Caracterización de regiones de formación estelar de alta masa: G353, L1482, y Vela.
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Date
2024
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Publisher
Universidad de Concepción
Abstract
El campo de la formación estelar a alta masa aún no es entendido del todo. Procesos tales como campos magnéticos, feedback estelar, e intrincados campos de velocidad agregan complejidad a la caracterización de estas regiones. Observatorios como ALMA, APEX, y el 30m de IRAM nos permiten acceder a escalas espaciales y espectrales pequeñas. En este contexto redujimos las observaciones de N2H+ de las 15 regiones del large program ALMA-IMF, y nos enfocamos en el análisis de la cinemática del gas denso del protocúmulo G353.41. Esta región está a una distancia de ∼ 2kpc, arraigado en un filamento de gran escala (∼ 8pc) y con una masa ∼ 2.5 × 103M⊙ en 1.3 ×1.3 pc2. Extrajimos la componente aislada de la emisión de N2H+ y ajustamos tres componentes de velocidad Gaussianas para identificar estructuras a escalas pequeñas. Identificamos varios gradientes de velocidad a escalas grandes (∼ 1pc) y pequeñas(∼0.2pc). Medimos nueve pares convergentes de gradientes de velocidad (VGs) los cuales llamamos “V-shapes” (∼ 20kms−1pc−1). Estos están en su mayoría localizados en filamentos y algunos están asociados a cores en el punto de convergencia. Interpretamos estos V-shapes como movimientos del gas hacia regiones mas densas, alimentando a los cores situados en la cercanía. Estimamos los tiempos asociados a estos V-shapes como VG−1. Estos tiempos son de alrededor de 67 kyr. Derivamos la taza de acreción de masa en estas estructuras, estando en el rango de (0.35 − 8.77) × 10−4 M⊙ yr−1. Estos movimientos del gas conlleva al colapso del filamento y la formación de nuevos cores. Sugerimos que el protocúmulo está colapsando a escalas grandes, pero la velocidad de colapso es mas lenta en comparación a solo caída libre. Por lo tanto, estos datos son consistentes con que el protocúmulo está bajo una contracción gravitatoria y rápida formación de cores dentro del mismo. Esto sugiere la formación de múltiples generaciones de estrellas a lo largo de la vida del protocúmulo. También analizamos la cinemática de las regiones L1482 south y Vela, dos sistemas masivos filamentarios dentro de 1kpc. Tanto HCO+ como C18O presentan emisión a escalas grandes, ambas con una discontinuidad en la posición del cúmulo NGC 1579. El campo de velocidad de ambos trazadores presenta múltiple gradientes de velocidad (“V-shapes”), siendo estos posibles indicadores de colapso gravitacional producto de movimientos del gas a escalas pequeñas hacia zonas mas densas. Esto también lo vemos en Vela, donde estos movimientos son a lo largo del filamento. Medimos el perfil de linea de masa de Vela y del filamento que contiene al protocúmulo G353. Vemos que el perfil de vela está ubicado en el medio de nuestro diagrama, entre estructuras en Orión, mientras que el f ilamento G353 tiene el perfil mas alto de nuestra muestra. Posiblemente las regiones ubicadas en la parte de arriba o abajo nuestro diagrama son jóvenes o presentan formación estelar muy ineficientes, y a medida que estas regiones forman estrellas, sus perfiles se mueven al medio de la distribución.
