metallicity

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metallicity

(met-ă-liss -ă-tee) (metal abundance) Symbol: Z . The fraction by mass of metals in a star, cluster of stars, or in some other astronomical entity. Since metals are produced by nucleosynthesis in stars, the metallicity of an object or class of objects depends on when it was formed: objects of later origin in general have a higher metallicity. Metallicity is determined by photometry or high-resolution spectroscopy, and is usually expressed relative to solar metallicity (see cosmic abundance), and as the ratio of iron to hydrogen, Fe/H. See also population I, population II.
References in periodicals archive ?
Context:The Milky Way is the one disk galaxy that we can observe in great detail and study individual stars that span a wide range of ages and metallicities. The older stars that we observe are stellar fossils, containing information from the epoch of Galaxy formation.
"Using the metallicities of the stars in the catalogues from the high quality spectral atlases of APOGEE and LAMOST, and with the distances at which the objects are situated, we have shown that there are an appreciable fraction of stars with higher metallicity, [a] characteristic of disc stars, further out than the previously assumed limit on the radius of the Galaxy disc," study co-author Carlos Allende said in a (https://www.eurekalert.org/pub_releases/2018-06/idad-tdo060718.php) statement.
Villar studies how different amounts of heavy elements, or metallicities, might alter the detonations.
The process of determining radial velocity dispersions and metallicities of clusters and galaxies is fundamental to most disciplines of astronomy.
To compare planets by their metallicities, scientists use the sun as a point of reference -- similar to describing how much caffeine different drinks have by comparing them to a standard cup of coffee.
Reference [305] found that the metallicities of half a dozen low-redshift (z < 0.3) LGRB hosts were lower than their equally luminous counterparts in the local star-forming galaxy population and proposed that LGRB formation was limited by a strong metallicity threshold.
metallicities (abundances of elements heavier than helium) encountered
Then, they conducted a statistical test to see if the sizes of the planets fell into natural groups, along with the stellar metallicities.
For the outer disks of the galaxies, we have found SSP-equivalent metallicities from the solar one down to [Z/H]=-0.4-0.7, rather high magnesium-to-iron ratios, [Mg/Fe]> +0.2, and mostly old SSP-equivalent ages.
Specific topics covered include the UV spectrum of the galactic bulge, helium and the hot horizontal branch, binary population synthesis and sdB stars at different metallicities, and hypervelocity stars.
Neptune and Uranus, which are smaller than the gas giants, are richer in heavier elements and have metallicities about 100 times that of the sun.
At this crucial scale, the MUSE-ALMA-HST Survey will provide a characterization of the SF history, stellar/gaseous surface densities, metallicities of stars and gas, the stellar radiation field, extinction, and stellar/gas kinematics, and thus uncover the physical conditions that control and regulate the SF process.