An Etymological Dictionary of Astronomy and Astrophysics
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فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory

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Number of Results: 21 Search : metal
alkali metal
  فلز ِ قلیایی   
felez-e qalyâyi (#)

Fr.: métal alcalin   

Any of the chemical elements belonging to group A of the → periodic table, which burn vigorously in air; i.e. → lithium, → sodium, → potassium, → rubidium, → cesium, and → francium. Alkali metals have a → valence of one and are softer and less dense than other metals.

alkali; → metal.

alkaline earth metal
  فلز ِ قلیایی ِ خاکی   
felez-e qalyâyi-ye xâki (#)

Fr.: terre alcaline   

Any of the metallic chemical elements belonging to group 2 of the → periodic table; i.e. → beryllium, → magnesium, → calcium, → strontium, → barium, and → radium. They are not found free in the nature because they are highly reactive.

alkaline; → earth; → metal.

Felez, → metal; qalyâyi, → alkaline; xâki "of or pertaining to soil," from xâk, → soil.

carbon-enhanced metal-poor star (CEMP)
  ستاره‌ی ِ کم‌فلز ِ کربون بلندیده   
setâre-ye kamfelez-e karbon bolandidé

Fr.: étoile pauvre en métaux enrichie en carbon   

A star that presents very low → iron  → abundances [Fe/H] < -4 but an → anomalous richness in carbon. CEMP stars have been defined as a subset of → metal-poor stars that exhibit elevated [C/Fe] ≥ +1.0. It has been recognized that ~15-20% of stars with [Fe/H] < -2.0 are carbon enhanced. This fraction rises to 30% for [Fe/H] < -3.0, to 40% for [Fe/H] < -3.5, and ~75% for [Fe/H] < -4.0. This increasing trend of CEMP-star frequency with declining [Fe/H] is confirmed by the observation of many thousands of CEMP stars (Daniela Carollo + ApJ 2014, 788, 180). See also → extremely metal-poor star (EMPS)

carbon; → enhance; → metal; → metal; → poor; → star.

critical metallicity
  فلزیگی ِ پرژنی   
felezigi-ye paržani

Fr.: métallicité critique   

The → metallicity of a → star-forming  → molecular cloud when → cooling → rates by → metals dominate the → gravitational  → heating during → protostellar collapse. The minimum → Jeans mass achieved by gravitational → fragmentation depends on the presence/absence of → coolants in the cloud. Since cooling rate in metal lines is more efficient than in primordial molecular lines (H2 and HD), metals favor fragmentation in gas and formation of → low-mass stars.

critical; → metallicity.

extremely metal-poor star (EMPS)
  ستاره‌ی ِ اُستومانه کم‌فلز   
stâre-ye ostomâné kamfelez

Fr.: étoile extrêmement faible en métaux   

A star with an iron abundance [Fe/H] < -3 found in a → galactic halo. These stars, whose → metallicity is typically less than one thousandth of the solar value, are believed to have formed shortly after the → Big Bang, 13.7 billion years ago. The number of such stars depends on the primordial → initial mass function. If the IMF were steep, there could, in principle, be a lot of EMPSs formed at high → redshifts. Thus many of them could have ended up in the halos of galaxies. See also → Population III star.

extreme; → metal; → poor; → star.

gas metallicity
  فلزیگی ِ گاز   
felezigi-ye gâz

Fr.: métallicité de gaz   

The metallicity derived from observations of the gas component of a galaxy. It is mainly measured from optical → emission lines using primarily oxygen abundances. The gas → metallicity is one of the most important tools to investigate the evolutionary history of galaxies. The reason is that the gas metallicity of galaxies is basically determined by their star-formation history. Recent observational studies has allowed the investigation of the gas metallicity even in → high redshift beyond z = 1, such as → Lyman break galaxies, submillimeter-selected high-z galaxies, and so on. Such observational insights on the metallicity evolution of galaxies provide constraints on the theoretical understandings of the formation and the evolution of galaxies.

gas; → metallicity.

low-metallicity environment
  پرگیر ِ کم‌فلز   
pargir-e kamfelez

Fr.: environnement faible en métaux   

A medium in which chemical elements have abundances smaller than the solar values.

low; → metallicity; → environment.

mass-metallicity relation (MZR)
  بازانش ِ جرم-فلزیگی   
bâzâneš-e jerm-felezigi

Fr.: relation masse-métallicité   

A correlation between the → stellar mass (or → luminosity) and the → gas metallicity of → star-forming galaxies (Lequeux et al. 1979) according to which massive galaxies have higher gas metallicities. Several large galaxy surveys, such as the → Sloan Digital Sky Survey (SDSS), have confirmed that galaxies at all → redshifts with higher stellar masses retain more metals than galaxies with lower stellar masses. Besides the dependence on stellar mass, other studies have found further dependences of gas metallicity on other physical properties at a given mass, such as → specific star formation rate, → star formation rate, and stellar age. These higher dimensional relations could provide additional constraints to the processes that regulate the metal enrichment in galaxies. In addition to gas metallicity, also the → stellar metallicity of galaxies is found to correlate with the stellar mass, suggesting the mass-metallicity relation already existed at early epochs of galaxy evolution (Lian et al., 2017, MNRAS 474, 1143, and references therein).

mass; → metallicity; → relation.

metal
  فلز   
felez (#)

Fr.: métal   

1) Chemistry: An → element in which the highest occupied energy band (→ conduction band) is only partially filled with electrons.
2) Astrophysics: Conventionally, any element heavier than → helium. The term "metal," as used for this concept, is in fact inappropriate. Same as → heavy element. See also → metallicity.

