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The Unified Astronomy Thesaurus is an open, interoperable and community-supported thesaurus of astronomical and astrophysical concepts and their relationships.
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New Concept: Hii galaxies #297

Open katieefrey opened 4 years ago

katieefrey commented 4 years ago

Name the new concept Hii galaxies

Describe the concept they are dwarf starburst galaxies, see https://link.springer.com/chapter/10.1007/978-94-009-3035-3_5 Could be narrower term for Starburst galaxies http://astrothesaurus.org/uat/1570

Please include any additional comments/feedback Suggestion from Sebastien Derriere, Observatoire de Strasbourg

katieefrey commented 4 years ago

Is "HII galaxies" better? "H II galaxies"?

Any relation to "H II regions"?

"HIl galaxies or detached extragalactic HII regions: This class of galaxy has small dimensions, spheroidal shape, a young and hot stellar population and spectroscopic properties indistinguishable from those of giant extragalactic Hn regions (Sargent and Searle 1970)." "HII galaxies are not to be confused with "blue compact galaxies", which exhibit qualitatively different properties." -- from the chapter suggested above by Sebastien Derriere (https://link-springer-com.ezp-prod1.hul.harvard.edu/chapter/10.1007/978-94-009-3035-3_5)

katieefrey commented 4 years ago

"HII Galaxies are compact dwarf starburst galaxies with strong, narrow emission lines superposed on a weak, blue continuum. The optical spectra of HII Galaxies are indistinguishable from those of Giant HII regions in local galaxies (Sargent & Searle 1970). It is now widely accepted that they are not bona fide young galaxies forming their first generation of stars, as was thought in the past, since they all show a population of old stars." "The morphologies of HII galaxies remain as first described, a “mixed bag” (Loose & Thuan 1986; Kunth et al. 1988). The general properties of HII galaxies and blue compact galaxies (BCG) broadly overlap (Kunth & Östlin 2000). They have irregular shapes, typically small physical sizes, and no signs of ordered structures such as disks. Their starburst regions, consisting of emsembles of massive ionizing clusters and their respective giant HII regions cover most of the extension of their optical images. More luminous HII galaxies seem to show some evidence of tails, fuzz in their outermost isophotes, and more disturbed overall morphologies, whereas the lower luminosity galaxies seem more compact (Telles et al. 1997). [...] Due to their low mass, low oxygen abundance, low dust content, and low-density environments, HII galaxies constitute the simplest starbursts at galactic scales."

Eduardo Telles and Jorge Melnick. Stellar populations of HII galaxies: A tale of three bursts. A&A 615, A55 (2018) https://www.aanda.org/articles/aa/full_html/2018/07/aa32275-17/aa32275-17.html

katieefrey commented 3 years ago

According to Etymological Dictionary of Astronomy and Astrophysics, H II galaxies are the same as blue compact dwarf galaxies. http://dictionary.obspm.fr/index.php?formSearchTextfield=blue+compact+dwarf+galaxy&formSubmit=Search&showAll=1

BartlettAstro commented 4 months ago

"H II" appears to be the preferred designation for ionized hydrogen.