On the meaning of a minimization procedure applied to a degenerate astrophysical problem

Detalhes bibliográficos
Autor(a) principal: Schmidt, Alex Andre
Data de Publicação: 1989
Outros Autores: Bica, Eduardo Luiz Damiani, Dottori, Horacio Alberto
Tipo de documento: Artigo
Idioma: eng
Título da fonte: Repositório Institucional da UFRGS
Texto Completo: http://hdl.handle.net/10183/88368
Resumo: We apply the MINOS optimization system to the population synthesis of galaxy nuclei using as basis a grid of star cluster spectral features as a function of age and metallicity. In inverse numerical problems, a minimization procedure is usually applied to provide a single optimal result which ignores, as a rule, a multitude of other equally good solutions whenever intrinsic errors are to be considered. We avoid this drawback by transforming the population synthesis into a series of optimization problems, each one corresponding to a fixed contribution of an individual basis component. In this way we sweep the vector space of solutions, generated by the basis components, rejecting the minimization results for which the differences between observed and synthetic equivalent widths are larger than the observational uncertainties. Consequently we map the space of mathematically similar solutions, determining the degeneracy degree of the problem. The astrophysical implications of the synthesis results are discussed. In particular, a noteworthy result is that for some classes of red galaxy nuclei, our constraint free population synthesis, consisting of 35 components which are widely distributed in the plane age versus metallicity, reproduces the chemical evolution scenario predicted by theoretical evolutionary models. The results for bluer nuclei tend to scatter more in the plane age versus metallicity, suggesting that additional information from complementary spectral ranges is necessary to produce a better focused solution in the plane. However, strong bursts of star formation are easily detected.
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spelling Schmidt, Alex AndreBica, Eduardo Luiz DamianiDottori, Horacio Alberto2014-03-13T01:50:39Z19890035-8711http://hdl.handle.net/10183/88368000014809We apply the MINOS optimization system to the population synthesis of galaxy nuclei using as basis a grid of star cluster spectral features as a function of age and metallicity. In inverse numerical problems, a minimization procedure is usually applied to provide a single optimal result which ignores, as a rule, a multitude of other equally good solutions whenever intrinsic errors are to be considered. We avoid this drawback by transforming the population synthesis into a series of optimization problems, each one corresponding to a fixed contribution of an individual basis component. In this way we sweep the vector space of solutions, generated by the basis components, rejecting the minimization results for which the differences between observed and synthetic equivalent widths are larger than the observational uncertainties. Consequently we map the space of mathematically similar solutions, determining the degeneracy degree of the problem. The astrophysical implications of the synthesis results are discussed. In particular, a noteworthy result is that for some classes of red galaxy nuclei, our constraint free population synthesis, consisting of 35 components which are widely distributed in the plane age versus metallicity, reproduces the chemical evolution scenario predicted by theoretical evolutionary models. The results for bluer nuclei tend to scatter more in the plane age versus metallicity, suggesting that additional information from complementary spectral ranges is necessary to produce a better focused solution in the plane. However, strong bursts of star formation are easily detected.application/pdfengMonthly Notices of the Royal Astronomical Society. London. Vol. 238, no. 3 (June 1989), p. 925-934Estruturas galaticasNucleo galaticoPopulacoes estelaresAstrofísicaOn the meaning of a minimization procedure applied to a degenerate astrophysical problemEstrangeiroinfo:eu-repo/semantics/articleinfo:eu-repo/semantics/publishedVersioninfo:eu-repo/semantics/openAccessreponame:Repositório Institucional da UFRGSinstname:Universidade Federal do Rio Grande do Sul (UFRGS)instacron:UFRGSORIGINAL000014809.pdf000014809.pdfTexto completo (inglês)application/pdf169245http://www.lume.ufrgs.br/bitstream/10183/88368/1/000014809.pdf29354e84fd360fb96463326fc0b618f7MD51TEXT000014809.pdf.txt000014809.pdf.txtExtracted Texttext/plain220http://www.lume.ufrgs.br/bitstream/10183/88368/2/000014809.pdf.txt7e6affd93c54ac341be37e3a4fd8b449MD52THUMBNAIL000014809.pdf.jpg000014809.pdf.jpgGenerated Thumbnailimage/jpeg1803http://www.lume.ufrgs.br/bitstream/10183/88368/3/000014809.pdf.jpgbc518fa8b3b278c8ff4b40817db20bcdMD5310183/883682024-09-07 06:17:18.768609oai:www.lume.ufrgs.br:10183/88368Repositório de PublicaçõesPUBhttps://lume.ufrgs.br/oai/requestopendoar:2024-09-07T09:17:18Repositório Institucional da UFRGS - Universidade Federal do Rio Grande do Sul (UFRGS)false
dc.title.pt_BR.fl_str_mv On the meaning of a minimization procedure applied to a degenerate astrophysical problem
title On the meaning of a minimization procedure applied to a degenerate astrophysical problem
spellingShingle On the meaning of a minimization procedure applied to a degenerate astrophysical problem
Schmidt, Alex Andre
Estruturas galaticas
Nucleo galatico
Populacoes estelares
Astrofísica
title_short On the meaning of a minimization procedure applied to a degenerate astrophysical problem
title_full On the meaning of a minimization procedure applied to a degenerate astrophysical problem
title_fullStr On the meaning of a minimization procedure applied to a degenerate astrophysical problem
title_full_unstemmed On the meaning of a minimization procedure applied to a degenerate astrophysical problem
title_sort On the meaning of a minimization procedure applied to a degenerate astrophysical problem
author Schmidt, Alex Andre
author_facet Schmidt, Alex Andre
Bica, Eduardo Luiz Damiani
Dottori, Horacio Alberto
author_role author
author2 Bica, Eduardo Luiz Damiani
Dottori, Horacio Alberto
author2_role author
author
dc.contributor.author.fl_str_mv Schmidt, Alex Andre
Bica, Eduardo Luiz Damiani
Dottori, Horacio Alberto
dc.subject.por.fl_str_mv Estruturas galaticas
Nucleo galatico
Populacoes estelares
Astrofísica
topic Estruturas galaticas
Nucleo galatico
Populacoes estelares
Astrofísica
description We apply the MINOS optimization system to the population synthesis of galaxy nuclei using as basis a grid of star cluster spectral features as a function of age and metallicity. In inverse numerical problems, a minimization procedure is usually applied to provide a single optimal result which ignores, as a rule, a multitude of other equally good solutions whenever intrinsic errors are to be considered. We avoid this drawback by transforming the population synthesis into a series of optimization problems, each one corresponding to a fixed contribution of an individual basis component. In this way we sweep the vector space of solutions, generated by the basis components, rejecting the minimization results for which the differences between observed and synthetic equivalent widths are larger than the observational uncertainties. Consequently we map the space of mathematically similar solutions, determining the degeneracy degree of the problem. The astrophysical implications of the synthesis results are discussed. In particular, a noteworthy result is that for some classes of red galaxy nuclei, our constraint free population synthesis, consisting of 35 components which are widely distributed in the plane age versus metallicity, reproduces the chemical evolution scenario predicted by theoretical evolutionary models. The results for bluer nuclei tend to scatter more in the plane age versus metallicity, suggesting that additional information from complementary spectral ranges is necessary to produce a better focused solution in the plane. However, strong bursts of star formation are easily detected.
publishDate 1989
dc.date.issued.fl_str_mv 1989
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dc.relation.ispartof.pt_BR.fl_str_mv Monthly Notices of the Royal Astronomical Society. London. Vol. 238, no. 3 (June 1989), p. 925-934
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