Fr.: transformation affine
biased galaxy formation
diseš-e varakdâr-e kahkašânhâ
Fr.: formation biaisée de galaxies
The theory that bright galaxies form preferentially from anomalously overdense perturbations in the → early Universe.
bimodal star formation
diseš-e domod-e setâregân
Fr.: formation bimodale d'étoile
A concept of → star formation in which → high-mass stars and → low-mass stars form in different physical conditions involving different → molecular clouds. Following the pioneering suggestion of Herbig (1962), successive investigations have generally supported the idea that star formation proceeds bimodally with respect to stellar mass. The star formation rate appears to differ both spatially and temporally for low mass and → massive stars. This is of considerable importance for galactic evolution, since the low-mass stars lock up mass and are long-lived, low luminosity survivors to the present epoch, whereas massive stars are short-lived, recycle and enrich interstellar gas, and leave dark remnants while producing a high luminosity per unit of mass (Silk, J., 1988, in Galactic and Extragalactic Star Formation, p. 503, eds. R. E. Pudritz and M. Fich).
bottom-up structure formation
diseš-e sâxtâr az pâyin bé bâlâ
Fr.: formation des structures du bas vers le haut
burst of star formation
belk-e diseš-e setâregân
Fr.: flambée de formation d'étoiles
An intense → star formation activity in a region of → interstellar medium or, more globally, in a → galaxy. It is characterized by a → star formation rate which is much higher than the corresponding average. Same as → starburst.
cluster formation efficiency (CFE)
kârâyiè-ye diseš-e xuše
Fr.: efficacité de formation d'amas
The fraction of → star formation which happens in → bound clusters. It is defined as the ratio between the → cluster formation rate and → star formation rate (Bastian, 2008, MNRAS 390, 759, arxiv/0807.4687).
cluster formation rate (CFR)
nerx-e diseš-e xuše
Fr.: taux de formation d'amas
A parameter used in star formation models representing the ratio of the total mass in → star clusters to the corresponding age range (Bastian, 2008, MNRAS 390, 759, arxiv/0807.4687).
Fr.: formation de CO
The chemical reaction that gives rise to → carbon monoxide in the → interstellar medium. According to models, several processes may lead to CO formation. For example, HCO+ + e → CO + H. The molecule HCO+ is itself produced through several paths, for example: H3+ + C → CH2+ + H, CH2+ + H2 → CH3+ + H, CH3+ + O → HCO+ + H. Alternatively: C+ + H2O → HCO+ + H. Another possibility: C+ + OH → CO+ + H, CO+ + H2→ HCO+ + H.
collective star formation
diseš-e gerdâmdi-ye setâregân
Fr.: formation collective d'étolies
Formation of stars, especially → massive stars, in group as opposed to individual formation.
Fr.: transformation de couleur
Empirical mathematical transformation applied to the observed magnitudes in order to convert them into a standard system, or into a different system.
cosmic star formation peak
cakâd-e keyhâni-ye diseš-e setâregân
Fr.: pic de formation stellaire cosmique
A crucial period in the history of the → Universe, when the bulk of stars in massive galaxies were likely formed. Observations of young stars in distant galaxies at different times in the past have indicated that the → star formation rate peaked at the → redshift of z ~ 2, some 10 billion years ago, before declining by a factor of around ten to its present value (P. Madau & Dickinson, 2014, arXiv:1403.0007).
vâdis, vâdiseš, vâdisâneš
Altering in the size or shape of a body. See also → deformable.
Verbal noun of → deform.
Fr.: déformation élastique
1) The act or process of forming or the state of being formed, such as
→ star formation.
Verbal noun of → form, + -ate + -ion.
Diseš, verbal noun of disidan, → from dis-, → form, + -eš.
Fr.: formation de galaxies
tarâdis-e Gâlile-yi (#)
Fr.: transformation galiléenne
The method of relating a measurement in one → reference frame to another moving with a constant velocity with respect to the first within the → Newtonian mechanics. The Galilean transformation between the coordinate systems (x,y,z,t) and (x',y',z',t') is expressed by the relations: x' = x - vt, y' = y, z' = z. Galilean transformations break down at high velocities and for electromagnetic phenomena and is superseded by the → Lorentz transformations.
tarâdis-e gaz (#)
Fr.: transformation de jauge
A change of the fields of a gauge theory that does not change the value of any measurable quantity.
Fr.: formation des grains
The process by which dust grains are assembled or produced.
hierarchical structure formation
diseš-e sâxtâr-e pâygâni
Fr.: formation de structures hiérarchiques
A cosmological → structure formation model in which the smallest gravitationally bound structures (→ quasars and galaxies) form first, followed by → groups, → galaxy clusters, and → superclusters of galaxies.
diseš-e vine, ~ tasvir
Fr.: formation de l'image
The meeting of light rays emanating from an object after crossing an optical system.