Line-strengths in early-type galaxies

We have analysed Mg, Hβ and Fe line-strengths in a sample of elliptical, SO and brightest cluster galaxies. For 15 galaxies, our spectra extend to approximately the half-light radius(r_e), and we are able to measure radial line-strength gradients. The metallic line-strength gradients vary markedly f...

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Detalles Bibliográficos
Autores: Gorgas García, Francisco Javier, Efstathiou, G., Aragón Salamanca, A.
Tipo de recurso: artículo
Fecha de publicación:1990
País:España
Institución:Universidad Complutense de Madrid (UCM)
Repositorio:Docta Complutense
Idioma:inglés
OAI Identifier:oai:docta.ucm.es:20.500.14352/59931
Acceso en línea:https://hdl.handle.net/20.500.14352/59931
Access Level:acceso abierto
Palabra clave:52
Astronomy & Astrophysics
Astrofísica
Astronomía (Física)
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spelling Line-strengths in early-type galaxiesGorgas García, Francisco JavierEfstathiou, G.Aragón Salamanca, A.52Astronomy & AstrophysicsAstrofísicaAstronomía (Física)We have analysed Mg, Hβ and Fe line-strengths in a sample of elliptical, SO and brightest cluster galaxies. For 15 galaxies, our spectra extend to approximately the half-light radius(r_e), and we are able to measure radial line-strength gradients. The metallic line-strength gradients vary markedly from object to object, and do not correlate strongly with parameters such as total luminosity and rotation, though we find sorne evidence that gradients in the Mg_2 index correlate with central velocity dispersion and central line-strength. The highly variable line-strength gradients in early-type galaxies shows that they have experienced different star formation histories. We suggest that this may be explained if they formed by the mergers of subunits in which star formation had proceeded to varying degrees of completion. We find that the line-strengths at r~r_e in elliptical galaxies are slightly larger than those of metal­ rich galactic globulars, suggesting that typical elliptical galaxies have roughly solar abundance at r~r_e and therefore that most ellipticals have relatively weak abundance gradients. The relative line-strengths in the outer parts of ellipticals differ from those in the nuclei of low-luminosity ellipticals, indicating that these stellar populations do not represent a simple one-parameter family governed by mean metal abundance. We find no significant differences in the central Mg and Fe line-strengths of the brightest cluster galaxies and normal ellipticals with the same central velocity dispersion. How­ ever, we find that two cD galaxies show Hβ in emission and are also at the centres of the prodigious cooling flows with mass-deposition rates of ≥ 100 M_⨀ yr^-1. Galaxies with cooling flows have identical Mg and Fe line-strengths to galaxies without cooling flows. We show that this implies that only a small fraction of the total luminosity of cooling flow galaxies could come from ongoing star formation with a normal stellar initial mass function.WileyUniversidad Complutense de Madrid19901990-07-1519901990-07-15journal articlehttp://purl.org/coar/resource_type/c_6501info:eu-repo/semantics/articleapplication/pdfhttps://hdl.handle.net/20.500.14352/59931reponame:Docta Complutenseinstname:Universidad Complutense de Madrid (UCM)Inglésengopen accesshttp://purl.org/coar/access_right/c_abf2info:eu-repo/semantics/openAccessoai:docta.ucm.es:20.500.14352/599312026-06-02T12:44:21Z
dc.title.none.fl_str_mv Line-strengths in early-type galaxies
title Line-strengths in early-type galaxies
spellingShingle Line-strengths in early-type galaxies
Gorgas García, Francisco Javier
52
Astronomy & Astrophysics
Astrofísica
Astronomía (Física)
title_short Line-strengths in early-type galaxies
title_full Line-strengths in early-type galaxies
title_fullStr Line-strengths in early-type galaxies
title_full_unstemmed Line-strengths in early-type galaxies
title_sort Line-strengths in early-type galaxies
dc.creator.none.fl_str_mv Gorgas García, Francisco Javier
Efstathiou, G.
Aragón Salamanca, A.
author Gorgas García, Francisco Javier
author_facet Gorgas García, Francisco Javier
Efstathiou, G.
Aragón Salamanca, A.
author_role author
author2 Efstathiou, G.
Aragón Salamanca, A.
author2_role author
author
dc.contributor.none.fl_str_mv Universidad Complutense de Madrid
dc.subject.none.fl_str_mv 52
Astronomy & Astrophysics
Astrofísica
Astronomía (Física)
topic 52
Astronomy & Astrophysics
Astrofísica
Astronomía (Física)
description We have analysed Mg, Hβ and Fe line-strengths in a sample of elliptical, SO and brightest cluster galaxies. For 15 galaxies, our spectra extend to approximately the half-light radius(r_e), and we are able to measure radial line-strength gradients. The metallic line-strength gradients vary markedly from object to object, and do not correlate strongly with parameters such as total luminosity and rotation, though we find sorne evidence that gradients in the Mg_2 index correlate with central velocity dispersion and central line-strength. The highly variable line-strength gradients in early-type galaxies shows that they have experienced different star formation histories. We suggest that this may be explained if they formed by the mergers of subunits in which star formation had proceeded to varying degrees of completion. We find that the line-strengths at r~r_e in elliptical galaxies are slightly larger than those of metal­ rich galactic globulars, suggesting that typical elliptical galaxies have roughly solar abundance at r~r_e and therefore that most ellipticals have relatively weak abundance gradients. The relative line-strengths in the outer parts of ellipticals differ from those in the nuclei of low-luminosity ellipticals, indicating that these stellar populations do not represent a simple one-parameter family governed by mean metal abundance. We find no significant differences in the central Mg and Fe line-strengths of the brightest cluster galaxies and normal ellipticals with the same central velocity dispersion. How­ ever, we find that two cD galaxies show Hβ in emission and are also at the centres of the prodigious cooling flows with mass-deposition rates of ≥ 100 M_⨀ yr^-1. Galaxies with cooling flows have identical Mg and Fe line-strengths to galaxies without cooling flows. We show that this implies that only a small fraction of the total luminosity of cooling flow galaxies could come from ongoing star formation with a normal stellar initial mass function.
publishDate 1990
dc.date.none.fl_str_mv 1990
1990-07-15
1990
1990-07-15
dc.type.none.fl_str_mv journal article
http://purl.org/coar/resource_type/c_6501
dc.type.openaire.fl_str_mv info:eu-repo/semantics/article
format article
dc.identifier.none.fl_str_mv https://hdl.handle.net/20.500.14352/59931
url https://hdl.handle.net/20.500.14352/59931
dc.language.none.fl_str_mv Inglés
eng
language_invalid_str_mv Inglés
language eng
dc.rights.none.fl_str_mv open access
http://purl.org/coar/access_right/c_abf2
dc.rights.openaire.fl_str_mv info:eu-repo/semantics/openAccess
rights_invalid_str_mv open access
http://purl.org/coar/access_right/c_abf2
eu_rights_str_mv openAccess
dc.format.none.fl_str_mv application/pdf
dc.publisher.none.fl_str_mv Wiley
publisher.none.fl_str_mv Wiley
dc.source.none.fl_str_mv reponame:Docta Complutense
instname:Universidad Complutense de Madrid (UCM)
instname_str Universidad Complutense de Madrid (UCM)
reponame_str Docta Complutense
collection Docta Complutense
repository.name.fl_str_mv
repository.mail.fl_str_mv
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score 15.228081

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