High mass star formation is a field not yet fully understood. Processes such as magnetic fields, stellar feedback, and intricate velocity fields add complexity to the characterization of these environments. Instruments such as ALMA, APEX, and the IRAM 30m allow us to access small spatial and spectral scales. In this work we analyze data obtained using these facilities with the goal to characterize massive star forming structures. In this context we imaged the N2H+ observations of all 15 ALMA-IMF Large Program regions, and then we focused on the analysis of the dense gas kinematics of the G353.41 protocluster, with a spatial resolution of ∼0.02 pc. G353.41, at a distance of ∼ 2kpc, is embedded in a larger-scale (∼ 8pc) filament and has a mass of ∼ 2.5 × 103M⊙ within 1.3×1.3 pc2. We extracted the N2H+ (1−0) isolated line component and decomposed it by fitting up to three Gaussian velocity components to identify velocity structures at small scales. We measured nine converging “V-shaped” velocity gradients (VGs; ∼ 20kms−1 pc−1) that are well resolved (sizes ∼ 0.1pc), mostly located in f ilaments, which are sometimes associated with cores near their point of convergence. We interpret these V-shapes as inflowing gas feeding the regions near cores. The timescales associated with the V-shapes is VG−1, and we interpret them as inflow timescales, with an average inflow timescale of ∼ 67 kyr. We derived mass accretion rates in the range of (0.35 − 8.77) × 10−4 M⊙ yr−1. We suggest that the protocluster is collapsing on large scales, but the velocity signature of collapse is slow compared to pure free-fall. Thus, these data are consistent with a comparatively slow global protocluster contraction under gravity, and faster core formation within, suggesting the formation of multiple generations of stars over the protocluster’s lifetime. We also analyze the kinematic of the L1482 south and Vela regions, two massive filamentary systems within 1kpc. In L1482 we detect in both HCO+ and C18O present large scale emission with a common discontinuity at the location of the NGC 1579 star cluster. In the velocity field of both tracers there are multiple V-shapes which might indicate the presence of small scale gas flows along the filament towards denser regions. These V shapes are also present in our APEX data of Vela, where these features are present along the filament. We increased the line-mass profiles sample by analyzing the mass distribution of Vela and the G353 parent filament. We see that the line-mass profile of Vela is located at the middle of our diagram, between structures in Orion, while the parent filament of G353 has the largest M/L profile from the probed environments. This suggest that regions located at the top (G353) or bottom (L1482) of this diagram are young or present an inefficient star formation rate, possible moving towards the middle of this diagram as they evolve.
High mass star formation is a field not yet fully understood. Processes such as magnetic fields, stellar feedback, and intricate velocity fields add complexity to the characterization of these environments. Instruments such as ALMA, APEX, and the IRAM 30m allow us to access small spatial and spectral scales. In this work we analyze data obtained using these facilities with the goal to characterize massive star forming structures. In this context we imaged the N2H+ observations of all 15 ALMA-IMF Large Program regions, and then we focused on the analysis of the dense gas kinematics of the G353.41 protocluster, with a spatial resolution of ∼0.02 pc. G353.41, at a distance of ∼ 2kpc, is embedded in a larger-scale (∼ 8pc) filament and has a mass of ∼ 2.5 × 103M⊙ within 1.3×1.3 pc2. We extracted the N2H+ (1−0) isolated line component and decomposed it by fitting up to three Gaussian velocity components to identify velocity structures at small scales. We measured nine converging “V-shaped” velocity gradients (VGs; ∼ 20kms−1 pc−1) that are well resolved (sizes ∼ 0.1pc), mostly located in f ilaments, which are sometimes associated with cores near their point of convergence. We interpret these V-shapes as inflowing gas feeding the regions near cores. The timescales associated with the V-shapes is VG−1, and we interpret them as inflow timescales, with an average inflow timescale of ∼ 67 kyr. We derived mass accretion rates in the range of (0.35 − 8.77) × 10−4 M⊙ yr−1. We suggest that the protocluster is collapsing on large scales, but the velocity signature of collapse is slow compared to pure free-fall. Thus, these data are consistent with a comparatively slow global protocluster contraction under gravity, and faster core formation within, suggesting the formation of multiple generations of stars over the protocluster’s lifetime. We also analyze the kinematic of the L1482 south and Vela regions, two massive filamentary systems within 1kpc. In L1482 we detect in both HCO+ and C18O present large scale emission with a common discontinuity at the location of the NGC 1579 star cluster. In the velocity field of both tracers there are multiple V-shapes which might indicate the presence of small scale gas flows along the filament towards denser regions. These V shapes are also present in our APEX data of Vela, where these features are present along the filament. We increased the line-mass profiles sample by analyzing the mass distribution of Vela and the G353 parent filament. We see that the line-mass profile of Vela is located at the middle of our diagram, between structures in Orion, while the parent filament of G353 has the largest M/L profile from the probed environments. This suggest that regions located at the top (G353) or bottom (L1482) of this diagram are young or present an inefficient star formation rate, possible moving towards the middle of this diagram as they evolve.
Description
Tesis presentada para optar al grado académico de Doctor en Física
Keywords
Astrofísica, Espectroscopía astronómica, Estrellas Evolución