Fr.: facteur intégrant
A function that converts a → differential equation, which is not exact, into an → exact differential equation. This is done by multiplying all terms of the original equation by the integrating factor.
Fr.: binaire en interaction
Fr.: galaxies en interaction
Galaxies that are close enough for their mutual gravitational attraction to produce perturbed shapes or extruded filaments of stellar material, called → tidal tails. Most galaxies are in clusters, and gravitational interactions between them are common.
Inspiring interest, holding the attention.
Adj. from → interest.
Fr.: extinction interstellaire
The dimming of light traveling in the interstellar space due to the combined effects of absorption and scattering by interstellar dust particles. Interstellar extinction increases at shorter (bluer) wavelengths, resulting in → interstellar reddening.
Continuing or remaining for a long time; enduring.
Fr.: magnitude limite
The faintest magnitude reachable by an instrument.
In stellar atmosphere models, the effect of metallic lines on the atmospheric structure of stars. The additional opacities of thousands of metallic lines alter the radiative transfer, leading to changes in the temperature. The emergent spectrum is consequently modified.
Fr.: liste, cotation, listing
1) A list; the act of compiling a list; something listed.
Fr.: extinction logarithmique
Same as → reddening coefficient.
Lyman alpha emitting galaxy (LAEs)
kahkešân-e gosilande-ye Lyman-alpha
Fr.: galaxie émettrice de Lyman alpha
A galaxy belonging to an important population of low mass → star-forming galaxies at → redshift z > 2. Their number increases with redshift. A large fraction of the → dwarf starburst galaxies during the → reionization epoch may be intrinsic LAEs, but their Lyα photons can be scattered by the → neutral hydrogen (H I) in the → intergalactic medium (IGM), which makes Lyα line a powerful probe of reionization. These high-z LAEs have low → metallicity, low stellar masses, low dust → extinction, and compact sizes. The current best nearby analogs of high-z LAEs are → Green Pea galaxies (Yang et al, 2017, arxiv/1706.02819 and references therein).
peyvastâr-e Lyman (#)
Fr.: continuum de Lyman
A continuous range of wavelengths in the spectrum of hydrogen at wavelengths less than the → Lyman limit. The Lyman continuum results from transitions between the → ground state of hydrogen and → excited states in which the single electron is freed from the atom by photons having an energy of 13.6 eV or higher.
Lyman continuum escape
goriz-e peyvastâr-e Lyman
Fr.: échappement du continuum de Lyman
The process whereby → Lyman continuum photons produced by → massive stars escape from a galaxy without being absorbed by interstellar material. Some observations indicate that the Lyman continuum escape fraction evolves with → redshift.
Fr.: dédoublement magnétique
A process whereby the (internal) → magnetic field of a star modifies the → pulsations by lifting some of its degeneracy. Instead of just one pulsation frequency, a multiplet of frequencies is then observed. This effect was proposed as a possible explanation for the observed frequency pattern of → Beta Cephei. In practice, the magnetic splitting is difficult to observe, because of the very small expected frequency difference between the peaks. However, when unaccounted for, it may lead to a wrong mode identification. The current best candidate to detect magnetic splitting is → HD 43317, since this star displays two close frequency patterns (Buysschaert et al., 2017, astro-ph/1709.02619).
sazkard-e reshteh-ye farist
Fr.: ajustement par la séquence principale
The method of determining the distance to a star cluster by overlaying its main sequence on the theoretical zero-age main sequence and noting the difference between the cluster's apparent magnitude and the zero-age main sequence's absolute magnitude.
Fr.: extinction en masse
An event in the history of life on Earth in which large numbers of species (sometimes more than 90% of some species) vanish in a relatively short period of time. In spite of controversy, it is generally recognized that there have been at least six major mass extinctions. These occurred in the late Cambrian (500 million years ago), in the late Ordovician (440 million years ago), in the late Devonian (365 million years ago), at the end of the Permian (245 million years ago), in the late Triassic (208 million years ago), and at the end of the Cretaceous (65 million years ago).
1) The act of coming together.
noqte-ye godâz (#)
Fr.: point de fusion
The temperature at which a solid changes to a liquid.
The area of computer science dealing with the use and development of microcomputers, and related peripheral devices and softwares. Also microinformatics.
âzmun-e âyené (#)
Fr.: test d'un miroir
The observation and measurement of the flatness of a mirror surface. The process generally is done before coating so as not to damage the delicate coated surface. For coated and curved surfaces, non-contact methods are often employed, generally using interference techniques.