Fr.: amas des Arches
One of the three → Galactic center clusters supposed to be the densest young → massive star cluster in the Milky Way. It contains the richest collection of → O stars and → WN Wolf-Rayet stars in any cluster in the Galaxy, thus representing the largest collection of the most massive stars in the Galaxy. With its estimated age of 2-3 million years, the Arches cluster is the youngest of the massive clusters in the Galactic center. → Quintuplet cluster; → Central cluster (Figer et al. 2002, ApJ 581, 258; and 1999, ApJ 525, 750).
Arches, from the presence of Galactic center thermal → arched filaments, about 100 → light-years in projection from the Galactic center (Morris & Yusef-Zadeh, 1985, AJ 90, 2511), from M.E. arche, O.Fr. arche "arch of a bridge," from L. arcus, → arc; → cluster.
Fr.: amas de la ruche
Fr.: amas lié
A cluster of astronomical objects, such as stars or galaxies, held together by their mutual gravitational attraction. → bound system.
Fr.: amas de Brocchi
Same as the → Coathanger and Collinder 399.
Named after the American amateur astronomer D. F. Brocchi who created a map of the cluster in the 1920s for calibrating photometers; → cluster.
Fr.: amas de la Balle, ~ du Boulet
A → cluster of galaxies at a → redshift of z = 0.296 undergoing a violent → merger process nearly in the → plane of the sky. Also known as 1E 0657-558. The head-on collision between the main cluster and a subcluster ramming with an apparent speed of about 4700 km s-1 occurred about 150 x 106 years ago. The two clusters are currently moving away from each other while the space between them is filled with a very hot gas (first observed in X-rays by → Chandra) resulting from the overheating due to the collision. The Bullet cluster has the highest X-ray luminosity and temperature of all known clusters. The X-ray gas of the bullet (amounting to 2 x 1013 solar masses) collides with the X-ray gas of the main cluster (1014 solar masses) and forms a well defined → supersonic (Mach 3) → bow shock. A significant offset between the distribution of X-ray emission and the mass distribution has been observed, and diversely interpreted.
The name Bullet refers to the smaller subcluster, that has created the bow shock; → cluster.
Fr.: superamas du Centaur
The nearest large → supercluster. It is dominated by the → galaxy cluster A3526 (→ Abell catalog). The Centaurus supercluster is a long structure that stretches away from us. The most distant of the clusters, A3581, is about 300 million → light-years away.
Fr.: amas central
One of the three obscured → Galactic center clusters, which contains the supermassive black hole → Sgr A*. The first stars observed in the Central cluster were evolved → massive stars showing strong He I emission lines (2.058 microns) in the near infrared K band. Subsequently more than 80 massive stars were detected including various types of → Wolf-Rayet stars, as well as → O-type and → B-type → supergiants and → dwarfs (see, e.g. Martins et al. 2007, A&A 468, 233).
1) xušé (#); 2) xušé bastan (#)
Fr.: 1) amas; 2) s'agglomérer, se grouper
1) A group of the same astronomical objects gathered or occurring closely
together, such as → cluster of galaxies,
→ globular cluster, → open cluster,
and so on.
O.E. clyster "cluster," probably akin to O.E. clott "clot".
Xušé "cluster, a bunch of grapes, an ear of corn," (Laki huša), from Mid.Pers. hošag or xušak; cf. Skt. guccha- "bundle, bunch of flowers, cluster of blossom, clump;" xušé bastan, with bastan "to bind, shut; to clot; to form seed buds", from Mid.Pers. bastan/vastan "to bind, shut," Av./O.Pers. band- "to bind, fetter," banda- "band, tie," Skt. bandh- "to bind, tie, fasten," PIE *bhendh- "to bind," cf. Ger. binden, E. bind.
Fr.: cœur d'amas
The central part of a cluster (globular, galaxies, etc.) where the spatial density of the objects making up the cluster is much higher than the average value.
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).
cluster mass function (CMF)
karyâ-ye jerm-e xušé
Fr.: fonction de masse d'amas
An empirical power-law relation representing the number of clusters as a function of their mass. It is defined as: N(M)dM ∝ M -αdM, where the exponent α has an estimated value of about 2 and dM is the mass interval. It is believed that this is a universal law applying to a variety of objects including globular clusters, massive young clusters, and H II regions.
cluster of galaxies
xuše-ye kahkašâni (#)
Fr.: amas de galaxies
Same as → galaxy cluster.
Fr.: agglomération, groupement
Grouping of a number of similar astronomical objects.
Noun from verb → cluster.
qânun-e xušé bandi
Fr.: loi de groupement
An empirical power-law representing the number of stellar clusters as a function of the number of stars per cluster within an interval. It is expressed as: N(N*) dN*∝ N*-α dN*, where N(N*) is the number of clusters containing N* stars and dN* is the interval in star number. It is believed that this relationship applies to a variety of systems, including stellar clusters, globular clusters, H II regions (Oey et al. 2004, AJ 127, 1632).
xuše-ye Gisu (#)
Fr.: amas de Coma
The nearest rich cluster of galaxies which contains more than a thousand known galaxies, is about 20 million light-years in diameter, and lies about 280 million light-years away in the → constellation → Coma Berenices. Also known as Abell 1656.
Fr.: amas de Fourneau
Galactic center cluster
xuše-ye markaz-e kahkešân
Fr.: amas du centre galactique
One of the three massive clusters located toward the → Galactic center: → Quintuplet cluster, → Arches cluster, → Central cluster. Heavily extinguished by the presence of dust clouds and only accessible at infrared (and longer) wavelengths or in X-rays, each of these clusters has a population of more than a hundred → massive stars. The three clusters are similar in most respects, each containing about 104 solar masses in stars. The Arches cluster is younger than the two others.
xuše-ye kahkešâni, ~ kahkešânhâ
Fr.: amas galactique
xuše-ye kahkašâni (#)
Fr.: amas de galaxies
An aggregation of galaxies, made up of a few to a few thousand members, which may or may not be held together by its own gravity. Same as → cluster of galaxies.