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: 5 Search : ad-
ad-
     

Fr.: ad-   

Prefix meaning "to, toward, addition to, near," from L. ad "to, toward." It is modified to ac- or af- or ag- or al- etc. according to the following consonant.

Cognate with E. at, from O.E. æt "near, by, at"; compare with O.N., Goth. at, O.Fris. et, O.H.G. az, Skt. adhi "near," PIE *ad- "to, near, at".

broad-band photometry
  شیدسنجی ِ پهن-باند   
šidsanji-ye pahn-bând

Fr.: photométrie à bande large   

Photometric measurements carried out through filters with a band-width (about one-tenth the central wavelength) in the range 30-100 nm. Typical examples are Johnson photometry, Krons-Cousins RI photometry, and the six-color system.

broad; → band; → photometry.

broad-line radio galaxy (BLRG)
  رادیو‌کهکشان ِ پهن-خط   
radio kahkašân-e pahn-xatt

Fr.: galaxie radio à raies larges   

A radio galaxy that shows broad optical emission lines. → broad-line region.

broad; → line; → radio galaxy.

broad-line region (BLR)
  ناحیه‌ی ِ پهن-خط   
nâhiye-ye pahn-xatt

Fr.: région à raies larges   

The inner region of a → quasar or an → active galactic nucleus exhibiting broad → spectral lines which indicate ionized matter moving with speeds in excess of 10,000 km sec-1, probably due to the presence of an → accretion disk surrounding a → supermassive black hole. Also called Type I AGN. See also → obscuring torus.

broad; → line; → region.

head-tail galaxy
  کهکشان ِ "سر-دم"   
kahkešân-e sar-dom

Fr.: galaxie tête-queue, ~ têtard   

A member of the class of radio galaxies (→ radio galaxy) that have a strong radio emission coming from a bright "head" and a more diffuse emission from a "tail." They are often found in clusters.

head; → tail; → galaxy.