Spectroscopic dissection of the Globular Cluster NGC 6569
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Date
2024
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Universidad de Concepción
Abstract
Análisis de la evolución quimiodinámica en cúmulos globulares (CGs) ha revelado un fenómeno exclusivo respecto a sus poblaciones estelares, mostrando variaciones anómalas de elementos ligeros de estrella a estrella no esperables de una evolución estelar estándar, conocido como múltiples poblaciones (MPs). Sin embargo, la investigación espectroscópica de MPs, particularmente en la Vía Láctea, se ha centrado en CGs del halo y del disco, descartando casi por completo aquellos del bulbo galáctico, donde los escenarios de formación de MPs aún deben ser probados. Recientemente, el cúmulo globular NGC 6569, con una relativamente alta metalicidad, cumplió con los requisitos para definir MPs mostrando dispersiones anti-correlacionadas de [Na/Fe] y [O/Fe]. No obstante, evita características espectrales clave para explicar sus patrones de abundancia y, por lo tanto, la fuente de material enriquecido. Realizamos un análisis espectral detallado de 10 gigantes rojas utilizando espectros de alta resolución en el infrarrojo cercano recolectados con APOGEE-2S, como parte del bulge Cluster APOgee survey(CAPOS), para caracterizar completamente sus MPs. Usamos el código BACCHUS para obtener simultáneamente abundancias de MPs y elementos de procesos s/r- para investigar las fuentes de contaminación y posibles escenarios de formación de MPs basados en variaciones de abundancia. Derivamos un valor promedio de [Fe/H] = -0.93 ± 0.05 dex con una dispersión compatible con errores intrínsecos, sin evidencia de dispersión de metalicidad. Las abundancias de elementos α presenta un valor promedio de [α/Fe] = 0.41 dex, compatible con hallazgos previos en este cúmulo. En cuanto a sus MPs, clasificamos por primera vez dos poblaciones estelares distintas basadas en nitrógeno y evidenciamos una clara anti-correlación entre [N/Fe] y [C/Fe]. Además, derivamos valores de [Ce/Fe] y [Nd/Fe] por primera vez en NGC 6569 y apoyamos la idea de un material contaminado dominante por procesos r en la evolución temprana, basado en la razón [Ce/Nd] = -0.20. Además, probamos la calidad de las abundancias obtenidas comparando los parámetros atmosféricos de APOGEE Stellar Parameters and Chemical Abundance Pipeline (ASPCAP) con aquellos de la fotometría de Gaia + 2MASS, resolviendo problemas adjudicados a la sobreestimación de la temperatura de las segundas poblaciones introducida por ASPCAP.
Chemodynamical evolution analysis in globular clusters (GCs) has revealed an exclusive phenomena regarding their stellar populations, exhibiting anomalous star- to-star variations in light elements not expected from standard stellar evolution, known as multiple populations(MPs). However, spectroscopic MPs research, particularly in the Milky way, has focused mainly on halo and disk GCs, almost completely discarding those of the Galactic bulge, where MPs formation scenarios remain to be tested. Recently, the relatively high-metallicity bulge GC NGC 6569 filled the requisites to define MPs showing anti-correlated [Na/Fe] and [O/Fe] spreads. Nevertheless, it avoids key spectral features to explain its abundance patterns and thus the enriched material source. We performed a detailed spectral analysis of 10 red giants members using high-resolution near-infrared spectra collected with Apache Point Observatory Galactic Evolution Experiment II(APOGEE-2S), as part of the bulge Cluster APOgee Survey(CAPOS) project, to fully characterize its MPs. We use the Brussels Automatic Code for Characterizing High accuracy Spectra(BACCHUS) code to obtained simultaneously MPs and s/r-process elements abundances to investigate pollution sources and possible MPs formation scenarios based on abundance variations. We derived a mean value of [Fe/H] = -0.93 ± 0.05 dex with star-to-star spread compatible with intrinsic errors, finding no evidence of metallicity spread. α-elements enhancement preclude a mean value of [α/Fe] = 0.41 dex, compatible with previous findings on this cluster. Regarding their MPs, we classify for the first time two distinct stellar population based on nitrogen and evidence a clear anti-correlation between [N/Fe] and [C/Fe]. In addition, we derived values of [Ce/Fe] and [Nd/Fe] for the first time in NGC 6569 and support the idea of dominant r-process polluted material on the early evolution based on the ratio [Ce/Nd] = -0.20. Moreover, we test the quality of the obtained abundances comparing the atmospheric parameters from APOGEE Stellar Parameters and Chemical Abundance Pipeline(ASPCAP) to those from Gaia + 2MASS photometry, disentangling problems adjudicated to the overestimation of temperature of second population introduced by ASPCAP.
Chemodynamical evolution analysis in globular clusters (GCs) has revealed an exclusive phenomena regarding their stellar populations, exhibiting anomalous star- to-star variations in light elements not expected from standard stellar evolution, known as multiple populations(MPs). However, spectroscopic MPs research, particularly in the Milky way, has focused mainly on halo and disk GCs, almost completely discarding those of the Galactic bulge, where MPs formation scenarios remain to be tested. Recently, the relatively high-metallicity bulge GC NGC 6569 filled the requisites to define MPs showing anti-correlated [Na/Fe] and [O/Fe] spreads. Nevertheless, it avoids key spectral features to explain its abundance patterns and thus the enriched material source. We performed a detailed spectral analysis of 10 red giants members using high-resolution near-infrared spectra collected with Apache Point Observatory Galactic Evolution Experiment II(APOGEE-2S), as part of the bulge Cluster APOgee Survey(CAPOS) project, to fully characterize its MPs. We use the Brussels Automatic Code for Characterizing High accuracy Spectra(BACCHUS) code to obtained simultaneously MPs and s/r-process elements abundances to investigate pollution sources and possible MPs formation scenarios based on abundance variations. We derived a mean value of [Fe/H] = -0.93 ± 0.05 dex with star-to-star spread compatible with intrinsic errors, finding no evidence of metallicity spread. α-elements enhancement preclude a mean value of [α/Fe] = 0.41 dex, compatible with previous findings on this cluster. Regarding their MPs, we classify for the first time two distinct stellar population based on nitrogen and evidence a clear anti-correlation between [N/Fe] and [C/Fe]. In addition, we derived values of [Ce/Fe] and [Nd/Fe] for the first time in NGC 6569 and support the idea of dominant r-process polluted material on the early evolution based on the ratio [Ce/Nd] = -0.20. Moreover, we test the quality of the obtained abundances comparing the atmospheric parameters from APOGEE Stellar Parameters and Chemical Abundance Pipeline(ASPCAP) to those from Gaia + 2MASS photometry, disentangling problems adjudicated to the overestimation of temperature of second population introduced by ASPCAP.
Description
Tesis presentada para optar al grado de Magíster en Astronomía
Keywords
Estrellas Cúmulos globulares, Espectroscopía astronómica, Poblaciones Estelares