Observations of low frequency recombination lines

Recombination lines have been detected in the radio part of the electromagnetic spectrum over a frequency range from about 200 MHz to 30 GHz. This corresponds to a range in principal quantum number, n, of n ∼ 300 to n ∼ 60. As well as emission from ionized hydrogen recombination lines have also been...

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Autor principal: Hart, Les
Formato: Articulo
Lenguaje:Español
Publicado: 1982
Materias:
Astronomía
Galaxias
Acceso en línea:http://sedici.unlp.edu.ar/handle/10915/111808
Aporte de:
SEDICI (UNLP) de Universidad Nacional de La Plata
id I19-R120-10915-111808
record_format dspace
spelling I19-R120-10915-1118082024-08-30T18:34:20Z http://sedici.unlp.edu.ar/handle/10915/111808 Observations of low frequency recombination lines Hart, Les 1982 2021-01-27T14:56:23Z es Astronomía Galaxias Recombination lines have been detected in the radio part of the electromagnetic spectrum over a frequency range from about 200 MHz to 30 GHz. This corresponds to a range in principal quantum number, n, of n ∼ 300 to n ∼ 60. As well as emission from ionized hydrogen recombination lines have also been detected from heavier elements such as helium, carbon and Silicon. Most of the recombination lines detected originate in hot gas, with an electron temperature Te ∼ 10³ -10⁴ K, which is associated with HII regions. At high frequencies the combination of the physics of recombination line emission and the fact that radio telescopes have smaller half-power beam-widths result in the observations being more sensitive to high density, high emission measure, small diameter sources such as compact HII regions. Conversely, at low density, low emission measure, large diameter sources such as extended HII regions. For the purpose of this article I shall consider only a transitions (Δn=1) from hydrogen and further that low frequency recombination lines are those which is close in frequency to the 21 cm line of neutral hydrogen. For reasons that will be given below this frequency at which the division is made is not as arbitrary as it may first seem. Asociación Argentina de Astronomía Articulo Articulo http://creativecommons.org/licenses/by-nc-sa/4.0/ Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International (CC BY-NC-SA 4.0) application/pdf
institution Universidad Nacional de La Plata
institution_str I-19
repository_str R-120
collection SEDICI (UNLP)
language Español
topic Astronomía
Galaxias
spellingShingle Astronomía
Galaxias
Hart, Les
Observations of low frequency recombination lines
topic_facet Astronomía
Galaxias
description Recombination lines have been detected in the radio part of the electromagnetic spectrum over a frequency range from about 200 MHz to 30 GHz. This corresponds to a range in principal quantum number, n, of n ∼ 300 to n ∼ 60. As well as emission from ionized hydrogen recombination lines have also been detected from heavier elements such as helium, carbon and Silicon. Most of the recombination lines detected originate in hot gas, with an electron temperature Te ∼ 10³ -10⁴ K, which is associated with HII regions. At high frequencies the combination of the physics of recombination line emission and the fact that radio telescopes have smaller half-power beam-widths result in the observations being more sensitive to high density, high emission measure, small diameter sources such as compact HII regions. Conversely, at low density, low emission measure, large diameter sources such as extended HII regions. For the purpose of this article I shall consider only a transitions (Δn=1) from hydrogen and further that low frequency recombination lines are those which is close in frequency to the 21 cm line of neutral hydrogen. For reasons that will be given below this frequency at which the division is made is not as arbitrary as it may first seem.
format Articulo
Articulo
author Hart, Les
author_facet Hart, Les
author_sort Hart, Les
title Observations of low frequency recombination lines
title_short Observations of low frequency recombination lines
title_full Observations of low frequency recombination lines
title_fullStr Observations of low frequency recombination lines
title_full_unstemmed Observations of low frequency recombination lines
title_sort observations of low frequency recombination lines
publishDate 1982
url http://sedici.unlp.edu.ar/handle/10915/111808
work_keys_str_mv AT hartles observationsoflowfrequencyrecombinationlines
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