# An Etymological Dictionary of Astronomy and AstrophysicsEnglish-French-Persian

## فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

### M. Heydari-Malayeri    -    Paris Observatory

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Number of Results: 20 Search : distribution
 binomial distribution   واباژش ِ دونامین   vâbâžeš-e donâminFr.: distribution binomiale   A probability distribution for independent events for which there are only two possible outcomes i.e., success and failure. The probability of x successes in n trials is: P(x) = [n!/x!(n - x)!] px.qn - x, where p is the probability of success and q = 1 - p the probability of failure on each trial. These probabilities are given in terms of the → binomial theorem expansion of (p + q)n.→ binomial; → distribution. Bose-Einstein distribution   واباژش ِ بوز-اینشتین   vâbâžeš-e Bose-EinsteinFr.: distribution de Bose-Einstein   For a → population of independent → bosons, a function that specifies the number of particles in each of the allowed → energy states.→ boson; → Einstein; → distribution. brightness distribution   واباژش ِ درخشندگی   vâbâžeš-e deraxšandegiFr.: distribution de brillance   A statistical distribution of the brightness of an astronomical extended object.Vâbâžeš, → distribution; deraxšandegi, → brightness. chi-square distribution   واباژش ِ خی-دو   vâbâžeš-e Xi-doFr.: loi du chi-deux   A probability density function, denoted χ2, that gives the distribution of the sum of squares of k independent random variables, each being drawn from the normal distribution with zero mean and unit variance. The integer k is the number of degrees of freedom. The distribution has a positive skew; the skew is less with more degrees of freedom. As degrees of freedom increase, the chi-square distribution approaches a normal distribution. The most common application is chi-square tests for goodness of fit of an observed distribution to a theoretical one. If χ2 = 0 the agreement is perfect.Chi Gk. letter of alphabet; → square; → distribution.Vâbâžeš, → distribution; do, → two. cumulative distribution function   کریای ِ واباژش ِ کومشی   karyâ-ye vâbâžeš-e kumešiFr.: fonction de distribution cumulée   A function that gives the probability that a → random variable X is less than or equal to x, at each possible outcome: F(x) = P(X ≤ x), for -∞ < x < ∞. Same as → distribution function.→ cumulative; → distribution; → function. distribution   واباژش   vâbâžeš (#)Fr.: distribution   An act or instance of distributing; the state or manner of being distributed; something that is distributed. → binomial distribution, → Bose-Einstein distribution, → brightness distribution, → chi-square distribution, → cumulative distribution function, → distribution function, → Gaussian distribution, → Gibbs canonical distribution, → lognormal distribution, → Maxwell-Boltzmann distribution, → normal distribution, → Poisson distribution, → power-law distribution, → probability distribution, → spectral energy distribution.Verbal noun of → distribute distribution function   کریای ِ واباژش   karyâ-ye vâbâžešFr.: fonction de distribution   A function that gives the relative frequency with which the value of a statistical variable may be expected to lie within any specified interval. For example, the Maxwellian distribution of velocities gives the number of particles, in different velocity intervals, in a unit volume.→ distribution; → function. family of distributions   خانواده‌ی ِ واباژش‌ها   xânevâde-ye vâbâžešhâFr.: famille de distributions   A set of distributions which have the same general mathematical → formula.→ family; → distribution. Gaussian distribution   واباژش ِ گاؤسی   vâbâžeš-e Gaussi (#)Fr.: distribution gaussienne   A theoretical frequency distribution for a set of variable data, usually represented by a bell-shaped curve with a mean at the center of the curve and tail widths proportional to the standard deviation of the data about the mean.→ Gaussian; → distribution. Gibbs canonical distribution   واباژش ِ هنجاروار ِ گیبس   vâbâžeš-e hanjârvâr-e GibbsFr.: distribution canonique de Gibbs   The probability distribution of the various possible states of a certain → quasi-closed subsystem. halo occupation distribution (HOD)   واباژش ِ هگش ِ هاله   vâbâžeš-e hageš-e hâléFr.: distribution d'occupation de halo   The → probability distribution of the → number of galaxies that a host → dark matter halo of a given mass contains. HOD is a powerful theoretical frame to populate dark matter halos with luminous galaxies. More specifically, it describes the bias between galaxies and dark matter by specifying (a) the probability P(N|M) that a halo of → virial mass M contains N galaxies of a particular class and (b) the relative spatial and velocity distributions of galaxies and dark matter within halos.