On the nature of a secondary main-sequence turn-off in the rich LMC cluster NGC 1868
Autor(a) principal: | |
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Data de Publicação: | 2002 |
Outros Autores: | , , |
Tipo de documento: | Artigo |
Idioma: | eng |
Título da fonte: | Repositório Institucional da UFRGS |
Texto Completo: | http://hdl.handle.net/10183/89977 |
Resumo: | Evidence for a second main-sequence turn-off in a deep colour–magnitude diagram (CMD) of NGC 1868 is presented. The data were obtained with Hubble Space Telescope (HST) WFPC2 and reach down to m555 -~ 25 mag. Besides the usual τ 0.8 Gyr turn-off found in previous analyses, another possible turn-off is seen at m555 - ~ 21 mag (MV - ~ 2.5), which is consistent with an age of τ - ~ 3 Gyr. This CMD feature stands out clearly especially when contaminating field Large Magellanic Cloud (LMC) stars are statistically removed. The background subtracted CMD also visibly displays a red subgiant branch extending about 1.5 mag below the younger turn-off and the clump of red giants. The significance of the secondary turn-off inNGC1868was confirmed with Monte Carlo simulations and bootstrapping techniques. Star counts in selected regions in the cluster CMD indicate a mass ratio of old population/young population in the range 5 < ~ Mold/Myoung < ~ 12 per cent, depending on the mass-function slope. The existence of such a subpopulation in NGC 1868 is significant even in the presence of uncertainties in background subtraction. The possibility that the secondary turn-off is associated with the field star population was examined by searching for similar features in CMDs of field stars. Statistically significant excesses of stars redwards of the main sequence were found in all such fields in the range 20 < ~ m555 < ~ 22 mag. These however are much broader features that do not resemble the main-sequence termination of a single population. We also discuss other alternative explanations for the feature at m555 - ~ 21 mag, such as unresolved binarism, peculiar stars or CMD discontinuities associated with the Böhm–Vitense gap. |
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Santiago, Basilio XavierKerber, Leandro de OliveiraCastro, RodrigoGrijs, Richard de2014-03-29T01:51:43Z20020035-8711http://hdl.handle.net/10183/89977000337499Evidence for a second main-sequence turn-off in a deep colour–magnitude diagram (CMD) of NGC 1868 is presented. The data were obtained with Hubble Space Telescope (HST) WFPC2 and reach down to m555 -~ 25 mag. Besides the usual τ 0.8 Gyr turn-off found in previous analyses, another possible turn-off is seen at m555 - ~ 21 mag (MV - ~ 2.5), which is consistent with an age of τ - ~ 3 Gyr. This CMD feature stands out clearly especially when contaminating field Large Magellanic Cloud (LMC) stars are statistically removed. The background subtracted CMD also visibly displays a red subgiant branch extending about 1.5 mag below the younger turn-off and the clump of red giants. The significance of the secondary turn-off inNGC1868was confirmed with Monte Carlo simulations and bootstrapping techniques. Star counts in selected regions in the cluster CMD indicate a mass ratio of old population/young population in the range 5 < ~ Mold/Myoung < ~ 12 per cent, depending on the mass-function slope. The existence of such a subpopulation in NGC 1868 is significant even in the presence of uncertainties in background subtraction. The possibility that the secondary turn-off is associated with the field star population was examined by searching for similar features in CMDs of field stars. Statistically significant excesses of stars redwards of the main sequence were found in all such fields in the range 20 < ~ m555 < ~ 22 mag. These however are much broader features that do not resemble the main-sequence termination of a single population. We also discuss other alternative explanations for the feature at m555 - ~ 21 mag, such as unresolved binarism, peculiar stars or CMD discontinuities associated with the Böhm–Vitense gap.application/pdfengMonthly notices of the royal astronomical society. Oxford. Vol. 336, no. 1 (Oct. 2002), p. 139-150Evolucao estelarFotometria estelarSimulação : Método Monte CarloHertzsprung–Russell (HR) diagramStars: statisticsGalaxies: star clustersOn the nature of a secondary main-sequence turn-off in the rich LMC cluster NGC 1868Estrangeiroinfo: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:UFRGSORIGINAL000337499.pdf000337499.pdfTexto completo (inglês)application/pdf478127http://www.lume.ufrgs.br/bitstream/10183/89977/1/000337499.pdf013c6ed3e93fb8b333671b6953e33b0dMD51TEXT000337499.pdf.txt000337499.pdf.txtExtracted Texttext/plain48035http://www.lume.ufrgs.br/bitstream/10183/89977/2/000337499.pdf.txt1a311cb043f97e70493f65726679c83cMD52THUMBNAIL000337499.pdf.jpg000337499.pdf.jpgGenerated Thumbnailimage/jpeg2078http://www.lume.ufrgs.br/bitstream/10183/89977/3/000337499.pdf.jpg259d0bcdb1a53caeabc0e5670de8e434MD5310183/899772023-07-04 03:50:51.403855oai:www.lume.ufrgs.br:10183/89977Repositório de PublicaçõesPUBhttps://lume.ufrgs.br/oai/requestopendoar:2023-07-04T06:50:51Repositório Institucional da UFRGS - Universidade Federal do Rio Grande do Sul (UFRGS)false |
