Constraints on the galactic inner halo assembly history from the age gradient of blue horizontal-branch stars

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dc.creatorWhitten, Devin D.
dc.creatorBeers, Timothy C.
dc.creatorPlacco, Vinicius Moris
dc.creatorSantucci, Rafael Miloni
dc.creatorDenissenkov, Pavel
dc.creatorTissera, Patricia Beatriz
dc.creatorMejías, Andrea
dc.creatorHernitschek, Nina
dc.creatorCarollo, Daniela
dc.date.accessioned2023-05-15T13:24:21Z
dc.date.available2023-05-15T13:24:21Z
dc.date.issued2019
dc.description.abstractWe present an analysis of the relative age distribution of the Milky Way halo, based on samples of blue horizontal branch (BHB) stars obtained from the Panoramic Survey Telescope and Rapid Response System and Galaxy Evolution Explorer photometry, as well a Sloan Digital Sky Survey spectroscopic sample. A machine-learning approach to the selection of BHB stars is developed, using support vector classification, with which we produce chronographic age maps of the Milky Way halo out to 40 kpc from the Galactic center. We identify a characteristic break in the relative age profiles of our BHB samples, corresponding to a Galactocentric radius of RGC ∼ 14 kpc. Within the break radius, we find an age gradient of −63.4 ± 8.2 Myr kpc−1 , which is significantly steeper than obtained by previous studies that did not discern between the inner- and outer-halo regions. The gradient in the relative age profile and the break radius signatures persist after correcting for the influence of metallicity on our spectroscopic calibration sample. We conclude that neither are due to the previously recognized metallicity gradient in the halo, as one passes from the inner-halo to the outer-halo region. Our results are consistent with a dissipational formation of the inner-halo population, involving a few relatively massive progenitor satellites, such as those proposed to account for the assembly of Gaia-Enceladus, which then merged with the inner halo of the Milky Way.pt_BR
dc.identifier.citationWHITTEN, Devin D.et al. Constraints on the galactic inner halo assembly history from the age gradient of blue horizontal-branch stars. The Astrophysical Journal, Bristol, v. 884, n. 1, e67, 2019. DOI: 10.3847/1538-4357/ab4269. Disponível em: https://iopscience.iop.org/article/10.3847/1538-4357/ab4269. Acesso em: 11 maio 2023.pt_BR
dc.identifier.doi10.3847/1538-4357/ab4269
dc.identifier.issn0004-637X
dc.identifier.urihttp://repositorio.bc.ufg.br/handle/ri/22533
dc.language.isoengpt_BR
dc.publisher.countryGra-bretanhapt_BR
dc.rightsAcesso Abertopt_BR
dc.rights.urihttp://creativecommons.org/licenses/by-nc-nd/4.0/*
dc.titleConstraints on the galactic inner halo assembly history from the age gradient of blue horizontal-branch starspt_BR
dc.typeArtigopt_BR

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