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).
Lyman break galaxy
kahkešân bâ bore-ye Lyman
Fr.: galaxie de la coupure de Lyman
A star-forming galaxy at → high redshift affected by the → Lyman break. Such a galaxy is detected in the red (R, → photometric band) but not in the blue (U and B bands). At those high redshfits (above 2.5), the → Lyman limit at 912 Å is shifted between the U and B bands.
Magellanic spiral galaxy
kakhešân-e mârpic-e Mâželâni
Fr.: galaxie spirale magellanique
A class of low-mass galaxies with relatively rare features. In particular, these galaxies are characterized by a → stellar bar whose center is displaced from that of the disk and a one-armed spiral. The → Large Magellanic Cloud (LMC) is considered the prototype of this class of objects. However, despite a wealth of data, there is still a good deal of uncertainty concerning the nature of the LMC's bar. The majority of the observed Magellanic spirals in the nearby Universe share the LMC's structure, in particular the evidence of an offset bar and a one-armed spiral structure. A good example of these systems is NGC 3906, which shows evidence of the bar offset from the photometric center of the galaxy by 1.2 kpc (Pardy et al., 2016, ApJ 827, 149).
Magellanic type galaxy
kahkešân-e gune-ye Magellani
Fr.: galaxie de type magellanique
kahkešân-e Markarian (#)
Fr.: galaxie de Markarian
A galaxy with abnormally strong emission in the ultraviolet continuum and broad emission lines arising in a bright, semi-stellar nucleus.
Named after B. E. Markarian (1913-1985), an Armenian astronomer who made a catalog of such galaxies (1967-81); → galaxy.
An obsolete term which once denoted the entire system of galaxies including the Milky Way.
Fr.: galaxie pauvre en métaux
Fr.: galaxie pauvre en métaux
Same as → metal-deficient galaxy.
Milky Way galaxy
kahkešân-e râh-e širi (#)
Fr.: Voie lactée
A → spiral galaxy, of which the
→ solar system is a small part.
It is the second largest in our → Local Group of galaxies.
The Milky Way is a disk-shaped system,
with a diameter of between 80,000 and 100,000 → light-years
and a thickness of about 2,000 light-years, containing more than
1011 stars. The stars are divided into two main categories,
→ Population II stars and
→ Population I stars.
Fr.: galaxie parente
Of a high redshift supernova, the galaxy in which the event has occurred.
Fr.: galaxie passive
A galaxy lacking optical emission-line activity (e.g., [O II], Hα, [O III]) and showing only stellar absorption lines (e.g., the 4000 Å → calcium break, Mg I, Na I). Also called passively evolving galaxy.
passively evolving galaxy
kahkešân bâ fargašt-e akâr
Fr.: galaxie en évolution passive
Same as → passive galaxy.
Fr.: galaxie particulière
An irregular galaxy that has an abnormal shape (neither elliptical, spiral, nor lenticular) and/or has another unusual characteristic.
power-law elliptical galaxy
kahkešân-e beyzigun bâ qânun-e tavâni
Fr.: galaxie elliptique en loi de puissance
An → elliptical galaxy whose → surface brightness can be approximated by a single → power law at small radii (r ≤ 10-20''). More modern interpretations have emphasized that these profiles can be better understood as the inward continuation of the galaxy's overall → Sersic profile, usually modified by an additional, nuclear-scale stellar component (S. P. Rusli et al., 2013, AJ 146, 160).
Fr.: galaxie primordiale
A high redshift, metal-deficient galaxy that formed very early in the history of the Universe.
Fr.: galaxie mère
A galaxy which is supposed to be at the origin of a specific event, for example a hypothetical galaxy in which globular clusters might have formed.
A huge mass of gas that by contraction and condensation becomes a galaxy of stars. A galaxy during the early phase, before it has developed its present shape and stellar/gas content.
râdio kahkešân, kahkešân-e râdioyi
A galaxy that is extremely luminous at radio wavelengths between 10 MHz and 100 GHz. The radio luminosity of a strong radio galaxy (1037-1039 watts) can be up to a million times greater than the radio output of an ordinary galaxy and up to a hundred times greater than the optical luminosity of a galaxy such as the Milky Way. The optical counterparts of radio galaxies are usually an → elliptical galaxy. Radio galaxies often exhibit jet structure from a compact nucleus. They typically display two → radio lobes that are often approximately aligned with the jets observed in the optical and that may extend for millions of → light-years.
kahkašân-e dur šavandé
Fr.: galaxie qui s'éloigne
A galaxy whose distance increases from other galaxies due to the global expansion of the Universe.
Kahkašân, → galaxy; dur šavandé "receding," from dur, → far, + šavandé agent noun of šodan "to go, to pass; to become, to be, to be doing;" Mid.Pers. šudan, šaw- "to go;" Av. š(ii)auu-, šiyav- "to move, go," šiyavati "goes," šyaoθna- "activity; action; doing, working;" O.Pers. šiyav- "to go forth, set," ašiyavam "I set forth;" cf. Skt. cyu- "to move to and fro, shake about; to stir," cyávate "stirs himself, goes;" Gk. kinein "to move;" Goth. haitan "call, be called;" O.E. hatan "command, call;" PIE base *kei- "to move to and fro."
Fr.: galaxie régulière
A galaxy which has a uniformly arranged, symmetrical morphology such as a spiral or elliptical galaxy. Opposite of → irregular galaxy.