→ halo; → occupation; → distribution. lognormal distribution   واباژش ِ لگاریتمی-هنجارور   vâbâžeš-e logâritmi-hanjârvarFr.: distribution logarithmico-normale   A → probability distribution in which the natural logarithm (logX) of the → random variable (X) has a → Gaussian distribution. Maxwell-Boltzmann distribution   واباژش ِ ماکسول-بولتسمان   vibâžš-e Maxwell-BoltzmannFr.: distribution de Maxwell-Boltzmann   The distribution law for kinetic energies (or, equivalently, speeds) of molecules of an ideal gas in equilibrium at a given temperature.→ maxwell; → Boltzmann's constant; → distribution. metallicity distribution function (MDF)   کریای ِ واباژش ِ فلزیگی   karyâ-ye vâbâžeš-e felezigiFr.: fonction de distribution de métallicité   A plot representing the number of stars (or systems) per metallicity interval, usually expressed in [Fe/H] (abundance of → iron relative to → hydrogen).→ metallicity; → distribution; → function. normal distribution   واباژش ِ هنجارور   vâbâžeš-e hanjârvarFr.: distribution normale   A theoretical frequency distribution for a set of variable data, usually represented by a bell-shaped curve with a mean at the center of the curve and tail widths proportional to the standard deviation of the data about the mean. Same as → Gaussian distribution.→ normal; → distribution. Planck distribution   واباژش ِ پلانک   vâbâžeš-e PlanckFr.: distribution de Planck   The distribution of radiation with wavelength for a blackbody, given by → Planck's radiation law.→ Planck; → distribution. Poisson distribution   واباژش ِ پو‌آسون   vâbâžeš-e PoissonFr.: distribution de Poisson   A → probability function that characterizes → discrete  → random events occurring independently of one another within some definite time or space. It may be regarded as an approximation of the → binomial distribution when the number of events becomes large and the probability of success becomes small. The Poisson distribution is expressed by: f(x) = (λxe-λ)/x!, where λ is the mean number of successes in the interval, e is the base of the → natural logarithm, and x is the number of successes we are interested in.Named after Siméon Denis Poisson (1781-1840), French mathematician, who developed the application of Fourier series to physical problems and made major contributions to the theory of probability and to the calculus of variations; → distribution. power-law distribution   واباژش با قانون ِ توانی   vâbâžeš bâ qânun-e tavâniFr.: distribution en loi de puissance   For a → random variable X, any → distribution which has the form: P(X ≥ x) = (k/x)α, where x is a value in the range defined for X, k > 0 is a parameter termed location parameter, and α > 0 is the → slope parameter.→ power; → law; → distribution. probability distribution   واباژش ِ شوانایی   vâbâžeš-e šavânâyiFr.: distribution de probabilité   The function that describes the range of possible values that a random variable can attain and the probability that the value of the random variable is within any (measurable) subset of that range.→ probability; → distribution. spectral energy distribution (SED)   واباژش ِ کاروژ ِ بینابی   vâbâžeš-e kâruž-e binâbiFr.: distribution de l'énergie spectrale   A plot showing the energy emitted by a source as a function of the radiation wavelength or frequency. It is used in many branches of astronomy to characterize astronomical sources, in particular mainly in → near infrared and → middle infrared to study → protostars or → young stellar objects. The SED of these objects is divided in four classes. Class 0 in which the SED represents a very embedded protostar, where the mass of the central core is small in comparison to the mass of the → accreting envelope. The SED is characterized by the → blackbody radiation of the envelope and peaks at → submillimeter wavelengths. Class I objects possess a SED that peaks in the → far infrared and is characterized by a weak contribution of the blackbody of the central protostar (detected in near infrared) and the emission of a thick disk and dense envelope. These objects have less mass in the envelope and more massive central cores with respect to Class 0. Class II objects are the → classical T Tauri stars with a SED due to the emission of a thin disk and the central star. They have accumulated most of their final mass and have dispersed almost completely their circumstellar envelope. Finally, Class III objects have pure photospheric spectra. Their SED is peaked in the optical and is well approximated by a blackbody emission with a faint → infrared excess due to the presence of a residual optically thin disk that may be the origin of → planetesimals. This classification scheme can be made more quantitative by defining a → spectral index.→ spectral; → energy; → distribution.