dc.title.pt_BR.fl_str_mv |
On the nature of a secondary main-sequence turn-off in the rich LMC cluster NGC 1868 |
title |
On the nature of a secondary main-sequence turn-off in the rich LMC cluster NGC 1868 |
spellingShingle |
On the nature of a secondary main-sequence turn-off in the rich LMC cluster NGC 1868 Santiago, Basilio Xavier Evolucao estelar Fotometria estelar Simulação : Método Monte Carlo Hertzsprung–Russell (HR) diagram Stars: statistics Galaxies: star clusters |
title_short |
On the nature of a secondary main-sequence turn-off in the rich LMC cluster NGC 1868 |
title_full |
On the nature of a secondary main-sequence turn-off in the rich LMC cluster NGC 1868 |
title_fullStr |
On the nature of a secondary main-sequence turn-off in the rich LMC cluster NGC 1868 |
title_full_unstemmed |
On the nature of a secondary main-sequence turn-off in the rich LMC cluster NGC 1868 |
title_sort |
On the nature of a secondary main-sequence turn-off in the rich LMC cluster NGC 1868 |
author |
Santiago, Basilio Xavier |
author_facet |
Santiago, Basilio Xavier Kerber, Leandro de Oliveira Castro, Rodrigo Grijs, Richard de |
author_role |
author |
author2 |
Kerber, Leandro de Oliveira Castro, Rodrigo Grijs, Richard de |
author2_role |
author author author |
dc.contributor.author.fl_str_mv |
Santiago, Basilio Xavier Kerber, Leandro de Oliveira Castro, Rodrigo Grijs, Richard de |
dc.subject.por.fl_str_mv |
Evolucao estelar Fotometria estelar Simulação : Método Monte Carlo |
topic |
Evolucao estelar Fotometria estelar Simulação : Método Monte Carlo Hertzsprung–Russell (HR) diagram Stars: statistics Galaxies: star clusters |
dc.subject.eng.fl_str_mv |
Hertzsprung–Russell (HR) diagram Stars: statistics Galaxies: star clusters |
description |
Evidence for a second main-sequence turn-off in a deep colour–magnitude diagram (CMD) of NGC 1868 is presented. The data were obtained with Hubble Space Telescope (HST) WFPC2 and reach down to m555 -~ 25 mag. Besides the usual τ 0.8 Gyr turn-off found in previous analyses, another possible turn-off is seen at m555 - ~ 21 mag (MV - ~ 2.5), which is consistent with an age of τ - ~ 3 Gyr. This CMD feature stands out clearly especially when contaminating field Large Magellanic Cloud (LMC) stars are statistically removed. The background subtracted CMD also visibly displays a red subgiant branch extending about 1.5 mag below the younger turn-off and the clump of red giants. The significance of the secondary turn-off inNGC1868was confirmed with Monte Carlo simulations and bootstrapping techniques. Star counts in selected regions in the cluster CMD indicate a mass ratio of old population/young population in the range 5 < ~ Mold/Myoung < ~ 12 per cent, depending on the mass-function slope. The existence of such a subpopulation in NGC 1868 is significant even in the presence of uncertainties in background subtraction. The possibility that the secondary turn-off is associated with the field star population was examined by searching for similar features in CMDs of field stars. Statistically significant excesses of stars redwards of the main sequence were found in all such fields in the range 20 < ~ m555 < ~ 22 mag. These however are much broader features that do not resemble the main-sequence termination of a single population. We also discuss other alternative explanations for the feature at m555 - ~ 21 mag, such as unresolved binarism, peculiar stars or CMD discontinuities associated with the Böhm–Vitense gap. |
publishDate |
2002 |
dc.date.issued.fl_str_mv |
2002 |
dc.date.accessioned.fl_str_mv |
2014-03-29T01:51:43Z |
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publishedVersion |
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http://hdl.handle.net/10183/89977 |
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0035-8711 |
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000337499 |
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http://hdl.handle.net/10183/89977 |
dc.language.iso.fl_str_mv |
eng |
language |
eng |
dc.relation.ispartof.pt_BR.fl_str_mv |
Monthly notices of the royal astronomical society. Oxford. Vol. 336, no. 1 (Oct. 2002), p. 139-150 |
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