From O.Fr. metal, from L. metallum "metal, mine, quarry, what is got by mining," from Gk. metallon "metal, ore," originally "mine, quarry, pit," probably from metalleuein "to mine, to quarry," of unknown origin, but related somehow to metallan "to seek after."

Felez "metal," loanword from Ar. filizz.

metal deficiency
  کم‌فلزی   
kamfelezi

Fr.: déficience en métaux   

The quality of being metal deficient, e.g. → metal-deficient galaxy.

metal; deficiency from L. deficientem (nominative deficiens), pr.p. of deficere "to desert, fail," from → de- "down, away" + facere "to do, perform" + -ency a noun suffix, equivalent to -ence.

Kamfelezi, from kam "little, few; deficient, wanting; scarce" (Mid.Pers. kam "little, small, few," O.Pers./Av. kamna- "small, few," related to keh "small, little, slender" (related to kâstan, kâhidan "to decrease, lessen, diminish," from Mid.Pers. kâhitan, kâstan, kâhênitan "to decrease, diminish, lessen;" Av. kasu- "small, little;" Proto-Iranian *kas- "to be small, diminish, lessen") + felezmetal + -i suffix denoting state.

metal-deficient galaxy
  کهکشان ِ کم‌فلز   
kahkešân-e kamfelez

Fr.: galaxie pauvre en métaux   

A galaxy whose → metallicity is smaller than that of the → Milky Way galaxy.

Adj. from → metal deficiency; → galaxy.

metal-poor galaxy
  کهکشان ِ کم‌فلز   
kahkešân-e kamfelez

Fr.: galaxie pauvre en métaux   

Same as → metal-deficient galaxy.

metal; → poor; → galaxy.

metal-rich environment
  پرگیر ِ پرفلز   
pargir-e porfelez

Fr.: environnement riche en métaux   

An environment (→ galaxy, → nebula) whose → metallicity is larger than that of the → Milky Way galaxy.

metal; → rich; → environment.

metalanguage
  متا-زبان   
matâ-zabâb

Fr.: métalangue   

Any language that is used to describe a language. See also → object language.

meta-; → language.

metallic
  فلزی   
felezi (#)

Fr.: métallique   

Of, relating to, or consisting of metal.

metal; → -ic.

metallic hydrogen
  هیدروژن ِ فلزی   
hidrožen-e felezi

Fr.: hydrogène métallique   

A kind of → degenerate matter resulting from hydrogen gas when it is sufficiently compressed to undergo a phase change to liquid or solid state. Metallic hydrogen is thought to be present in compressed astronomical objects, such as the interiors of the solar system planets Jupiter and Saturn. Above the core of these planets (at a temperature of 10,000 degrees and a pressure of 3 million bars) the electrons are squeezed out of the hydrogen atoms and the fluid starts to conduct like a metal.

metallic; → hydrogen.

metallicity
  فلزیگی   
felezigi

Fr.: métallicité   

In a star, nebula, or galaxy, the proportion of the material that is made up of → metals, that is elements heavier than → helium. It is generally denoted by Z. The term "metallicity" is a misnomer used in astrophysics.
1) In practice, the metallicity of stars is usually expressed by the number ratio of → iron atoms to → hydrogen atoms per unit volume, with respect to the solar values: [Fe/H] = log10(NFe/NH)star - log10(NFe/NH)Sun, where NFe and NH are the numbers of iron and hydrogen atoms per unit volume. In fact it is taken to be equal to the iron → abundance with respect to the solar value. The solar logarithmic iron abundance is 7.50 ± 0.04 (Asplund et al. 2009, ARAA 47, 481), with respect to that of hydrogen which, by convention, is 12.00. Stellar metallicity is often expressed in mass fraction. See also → solar metallicity.
2) Nebular metallicity is often defined as the relative abundance of → oxygen: (NO/NH)neb/(NO/NH)Sun, where NO and NH represent the numbers of oxygen and hydrogen atoms per unit volume.

From metallic, from → metal + → -ity.

metallicity distribution function (MDF)
  کریای ِ واباژش ِ فلزیگی   
karyâ-ye vâbâžeš-e felezigi

Fr.: 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.

metallicity gradient
  زینه‌ی ِ فلزیگی   
zine-ye felezigi

Fr.: gradient de métallicité   

The decrease in the → abundances of → heavy elements in a → disk galaxy as a function of distance from the center. Radial metallicity gradients are observed in many galaxies, including the → Milky Way and other galaxies of the → Local Group. In the case of the Milky Way, several objects can be used to determine the gradients: → H II regions, → B stars, → Cepheids, → open clusters, and → planetary nebulae. The main diagnostic elements are oxygen, sulphur, neon, and argon in photoionized nebulae, and iron and other elements in Cepheids, open clusters, and stars. Cepheids are probably the most accurate indicators of abundance gradients in the Milky Way. They are bright enough to be observed at large distances, so that accurate distances and spectroscopic abundances of several elements can be obtained. Average abundance gradients are generally between -0.03 → dex/kpc and -0.10 dex/kpc, with a a flattening out of the gradients at large galactocentric distances (≥ 10 kpc). The existence of these gradients offers the opportunity to test models of → chemical evolution of galaxies and stellar → nucleosynthesis.

metallicity; → gradient.

solar metallicity
  فلزیگی ِ خورشیدی   
felezigi-ye xoršidi

Fr.: métallicité solaire   

The proportion of the solar matter made up of → chemical elements heavier than → helium. It is denoted by Z, which represents the sum of all elements heavier than → helium, in mass fraction. The most recent determination of the solar Z gives a value of 0.0134 (Asplund et al. 2009, ARAA 47, 481), corresponding to the present-day photospheric composition.

solar; → metallicity.

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