitude Alt-azimutal azimut sv:sky.azimuth Alt-azimutal zenith distance sv:sky.zenithDistance Barycenter sv:location.barycentric Body related coordinates Body related coordinate (altitude on the body) Body related coordinate (latitude on the body) Body related coordinate (longitude on the body) Cartesian (rectangular) coordinates Cartesian coordinate along the x-axis Cartesian coordinate along the y-axis Cartesian coordinate along the z-axis Cosmic Microwave Background reference frame Direction cosine Linear distance Coordinates related to Earth Altitude, height on Earth above sea level Latitude on Earth Longitude on Earth Ecliptic coordinates Ecliptic latitude Ecliptic longitude Earth orientation parameters Earth nutation Ephemeris Equatorial coordinates Declination in equatorial coordinates Hour-angle Right ascension in equatorial coordinates South polar distance in equatorial coordinates Positional error ellipse Reference frame used for positions Galactic coordinates Latitude in galactic coordinates Longitude in galactic coordinates Galactocentric coordinate system Geocentric coordinate system Hierarchical Equal Area IsoLatitude Pixelization Heliocentric position coordinate (solar system bodies) Hierarchical Triangular Mesh Lambert projection Local Group reference frame Local Standard of Rest reference frame Lunar coordinates Occultation by lunar limb Parallax Dynamical parallax Photometric parallaxes Spectroscopic parallax Trigonometric parallax Phase angle, e.g. elongation of earth from sun as seen from a third cel. object Proper motion sv:source.properMotion Position angle of a given vector Precession (in equatorial coordinates) Supergalactic coordinates Latitude in supergalactic coordinates Longitude in supergalactic coordinates WCS keywords WCS CDMATRIX WCS CRPIX WCS CRVAL WCS CTYPE WCS NAXES WCS NAXIS WCS scale or scale of an image Spectroscopy Spectral bin size Continuum spectrum Doppler parameter b Radial velocity, derived from the shift of some spectral feature Radial velocity derived from a wavelength shift using the optical convention Radial velocity derived from a frequency shift using the radio convention Spectral index Spectral line Line asymmetry Spectral line broadening Stark line broadening coefficient Zeeman broadening Line equivalent width Line intensity Line profile Spectral line strength S Spectral line fwhm Spectral (or velocity) resolution Observed source viewed on the sky sv:source Calibration source sv:source.calibration Guide star Source classification (star, galaxy, cluster...) Color classification Distance class e.g. Abell Luminosity class Richness class e.g. Abell Star/galaxy discriminator, stellarity index Structure classification e.g. Bautz-Morgan Density of sources Source ellipticity Impact parameter Morphology structure Morphological parameter Scale length for a galactic component (disc or bulge) Hubble morphological type (galaxies) Qualifier indicating that a quantity (e.g. flux) is background subtracted rather than total Orbital parameters Orbit eccentricity Orbit inclination Orbit mean anomaly Mean motion Ascending node Periastron Redshift Photometric redshift Sample Spectral type MK Variability of source Amplitude of variation Variability index Pulse Statistical parameters sv:stat Fourier coefficient Amplitude Fourier coefficient Correlation between two parameters Covariance between two parameters Statistical error Systematic error Filling factor (volume, time, ..) Fit Chi-square distribution, test Degrees of freedom Goodness or significance of fit Observed minus computed Parameter of fit Residual fit Likelihood Maximum or upper limit Mean, average value Median value Minimum or lowest limit Parameter Probability Signal to noise ratio Standard deviation Qualifier of a generic incalibrated quantity Miscellaneous value Variance Statistical weight Time, generic quantity in units of time or date sv:time Age Creation time/date (of dataset, file, catalogue,...) Crossing time Interval of time describing the duration of a generic event or phenomenon End time/date of a generic event Instant of time related to a generic event (epoch, date, Julian date, time stamp/tag,...) Equinox Time interval, time-bin, time elapsed between two events, not the duration of an event Lifetime Period, interval of time between the recurrence of phases in a periodic phenomenon Phase, position within a period A time/date associated with the processing of data Publication year Relaxation time The time/date data is available to the public Time resolution Timescale Start time/date of generic event